2CH PWM DC/DC Controller
R1280D002X Series
2001.6.16
Rev. 1.10 - 1 -
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OUTLINE
The R1280D002X Series are 2-channel PWM Step-up (as Channel 1)/Inverting (as Channel 2) DC/DC converter
controllers with CMOS process.
Each of the R1280D002X Series consists of an oscillator, a PWM control circuit, a reference voltage unit, an error
amplifier, a reference current unit, a protection circuit, and an under voltage lockout (UVLO) circuit. A high efficiency
Step-up/Inverting DC/DC converter can be composed of this IC with inductors, diodes, power MOSFETs, resisters,
and capacitors. Each Output Voltage can be adjustable with external resistors, while soft-start time can be adjustable
with external capacitors..
Maximum Duty Cycle of R1280D002A and C series can be also adjustable with external resistors.
Maximum Duty Cycle of R1280D002B is built-in as 90%(TYP.).
When CE pin of R1280D002B is set at GND level, this IC turns off external power MOSFETs of Step-up/Inverting as
Standby-mode.
Standby current is typically 0
A.
As for a protection circuit, if Maximum duty cycle of either Step-up DC/DC converter side or Inverting DC/DC
converter side is continued for a certain time, the R1280D Series latch both external drivers with their off state by its
Latch-type protection circuit. Delay time for protection is internally fixed typically at 100ms. To release the protection
circuit, restart with power-on (Voltage supplier is equal or less than UVLO detector threshold level), or as for
R1280D002B, once after making the circuit be stand-by with chip enable pin and enable the circuit again.
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FEATURES
q
Input Voltage Range
2.5V to 5.5V
q Built-in Latch-type Protection Function by monitoring duty cycle (Fixed Delay Time TYP. 100ms)
q Oscillator Frequency
700kHz(R1280D002A,B)/200kHz(r1280D002C)
q Maximum Duty Cycle
TYP. 90%(Only applied to R1280D002B Series)
q High Reference Voltage Accuracy
1.5%
q U.V.L.O. Threshold
TYP. 2.2V (Hysteresis: TYP. 0.1V)
q Small Package
thin SON-10 (package thickness MAX. 0.9mm)
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APPLICATIONS
q Constant Voltage Power Source for portable equipment.
q Constant Voltage Power Source for LCD and CCD.
Rev.1.10 - 2 -
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s
BLOCK DIAGRAM
q
R1280D002A/C
V
IN
E X T 1
O S C
V ref1
La tch
D T C 2
V
F B 2
V refout
E X T 2
U V L O
G N D
A M P O U T 1
V
F B 1
V refout
D T C 1
D elay C ircu it
C H
C H
q
R1280D002B
V
IN
EXT1
OSC
Vref1
Latch
DTC2
V
FB2
Vrefout
EXT2
UVLO
GND
CE
V
FB1
Vrefout
DTC1
Delay Circuit
CHIP ENABLE
CH1
CH
Rev. 1.10 - 3 -
s
SELECTION GUIDE
The mask option for the ICs can be selected at the user's request. The selection can be made with designating the
part number as shown below;
R1280D002X-TR
Part Number
a b
Code
Contents
a
Designation of Mask Option :
A version: fosc=700kHz, with External Phase Compensation for Channel 1.
B version: fosc=700kHz, with Internal Phase Compensation and standby mode.
C version: fosc=200kHz, with External Phase Compensation for Channel 1
b
Designation of Taping Type :
(Refer to Taping Specifications.)
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PIN CONFIGURATION
q
SON10
10 6
1 5
(mark side)
s
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s
PIN DESCRIPTION
q
R1280D002A/C
Pin No.
Symbol
Description
1
EXT1
External Transistor of Channel 1 Drive Pin (CMOS Output)
2
GND
Ground Pin
3
AMPOUT1
Amplifier Output Pin of Channel 1
4
DTC1
Maximum Duty Cycle of Channel 1 Setting Pin
5
V
FB1
Feedback pin of Channel 1
6
V
FB2
Feedback pin of Channel 2
7
DTC2
Maximum Duty Cycle of Channel 2 Setting Pin
8
Vrefout
Reference Output Pin
9
V
IN
Voltage Supply Pin of the IC
10
EXT2
External Transistor of Channel 2 Drive Pin (CMOS Output)
Rev.1.10 - 4 -
q
R1280D002B
Pin No.
Symbol
Description
1
EXT1
External Transistor of Channel 1 Drive Pin (CMOS Output)
2
GND
Ground Pin
3
CE
Chip Enable Pin
4
DTC1
Maximum Duty Cycle of Channel 1 Setting Pin
5
V
FB1
Feedback pin of Channel 1
6
V
FB2
Feedback pin of Channel 2
7
DTC2
Maximum Duty Cycle of Channel 2 Setting Pin
8
Vrefout
Reference Output Pin
9
V
IN
Voltage Supply Pin of the IC
10
EXT2
External Transistor of Channel 2 Drive Pin (CMOS Output)
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ABSOLUTE MAXIMUM RATINGS
q
R1280D002A/C
Symbol
Item
Rating
Unit
V
IN
V
IN
Pin Voltage
6.5
V
V
EXT1,2
V
EXT1,2
Pin Output Voltage
-0.3
V
IN
+0.3
V
V
AMPOUT1
AMPOUT1 Pin Voltage
-0.3
V
IN
+0.3
V
V
DTC1,2
DTC1,2 Pin Voltage
-0.3
V
IN
+0.3
V
V
refout
V
REFOUT
Pin Voltage
-0.3
V
IN
+0.3
V
V
FB1,2
V
FB1
,V
FB2
Pin Voltage
-0.3
V
IN
+0.3
V
I
EXT1,2
EXT1,2 Pin Output Current
50
mA
P
D
Power Dissipation
250
mW
Topt
Operating Temperature Range
-40 to +85
C
Tstg
Storage Temperature Range
-55 to +125
C
q
R1280D002B
Symbol
Item
Rating
Unit
V
IN
V
IN
Pin Voltage
6.5
V
V
EXT1,2
V
EXT1,2
Pin Output Voltage
-0.3
V
IN
+0.3
V
V
CE
CE Pin Voltage
-0.3
V
IN
+0.3
V
V
DTC1,2
DTC1,2 Pin Voltage
-0.3
V
IN
+0.3
V
V
refout
V
REFOUT
Pin Voltage
-0.3
V
IN
+0.3
V
V
FB1,2
V
FB1
,V
FB2
Pin Voltage
-0.3
V
IN
+0.3
V
I
EXT1,2
EXT1,2 Pin Output Current
50
mA
P
D
Power Dissipation
250
mW
Topt
Operating Temperature Range
-40 to +85
C
Tstg
Storage Temperature Range
-55 to +125
C
Rev. 1.10 - 5 -
s
ELECTRICAL CHARACTERISTICS
q
R1280D002A
(Topt=25
C)
Symbol
Item
Conditions
MIN.
