Page 1
2001.6.16
2CH PWM DC/DC Controller
R1280D002X Series
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 0µA.
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.
FEATURES
■■■■
●
Input Voltage Range • • • • • • • • • • • • • 2.5V to 5.5V
● Built-in Latch-type Protection Function by monitoring duty cycle (Fixed Delay Time TYP. 100ms)
● Oscillator Frequency • • • • • • • • • • • • • 700kHz(R1280D002A,B)/200kHz(r1280D002C)
● Maximum Duty Cycle • • • • • • • • • • • • • TYP. 90%(Only applied to R1280D002B Series)
● High Reference Voltage Accuracy • • • • • • ±1.5%
● U.V.L.O. Threshold • • • • • • • • • • • TYP. 2.2V (Hysteresis: TYP. 0.1V)
● Small Package • • • • • • • • • • • • • • • • thin SON-10 (package thickness MAX. 0.9mm)
APPLICATIONS
■■■■
● Constant Voltage Power Source for portable equipment.
● Constant Voltage Power Source for LCD and CCD.
Rev. 1.10 - 1 -
Page 2
BLOCK DIAGRAM
A
■■■■
●
R1280D002A/C
V
FB1
DTC1
MPOUT1
Vrefout
●
R1280D002B
OSC
CH
１
Vref1
Vrefout
V
FB2
DTC2
CH
UVLO
Latch
Delay Circuit
２
EXT1
V
IN
GND
EXT2
DTC1
V
FB1
CE
Vrefout
V
FB2
CHIP ENABLE
Vrefout
OSC
CH1
Vref1
DTC2
CH
UVLO
２
Latch
Delay Circuit
EXT1
V
IN
GND
EXT2
Rev.1.10 - 2 -
Page 3
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
↑
a b
Code Contents
Designation of Mask Option :
a
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
↑
←
Part Number
b
PIN CONFIGURATION
■■■■
●
SON10
10 6
mark side
1 5
PIN DESCRIPTION
■■■■
Designation of Taping Type :
(Refer to Taping Specifications.)
●
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
5V
6V
7 DTC2 Maximum Duty Cycle of Channel 2 Setting Pin
8 Vrefout Reference Output Pin
9V
10 EXT2 External Transistor of Channel 2 Drive Pin (CMOS Output)
Rev. 1.10 - 3 -
FB1
FB2
IN
Feedback pin of Channel 1
Feedback pin of Channel 2
Voltage Supply Pin of the IC
Page 4
●
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
5V
6V
FB1
FB2
Feedback pin of Channel 1
Feedback pin of Channel 2
7 DTC2 Maximum Duty Cycle of Channel 2 Setting Pin
8 Vrefout Reference Output Pin
9V
IN
Voltage Supply Pin of the IC
10 EXT2 External Transistor of Channel 2 Drive Pin (CMOS Output)
ABSOLUTE MAXIMUM RATINGS
■■■■
●
R1280D002A/C
Symbol Item Rating Unit
V
IN
V
EXT1,2
V
AMPOUT1
V
DTC1,2
V
refout
V
FB1,2
I
EXT1,2
P
D
V
Pin Voltage 6.5 V
IN
V
Pin Output Voltage
EXT1,2
AMPOUT1 Pin Voltage
