PWM STEP-UP DC/DC CONVERTER
RH5RH××1A/××2B/××3B SERIES
APPLICATION MANUAL
ELECTRONIC DEVICES DIVISION
NO.EA-023-9803
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RH5RH SERIES
APPLICATION MANUAL
CONTENTS
......................................................................................................
OUTLINE
1
1
1
2
2
3
3
....................................................................................................
FEATURES
.............................................................................................
APPLICATIONS
BLOCK DIAGRAM
SELECTION GUIDE
PIN CONFIGURATION
.........................................................................................
.......................................................................................
...................................................................................
........................................................................................
PIN DESCRIPTION
...................................................................
...................................................................
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERITICS
OPERATION OF STEP-UP DC/DC CONVERTER
4
5
...........................................
10
13
13
14
15
15
16
17
18
18
18
18
18
18
19
19
20
20
20
21
22
22
......................................................................
TYPICAL CHARACTERISTICS
1) Output Voltage vs. Output Current .......................................................................
2) Efficiency vs. Output Current.............................................................................
3) Supply Current (No Load) vs. Input Voltage ..............................................................
4) Output Current vs. Ripple Voltage........................................................................
5) Start-up/Hold-on Voltage vs. Output Current (Topt=25˚C) ...............................................
6) Output Voltage vs. Temperature .........................................................................
7) Start-up Voltage vs. Temperature ........................................................................
8) Hold-on Voltage vs. Temperature ........................................................................
9) Supply Current 1 vs. Temperature .......................................................................
10) Supply Current 2 vs. Temperature .......................................................................
11) Lx Switching Current vs. Temperature ...................................................................
12) Lx Leakage Current vs. Temperature ....................................................................
13) Oscillator Frequency vs. Temperature....................................................................
14) Oscillator Duty Cycle vs. Temperature ...................................................................
15) Vlx Voltage Limit vs. Temperature........................................................................
16) EXT “H” Output Current vs. Temperature ................................................................
17) EXT “L” Output Current vs. Temperature.................................................................
18) Load Transient Response ................................................................................
19) Distribution of Output Voltage ............................................................................
20) Distribution of Oscillator Frequency ......................................................................
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............................................................................
TYPICAL APPLICATIONS
23
23
23
24
22
26
26
26
27
28
28
• RH5RH××1A .................................................................................................
• RH5RH××2B..................................................................................................
• RH5RH××3B..................................................................................................
• CE pin Drive Circuit............................................................................................
.............................................................................
APPLICATION CIRCUITS
• 12V Step-up Circuit............................................................................................
• Step-down Circuit..............................................................................................
• Step-up/Step-down Circuit with Flyback .......................................................................
..............................................................................
PACKAGE DIMENSIONS
TAPING SPECIFICATIONS
...........................................................................
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PWM STEP-UP DC/DC CONVERTER
RH5RH××1A/××2B/××3B SERIES
OUTLINE
The RH5RH××1A/××2B/××3B Series are PWM Step-up DC/DC converter ICs by CMOS process.
The RH5RH××1A IC consists of an oscillator, a PWM control circuit, a driver transistor (Lx switch), a refer-
ence voltage unit, an error amplifier, a phase compensation circuit, resistors for voltage detection, a soft-start cir-
cuit, and an Lx switch protection circuit. A low ripple, high efficiency step-up DC/DC converter can be constructed
of this RH5RH××1A IC with only three external components, that is, an inductor, a diode and a capacitor.
These RH5RH××1A/××2B/××3B ICs can achieve ultra-low supply current (no load) –TYP. 15µA –by a new-
ly developed PWM control circuit, equivalent to the low supply current of a VFM (chopper) Step-up DC/DC con-
verter.
Furthermore, these ICs can hold down the supply current to TYP. 2µA by stopping the operation of the oscil-
lator when the input voltage > (the output voltage set value + the dropout voltage by the diode and the inductor).
These RH5RH××1A/××2B/××3B Series ICs are recommendable to the user who desires a low ripple PWM
DC/DC converter, but cannot adopt a conventional PWM DC/DC converter because of its too large supply current.
The RH5RH××2B/××3B Series ICs use the same chip as that employed in the RH5RH××1A IC and are pro-
vided with a drive pin (EXT) for an external transistor. Because of the use of the drive pin (EXT), an external
transistor with a low saturation voltage can be used so that a large current can be caused to flow through the
inductor and accordingly a large output current can be obtained. Therefore, these RH5RH××2B/××3B Series ICs
are recommendable to the user who need a current as large as several tens mA to several hundreds mA.
The RH5RH××3B IC also includes an internal chip enable circuit so that it is possible to set the standby sup-
ply current at MAX. 0.5µA.
These RH5RH××1A/××2B/××3B ICs are suitable for use with battery-powered instruments with low noise
and low supply current.
FEATURES
..........
•
××
Small Number of External Components
Only an inductor, a diode and a capacitor (RH5RH 1A)
...........................................
•
•
•
•
•
•
Low Supply Current
Low Ripple and Low Noise
Low Start-up Voltage (when the output current is 1mA)
TYP. 15µA (RH5RH301A)
..................
MAX. 0.9V
..........................
High Output Voltage Accuracy
±2.5%
...................................................
High Efficiency
TYP. 85%
......................
Low Temperature-Drift Coefficient of Output Voltage
TYP. ±50 ppm/˚C
.............................................................
•
•
Soft-Start
MIN. 500µs
SOT-89 (RH5RH 1A, RH5RH 2B),
SOT-89-5 (RH5RH
...................................................
××
××
××
Small Packages
3B)
APPLICATIONS
•
Power source for battery-powered equipment.
•
Power source for cameras, camcorders, VCRs, PDAs, electronic data banks,and hand-held communication
equipment.
•
•
Power source for instruments which require low noise and low supply current, such as hand-held audio equip-
ment.
Power source for appliances which require higher cell voltage than that of batteries used in the appliances.