TYP.
MAX.
Unit
V
IN
Operating Input Voltage
2.5
5.5
V
V
REFOUT
V
REFOUT
Voltage Tolerance
V
IN
=3.3V, I
OUT
=1mA
1.478
1.500
1.522
V
I
ROUT
V
REFOUT
Output Current
V
IN
=3.3V
20
mA
VREFOUT
/
V
IN
V
REFOUT
Line Regulation
2.5V
V
IN
5.5V
2
6
mV
VREFOUT
/
I
OUT
V
REFOUT
Load Regulation
1mA
I
ROUT
10mA
V
IN
=3.3V
6
12
mV
I
LIM
V
REFOUT
Short Current Limit V
IN
=3.3V, V
REFOUT
=0V
25
mA
VREFOUT
/
T
V
REFOUT
Voltage
Temperature Coefficient
-40
C
Topt
85
C
150
ppm/
C
V
FB1
V
FB1
Voltage
V
IN
=3.3V
0.985
1.000
1.015
V
VFB1
/
T V
FB1
Voltage
Temperature Coefficient
-40
C
Topt
85
C
150
ppm/
C
I
FB1,2
I
FB1,2
Input Current
V
IN
=5.5V,V
FB1
or V
FB2
=0V or 5.5V
-0.1
0.1
A
f
OSC
Oscillator Frequency
EXT1,2 Pins at no load, V
IN
=3.3V
595
700
805
kHz
I
DD1
Supply Current
V
IN
=5.5V, EXT1,2 pins at no load
1.4
3.0
mA
R
EXTH1
EXT1 "H" ON Resistance
V
IN
=3.3V, I
EXT
=-20mA
4.0
8.0
R
EXTL1
EXT1 "L" ON Resistance
V
IN
=3.3V, I
EXT
=20mA
2.7
5.0
R
EXTH2
EXT2 "H" ON Resistance
V
IN
=3.3V, I
EXT
=-20mA
4.0
8.0
R
EXTL2
EXT2 "L" ON Resistance
V
IN
=3.3V, I
EXT
=20mA
3.7
8.0
T
DLY
Delay Time for Protection
V
IN
=3.3V, V
FB1
=1.1V
0V
60
100
140
ms
V
UVLOD
UVLO Detector Threshold
2.10
2.20
2.35
V
V
UVLO
UVLO Released Voltage
V
UVLOD
+0.10
2.45
V
V
DTC10
CH1 Duty=0%
V
IN
=3.3V
0.1
0.2
0.3
V
V
DTC1100
CH1 Duty=100%
V
IN
=3.3V
1.1
1.2
1.3
V
V
DTC20
CH2 Duty=0%
V
IN
=3.3V
0.1
0.2
0.3
V
V
DTC2100
CH2 Duty=100%
V
IN
=3.3V
1.1
1.2
1.3
V
A
V1
CH1 Open Loop Gain
V
IN
=3.3V
110
dB
F
T1
CH1 Single Gai n Frequency
Band
V
IN
=3.3V, A
V1
=0dB
1.9
MHz
V
ICR1
CH1 Input Voltage Range
V
IN
=3.3V
0.7 to
V
IN
V
I
AMPL
CH1 Sink Current
V
IN
=3.3V, V
AMPOUT1
=1.0V,
V
FB1
=V
FB1
+ 0.1V
70
115
A
I
AMPH
CH1 Source Current
V
IN
=3.3V, V
AMPOUT1
=1.0V,
V
FB1
=V
FB1-
0.1V
-1.4
-0.7
mA
A
V2
CH2 Open Loop Gain
V
IN
=3.3V
60
dB
F
T1
CH2 Single Gain Frequency
Band
V
IN
=3.3V, A
V2
=0dB
3
MHz
V
ICR1
CH2 Input Voltage Range
V
IN
=3.3V,
-0.2 to
V
IN
-1.3
V
V
FB2
CH2 Input Offset Voltage
V
IN
=3.3V,
-12
12
mV
Rev.1.10 - 6 -
q
R1280D002B
(Topt=25
C)
Symbol
Item
Conditions
MIN.
TYP.
MAX.
Unit
V
IN
Operating Input Voltage
2.5
5.5
V
V
REFOUT
V
REFOUT
Voltage Tolerance
V
IN
=3.3V, I
OUT
=1mA
1.478
1.500
1.522
V
I
ROUT
V
REFOUT
Output Current
V
IN
=3.3V
20
mA
VREFOUT
/
V
IN
V
REFOUT
Line Regulation
2.5V
V
IN
5.5V
2
6
mV
VREFOUT
/
I
OUT
V
REFOUT
Load Regulation
1mA
I
ROUT
10mA
V
IN
=3.3V
6
12
mV
I
LIM
V
REFOUT
Short Current Limit V
IN
=3.3V, V
REFOUT
=0V
25
mA
VREFOUT
/
T
V
REFOUT
Voltage
Temperature Coefficient
-40
C
Topt
85
C
150
ppm/
C
V
FB1
V
FB1
Voltage
V
IN
=3.3V
0.985
1.000
1.015
V
VFB1
/
T V
FB1
Voltage
Temperature Coefficient
-40
C
Topt
85
C
150
ppm/
C
I
FB1,2
I
FB1,2
Input Current
V
IN
=5.5V,V
FB1
or V
FB2
=0V or 5.5V
-0.1
0.1
A
f
OSC
Oscillator Frequency
EXT1,2 Pins at no load, V
IN
=3.3V
595
700
805
kHz
I
DD1
Supply Current
V
IN
=5.5V, EXT1,2 pins at no load
1.4
3.0
mA
Maxdty
Maximum Duty Cycle
V
IN
=3.3V, C
DTC1,2=
1000pF
84
90
95
%
R
EXTH1
EXT1 "H" ON Resistance
V
IN
=3.3V, I
EXT
=-20mA
4.0
8.0
R
EXTL1
EXT1 "L" ON Resistance
V
IN
=3.3V, I
EXT
=20mA
2.7
5.0
R
EXTH2
EXT2 "H" ON Resistance
V
IN
=3.3V, I
EXT
=-20mA
4.0
8.0
R
EXTL2
EXT2 "L" ON Resistance
V
IN
=3.3V, I
EXT
=20mA
3.7
8.0
T
DLY
Delay Time for Protection
V
IN
=3.3V, V
FB1
=1.1V
0V
60
100
140
ms
Tss1
Soft Start Time1 for Ch1
V
IN
=3.3V, C
DTC1
=0.33
F
10
ms
Tss2
Soft Start Time2 for Ch2
V
IN
=3.3V, C
DTC2
=0.33
F
15
ms
V
CEH
CE "H" Input Voltage
V
IN
=5.5V
1.5
V
V
CEL
CE "L" Input Voltage
V
IN
=2.5V
0.3
V
V
UVLOD
UVLO Detector Threshold
2.10
2.20
2.35
V
V
UVLO
UVLO Released Voltage
V
UVLOD
+0.10
2.45
V
I
CEH
CE "H" Input Current
V
IN
= V
CE
=5.5V
-0.1
0.1
A
I
CEL
CE "L" Input Current
V
IN
=5.5V, V
CE
=0.0V
-0.1
0.1
A
I
STB
Standby Current
V
IN
=5.5V, V
CE
=0.0V
0
2
A
V
OFF2
Input Offset Voltage of Ch2.