DTC1,2 Pin Voltage
V
REFOUT
V
FB1,VFB2
Pin Voltage
EXT1,2 Pin Output Current
Power Dissipation 250 mW
Topt Operating Temperature Range -40 to +85
Tstg Storage Temperature Range -55 to +125
Pin Voltage
-0.3∼V
-0.3∼V
-0.3∼V
-0.3∼V
-0.3∼V
±
50
IN
IN
IN
IN
IN
+0.3
+0.3
+0.3
+0.3
+0.3
V
V
V
V
V
mA
°
C
°
C
●
R1280D002B
Symbol Item Rating Unit
V
IN
V
EXT1,2
V
CE
V
DTC1,2
V
refout
V
FB1,2
I
EXT1,2
P
D
Topt Operating Temperature Range -40 to +85
Tstg Storage Temperature Range -55 to +125
V
Pin Voltage 6.5 V
IN
V
Pin Output Voltage
EXT1,2
CE Pin Voltage
DTC1,2 Pin Voltage
V
REFOUT
V
FB1,VFB2
Pin Voltage
Pin Voltage
EXT1,2 Pin Output Current
-0.3∼V
-0.3∼V
-0.3∼V
-0.3∼V
-0.3∼V
±
50
IN
IN
IN
IN
IN
+0.3
+0.3
+0.3
+0.3
+0.3
V
V
V
V
V
mA
Power Dissipation 250 mW
°
C
°
C
Rev.1.10 - 4 -
Page 5
ELECTRICAL CHARACTERISTICS
■
●
R1280D002A
(Topt=25°C)
Symbol Item Conditions MIN. TYP. MAX. Unit
V
V
REFOUT
I
ROUTVREFOUT
VREFOUT
∆
∆
/
VREFOUT
∆
∆
I
/
I
LIM
VREFOUT
∆
∆
/
V
VFB1
∆
Operating Input Voltage 2.5 5.5 V
IN
V
REFOUT
Voltage Tolerance
VIN=3.3V, I
=1mA 1.478 1.500 1.522 V
OUT
Output Current VIN=3.3V 20 mA
V
REFOUT
V
IN
V
REFOUT
OUT
V
REFOUT
V
REFOUT
T
Temperature Coefficient
FB1VFB1
V
FB1
∆
T
/
Line Regulation
Load Regulation
Short Current Limit VIN=3.3V, V
Voltage
Voltage VIN=3.3V 0.985 1.000 1.015 V
Voltage
ROUT
=3.3V
≤ 5.5V
IN
≤ 10mA
REFOUT
2.5V≤ V
1mA≤ I
V
IN
-40°C≤ Topt ≤ 85°C
-40°C≤ Topt ≤ 85°C
=0V 25 mA
26 mV
612 mV
±
150 ppm/°C
±
150 ppm/°C
Temperature Coefficient
I
FB1,2IFB1,2
f
OSC
I
DD1
R
EXTH1
Input Current VIN=5.5V,V
FB1
or V
=0V or 5.5V -0.1 0.1
FB2
Oscillator Frequency EXT1,2 Pins at no load, VIN=3.3V 595 700 805 kHz
Supply Current VIN=5.5V, EXT1,2 pins at no load 1.4 3.0 mA
EXT1 “H” ON Resistance VIN=3.3V, I
=-20mA 4.0 8.0
EXT
µ
A
Ω
R
EXTL1
R
EXTH2
R
EXTL2
T
DLY
V
UVLOD
V
UVLO
V
DTC10
V
DTC1100
V
DTC20
V
DTC2100
A
F
V
ICR1
I
AMPL
I
AMPH
A
F
V
ICR1
V
FB2
EXT1 “L” ON Resistance VIN=3.3V, I
EXT2 “H” ON Resistance VIN=3.3V, I
EXT2 “L” ON Resistance VIN=3.3V, I
Delay Time for Protection
=3.3V, V
V
IN
=20mA 2.7 5.0
EXT
=-20mA 4.0 8.0
EXT
=20mA 3.7 8.0
EXT
=1.1V→0V
FB1
60 100 140 ms
UVLO Detector Threshold 2.10 2.20 2.35 V
UVLO Released Voltage V
UVLOD
2.45 V
+0.10
CH1 Duty=0% VIN=3.3V 0.1 0.2 0.3 V
CH1 Duty=100% VIN=3.3V 1.1 1.2 1.3
CH2 Duty=0% VIN=3.3V 0.1 0.2 0.3 V
CH2 Duty=100% VIN=3.3V 1.1 1.2 1.3 V