1
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RH5RH
BLOCK DIAGRAM
VLX limiter
Buffer
Slow start
Vref
Lx
OUT
Phase Comp.
Vss
LxSW
PWM control
–
+
EXT
OSC
Error Amp.
Chip Enable
CE
Error Amp. (Error Amplifier) has a DC gain of 80dB, and Phase Comp. (Phase Compensation Circuit)
provides the frequency characteristics including the 1st pole (fp=0.25Hz) and the zero point (fz=2.5kHz).
Furthermore, another zero point (fz=1.0kHz) is also obtained by the resistors and a capacitor connected to
the OUT pin.
............
(Note) Lx Pin
only for RH5RH××1A and RH5RH××3B
only for RH5RH××2B and RH5RH××3B
only for RH5RH××3B
.........
EXT Pin
...........
CE Pin
SELECTION GUIDE
In RH5RH Series, the output voltage, the driver, and the taping type for the ICs can be selected at the user's
request. The selection can be made by designating the part number as shown below :
RH5RH×××× – ×× ← Part Number
↑
↑
↑
a b
c
Code
Description
Setting Output Voltage (VOUT):
a
Stepwise setting with a step of 0.1V in the range of 2.7V to 7.5V is possible.
Designation of Driver:
1A: Internal Lx Tr. Driver (Oscillator Frequency 50kHz)
2B: External Tr. Driver (Oscillator Frequency 100kHz)
3B: Internal Tr./External Tr. (selectively available) (Oscillator Frequency 100kHz, with chip
enable function)
b
c
Designation of Taping Type :
:
Ex. SOT-89
T1, T2
:
SOT-89-5 T1, T2
(refer to Taping Specifications)
“T1” is prescribed as a standard.
For example, the product with Output Voltage 5.0V, the External Driver (the Oscillator Frequency 100kHz)
and Taping Type T1, is designated by Part Number RH5RH502B-T1.
2
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RH5RH
PIN CONFIGURATION
•
•
SOT-89
SOT-89-5
5
4
(mark side)
2
(mark side)
2
1
3
1
3
PIN DESCRIPTION
Pin No.
Symbol
Description
××1B
××2B
××3B
1
2
1
2
5
2
4
3
1
VSS
OUT
Lx
Ground Pin
Step-up Output Pin, Power Supply (for device itself)
Switching Pin (Nch Open Drain)
3
—
3
—
—
EXT
CE
External Tr. Drive Pin (CMOS Output)
Chip Enable Pin (Active Low)
—
3
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RH5RH
ABSOLUTE MAXIMUM RATINGS
Vss=0V
Symbol
VOUT
VLX
Item
Rating
Unit
V
Note
Output Pin Voltage
Lx Pin Voltage
+12
+12
V
Note1
Note2
Note3
VEXT
VCE
EXT Pin Voltage
– 0.3 to VOUT+0.3
V
CE Pin Voltage
–0.3 to VOUT+0.3
V
ILX
Lx Pin Output Current
EXT Pin Current
250
mA Note1
IEXT
±50
mA Note2
PD
Power Dissipation
500
–30 to +80
mW
˚C
Topt
Tstg
Tsolder
Operating Temperature Range
Storage Temperature Range
Lead Temperature(Soldering)
–55 to +125
˚C
260˚C,10s
(Note 1) Applicable to RH5RH××1A and RH5RH××3B.
(Note 3) Applicable to RH5RH××3B.
(Note 2) Applicable to RH5RH××2B and RH5RH××3B.
ABSOLUTE MAXIMUM RATINGS
Absolute Maximum ratings are threshold limit values that must not be exceeded even for an instant under any
conditions. Moreover, such values for any two items must not be reached simultaneously. Operation above
these absolute maximum ratings may cause degradation or permanent damage to the device. These are stress
ratings only and do not necessarily imply functional operation below these limits.
4
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RH5RH
ELECTRICAL CHARACTERISTICS
• RH5RH301A
VOUT=3.0V
Symbol
VOUT
VIN
Item
Output Voltage
Input Voltage
Conditions
MIN.
TYP. MAX.
Unit
V
Note
2.925 3.000 3.075
8
V
Vstart
Vhold
Start-up Voltage
Hold-on Voltage
IOUT=1mA,VIN : 0→2V
0.8
0.9
V
IOUT=1mA,VIN : 2→0V
0.7
V
To be measured at OUT Pin
(excluding Switching Current)
IDD1
Supply Current 1
15
2
25
5
µA
To be measured at OUT Pin
(excluding Switching Current)
VIN=3.5V
IDD2
Supply Current 2
µA
ILX
ILXleak
fosc
Lx Switching Current
Lx Leakage Current
Oscillator Frequency
VLX=0.4V
60
mA
VLX=6V,VIN=3.5V
0.5
60
µA
40
70
50
80
kHz
Oscillator Maximum Duty
Cycle
Maxdty
η
on (VLX “L” ) side
90
%
Efficiency
70
85
%
Time required for the rising
of VOUT up to 3V.
tstart
Soft-Start Time
0.5
2.0
ms
Note1
Note2
VLXlim
VLX Voltage Limit
Lx Switch ON
0.65
0.8
1.0
V
Unless otherwise provided, VIN=1.8V, VSS=0V, IOUT=10mA, Topt=25˚C, and use External Circuit of Typical
Application (FIG. 1).
(Note 1) Soft-Start Circuit is operated in the following sequence :
(1) VIN is applied.
(2) The voltage (Vref) of the reference voltage unit is maintained at 0V for about 200µs after the application of VIN.
(3) The output of Error Amp. is raised to “H” level during the maintenance of the voltage (Vref) of the reference voltage unit.
(4) After the rise of Vref, the output of Internal Error Amp. is gradually decreased to an appropriate value by the function of Internal Phase
Compensation Circuit, and the Output Voltage is gradually increased in accordance with the gradual decrease of the output of Internal Error
Amp.
(Note 2) ILX is gradually increased after Lx Switch is turned ON. In accordance with the increase of ILX, VLX is also increased. When VLX reaches VLXlim,
Lx Switch is turned OFF by an Lx Switch Protection Circuit.