V
IN
=3.3V
-12
12
mV
Rev. 1.10 - 7 -
q
R1280D002C
(Topt=25
C)
Symbol
Item
Conditions
MIN.
TYP.
MAX.
Unit
V
IN
Operating Input Voltage
2.5
5.5
V
V
REFOUT
V
REFOUT
Voltage Tolerance
V
IN
=3.3V, I
OUT
=1mA
1.478
1.500
1.522
V
I
ROUT
V
REFOUT
Output Current
V
IN
=3.3V
20
mA
VREFOUT
/
V
IN
V
REFOUT
Line Regulation
2.5V
V
IN
5.5V
2
6
mV
VREFOUT
/
I
OUT
V
REFOUT
Load Regulation
1mA
I
ROUT
10mA
V
IN
=3.3V
6
12
mV
I
LIM
V
REFOUT
Short Current Limit V
IN
=3.3V, V
REFOUT
=0V
25
mA
VREFOUT
/
T
V
REFOUT
Voltage
Temperature Coefficient
-40
C
Topt
85
C
150
ppm/
C
V
FB1
V
FB1
Voltage
V
IN
=3.3V
0.985
1.000
1.015
V
VFB1
/
T V
FB1
Voltage
Temperature Coefficient
-40
C
Topt
85
C
150
ppm/
C
I
FB1,2
I
FB1,2
Input Current
V
IN
=5.5V,V
FB1
or V
FB2
=0V or 5.5V
-0.1
0.1
A
f
OSC
Oscillator Frequency
EXT1,2 Pins at no load, V
IN
=3.3V
160
200
240
kHz
I
DD1
Supply Current
V
IN
=5.5V, EXT1,2 pins at no load
0.7
1.2
mA
R
EXTH1
EXT1 "H" ON Resistance
V
IN
=3.3V, I
EXT
=-20mA
4.0
8.0
R
EXTL1
EXT1 "L" ON Resistance
V
IN
=3.3V, I
EXT
=20mA
2.7
5.0
R
EXTH2
EXT2 "H" ON Resistance
V
IN
=3.3V, I
EXT
=-20mA
4.0
8.0
R
EXTL2
EXT2 "L" ON Resistance
V
IN
=3.3V, I
EXT
=20mA
3.7
8.0
T
DLY
Delay Time for Protection
V
IN
=3.3V, V
FB1
=1.1V
0V
50
100
150
ms
V
UVLOD
UVLO Detector Threshold
2.10
2.20
2.35
V
V
UVLO
UVLO Released Voltage
V
UVLOD
+0.10
2.45
V
V
DTC10
CH1 Duty=0%
V
IN
=3.3V
0.15
0.25
0.35
V
V
DTC1100
CH1 Duty=100%
V
IN
=3.3V
1.1
1.2
1.3
V
V
DTC20
CH2 Duty=0%
V
IN
=3.3V
0.15
0.25
0.35
V
V
DTC2100
CH2 Duty=100%
V
IN
=3.3V
1.1
1.2
1.3
V
A
V1
CH1 Open Loop Gain
V
IN
=3.3V
110
dB
F
T1
CH1 Single Gain Frequency
Band
V
IN
=3.3V, A
V1
=0dB
1.9
MHz
V
ICR1
CH1 Input Voltage Range
V
IN
=3.3V
0.7 to
V
IN
V
I
AMPL
CH1 Sink Current
V
IN
=3.3V, V
AMPOUT1
=1.0V,
V
FB1
=V
FB1
+ 0.1V
70
115
A
I
AMPH
CH1 Source Current
V
IN
=3.3V, V
AMPOUT1
=1.0V,
V
FB1
=V
FB1-
0.1V
-1.4
-0.7
mA
A
V2
CH2 Open Loop Gain
V
IN
=3.3V
60
dB
F
T1
CH2 Single Gain Frequency
Band
V
IN
=3.3V, A
V2
=0dB
3
MHz
V
ICR1
CH2 Input Voltage Range
V
IN
=3.3V,
-0.2 to
V
IN-1.3
V
V
FB2
CH2 Input Offset Voltage
V
IN
=3.3V,
-12
12
mV
Rev.1.10 - 8 -
s
Operation of Step-up DC/DC Converter and Output Current
Step-up DC/DC Converter makes higher output voltage than input voltage by releasing the energy accumulated
during on time of Lx Transistor on input voltage.
<Basic Circuit>
Inductor
Diode
C
L
Lx Tr
V
IN
V
OUT
I
OUT
ILxmax
ILxmin
Ton
Toff
T=1/fosc
Tf
IL
Discontinuous Mode
t
ILxmax
ILxmin
Ton
Toff
T=1/fosc
t
IL
Iconst
Continuous Mode
<Current through L>
GND
i1
i2
Step 1. Lx Tr. is on, then the current IL=i1 flows, and the energy is charged in L. In proportion to the on time of Lx Tr.
(Ton), IL=i1 increases from IL=ILxmin=0 and reaches ILxmax.
Step 2. When the Lx Tr. is off, L turns on Schottky Diode (SD), and IL=i2 flows to maintain IL=ILxmax.
Step 3. IL=i2 gradually decreases, and after Tf passes, IL=ILxmin=0 is true, then SD turns off. Note that in the case of
the continuous mode, before IL=ILxmin=0 is true, Toff passes, and the next cycle starts, then Lx Tr. turns on again.
In this case, ILxmin>0, therefore IL=ILxmin>0 is another starting point and ILx max increases.
With the PWM controller, switching times during the time unit are fixed. By controlling Ton, output voltage is
maintained.
s
Output Current and Selection of External Components
Output Current of Step-up Circuit and External Components
There are two modes, or discontinuous mode and continuous mode for the PWM step-up switching regulator
depending on the continuous characteristic of inductor current.
During on time of the transistor, when the voltage added on to the inductor is described as V
IN
, the current is V
IN
t/L.
Therefore, the electric power, P
ON
, which is supplied with input side, can be described as in next formula.