CH1 Open Loop Gain VIN=3.3V 110 dB
V1
CH1 Single Gai n Frequency
T1
VIN=3.3V, AV1=0dB 1.9 MHz
Band
CH1 Input Voltage Range VIN=3.3V 0.7 to
V
IN
CH1 Sink Current VIN=3.3V, V
V
FB1=VFB1
CH1 Source Current VIN=3.3V, V
V
FB1=VFB1-
CH2 Open Loop Gain VIN=3.3V 60 dB
V2
CH2 Single Gain Frequency
T1
VIN=3.3V, AV2=0dB 3 MHz
AMPOUT1
+ 0.1V
AMPOUT1
0.1V
=1.0V,
=1.0V,
70 115
-1.4 -0.7 mA
Band
CH2 Input Voltage Range VIN=3.3V, -0.2 to
-1.3
V
IN
CH2 Input Offset Voltage VIN=3.3V, -12 12 mV
Ω
Ω
Ω
V
V
µ
A
V
Rev. 1.10 - 5 -
Page 6
●
R1280D002B
(Topt=25°C)
Symbol Item Conditions MIN. TYP. MAX. Unit
V
V
REFOUT
I
ROUTVREFOUT
VREFOUT
∆
∆
/
VREFOUT
∆
∆
I
/
I
LIM
VREFOUT
∆
∆
/
V
VFB1
∆
Operating Input Voltage 2.5 5.5 V
IN
V
REFOUT
Voltage Tolerance
VIN=3.3V, I
=1mA 1.478 1.500 1.522 V
OUT
Output Current VIN=3.3V 20 mA
V
REFOUT
V
IN
V
REFOUT
OUT
V
REFOUT
V
REFOUT
T
Temperature Coefficient
V
FB1
FB1
V
FB1
∆
T
/
Line Regulation
Load Regulation
Short Current Limit VIN=3.3V, V
Voltage
Voltage VIN=3.3V 0.985 1.000 1.015 V
Voltage
ROUT
=3.3V
≤ 5.5V
IN
≤ 10mA
REFOUT
2.5V≤ V
1mA≤ I
V
IN
-40°C≤ Topt ≤ 85°C
-40°C≤ Topt ≤ 85°C
=0V 25 mA
26 mV
612 mV
±
150 ppm/°C
±
150 ppm/°C
Temperature Coefficient
I
FB1,2IFB1,2
f
OSC
I
DD1
Maxdty
R
EXTH1
Input Current VIN=5.5V,V
FB1
or V
=0V or 5.5V -0.1 0.1
FB2
Oscillator Frequency EXT1,2 Pins at no load, VIN=3.3V 595 700 805 kHz
Supply Current VIN=5.5V, EXT1,2 pins at no load 1.4 3.0 mA
Maximum Duty Cycle
EXT1 “H” ON Resistance VIN=3.3V, I
VIN=3.3V, C
DTC1,2=
EXT
1000pF 84 90 95 %
=-20mA 4.0 8.0
µ
A
Ω
R
EXTL1
R
EXTH2
R
EXTL2
T
EXT1 “L” ON Resistance VIN=3.3V, I
EXT2 “H” ON Resistance VIN=3.3V, I
EXT2 “L” ON Resistance VIN=3.3V, I
Delay Time for Protection
DLY
Tss1 Soft Start Time1 for Ch1
Tss2 Soft Start Time2 for Ch2
V
CEH
V
V
UVLOD
V
UVLO
I
CEH
I
CEL
I
STB
V
OFF2
CE “H” Input Voltage
CE “L” Input Voltage
CEL
UVLO Detector Threshold 2.10 2.20 2.35 V
UVLO Released Voltage V
CE “H” Input Current VIN= VCE =5.5V -0.1 0.1
CE “L” Input Current VIN=5.5V, VCE=0.0V -0.1 0.1
Standby Current VIN=5.5V, VCE=0.0V 0 2
Input Offset Voltage of Ch2. VIN=3.3V -12 12 mV
=20mA 2.7 5.0
EXT
=-20mA 4.0 8.0
EXT
=20mA 3.7 8.0
EXT
=3.3V, V
V
IN
=3.3V, C
V
IN
=3.3V, C
V
IN
=1.1V→0V
FB1
=0.33µF
DTC1
=0.33µF
DTC2
60 100 140 ms
10 ms
15 ms
VIN=5.5V 1.5 V
VIN=2.5V 0.3 V
UVLOD
2.45 V
+0.10
µ
µ
µ
Ω
Ω
Ω
A
A
A
Rev.1.10 - 6 -
Page 7
●