5
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RH5RH
• RH5RH501A
VOUT=5.0V
Symbol
VOUT
VIN
Item
Output Voltage
Input Voltage
Conditions
MIN.
TYP. MAX.
Unit
V
Note
4.875 5.000 5.125
8
V
Vstart
Vhold
Start-up Voltage
Hold-on Voltage
Iout=1mA,Vin:0→2V
0.8
0.9
V
Iout=1mA,Vin:2→0V
0.7
V
To be measured at OUT Pin
(excluding Switching Current)
IDD1
Supply Current 1
30
2
45
5
µA
µA
To be measured at OUT Pin
(excluding Switching Current)
VIN=5.5V
IDD2
Supply Current 2
ILX
ILXleak
fosc
Lx Switching Current
Lx Leakage Current
Oscillator Frequency
VLX=0.4V
80
mA
µA
VLX=6V,VIN=5.5V
0.5
60
40
70
50
80
kHz
Oscillator Maximum Duty
Cycle
Maxdty
η
on (VLX “L” ) side
90
%
Efficiency
70
85
%
Time required for the rising
of VOUT up to 5V.
tstart
Soft-Start Time
0.5
2.0
ms
Note1
Note2
VLXlim
VLX Voltage Limit
Lx Switch ON
0.65
0.8
1.0
V
Unless otherwise provided, VIN=3V, Vss=0V, IOUT=10mA, Topt=25˚C, and use External Circuit of Typical
Application (FIG. 1).
(Note 1) Soft-Start Circuit is operated in the following sequence :
(1) VIN is applied.
(2) The voltage (Vref) of the reference voltage unit is maintained at 0V for about 200µs after the application of VIN.
(3) The output of Error Amp. is raised to “H” level during the maintenance of the voltage (Vref) of the reference voltage unit.
(4) After the rise of Vref, the output of Internal Error Amp. is gradually decreased to an appropriate value by the function of Internal Phase
Compensation Circuit, and the Output Voltage is gradually increased in accordance with the gradual decrease of the output of Internal Error
Amp.
(Note 2) ILX is gradually increased after Lx Switch is turned ON. In accordance with the increase of ILX, VLX is also increased. When VLX reaches VLXlim,
Lx Switch is turned OFF by an Lx Switch Protection Circuit.
6
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RH5RH
• RH5RH302B
Symbol
VOUT
VOUT=3.0V
Item
Conditions
MIN.
TYP.
MAX.
Unit
V
Note
Output Voltage
2.925 3.000 3.075
8
VIN
Input Voltage
V
Vstart
Oscillator Start-up Voltage
Supply Current 1
EXT no load,VOUT :0→2V
EXT no load,VOUT=2.88V
EXT no load,VOUT=3.5V
VEXT=VOUT–0.4V
0.7
30
2
0.8
50
5
V
IDD
IDD
µA
µA
mA
mA
kHz
1
Supply Current 2
2
IEXTH
IEXTL
fosc
EXT “H” Output Current
EXT “L” Output Current
Oscillator Frequency
–1.5
1.5
80
VEXT=0.4V
100
80
120
90
Oscillator Maximum Duty
Cycle
Maxdty
tstart
VEXT “H” side
70
%
Time required for the rising
of VOUT up to 3V
Soft-Start Time
0.5
2.0
ms
Note1
Unless otherwise provided, VIN=1.8V, Vss=0V, IOUT=10mA, Topt=25˚C, and use External Circuit of Typical
Application (FIG. 2).
VOUT=5.0V
• RH5RH502B
Symbol
VOUT
VIN
Item
Conditions
MIN.
TYP.
MAX.
Unit
V
Note
Output Voltage
4.875 5.000 5.125
8
Input Voltage
V
Vstart
Oscillator Start-up Voltage
Supply Current 1
EXT no load,VOUT :0→2V
EXT no load,VOUT=4.8V
EXT no load,VOUT=5.5V
VEXT=VOUT–0.4V
0.7
60
2
0.8
90
5
V
IDD
IDD
µA
µA
mA
mA
kHz
1
Supply Current 2
2
IEXTH
IEXTL
fosc
EXT “H” Output Current
EXT “L” Output Current
Oscillator Frequency
–2
2
VEXT=0.4V
80
100
80
120
90
Oscillator Maximum Duty
Cycle
Maxdty
VEXT “H” side
70
%
Time required for the rising
of VOUT up to 5V
start
t
Soft-Start Time
0.5
2.0
ms
Note1
Unless otherwise provided, VIN=3V, Vss=0V, IOUT=10mA, Topt=25˚C and use External Circuit of Typical
Application (FIG. 2).
(Note 1) refer to page 5 (Note 1)
7
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RH5RH
• RH5RH303B
Symbol
VOUT=3.0V
Item
Output Voltage
Input Voltage
Start-up Voltage
Hold-on Voltage
Efficiency
Conditions
MIN.
TYP.
MAX.
Unit
V
Note
VOUT
VIN
2.925 3.000 3.075
8
V
→
Vstart
Vhold
η
IOUT=1mA,VIN : 0 2V
0.8
0.9
V
→
IOUT=1mA,VIN : 2 0V
0.7
70
V
85
30
%
IDD1
Supply Current 1
To be measured at OUT pin
50
5
µA
To be measured at OUT pin
VIN=3.5V
2
µA
IDD2
Supply Current 2
ILX
Lx Switching Current
Lx Leakage Current
EXT “H” Output Current
EXT “L” Output Current
CE “H” Level 1
VLX=0.4V
VLX=6V,VIN=3.5V
VEXT=VOUT–0.4V
VEXT=0.4V
60
mA
µA
mA
mA
V
0.5
ILXleak
IEXTH
IEXTL
VCEH1
VCEL1
VCEH2
VCEL2
ICEH
–1.5
1.5
VOUT≥1.5V
V
OUT–0.4
CE “L” Level 1
VOUT≥1.5V
0.4
V
CE “H” Level 2
0.8V≤VOUT<1.5V
0.8V≤VOUT<1.5V
CE=3V
V
OUT–0.1
V
CE “L” Level 2
0.1
0.5
V
CE “H” Input Current
CE “L” Input Current
Oscillator Frequency
µA
µA
kHz
ICEL
CE=0V
–0.5
80
fosc
100
80
120
90
Oscillator Maximum Duty
Cycle
Maxdty
on (VLX “L” )side
70
%
Time required for the rising
of VOUT up to 3V.