T
ON
P
ON
=
V
IN
2
t/L dt
Formula 1
0
With the step-up circuit, electric power is supplied from power source also during off time. In this case, input current is
described as (V
OUT
-V
IN
)
t/L, therefore electric power, P
OFF
is described as in next formula.
Rev. 1.10 - 9 -
Tf
P
OFF
=
V
IN
(V
OUT
-V
IN
)
t/L dt
Formula 2
0
In this formula, Tf means the time of which the energy saved in the inductance is being emitted. Thus average
electric power, P
AV
is described as in the next formula.
T
ON
Tf
P
AV
=1/(Ton+Toff)
{
V
IN
2
t/L dt +
V
IN
(V
OUT
-V
IN
)
t/L dt} Formula 3
0 0
In PWM control, when Tf=Toff is true, the inductor current becomes continuos, then the operation of switching
regulator becomes continuous mode.
In the continuous mode, the deviation of the current is equal between on time and off time.
V
IN
Ton/L=(V
OUT
-V
IN
)
Toff/L
Formula 4
Further, the electric power, P
AV
is equal to output electric power, V
OUT
I
OUT
, thus,
I
OUT
= f
OSC
V
IN
2
T
ON
2
/{2
L
(V
OUT
-V
IN
)}=V
IN
2
T
ON
/(2
L
V
OUT
)
Formula 5
When I
OUT
becomes more than formula 5, the current flows through the inductor, then the mode becomes
continuous. The continuous current through the inductor is described as Iconst, then,
I
OUT
= f
OSC
V
IN
2
t
ON
2
/(2
L
(V
OUT
-V
IN
))+V
IN
Iconst/V
OUT
Formula 6
In this moment, the peak current, ILxmax flowing through the inductor and the driver Tr. is described as follows:
ILxmax = Iconst +V
IN
Ton/L
Formula 7
With the formula 4,6, and ILxmax is,
ILxmax = V
OUT
/V
IN
I
OUT
+V
IN
Ton/(2
L)
Formula 8
Therefore, peak current is more than I
OUT
. Considering the value of ILxmax, the condition of input and output, and
external components should be selected.
In the formula 7, peak current ILxmax at discontinuous mode can be calculated. Put Iconst=0 in the formula.
The explanation above is based on the ideal calculation, and the loss caused by Lx switch and external components
is not included. The actual maximum output current is between 50% and 80% of the calculation. Especially, when the
ILx is large, or V
IN
is low, the loss of V
IN
is generated with the on resistance of the switch. As for V
OUT,
Vf (as much as
0.3V) of the diode should be considered.
s
Operation of Inverting DC/DC converter and Output Current
Inverting DC/DC converter saves energy during on time of Lx transistor, and supplies the energy to output during off
time, output voltage opposed to input voltage is obtained.
Lx Tr
Inductor
Diode
CL
V
IN
V
OUT
I
OUT
GND
i1
i2
Rev.1.10 - 10 -
ILxmax
ILxmin
Ton
Toff
T=1/fosc
Tf
IL
Discontinuous Mode
t
ILxmax
ILxmin
Ton
Toff
T=1/fosc
t
IL
Iconst
Continuous Mode
<Current through L>
Step 1. Lx Tr. turns on, current, IL=i1 flows, energy is charged in L. In proportion to the on time, Ton, of Lx Tr. IL=i1
increases from IL=ILxmin=0 and reaches ILxmax.
Step 2. When the Lx Tr. turns off, L turns on Shottky diode (SD) and flow IL=i2 to maintain IL = ILxmax.
Step 3. IL=i2 decreases gradually, after Tf passes, IL=ILxmin=0 is true, then SD turns off. Note that in the case of
continuous mode, before IL=ILxmin=0 is true, Toff passes and next cycle starts, then Lx Tr. turns on. In this case,
ILxmin>0, therefore IL increases from IL=ILxmin>0.
With the PWM controller, switching time (fosc) in the time unit is fixed, and by controlling Ton, output voltage is
maintained.
s
Output Current and Selection of External Components
There are also two modes, or discontinuous mode and continuous mode for the PWM inverting switching regulator
depending on the continuous characteristic of inductor current.
During on time of the transistor, when the voltage added on to the inductor is described as V
IN
, the current is V
IN
t/L.
Therefore, the electric power, P, which is supplied with input side, can be described as in next formula.
T
ON
P=
V
IN
2
t/L dt
Formula 9
0
Thus average electric power in one cycle, P
AV
is described as in the next formula.
T
ON
P
AV
=1/(Ton +Toff)
V
IN
2
t/L dt =V
IN
2
Ton
2
/(2
L
(Ton + Toff))
Formula 10
0
This electric power P
AV
equals to output electric power V
OUT
I
OUT,
thus,
I
OUT
= f
OSC
V
IN
2
T
ON
2
/(2
L
V
OUT
)
Formula 11
When I
OUT
becomes more than formula 11, the current flows through the inductor continuously, then the mode
becomes continuous. In the continuous mode, the deviation of the current equals between Ton and Toff, therefore,
V
IN
Ton/L=V
OUT
Toff/L
Formula 12
In this moment, the current flowing continuously through L, is assumed as Iconst, I
OUT
is described as in the next
formula:
I
OUT
= f
OSC
V
IN
2
T
ON
2
/(2
L
V
OUT
)+Ton/(Ton + Toff)
V
IN
Iconst /V
OUT
Formula 13
In this moment, the peak current, ILxmax flowing through the inductor and the driver Tr. is described as follows:
ILxmax = Iconst +V
IN
Ton/L
Formula 14
With the formula 12,13, ILxmax is,
ILxmax = (Ton+Toff)/Toff
I
OUT
+V
IN
Ton/(2
L)
Formula 15
Therefore, peak current is more than I
OUT
. Considering the value of ILxmax, the condition of input and output, and
external components should be selected.
In the formula 14, peak current ILxmax at discontinuous mode can be calculated. Put Iconst=0 in the formula.
The explanation above is based on the ideal calculation, and the loss caused by Lx switch and external components
is not included. The actual maximum output current is between 50% and 80% of the calculation. Especially, when the
ILx is large, or V
IN
is low, the loss of V
IN
is generated with the on resistance of the switch. As for V
OUT,
Vf (as much as
0.3V) of the diode should be considered.