R1280D002C
(Topt=25°C)
Symbol Item Conditions MIN. TYP. MAX. Unit
V
V
REFOUT
I
ROUTVREFOUT
VREFOUT
∆
∆
/
VREFOUT
∆
∆
I
/
I
LIM
VREFOUT
∆
∆
/
V
VFB1
∆
Operating Input Voltage 2.5 5.5 V
IN
V
REFOUT
Voltage Tolerance
VIN=3.3V, I
=1mA 1.478 1.500 1.522 V
OUT
Output Current VIN=3.3V 20 mA
V
REFOUT
V
IN
V
REFOUT
OUT
V
REFOUT
V
REFOUT
T
Temperature Coefficient
V
FB1
FB1
V
FB1
∆
T
/
Line Regulation
Load Regulation
Short Current Limit VIN=3.3V, V
Voltage
Voltage VIN=3.3V 0.985 1.000 1.015 V
Voltage
ROUT
=3.3V
≤ 5.5V
IN
≤ 10mA
REFOUT
2.5V≤ V
1mA≤ I
V
IN
-40°C≤ Topt ≤ 85°C
-40°C≤ Topt ≤ 85°C
=0V 25 mA
26 mV
612 mV
±
150 ppm/°C
±
150 ppm/°C
Temperature Coefficient
I
FB1,2IFB1,2
f
OSC
I
DD1
R
EXTH1
Input Current VIN=5.5V,V
FB1
or V
=0V or 5.5V -0.1 0.1
FB2
Oscillator Frequency EXT1,2 Pins at no load, VIN=3.3V 160 200 240 kHz
Supply Current VIN=5.5V, EXT1,2 pins at no load 0.7 1.2 mA
EXT1 “H” ON Resistance VIN=3.3V, I
=-20mA 4.0 8.0
EXT
µ
A
Ω
R
EXTL1
R
EXTH2
R
EXTL2
T
DLY
V
UVLOD
V
UVLO
V
DTC10
V
DTC1100
V
DTC20
V
DTC2100
A
F
V
ICR1
I
AMPL
I
AMPH
A
F
V
ICR1
V
FB2
EXT1 “L” ON Resistance VIN=3.3V, I
EXT2 “H” ON Resistance VIN=3.3V, I
EXT2 “L” ON Resistance VIN=3.3V, I
Delay Time for Protection
=3.3V, V
V
IN
=20mA 2.7 5.0
EXT
=-20mA 4.0 8.0
EXT
=20mA 3.7 8.0
EXT
=1.1V→0V
FB1
50 100 150 ms
UVLO Detector Threshold 2.10 2.20 2.35 V
UVLO Released Voltage V
UVLOD
2.45 V
+0.10
CH1 Duty=0% VIN=3.3V 0.15 0.25 0.35 V
CH1 Duty=100% VIN=3.3V 1.1 1.2 1.3
CH2 Duty=0% VIN=3.3V 0.15 0.25 0.35 V
CH2 Duty=100% VIN=3.3V 1.1 1.2 1.3 V
CH1 Open Loop Gain VIN=3.3V 110 dB
V1
CH1 Single Gain Frequency
T1
VIN=3.3V, AV1=0dB 1.9 MHz
Band
CH1 Input Voltage Range VIN=3.3V 0.7 to
V
IN
CH1 Sink Current VIN=3.3V, V
V
FB1=VFB1
CH1 Source Current VIN=3.3V, V
V
FB1=VFB1-
CH2 Open Loop Gain VIN=3.3V 60 dB
V2
CH2 Single Gain Frequency
T1
VIN=3.3V, AV2=0dB 3 MHz
AMPOUT1
+ 0.1V
AMPOUT1
0.1V
=1.0V,
=1.0V,
70 115
-1.4 -0.7 mA
Band
CH2 Input Voltage Range VIN=3.3V, -0.2 to
V
IN-1.3
CH2 Input Offset Voltage VIN=3.3V, -12 12 mV
Ω
Ω
Ω
V
V
µ
A
V
Rev. 1.10 - 7 -
Page 8
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>
i2
OUT
I
OUT
V
C
L
Continuous Mode
ILxmax
IL
ILxmin
IN
V
GND
Discontinuous Mode
ILxmax
Inductor
i1
<Current through L>
Tf
Diode
Lx Tr
IL
ILxmin
Iconst
Ton Toff
T=1/fosc
t
Ton Toff
T=1/fosc
t
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.