0.5
2.0
0.8
ms
V
Note1
Note2
tstart
Soft-Start Time
VLXlim
VLX Voltage Limit
Lx Switch ON
0.65
1.0
Unless otherwise provided, VIN=1.8V, VSS=0V, IOUT=10mA, Topt=25˚C, and use External Circuit of Typical
Application (FIG. 3).
(Note 1) Soft-Start Circuit is operated in the following sequence :
(1) VIN is applied.
(2) The voltage (Vref) of the reference voltage unit is maintained at 0V for about 200µs after the application of VIN.
(3) The output of Error Amp. is raised to “H” level during the maintenance of the voltage (Vref) of the reference voltage unit.
(4) After the rise of Vref, the output of Internal Error Amp. is gradually decreased to an appropriate value by the function of Internal Phase Com
pensation Circuit, and the Output Voltage is gradually increased in accordance with the gradual decrease of the output of Internal Error Amp.
(Note 2) ILX is gradually increased after Lx Switch is turned ON. In accordance with the increase of ILX, VLX is also increased. When VLX reaches VLXlim,
Lx Switch is turned OFF by an Lx Switch Protection Circuit.
8
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RH5RH
• RH5RH503B
Symbol
VOUT=5.0V
Item
Output Voltage
Input Voltage
Start-up Voltage
Hold-on Voltage
Efficiency
Conditions
MIN.
TYP.
MAX.
Unit
V
Note
VOUT
VIN
4.875 5.000 5.125
8
V
→
Vstart
Vhold
η
IOUT=1mA,VIN : 0 2V
0.8
0.9
V
→
IOUT=1mA,VIN : 2 0V
0.7
70
V
85
60
%
IDD1
Supply Current 1
To be measured at OUT pin
90
5
µA
To be measured at OUT pin
VIN=5.5V
2
µA
IDD2
Supply Current 2
ILX
Lx Switching Current
Lx Leakage Current
EXT “H” Output Current
EXT “L” Output Current
CE “H” Level 1
VLX=0.4V
VLX=6V,VIN=5.5V
VEXT=VOUT–0.4V
VEXT=0.4V
80
mA
µA
mA
mA
V
0.5
ILXleak
IEXTH
IEXTL
VCEH1
VCEL1
VCEH2
VCEL2
ICEH
–2.0
2.0
VOUT≥1.5V
V
OUT–0.4
CE “L” Level 1
VOUT≥1.5V
0.4
V
CE “H” Level 2
0.8V≤VOUT<1.5V
0.8V≤VOUT<1.5V
CE=5V
V
OUT–0.1
V
CE “L” Level 2
0.1
0.5
V
CE “H” Input Current
CE “L” Input Current
Oscillator Frequency
µA
µA
kHz
ICEL
CE=0V
–0.5
80
fosc
100
80
120
90
Oscillator Maximum Duty
Cycle
Maxdty
on (VLX “L” )side
70
%
Time required for the rising
of VOUT up to 5V.
0.5
2.0
0.8
ms
V
Note1
Note2
tstart
Soft-Start Time
VLXlim
VLX Voltage Limit
Lx Switch ON
0.65
1.0
Unless otherwise provided, VIN=3V, VSS=0V, IOUT=10mA, Topt=25˚C, and use External Circuit of Typical
Application (FIG. 3).
(Note 1) Soft-Start Circuit is operated in the following sequence :
(1) VIN is applied.
(2) The voltage (Vref) of the reference voltage unit is maintained at 0V for about 200µs after the application of VIN.
(3) The output of Error Amp. is raised to “H” level during the maintenance of the voltage (Vref) of the reference voltage unit.
(4) After the rise of Vref, the output of Internal Error Amp. is gradually decreased to an appropriate value by the function of Internal Phase Com
pensation Circuit, and the Output Voltage is gradually increased in accordance with the gradual decrease of the output of Internal Error Amp.
(Note 2) ILX is gradually increased after Lx Switch is turned ON. In accordance with the increase of ILX, VLX is also increased. When VLX reaches VLXlim,
Lx Switch is turned OFF by an Lx Switch Protection Circuit.
9
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RH5RH
OPERATION OF STEP-UP DC/DC CONVERTER
Step-up DC/DC Converter charges energy in the inductor when Lx Transistor (LxTr) is on, and discharges the
energy with the addition of the energy from Input Power Source thereto, so that a higher output voltage than the
input voltage is obtained.
The operation will be explained with reference to the following diagrams :
< Basic Circuits >
< Current through L >
IL
i2
SD
ILmax
ILmin
topen
IOUT
L
VIN
VOUT
i1
t
Lx Tr
CL
toff
ton
T=1/fosc
Step 1 : LxTr is turned ON and current IL (= i1 ) flows, so that energy is charged in L. At this moment, IL(=i1 ) is
increased from ILmin (= 0) to reach ILmax in proportion to the on-time period (ton) of LxTr.
Step 2 : When LxTr is turned OFF, Schottky diode (SD) is turned ON in order that L maintains IL at ILmax, so
that current IL (= i2) is released.
Step 3 : IL (=i2) is gradually decreased, and in the case of discontinuous mode, IL reaches ILmin (=0) after a time
period of topen, so that SD is turned OFF. However, in the case of a continuous mode which will be mentioned
later,the time period (toff) runs out before IL reaches ILmin (=0), so that LxTr is turned ON in the next
cycle, and SD is turned OFF. In this case, ILmin does not reach zero, and IL (=i1) increases from ILmin (> 0).