Rev. 1.10 - 11 -
s
TEST CIRCUITS
q
Test Circuit 1
q
Test Circuit 2
C1
C2
EXT1 EXT2
GND
V
IN
AMPOUT
Vrefout
DTC1 DTC2
V
FB1
V
FB2
OSCILLOSCOPE
C1
C2
EXT1 EXT2
GND
V
IN
AMPOUT
Vrefout
DTC1 DTC2
V
FB1
V
FB2
OSCILLOSC OPE
q
Test Circuit 3
q
Test Circuit 4
C1
C2
EXT1 EXT2
GND
V
IN
AMPOUT
Vrefout
DTC1 DTC2
V
FB1
V
FB2
OSCILLOSCOPE
C1
C2
EXT1 EXT2
GND V
IN
AMPOUT
Vrefout
DTC1 DTC2
V
FB1
V
FB2
OSCILLOSCOPE
q
Test Circuit 5
q
Test Circuit 6
EXT1 EXT2
GND V
IN
AMPOUT
Vrefout
DTC1 DTC2
V
FB1
V
FB2
V
C1
C2
EXT1 EXT2
GND V
IN
AMPOUT
Vrefout
DTC1 DTC2
V
FB1
V
FB2
A
V
C1
C2
q
Test Circuit 7
q
Test Circuit 8
C1
C2
EXT1 EXT2
GND
V
IN
AMPOUT
Vrefout
DTC1 DTC2
V
FB1
V
FB2
OSCILLOSCOPE
C1
EXT1 EXT2
GND
V
IN
AMPOUT
Vrefout
DTC1 DTC2
V
FB1
V
FB2
OSCILLOSC OPE
Rev.1.10 - 12 -
q
Test Circuit 9
q
Test Circuit 10
A
C1
C2
EXT1 EXT2
GND V
IN
AMPOUT
Vrefout
DTC1 DTC2
V
FB1
V
FB2
C1
C2
EXT1 EXT2
GND V
IN
CE Vrefout
DTC1 DTC2
V
FB1
V
FB2
OSCILLOSCOPE
C3
q
Test Circuit 11
q
Test Circuit 12
C1
C2
EXT1 EXT2
GND V
IN
CE Vrefout
DTC1 DTC2
V
FB1
V
FB2
OSCILLOSCOPE
C4
C1
C2
EXT1 EXT2
GND V
IN
CE Vrefout
DTC1 DTC2
V
FB1
V
FB2
OSCILLOSCOPE
q
Test Circuit 13
q
Test Circuit 14
C1
C2
EXT1
EXT2
GND V
IN
CE
Vrefout
DTC1 DTC2
V
FB1
V
FB2
OSCILLOSCOPE
EXT1 EXT2
GND V
IN
CE Vrefout
DTC1 DTC2
V
FB1
V
FB2
V
C1
C2
q
Test Circuit 15
q
Test Circuit 16
EXT1 EXT2
GND V
IN
CE Vrefout
DTC1 DTC2
V
FB1
V
FB2
A
V
C1
C2
C1
C2
EXT1 EXT2
GND
V
IN
CE Vrefout
DTC1 DTC2
V
FB1
V
FB2
OSCILLOSCOPE
Rev. 1.10 - 13 -
q
Test Circuit 17
q
Test Circuit 18
C1
C2
EXT1 EXT2
GND
V
IN
CE Vrefout
DTC1 DTC2
V
FB1
V
FB2
OSCILLOSCOPE
OSCILLOSCOPE
EXT1 EXT2
GND
V
IN
CE Vrefout
DTC1 DTC2
V
FB1
V
FB2
C1
C4
C3
C2
OSCILLOSCOPE
Typical Characteristics shown in the following pages are obtained with test circuits shown above.
q
R1280D002A/C
Test Circuit 1,2: Typical Characteristic 4)
Test Circuit 3: Typical Characteristic 6)
Test Circuit 4: Typical Characteristic 7)
Test Circuit 5: Typical Characteristic 8)
Test Circuit 6: Typical Characteristics 9) 10)
Test Circuit 7: Typical Characteristic 11)
Test Circuit 8: Typical Characteristic 12)
Test Circuit 9: Typical Characteristics 13) 14)
q
R1280D002B
Test Circuit 10,11: Typical Characteristics 4) 5)
Test Circuit 12: Typical Characteristic 6)
Test Circuit 13: Typical Characteristic 7)
Test Circuit 14: Typical Characteristic 8)
Test Circuit 15: Typical Characteristics 9) 10)
Test Circuit 16: Typical Characteristic 11)
Test Circuit 17: Typical Characteristics 15) 16)
Test Circuit 18: Typical Characteristics 17) 18)
Standard Circuit Example: Typical Characteristics 1) 2) 3) 19) 20)
Note) Capacitors' values of test circuits
Capacitors: Ceramic Type:
C1=4.7
F, C2=1.0
F, C3=C4=1000pF
Efficiency
(%) can be calculated with the next formula:
=(V
OUT1
I
OUT1
+V
OUT2
I
OUT2
)/(V
IN
I
IN
)
100
Rev.1.10 - 14 -
s
TYPICAL CHARACTERISTICS
1) Output Voltage vs. Output Current
Topt=25
C
L1=6.8uH,C1=10uF, V
OUT2
=-10V,I
OUT2
=0mA
L2=6.8uH,C2=10uF, V
OUT1
=10V,I
OUT1
=0mA
R1280D002A
9.90
9.95
10.00
10.05
10.10
0
50
100
150
200
Output Current I
OUT1
(mA)
Output Voltage V
OUT1
(V)
VIN=2.5V
VIN=3.3V
VIN=5.5V
R1280D002A
-10.10
-10.05
-10.00
-9.95
-9.90
-200
-150
-100
-50
0
Output Current I
OUT2
(mA)
Output Voltage V
OUT2
(V)
VIN=2.5V
VIN=3.3V
VIN=5.5V
L1=6.8uH,C1=10uF, V
OUT2
=-10V,I
OUT2
=0mA
L2=6.8uH,C2=10uF, V
OUT1
=10V,I
OUT1
=0mA
R1280D002B
9.90
9.95
10.00
10.05
10.10
0
50
100
150
200
Output Current I
OUT1
(mA)
Output Voltage V
OUT1
(V)
VIN=2.5V
VIN=3.3V
VIN=5.5V
R1280D002B
-10.10
-10.05
-10.00
-9.95
-9.90
-200
-150
-100
-50
0
Output Current I
OUT2
(mA)
Output Voltage V
OUT2
(V)
VIN=2.5V
VIN=3.3V
VIN=5.5V
L1=22uH,C1=10uF, V
OUT2
=-10V,I
OUT2
=0mA
L2=22uH,C2=10uF, V
OUT1
=10V,I
OUT1
=0mA
R1280D002C
9.90
9.95
10.00
10.05
10.10
0
50
100
150
200
Output Current I
OUT1
(mA)
Output Voltage V
OUT1
(V)
VIN=2.5V
VIN=3.3V
VIN=5.5V
R1280D002C
-10.10
-10.05
-10.00
-9.95
-9.90
-150
-100
-50
0
Output Current I
OUT2
(mA)
Output Voltage V
OUT2
(V)
VIN=2.5V
VIN=3.3V
VIN=5.5V
Rev. 1.10 - 15 -
2) Efficiency vs. Output Current
VIN=3.3V, Topt=25
C
L1=6.8uH,C1=10uF, V
OUT2
=-VOUT1,I