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
Therefore, the electric power, P
ON
T
PON=∫V
0
2
IN
×
t/L dt Formula 1
ON
, which is supplied with input side, can be described as in next formula.
IN
, the current is V
IN
×
t/L.
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-VIN
)×t/L, therefore electric power, P
OFF
is described as in next formula.
Rev.1.10 - 8 -
Page 9
Tf
OFF
P
0
=∫V
IN
×
(V
OUT-VIN
)×t/L dt Formula 2
In this formula, Tf means the time of which the energy saved in the inductance is being emitted. Thus average
AV
electric power, P
T
PAV=1/(Ton+Toff)
0 0
is described as in the next formula.
ON
2
IN
×{∫
×
V
t/L dt + ∫V
Tf
IN
OUT-VIN
×
(V
)×t/L dt} Formula 3
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.
IN
×
Ton/L=(V
V
Further, the electric power, P
OUT
= f
I
When I
continuous. The continuous current through the inductor is described as Iconst, then,
OUT
= f
I
OUT-VIN
OSC
×
V
OUT
becomes more than formula 5, the current flows through the inductor, then the mode becomes
OSC
IN
×
V
)×Toff/L Formula 4
AV
is equal to output electric power, V
/{2×L ×(V
OUT-VIN
OUT-VIN
))+V
)}=V
IN
2
IN
×
T
×
Iconst/V
ON
/(2×L×V
IN
2
2
×
×
t
T
ON
ON
2
2
/(2×L×(V
OUT
OUT
OUT
×
I
, thus,
OUT
)Formula 5
Formula 6
In this moment, the peak current, ILxmax flowing through the inductor and the driver Tr. is described as follows:
IN
×
ILxmax = Iconst +V
Ton/L Formula 7
With the formula 4,6, and ILxmax is,
ILxmax = V
OUT/VIN
Therefore, peak current is more than I
OUT+VIN
×
I
×
Ton/(2×L) Formula 8
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 VIN 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.
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.
IN
V
GND
Lx Tr
i1
Inductor
Diode
i2
CL
OUT
I
V
OUT
Rev. 1.10 - 9 -
Page 10
IL
ILxmin
Discontinuous Mode
ILxmax
<Current through L>
Continuous Mode
ILxmax
IL
ILxmin
Tf
Iconst
To n
T=1/fosc
To ff
t
To n
T=1/fosc
To ff
t
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.
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.
ON
T
2
IN
×
P=∫V
0
t/L dt Formula 9
Thus average electric power in one cycle, PAV is described as in the next formula.