In the case of PWM control system, the output voltage is maintained constant by controlling the on-time peri-
od (ton), with the oscillator frequency (fosc) being maintained constant.
•
Discontinuous Conduction Mode and Continuous Conduction Mode
In the above two diagrams, the maximum value (ILmax) and the minimum value (ILmin) of the current which
flows through the inductor are the same as those when LxTr is ON and also when LxTr is OFF.
The difference between ILmax and ILmin, which is represented by ∆I, is :
.........................................
∆I=ILmax–ILmin=VIN · ton/L=(VOUT–VIN) · topen/L
Equation 1
wherein T=1/fosc=ton+toff
duty (%)=ton/T · 100=ton · fosc · 100
topen≤toff
In Equation 1, VIN · ton/L and (VOUT–VIN) · topen/L are respectively show the change in the current at ON, and the
change in the current at OFF.
10
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RH5RH
When the output current (IOUT) is relatively small, topen<toff as illustrated in the above diagram. In this case,
the energy charged in the inductor during the time period of ton is discharged in its entirely during the time peri-
od of toff, so that ILmin becomes zero (ILmin=0). When IOUT is gradually increased, topen eventually becomes
equal to toff (topen=toff), and when IOUT is further increased. ILmin becomes larger than zero (ILmin>0). The
former mode is referred to as the discontinuous mode and the latter mode is referred to as the continuous mode.
In the continuous mode, when Equation 1 is solved for ton and the solution is tonc,
................................................................................................
tonc =T · (1–VIN/VOUT)
Equation 2
When ton<tonc, the mode is the discontinuous mode, and when ton=tonc, the mode is the continuous mode.
•
Output Current in Discontinuous Mode
In the discontinuous mode, when LxTr is on, the energy PON charged in the inductor is provided by Equation 3
as follows :
ton
2
PON=∫ 0ton VIN · IL (t) dt =∫ 0 (VIN · t/L) dt
2
2
.................................................................................................
=VIN · ton /(2 · L)
Equation 3
In the case of the step-up DC/DC converter, the energy is also supplied from the input power source at the time
of OFF.
Thus, POFF=∫topen VIN · IL (t) dt =∫topen ((VOUT–VIN) · t/L)dt
0
0
=VIN · (VOUT–VIN) · topen2/(2 · L)
Here, topen=VIN · ton/(VOUT–VIN) from Equation 1, and when this is substituted into the above equation.
3
2
..........................................................................
=VIN · ton /(2 · L · (VOUT–VIN)
Equation 4
Input power is (PON+POFF)/T. When this is converted in its entirely to the output.
PIN=(PON+POFF)/T=VOUT · IOUT=POUT .....................................................................
Equation 5
Equation 6 can be obtained as follows by solving Equation 5 for IOUT by substituting Equations 3 and 4 into
Equation 5 :
2
2
.....................................................................
IOUT=VIN · ton /(2 · L · T · (VOUT–VIN))
Equation 6
The peak current which flows through L · LxTr · SD is
......................................................................................................
ILmax=VIN · ton/L
Equation 7
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RH5RH
Therefore it is necessary that the setting of the input/output conditions and the selection of peripheral compo-
nents should be made with ILmax taken into consideration.
•
Output Current in Continuous Conduction Mode
When the operation enters into the continuous conduction mode by increasing the IOUT, ILmin becomes equal
to Iconst (> 0), and this current always flows through the inductor. Therefore, VIN · Iconst is added to PIN in
Equation 5.
Thus, PIN=VIN · Iconst+(PON+POFF)/T=VOUT · IOUT=POUT
When the above Equation is solved for IOUT,
2
2
IOUT=VIN · tonc /(2 · L · T · (VOUT–VIN))+VIN · Iconst/VOUT ............................................
Equation 8
Equation 9
The peak current which flows through L · LxTr · SD is
...................................................................................................
ILmax=VIN · ton/L+Iconst
From Equations 6 and 9, the larger the value of L, the smaller the load current at which the operation enters
into the continuous mode, and the smaller the difference between ILmax and ILmin, and the smaller the value of
ILmax.
Therefore, when the load current is the same, the larger the value of L, the easier the selection of peripheral
components with a small allowable current becomes, and the smaller the ripple of the peripheral components can
be made. In this case, however, it must be noted from Equation 6 that IOUT becomes small when the allowable cur-
rent of the inductor is small or when VIN is so small that the operation cannot enter into the continuous mode.
HINTS
The above explanation is directed to the calculation in an ideal case where there is no energy loss caused by the
resistance in the external components and LxSW. In an actual case, the maximum output current will be 50
to 80% of the above calculated maximum output current. In particular, care must be taken because VIN is
decreased in an amount corresponding to the voltage drop caused by LxSW when IL is large or VIN is low.
Furthermore, it is required that with respect to VOUT, Vf of the diode (about 0.3V in the case of a Schottky type
diode) be taken into consideration.