OUT2
=0mA
L2=6.8uH,C2=10uF, V
OUT1
=-VOUT2,I
OUT1
=0mA
R1280D002A
0
10
20
30
40
50
60
70
80
90
0
50
100
150
200
Output Current I
OUT1
(mA)
Efficiency (%)
Vout1=5V
Vout1=10V
Vout1=15V
R1280D002A
0
10
20
30
40
50
60
70
80
90
-200
-150
-100
-50
0
Output Current I
OUT2
(mA)
Efficiency (%)
Vout2=-5V
Vout2=-10V
Vout2=-15V
L1=6.8uH,C1=10uF, V
OUT2
=-VOUT1,I
OUT2
=0mA
L2=6.8uH,C2=10uF, V
OUT1
=-VOUT2,I
OUT1
=0mA
R1280D002B
0
10
20
30
40
50
60
70
80
90
0
50
100
150
200
Output Current I
OUT1
(mA)
Efficiency (%)
Vout1=5V
Vout1=10V
Vout1=15V
R1280D002B
0
10
20
30
40
50
60
70
80
90
-200
-150
-100
-50
0
Output Current I
OUT2
(mA)
Efficiency (%)
Vout2=-5V
Vout2=-10V
Vout2=-15V
L1=22uH,C1=10uF, V
OUT2
=-VOUT1,I
OUT2
=0mA
L2=22uH,C2=10uF, V
OUT1
=-VOUT2,I
OUT1
=0mA
R1280D002C
0
10
20
30
40
50
60
70
80
90
0
50
100
150
200
Output Current I
OUT1
(mA)
Efficiency (%)
Vout1=5V
Vout1=10V
Vout1=15V
R1280D002C
0
10
20
30
40
50
60
70
80
90
-150
-125
-100
-75
-50
-25
0
Output Current I
OUT2
(mA)
Efficiency (%)
Vout2=-5V
Vout2=-10V
Vout2=-15V
Rev.1.10 - 16 -
3) Output Voltage vs. Temperature
VIN=3.3V
L1=6.8uH,C1=10uF
L2=6.8uH,C2=10uF
R1280D002A
9.0
9.5
10.0
10.5
11.0
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Output Voltage V
OUT1
(V)
IOUT=10mA
IOUT=100mA
R1280D002A
-11.0
-10.5
-10.0
-9.5
-9.0
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Output Voltage V
OUT2
(V)
IOUT=-10mA
L1=6.8uH,C1=10uF
L2=6.8uH,C2=10uF
R1280D002B
9.0
9.5
10.0
10.5
11.0
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Output Voltage V
OUT1
(V)
IOUT=10mA
IOUT=100mA
R1280D002B
-11.0
-10.5
-10.0
-9.5
-9.0
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Output Voltage V
OUT2
(V)
IOUT=-10mA
L1=22uH,C1=10uF
L2=22uH,C2=10uF
R1280D002C
9.0
9.5
10.0
10.5
11.0
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Output Voltage V
OUT1
(V)
IOUT=10mA
IOUT=100mA
R1280D002C
-11.0
-10.5
-10.0
-9.5
-9.0
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Output Voltage V
OUT2
(V)
IOUT=-10mA
(
C)
(
C)
(
C)
(
C)
(
C)
(
C)
Rev. 1.10 - 17 -
4) Frequency vs. Temperature
R1280D002A
550
600
650
700
750
800
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Frequency fosc (kHz)
VIN=2.5V
VIN=3.3V
VIN=5.5V
R1280D002B
550
600
650
700
750
800
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Frequency fosc (kHz)
VIN=2.5V
VIN=3.3V
VIN=5.5V
R1280D002C
150
170
190
210
230
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Frequency fosc (kHz)
VIN=2.5V
VIN=3.3V
VIN=5.5V
5) Maximum Duty Cycle vs. Temperature
VIN=3.3V
R1280D002B
86
88
90
92
94
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Maximum Duty Cycle
maxduty1(%)
R1280D002B
86
88
90
92
94
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Maximum Duty Cycle maxduty2
(%)
(
C)
(
C)
(
C)
(
C)
(
C)
Rev.1.10 - 18 -
6) Feedback Voltage vs. Temperature
7) Input Offset Voltage vs. Temperature
VIN=3.3V
R1280D002A/B/C
0.97
0.98
0.99
1.00
1.01
1.02
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Feedback Voltage V
FB1
(V)
R1280D002A/B/C
-10.0
-5.0
0.0
5.0
10.0
-60 -40 -20
0
20
40
60
80 100
Temperature Topt
Input Offset Voltage V
FB2
(mV)
8) Vrefout Output Voltage vs. Temperature
9) Vrefout Output Voltage vs. Output Current
VIN=3.3V
R1280D002A/B/C
1.45
1.47
1.49
1.51
1.53
1.55
-60 -40 -20
0
20
40
60
80 100
Temperature Topt
Vrefout Voltage
(V)
R1280D002A/B/C
0
0.3
0.6
0.9
1.2
1.5
1.8
0
10
20
30
40
50
60
I
ROUT
(mA)
Vrefout Voltage(V)
10) Vrefout Output Voltage vs. Output Current
11) Protection Circuit Delay Time vs. Temperature
VIN=3.3V
R1280D002A/B/C
1.498
1.500
1.502
1.504
1.506
1.508
0
5
10
15
20
I
ROUT
(mA)
Vrefout Voltage(V)
R1280D002A/B/C
60
80
100
120
140
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Protection Circuit Delay Time
TDLY (ms)
(
C)
(
C)
(
C)
(
C)
Rev. 1.10 - 19 -
12) Duty Cycle vs. DTC Voltage
VIN=3.3V, EXT=1000pF
VIN=3.3V, EXT=1000pF
R1280D002A
0
20
40
60
80
100
0
0.2
0.4
0.6
0.8
1
1.2
1.4
V
DTC
(V)
Duty Cycle Duty(%)
R1280D002C
0
20
40
60
80
100
0
0.2
0.4
0.6
0.8
1
1.2
1.4
V
DTC
(V)
Duty Cycle Duty(%)
13) Output Sink Current vs. Temperature
14) Output Source Current vs. Temperature