T
PAV=1/(Ton +Toff)×∫V
0
ON
IN
2
×
t/L dt =V
IN
2
2
×
Ton
/(2×L×(Ton + Toff)) Formula 10
OUT
OUT,
×
This electric power PAV equals to output electric power V
OUT
I
When I
= f
OSC
OUT
2
×
ON
T
2
/(2×L ×V
OUT
)Formula 11
IN
×
V
becomes more than formula 11, the current flows through the inductor continuously, then the mode
I
thus,
becomes continuous. In the continuous mode, the deviation of the current equals between Ton and Toff, therefore,
IN
×
Ton/L=V
V
In this moment, the current flowing continuously through L, is assumed as Iconst, I
formula:
OUT
= f
I
OSC
OUT
×
Toff/L Formula 12
2
IN
×
V
2
ON
×
T
/(2×L×V
OUT
)+Ton/(Ton + Toff)×V
IN
×
Iconst /V
OUT
OUT
Formula 13
is described as in the next
In this moment, the peak current, ILxmax flowing through the inductor and the driver Tr. is described as follows:
IN
×
ILxmax = Iconst +V
Ton/L Formula 14
With the formula 12,13, ILxmax is,
ILxmax = (Ton+Toff)/Toff×I
OUT+VIN
Therefore, peak current is more than I
×
Ton/(2×L) Formula 15
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 VIN 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 - 10 -
Page 11
TEST CIRCUITS
A
■
●
Test Circuit 1
C1
●
Test Circuit 3
C1
EXT1 EXT2
GND
V
AMPOUT
Vrefout
DTC1 DTC2
V
FB1VFB2
EXT1 EXT2
V
GND
AMPOUT
Vrefout
DTC1 DTC2
●
Test Circuit 2
OSCILLOSCOPE
IN
C1
C2
●
Test Circuit 4
OSCILLOSCOPE
IN
C2
C1
AMPOUT
EXT
EXT1
V
GND
AMPOUT
Vrefout
DTC1 DTC2
FB1VFB2
V
EXT
EXT1
GND V
DTC1 DTC2
2
IN
Vrefout
2
OSC
IN
C2
OSCILLOSCOPE
C2
ILLOSC OPE
●
Test Circuit 5
C1
●
Test Circuit 7
C1
FB1VFB2
V
EXT1 EXT2
GND V
AMPOUT
DTC1 DTC2
V
AMPOUT
IN
Vrefout
FB1VFB2
EXT1
EXT2
GND
Vrefout
V
FB1VFB2
●
Test Circuit 6
EXT1 EXT2
C1
GND V
C2
V
●
Test Circuit 8
OSCILLOSCOPE
OSCILLOSCOPE
IN
V
C1
AMPOUT
DTC1 DTC2
FB1VFB2
V
C2
IN
Vrefout
EXT1 EXT
V
GND
AMPOUT
Vrefout
C2
V
2
IN
DTC1 DTC2
FB1VFB2
V
DTC1 DTC2
V
FB1VFB2
Rev. 1.10 - 11 -
Page 12
●
Test Circuit 9
C1
A
EXT1 EXT2
GND V
AMPOUT
Vrefout
DTC1 DTC2
FB1
V
V
FB2
●
Test Circuit 10
IN
C2
C1
C3
EXT1 EXT2
GND V
CE Vrefout
DTC1 DTC2
FB1VFB2
V
IN
OSCILLOSCOPE
C2
●
Test Circuit 11
C1
●
Test Circuit 13
C1
EXT1 EXT2
GND V
CE Vrefout
DTC1 DTC2
FB1VFB2
V
EXT1
EXT2
GND V
Vrefout
CE
DTC1 DTC2
V
FB1VFB2
OSCILLOSCOPE
IN
C2
IN
C4
OSCILLOSCOPE
C2
●
Test Circuit 12
C1
●
Test Circuit 14
C1
EXT1 EXT2
GND V
CE Vrefout
DTC1 DTC2
FB1VFB2
V
EXT1 EXT2
GND V
CE Vrefout
DTC1 DTC2
FB1VFB2
V
IN
IN
OSCILLOSCOPE
C2
C2
V
●
Test Circuit 15
EXT1 EXT2
GND V
IN
C1
C2
CE Vrefout
A
DTC1 DTC2
V
V
FB1VFB2
Rev.1.10 - 12 -
●
Test Circuit 16
C1
EXT1 EXT2
V
GND
CE Vrefout
DTC1 DTC2
FB1VFB2
V
IN
OSCILLOSCOPE
C2
Page 13
●
Test Circuit 17
●
Test Circuit 18
C1
EXT1 EXT2
GND
CE Vrefout
DTC1 DTC2
V
FB1
V
FB2
V
IN
OSCILLOSCOPE
C2
C1
C3
OSCILLOSCOPE
EXT1
GND
CE Vrefout
DTC1 DTC2
FB1VFB2
V
EXT
V
2
IN
Typical Characteristics shown in the following pages are obtained with test circuits shown above.