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RH5RH
TYPICAL CHARACTERISTICS
1) Output Voltage vs. Output Current
RH5RH301A
RH5RH301A
L=270µH
L=120µH
3.1
3.1
3.0
2.9
2.8
2.7
2.6
2.5
3.0
2.9
2.8
2.7
1.5V
2.0V
1.5V
2.6
2.5
VIN=1.0V
20
2.0V
50
VIN =1.0V
0
10
30
40
60
0
20
60
40
Output Current IOUT(mA)
Output Current IOUT(mA)
RH5RH501A
RH5RH501A
L=120µH
L=270µH
5.2
5.0
4.8
4.6
4.4
4.2
4.0
5.2
5.0
4.8
4.6
4.4
4.2
4.0
4.0V
3.0V
2.0V
3.0V
2.0V
50
4.0V
VIN=
1.0V
VIN=1.0V
0
100
150
0
50
100
150
Output Current IOUT(mA)
Output Current IOUT(mA)
RH5RH302B
RH5RH502B
L=28µH
2.5V
L=28µH
4.0V
3.1
5.2
5.0
4.8
4.6
4.4
3.0V
2.0V
2.0V
1.5V
3.0
2.9
2.8
VIN=0.9V
VIN=1.5V
0
200
400
600
0
500
1000
Output Current IOUT(mA)
Output Current IOUT(mA)
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RH5RH
2) Efficiency vs. Output Current
RH5RH301A
RH5RH301A
L=120µH
2.0V
L=270µH
2.0V
90
100
90
80
70
60
50
40
80
70
60
1.5V
VIN=1.0V
VIN=1.0V
1.5V
50
40
0
10
30
20
0
10
20
30
40
Output Current IOUT(mA)
Output Current IOUT(mA)
RH5RH501A
RH5RH501A
L=270µH
L=120µH
4.0V
100
90
100
90
80
70
60
80
70
4.0V
3.0V
2.0V
VIN=
1.0V
3.0V
60
50
40
VIN=1.0V
2.0V
50
40
0
50
100
150
0
50
150
100
Output Current IOUT(mA)
Output Current IOUT(mA)
RH5RH302B
RH5RH502B
L=28µH
4.0V
L=28µH
2.5V
100
100
80
80
60
40
20
0
3.0V
2.0V
2.0V
1.5V
60
40
VIN=0.9V
VIN=1.5V
20
0
0
500
1000
200
Output Current IOUT(mA)
600
0
400
Output Current IOUT(mA)
14
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RH5RH
3) Supply Curret (No Load) vs. Input Voltage
RH5RH301A
RH5RH301A
L=270µH
L=120µH
70
60
50
40
70
60
50
40
30
20
10
0
30
20
10
0
1.0
1.2
1.4
1.6
1.8
2.0
1.0
1.2
1.6
1.8
2.0
1.4
Input Voltage VIN(V)
Input Voltage VIN(V)
RH5RH501A
RH5RH501A
L=270µH
L=120µH
200
200
150
100
150
100
50
0
50
0
1
2
3
4
1
2
3
4
Input Voltage VIN(V)
Input Voltage VIN(V)
4) Output Current vs.Ripple Voltage
RH5RH301A
RH5RH501A
L=120µH
L=120µH
100
80
90
80
70
60
50
70
60
2.0V
4.0V
3.0V
3.0V
2.0V
VIN=0.9V
50
40
30
20
10
VIN=0.9V
40
30
20
10
0
0
50 60 70 80 90 100
1
5
10 20 30 40
5
50 60 70 80 90 100
1
10 20 30 40
Output Current IOUT(mA)
Output Current IOUT(mA)
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RH5RH
RH5RH301A
RH5RH501A
L=270µH
4.0V
L=270µH
3.0V
80
70
60
50
40
70
60
50
3.0V
40
30
20
10
0
VIN=0.9V
2.0V
30
20
10
0
2.0V
VIN=0.9V
1
10 20 30 40 50 60 70 80 90
Output Current IOUT(mA)
1
10
20 30 40 50 60
Output Current IOUT(mA)
70 80
RH5RH302B
RH5RH502B
L=28µH
3.0V
L=28µH
70
60
50
120
100
80
60
40
20
0
VIN=0.9V
2.0V
3.0V
2.0V
40
30
20
4.0V
VIN=0.9V
10
0
1
50
100
150
200
1
50
100
150
200
250
Output Current IOUT(mA)
Output Current IOUT(mA)
5) Start-up/Hold-on Voltage vs. Output Current (Topt=25˚C)
RH5RH301A
RH5RH501A
L=120µH
L=120µH
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
Vstart
Vstart
Vhold
Vhold
0
10
20
Output Current IOUT(mA)
30
0
30
10
20
Output Current IOUT(mA)
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RH5RH
RH5RH502B
RH5RH302B
L=28µH
L=28µH
1.4
1.2
1.0
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
Vstart
Vhold
Vstart
Vhold
0.8
0.6
0.4
0.2
0
20
40
60
80
100
0
20
40
60
80
100
0
Output Current IOUT(mA)
Output Current IOUT(mA)
6) Output Voltage vs.Temperature
IOUT=10mA
VIN=2V
L=120µH
IOUT=10mA
VIN=3V
L=120µH
RH5RH301A
RH5RH501A
3.2
5.2
5.1
5.0
3.1
3.0
2.9
2.8
2.7
4.9
4.8
4.7
–40
0
20
40
60
80
100
–20
–40
0
20
40
60
80
–20
100
Temperature Topt(˚C)
Temperature Topt(˚C)
IOUT=10mA
VIN=2V
L=28µH
IOUT=10mA
VIN=3V
L=28µH
RH5RH302B
RH5RH502B
3.2
5.2
5.1
5.0
4.9
4.8
3.1
3.0
2.9
2.8
2.7
–40
4.7
–40 –20
0
20
40
60
80
100
–20
0
20
40
60
80
100
Temperature Topt(˚C)
Temperature Topt(˚C)
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RH5RH
7) Start-up Voltage vs. Temperature
8) Hold-on Voltage vs. Temperature
RH5RH501A
RH5RH501A
1.0
1.2
1.0
0.8
0.6
0.4
0.2
0
0.8
0.6
0.4
0.2
0
–40
–20
0
20
40
60
80
–40 –20
0
40
60
80
20
Temperature Topt(˚C)
Temperature Topt(˚C)