VIN=3.3V
VIN=3.3V
R1280D002A/C
90
100
110
120
130
-60 -40 -20
0
20
40
60
80 100
Temperature Topt
Output Sink Current
I
AMPL
(uA)
R1280D002A/C
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
-60
-40
-20
0
20
40
60
80
100
Temperature Topt
Output Sink Current I
AMPH
(mA)
15) CE "H" Input Voltage vs. Temperature
16) CE "L" Input Voltage vs. Temperature
VIN=5.5V
VIN=2.5V
R1280D002B
0.25
0.50
0.75
1.00
1.25
-50
0
50
100
Temperature Topt
CE"H" Input Voltage V
CEH
(V)
R1280D002B
0.25
0.5
0.75
1
1.25
-50
0
50
100
Temperature Topt
CE"L" Input Voltage V
CEL
(V)
(
C)
(
C)
(
C)
(
C)
Rev.1.10 - 20 -
17) Soft Starting Time vs. Capacitance value
VIN=3.3V
R1280D002B
0
10
20
30
40
0
0.2
0.4
0.6
0.8
1
1.2
Capacitance value for Soft Start(uF)
Soft Starting Time T
SS1
(ms)
R1280D002B
0
10
20
30
40
50
0
0.2
0.4
0.6
0.8
1
1.2
Capacitance value for Soft Start(uF)
Soft Starting Time T
SS2
(ms)
18) Soft Starting Time vs. Temperature
VIN=3.3V
CDTC1=0.33
F
CDTC2=0.33
F
R1280D002B
0
5
10
15
20
-50
0
50
100
Temperature Topt
Soft Starting Time T
SS1
(ms)
R1280D002B
0
5
10
15
20
25
30
-50
0
50
100
Temperature Topt
Soft Starting Time T
SS2
(ms)
19) Load Transient Response(Step-up Side)
VIN=3.3V
L1=6.8
H
L1=6.8
H
R1280D002A
7.5
8
8.5
9
9.5
10
10.5
0
0.0005
0.001
0.0015
0.002
Time (sec)
Output Voltage V
OUT1
(V)
Output Current I
OUT
(mA)
100
0.1
R1280D002A
8.5
9
9.5
10
10.5
11
11.5
0
0.01
0.02
0.03
0.04
0.05
Time (sec)
Output Voltage V
OUT1
(V)
Output Current I
OUT
(mA)
100
0.1
(
C)
(
C)
Rev. 1.10 - 21 -
L1=6.8
H
L1=6.8
H
R1280D002B
7.5
8
8.5
9
9.5
10
10.5
0
0.0005
0.001
0.0015
0.002
Time (sec)
Output Voltage V
OUT1
(V)
Output Current I
OUT
(mA)
100
0.1
R1280D002B
8.5
9
9.5
10
10.5
11
11.5
0
0.01
0.02
0.03
0.04
0.05
Time (sec)
Output Voltage V
OUT1
(V)
Output Current I
OUT
(mA)
100
0.1
L1=22
H
L1=22
H
R1280D002C
7.5
8
8.5
9
9.5
10
10.5
0
0.0005
0.001
0.0015
0.002
Time (s)
Output Voltage V
OUT1
(V)
Output Curren I
OUT
(mA)
100
0.1
R1280D002C
8.5
9
9.5
10
10.5
11
11.5
0
0.01
0.02
0.03
0.04
0.05
Time (sec)
Output Voltage V
OUT1
(V)
Output Current I
OUT
(mA)
100
0.1
20) Load Transient Response (Inverting Side)
VIN=3.3V
L2=6.8
H
L2=6.8
H
R1280D002A
-11.5
-11
-10.5
-10
-9.5
-9
0.000
0
0.000
1
0.000
2
0.000
3
0.000
4
0.000
5
0.000
6
Time (sec)
Output Voltage V
OUT2
(V)
Output Current I
OUT
(mA)
-50
-0.1
R1280D002A
-12
-11.5
-11
-10.5
-10
-9.5
0.000
0.005
0.010
0.015
0.020
Time (sec)
Output Voltage V
OUT2
(V)
Output Current I
OUT
(mA)
-50
-0.1
Rev.1.10 - 22 -
L2=6.8
H
L2=6.8
H
R1280D002B
-11.5
-11
-10.5
-10
-9.5
-9
0.000
0
0.000
1
0.000
2
0.000
3
0.000
4
0.000
5
0.000
6
Time (sec)
Output Voltage V
OUT2
(V)
Output Current I
OUT
(mA)
-50
-0.1
R1280D002B
-12
-11.5
-11
-10.5
-10
-9.5
0.000
0.005
0.010
0.015
0.020
Time (sec)
Output Voltage V
OUT2
(V)
Output Current I
OUT
(mA)
-50
-0.1
L2=22
H
L2=22
H
R1280D002C
-11.5
-11
-10.5
-10
-9.5
-9
0.0000 0.0001 0.0002 0.0003 0.0004 0.0005 0.0006
Time(s)
Output Voltage V
OUT2
(V)
Output Current I
OUT
(mA)
-50
-0.1
R1280D002C
-12
-11.5
-11
-10.5
-10
-9.5
0.000
0.005
0.010
0.015
0.020
Time(s)
Output Voltage V
OUT2
(V)
Output Current I
OUT
(mA)
-50
-0.1
Rev. 1.10 - 23 -
s
TYPICAL APPLICATION AND TECHNICAL NOTES
q
R1280D002A/C
C7
R6
L1
NMOS
EXT1EXT2
V
IN
GND
AMPOUT
1
V
refout
DTC1
DTC2
V
FB1
V
FB2
R1
R2
C1
PMOS
C8
R3
R4
C3
L2
C2
C9
C4
R11
R10
C6
VOUT1
VOUT2
R7
R8
R5
C5
R9
Diode
External Components
Inductor L1,2: 6.8
H, LDR655312T(TDK) for A type, 22
H for C type
Diode: FS1J3 (Origin Electronics)
NMOS: IR7601 (International Rectifier)
PMOS: Si3443 (Siliconix)
Resistors: R1, R2, R3, R4 for Setting Output Voltage. Recommendation values are R1+R2
100k
or R3+R4
100k
R5=43k
, R6=10k
, R7=R9=22k
, R8=R10=43k
, R11=220k
Capacitors: Ceramic Capacitor
(Example)
R1280D002A: C1=C2=10
F, C3=4.7
F, C4=0.22
F, C5=0.47
F, C6=120pF, C7=50pF, C8=1
F, C9=1000pF
R1280D002C: C1=C2=10
F, C3=4.7
F, C4=0.22
F, C5=0.47
F, C6=220pF, C7=330pF, C8=1
F, C9=1000pF
Note: Maximum voltage tolerance of each component should be considered. With the transistor shown above is
appropriate to set up to
15V as output voltage.