●
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)
●
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)
C2
C4
OSCILLOSCOPE
Note) Capacitors' values of test circuits
Capacitors: Ceramic Type:
C1=4.7µF, C2=1.0µF, C3=C4=1000pF
Efficiency η(%) can be calculated with the next formula:
η
=(V
OUT1
OUT1+VOUT2
×
I
×
OUT2
I
)/(V
IN
×
IN
I
)×100
Rev. 1.10 - 13 -
Page 14
TYPICAL CHARACTERISTICS
■
1) Output Voltage vs. Output Current
L1=6.8uH,C1=10uF, V
R1280D002A
10.10
10.05
(V)
OUT1
10.00
9.95
Output Voltage V
9.90
0 50 100 150 200
Output Current I
L1=6.8uH,C1=10uF, V
R1280D002B
10.10
OUT1
OUT2
(mA)
OUT2
=-10V,I
=-10V,I
Topt=25°C
OUT2
=0mA L2=6.8uH,C2=10uF, V
VIN=2.5V
VIN=3.3V
VIN=5.5V
-9.90
-9.95
(V)
OUT2
R1280D002A
-10.00
-10.05
Output Voltage V
-10.10
Output Current I
OUT2
=0mA L2=6.8uH,C2=10uF, V
R1280D002B
-9.90
OUT2
OUT1
(mA)
OUT1
=10V,I
VIN=2.5V
VIN=3.3V
VIN=5.5V
=10V,I
OUT1
OUT1
=0mA
-200-150-100-500
=0mA
(V)
10.05
OUT1
10.00
9.95
Output Voltage V
9.90
0 50 100 150 200
10.10
10.05
10.00
9.95
Output Voltage VOUT1(V)
Output Current I
L1=22uH,C1=10uF, V
R1280D002C
OUT1
VIN=2.5V
VIN=3.3V
VIN=5.5V
(mA)
OUT2
=-10V,I
VIN=2.5V
VIN=3.3V
VIN=5.5V
-9.95
-10.00
-10.05
Output Voltage VOUT2(V)
-10.10
Output Current I
OUT2
=0mA L2=22uH,C2=10uF, V
R1280D002C
-9.90
-9.95
-10.00
-10.05
Output Voltage VOUT2(V)
OUT2
(mA)
OUT1
VIN=2.5V
VIN=3.3V
VIN=5.5V
=10V,I
VIN=2.5V
VIN=3.3V
VIN=5.5V
OUT1
-200-150-100-500
=0mA
9.90
0 50 100 150 200
Output Current I
OUT1
(mA)
Rev.1.10 - 14 -
-10.10
Output Current I
OUT2
-150-100-500
(mA)
Page 15
2) Efficiency vs. Output Current
L1=6.8uH,C1=10uF, V
R1280D002A
90
80
70
60
50
40
30
Efficiency (%)
20
10
0
0 50 100 150 200
Output Current I
L1=6.8uH,C1=10uF, V
OUT2
Vout1=5V
Vout1=10V
Vout1=15V
OUT1
(mA)
OUT2
=-VOUT1,I
=-VOUT1,I
VIN=3.3V, Topt=25°C
OUT2
=0mA L2=6.8uH,C2=10uF, V
R1280D002A
90
80
70
60
50
40
Efficiency (%)
30
20
10
0
Output Current I
OUT2
=0mA L2=6.8uH,C2=10uF, V
OUT2
OUT1
=-VOUT2,I
Vout2=-5V
Vout2=-10V
Vout2=-15V
(mA)
OUT1
=-VOUT2,I
OUT1
-200-150-100-500
OUT1
=0mA
=0mA
90