9) Supply Current 1 vs.Temperature
10) Supply Current 2 vs.Temperature
RH5RH501A
RH5RH501A
100
5
80
60
4
3
2
40
20
0
1
0
–40
0
20
40
60
80
–20
–40
0
20
40
60
80
–20
Temperature Topt(˚C)
Temperature Topt(˚C)
11) Lx Switching Current vs.Temperature
12) Lx Leakage Current vs.Temperature
RH5RH501A
RH5RH501A
1.0
150
125
100
75
50
25
0
0.8
0.6
0.4
0.2
0
–40
–20
0
20
40
60
80
–40
0
20
40
60
80
–20
Temperature Topt(˚C)
Temperature Topt(˚C)
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RH5RH
13) Oscillator Frequency vs. Temperature
IOUT=10mA
RH5RH301A
IOUT=10mA
RH5RH501A
VIN=2V
VIN=3V
L=120µH
L=120µH
100
100
90
80
70
60
50
40
30
20
10
0
90
80
70
60
50
40
30
20
10
0
–40 –20
0
20
40
60
80 100
–40 –20
0
20
40
60
80
100
Temperature Topt(˚C)
Temperature Topt(˚C)
IOUT=10mA
VIN=2V
L=28µH
RH5RH302B
RH5RH502B
IOUT=10mA
VIN=3V
L=28µH
140
140
120
100
80
60
40
20
0
120
100
80
60
40
20
0
–40 –20
0
20
40
60
80
100
–40 –20
0
20
40
60
80
100
Temperature Topt(˚C)
Temperature Topt(˚C)
14) Oscillator Duty Cycle vs. Temperature
RH5RH301A
IOUT=10mA
VIN=2V
L=120µH
RH5RH501A
IOUT=10mA
VIN=3V
L=120µH
100
90
80
70
60
50
100
90
80
70
60
50
60
80
–40
–20
0
20
40
–40
–20
0
20
40
60
80
Temperature Topt(˚C)
Temperature Topt(˚C)
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RH5RH
IOUT=10mA
VIN=2V
L=28µH
IOUT=10mA
VIN=3V
L=28µH
RH5RH502B
RH5RH302B
100
90
100
90
80
70
60
50
80
70
60
50
–40
–20
0
20
40
60
80
–40
–20
0
20
40
60
80
Temperature Topt(˚C)
Temperature Topt(˚C)
15) VLX Voltage Limit vs. Temperature
RH5RH501A
1.2
1.0
0.8
0.6
0.4
0.2
0.0
80
–40
–20
0
60
20
40
Temperature Topt(˚C)
16) EXT “H” Output Current vs. Temperature
17) EXT “L” Output Current vs. Temperature
RH5RH501A
RH5RH501A
10
10
8
6
4
2
8
6
4
2
0
0
–40
–40
–20
0
20
40
60
80
–20
0
20
40
60
80
Temperature Topt(˚C)
Temperature Topt(˚C)
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RH5RH
18) Load Transient Response
RH5RH301A
IOUT=1mA-30mA
VIN=2V
RH5RH501A
IOUT=1mA-30mA
VIN=3V
L=120µH
L=120µH
5.0
4.5
4.0
240
7.0
6.5
6.0
5.5
240
210
180
210
180
150
Output Voltage
Output Current
3.5
150
120
90
Output Voltage
3.0
2.5
2.0
120
90
60
30
0
5.0
4.5
4.0
3.5
60
Output Current
30
0
1.5
1.0
3.0
20
40
60
0
80
0
20
40
60
80
Time t(ms)
Time t(ms)
RH5RH302B
RH5RH502B
IOUT=1mA-30mA
VIN=3V
IOUT=1mA-30mA
VIN=2V
L=28µH
L=28µH
7.0
240
240
5.0
4.5
4.0
3.5
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
210
180
210
180
Output Voltage
Output Voltage
Output Current
150
120
90
150
120
90
60
30
0
3.0
2.5
60
30
0
2.0
1.5
Output Current
1.0
0
20
40
Time t(ms)
60
80
0
20
40
60
80
Time t(ms)
21
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RH5RH
19) Distribution of Output Voltage
RH5RH501A
5.18~5.20
5.16~5.18
5.14~5.16
5.12~5.14
5.10~5.12
5.08~5.10
5.06~5.08
5.04~5.06
5.02~5.04
5.00~5.02
4.98~5.00
4.96~4.98
4.94~4.96
4.92~4.94
4.90~4.92
4.88~4.90
4.86~4.88
4.84~4.86
4.82~4.84
4.80~4.82
0
5
10
15
20
25
30
35
Distribution (%)
20) Distribution of Oscillator Frequency
RH5RH501A
59~60
58~59
57~58
56~57
55~56
54~55
53~54
52~53
51~52
50~51
49~50
48~49
47~48
46~47
45~46
44~45
43~44
42~43
41~42
40~41
0
5
10
15
Distribution (%)
20
25
22
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RH5RH
TYPICAL APPLICATIONS
• RH5RH××1A
Diode
Inductor
VOUT
Lx
OUT
Vss
+
VIN
Capacitor
Components Inductor (L)
Diode (D)
: 120µH (Sumida Electric Co., Ltd.)
: MA721 (Matsushita Electronics Corporation, Schottky Type)
: 22µF (Tantalum Type)
Capacitor (CL)
FIG. 1
• RH5RH××2B
Inductor
Diode
VOUT
Cb
Rb
OUT
EXT
Vss
+
VIN
Capacitor
Tr
Components Inductor (L)
: 28µH (Troidal Core)
Diode (D)
: HRP22 (Hitachi, Schottky Type)
: 100µF (Tantalum Type)
: 2SD1628G
Capacitor (CL)
Transistor (Tr)
Base Resistor (Rb)
: 300Ω
Base Capacitor (Cb) : 0.01µF
FIG. 2
23
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RH5RH
• RH5RH××3B
Diode
Inductor
VOUT
Lx
OUT
NC
EXT
CE Vss
+
VIN
Capacitor
Components Inductor (L)
Diode (D)
: 120µH (Sumida Electric Co., Ltd.)