q
R1280D002B
L1
C7
R6
L1
NMOS
EXT1EXT2
V
IN
GND
CE
DTC1DTC2
V
FB1
V
FB2
R1
R2
C1
PMOS
C8
R3
R4
C3
L2
C4
C6
V
OUT1
C5
Diode
R5
Rev.1.10 - 24 -
External Components
Inductor L1,2: 6.8
H, LDR655312T(TDK)
Diode: FS1J3 (Origin Electronics)
NMOS: IR7601 (International Rectifier)
PMOS: Si3443 (Siliconix)
Resistors: R1, R2, R3, R4 for Setting Output Voltage. Recommendation values are R1+R2
100k
or R3+R4
100k
R5=43k
, R6=10k
Capacitors: Ceramic Capacitor
(Example)
C1=C2=10
F, C3=4.7
F, C4=0.33
F, C5=0.33
F, C6=120pF, C7=50pF, C8=1
F
Note: Maximum voltage tolerance of each component should be considered. With the transistor shown above is
appropriate to set up to
15V as output voltage.
s
APPLICATION EXAMPLE
q
R1280D002A/C
L1
NMOS
EXT1
EXT2
GND V
IN
AMPOUT1
Vrefout
DTC1
DTC2
V
FB1
V
FB2
R1
R2
C1
PMOS
C8
R3
R4
C3
L2
C2
C9
C4
R11
R10
C6
VOUT1
VOUT2
R7
R8
R5
C5
R9
Diode
VOUT3
C10
C11
C7
R6
External Components
Inductor L1,2: 6.8
H, LDR655312T(TDK) for A version, 22
H for R1280D002C
Diode: FS1J3 (Origin Electronics)
NMOS: IR7601 (International Rectifier)
PMOS: Si3443 (Siliconix)
Resistors: R1, R2, R3, R4 for Setting Output Voltage. Recommendation values are R1+R2
100k
or R3+R4
100k
R5=43k
, R6=10k
, R7=R9=22k
, R8=R10=43k
, R11=220k
Capacitors: Ceramic Capacitor
(Example)
R1280D002A: C1=C2=10
F, C3=4.7
F, C4=0.22
F, 5=0.47
F,C6=120pF,C7=50pF,C8=C10=C11=1
F,C9=1000pF
R1280D002C:C1=C2=10
F,C3=4.7
F, C4=0.22
F,C5=0.47
F,C6=220pF,C7=330pF,C8=C10=C11=1
F,C9=1000pF
This IC can be used 3 Output TFT Bias Circuit as shown above. V
OUT3
=2
V
OUT1
-Vf
Note: Maximum voltage tolerance of each component should be considered. With the transistor shown above is
appropriate to set up to +15V as V
OUT1
, -15V as V
OUT2,
30V as V
OUT3.
Rev. 1.10 - 25 -
q
R1280D002B
C7
R6
L1
NMOS
EXT1
EXT2
GND V
IN
CE
Vrefout
DTC1DTC2
V
FB1
V
FB2
R1
R2
C1
PMOS
C8
R3
R4
C3
L2
C4
C6
VOUT1
VOUT2
C5
Diode
R5
VOUT3
C10
C11
External Components
Inductor L1,2: 6.8
H, LDR655312T(TDK)
Diode: FS1J3 (Origin Electronics)
NMOS: IR7601 (International Rectifier)
PMOS: Si3443 (Siliconix)
Resistors: R1, R2, R3, R4 for Setting Output Voltage. Recommendation values are R1+R2
100k
or R3+R4
100k
R5=43k
, R6=10k
Capacitors: Ceramic Capacitor
(Example)
R1280D002B: C1=C2=10
F, C3=4.7
F, C4=0.33
F, 5=0.33
F, C6=120pF,C7=50pF,C8=C10=C11=1
F
This IC can be used 3 Output TFT Bias Circuit as shown above. V
OUT3
=2
V
OUT1
-Vf
Note: Maximum voltage tolerance of each component should be considered. With the transistor shown above is
appropriate to set up to +15V as V
OUT1
, -15V as V
OUT2,
30V as V
OUT3
s
EXTERNAL COMPONENTS
1. How to set the output voltages
As for step-up side, feedback (V
FB1
) pin voltage is controlled to maintain 1V, therefore,
V
OUT1
: R1+R2=V
FB1
: R2
Thus, V
OUT1
=V
FB1
(R1+R2)/R2
Output Voltage is adjustable with R1 and R2.
As for inverting side, Feedback (VFB2) pin voltage is controlled to maintain 0V, therefore,
Vrefout : R3=|-V
OUT2
|:R4
Thus, |-V
OUT2
|=Vrefout
R4/R3
Output Voltage is adjustable with R3 and R4.
2. How to set Soft Starting Time
As for R1280D002B, soft start time is adjustable with connecting a capacitor to DTC pin.
Soft starting time, T
SS1
and
T
SS2
are adjustable. Soft starting time can be set with the time constant of RC.
Soft starting time can be described as in next formula. (Topt=25
C)
T
SS1
RS1
C4, T
SS2
RS2
C5
In the above formulas, RS1 value is TYP. 32k
, while RS2 value is TYP. 45k
. Tolerance of these values is
25%
caused by dispersion of wafer process parameters.
On the other hand, as for R1280D002A/C, each soft start time is set with the time constant of each external resistor
Rev.1.10 - 26 -
and capacitor.
s
TECHNICAL NOTES on EXTERNAL COMPONENTS
q
External components should be set as close to this IC as possible. Especially, wiring of the capacitor connected
to V
IN
pin should be shortest.
q
Enforce the ground wire. Large current caused by switching operation flows through GND pin. If the impedance
of ground wire is high, internal voltage level of this IC might fluctuate and operation could be unstable.
q
Recommended capacitance value of C3 is equal or more than 4.7
F. Recommended maximum voltage
tolerance of C3 is three times as large as set output voltage or more, because the external transistor might
generate hi voltage with a shape of spike because of an effect from inductor.
q
If the spike noise of V
OUT
is too large, the noise is feedback from V
FB1
pin and operation might be unstable. In
that case, use the resistor ranging from 10k
to 50k
as R5 and try to reduce the noise level. In the case of
V
OUT2
, use the resistor as much as 10k
as R6.
q
Select an inductor with low D.C. current, large permissible current, and uneasy to cause magnetic saturation. If
the inductance value is too small, I
LX
might be beyond the absolute maximum rating at the maximum load.
q
Select a Schottky diode with fast switching speed and large enough permissible current.
q
Recommended capacitance value of C1 and C2 is as much as Ceramic 10
F. In case that the operation with the
system of DC/DC converter would be unstable, use tantalum capacitors with higher ESR than ceramic capacitor.
Use a capacitor with three times as large as voltage tolerance of the capacitor.
q
In this IC, for the test efficiency, Latch release function is included. By forcing (V
IN
-0.3) V or more voltage to
DTC1 pin or DTC2 pin, Latch release function works.
q
Consider the threshold voltage of Power MOSFET transistor. Select an appropriate MOSFET transistor,
depending on the input voltage in order to make the MOSFET turn on completely.
q
Performance of the power controller with using this IC depends on external components. Each component,
layout should not be beyond each absolute maximum rating such as voltage, current, and power dissipation.
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