: MA721 (Matsushita Electronics Corporation, Schottky Type)
: 22µF (Tantalum Type)
Capacitor (CL)
FIG. 3
Inductor
Diode
VOUT
NC
Lx
Cb
Rb
OUT
EXT
CE
Vss
+
VIN
Capacitor
Tr
Components Inductor (L)
Diode (D)
: 28µH (Troidal Core)
: HRP22 (Hitachi, Schottky Type)
: 100µF (Tantalum Type)
: 2SD1628G
Capacitor (CL)
Transistor (Tr)
Base Resistor (Rb)
: 300Ω
Base Capacitor (Cb) : 0.01µF
FIG. 4
24
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RH5RH
• CE pin Drive Circuit
Diode
Inductor
RH5RH××3B
VOUT
Lx
OUT
NC
EXT
CE
Vss
Pull-up
resistor
+
Capacitor
VIN
CE
Tr
FIG. 5
25
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RH5RH
APPLICATION CIRCUITS
• 12V Step-up Circuit
Inductor
Diode
VOUT
ZD:6.8V
RH5RH502B
Cb
Rb
OUT
EXT
+
Capacitor
VIN
Vss
RZD
Tr
Starter Circuit
(Note) When the Output Current is small or the Output Voltage is unstable,use the Rzd for flowing the bias current through the Zener diode ZD.
FIG. 6
• Step-down Circuit
Inductor
VOUT
PNP
Tr
Diode
RH5RH××1A
OUT
Rb2
Lx
VIN
Rb1
+
Vss
Capacitor
Starter Circuit
(Note) When the LX pin Voltage is over the rating at the time PNP Tr is OFF,use a RH5RH××2B and drive the PNP Tr. by the external NPN Tr.
FIG. 7
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RH5RH
• Step-up/Step-down Circuit with Flyback
Diode
VOUT
Trance1:1
RH5RH××1A
OUT
Lx
VIN
+
Vss
Capacitor
Starter Circuit
(Note) Use a RH5RH××2B,depend on the Output Current.
FIG. 8
The Starter Circuit is necessary for all above circuits.
*
1.for Step-up Circuit.
VOUT side
VIN side
Starter Circuit
2.for Step-down and Step-up/Step-down Circuit.
VIN side
VOUT side
Tr
RST
Starter Circuit
ZDST
ZDst 2.5V≤/ZDst≤Designation of Output Voltage
Rst Input Bias Current of ZDst and Tr.
(several kΩ to several hundreds kΩ)
27
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RH5RH
PACKAGE DIMENSIONS (Unit: mm)
• SOT-89
• SOT-89-5
4.5±0.1
1.6±0.2
4.5±0.1
1.5±0.1
1.5±0.1
1.6±0.2
0.4±0.1
0.42±0.1
0.4±0.1
4
5
ø1.0
ø1.0
3
1
2
0.4±0.1
3
1
2
0.4±0.1
0.42
±0.1
0.47
±0.1
0.42
±0.1
0.42
±0.1
0.47
±0.1
0.42
±0.1
1.5±0.1
1.5±0.1
1.5±0.1
1.5±0.1
TAPING SPECIFICATIONS (Unit: mm)
• SOT-89
+0.1
ø 1.5
4.0±0.1
–0
0.3±0.1
2.0±0.05
5.0
8.0±0.1
2.5MAX.
T 2
T 1
User Direction of Feed.
• SOT-89-5
4.0±0.1
+0.1
–0
ø 1.5
5.0
0.3±0.1
2.0±0.05
4.7
8.0±0.1
2.5MAX.
T 2
T 1
User Direction of Feed.
28
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RH5RH
APPLICATION HINTS
When using these ICs, be sure to take care of the following points :
•
•
•
Set external components as close as possible to the IC and minimize the connection between the components
and the IC. In particular, when an external component is connected to OUT Pin, make minimum connection
with the capacitor.
Make sufficient grounding. A large current flows through Vss Pin by switching. When the impedance of the
Vss connection is high, the potential within the IC is varied by the switching current. This may result in
unstable operation of the IC.
Use capacitor with a capacity of 10µF or more, and with good high frequency characteristics such as tanta-
lum capacitor. We recommend the use of a capacitor with a resistance to the voltage being at least three
times the output set voltage. This is because there may be the case where a spike-shaped high voltage is gen-
erated by the inductor when Lx transistor is turned OFF.
•
Take the utmost care when choosing a inductor. Namely, choose such an inductor that has sufficiently small
d.c. resistance and large allowable current, and hardly reaches magnetic saturation. When the inductance
value of the inductor is small, there may be the case where ILX exceeds the absolute maximum ratings at the
maximum load. Use an inductor with an appropriate inductance.
•
•
Use a diode of a Schottky type with high switching speed, and also take care of the rated current.
These ICs are provided with a soft-start circuit. However, there may be the case where the overshoot of the
out put voltage takes place depending upon the peripheral circuits employed and the input/output condi-
tions. In particular, when the input voltage is increased slowly, the occurrence of the overshoot of the output
voltage becomes conspicuous. Therefore in the case where the overshoot becomes a problem, take a counter-
measure against this problem, for example, by clamping the output (OUT Pin) by use of a Zener diode.
The transient response characteristics corresponding to the variations in the input and output are set so as
to be slightly delayed by an internal phase compensation circuit in order to prevent the oscillation. because
of such setting of the transient response characteristics, take care of the occurrence of the overshoot and/or
undershoot of the output voltage.
•
•
The internal phase compensation circuit is designed with the avoidance of the problem of the occurrence of
the oscillation fully taken into consideration. However, there may be the case the oscillation takes place
depending upon the conditions for the attachment of external components. In particular, take the utmost
care when an inductor with a large inductance is used.
The performance of power source circuits using these ICs largely depends upon the peripheral circuits. Take the utmost care in the
selection of the peripheral circuits. In particular, design the peripheral circuits in such a manner that the values such as voltage, current
and power of each component, PCB patterns and the IC do not exceed their respective rated values.
29
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HEADQUARTERS
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Phone 81-727-53-1111 Fax 81-727-53-6011
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JAPAN
Phone 81-45-477-1697 Fax 81-45-477-1694·1695
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ELECTRONIC DEVICES DIVISION
SAN JOSE OFFICE
3001 Orchard Parkway, San Jose, CA 95134-2088, U.S.A.
Phone 1-408-432-8800 Fax 1-408-432-8375
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