R1280D002B
80
70
60
50
40
Efficiency (%)
30
20
Vout1=5V
Vout1=10V
Vout1=15V
10
0
0 50 100 150 200
OUT1
Output Current I
L1=22uH,C1=10uF, V
R1280D002C
(mA)
OUT2
=-VOUT1,I
90
80
70
60
50
40
Efficiency (%)
30
Vout1=5V
Vout1=10V
Vout1=15V
20
10
0
0 50 100 150 200
Output Current I
OUT1
(mA)
R1280D002B
90
80
70
60
50
40
Efficiency (%)
30
20
10
0
Output Current I
OUT2
=0mA L2=22uH,C2=10uF, V
R1280D002C
90
80
70
60
50
40
Efficiency (%)
30
20
10
0
Output Current I
OUT2
(mA)
OUT1
Vout2=-5V
Vout2=-10V
Vout2=-15V
OUT2
(mA)
Vout2=-5V
Vout2=-10V
Vout2=-15V
=-VOUT2,I
OUT1
-200-150-100-500
=0mA
-150-125-100-75-50-250
Rev. 1.10 - 15 -
Page 16
3) Output Voltage vs. Temperature
VIN=3.3V
L1=6.8uH,C1=10uF L2=6.8uH,C2=10uF
R1280D002A
11.0
IOUT=10mA
(V)
10.5
OUT1
IOUT=100mA
10.0
9.5
Output Voltage V
9.0
-60 -40 -20 0 20 40 60 80 100
Temperature Topt
R1280D002B
(°C)
L1=6.8uH,C1=10uF L2=6.8uH,C2=10uF
11.0
(V)
10.5
OUT1
10.0
R1280D002A
-9.0
(V)
-9.5
OUT2
-10.0
-10.5
IOUT=-10mA
Output Voltage V
-11.0
-60 -40 -20 0 20 40 60 80 100
(°C)
-9.0
(V)
-9.5
OUT2
-10.0
Temperature Topt
R1280D002B
9.5
Output Voltage V
IOUT=10mA
IOUT=100mA
9.0
-60 -40 -20 0 20 40 60 80 100
Temperature Topt
R1280D002C
(°C)
L1=22uH,C1=10uF L2=22uH,C2=10uF
11.0
(V)
10.5
OUT1
IOUT=10mA
IOUT=100mA
10.0
9.5
Output Voltage V
9.0
-60 -40 -20 0 20 40 60 80 100
Temperature Topt
(°C)
IOUT=-10mA
-10.5
Output Voltage V
-11.0
-60 -40 -20 0 20 40 60 80 100
Temperature Topt
R1280D002C
(°C)
-9.0
(V)
-9.5
OUT2
-10.0
-10.5
IOUT=-10mA
Output Voltage V
-11.0
-60 -40 -20 0 20 40 60 80 100
Temperature Topt
(°C)
Rev.1.10 - 16 -
Page 17
4) Frequency vs. Temperature
R1280D002A
800
750
700
650
600
Frequency fosc (kHz)
VIN=2.5V
VIN=3.3V
VIN=5.5V
550
-60 -40 -20 0 20 40 60 80 100
Temperature Topt
R1280D002C
(°C)
230
210
190
VIN=2.5V
170
Frequency fosc (kHz)
VIN=3.3V
VIN=5.5V
R1280D002B
800
750
700
650
600
Frequency fosc (kHz)
VIN=2.5V
VIN=3.3V
VIN=5.5V
550
-60 -40 -20 0 20 40 60 80 100
Temperature Topt
(°C)
150
-60 -40 -20 0 20 40 60 80 100
Temperature Topt
5) Maximum Duty Cycle vs. Temperature
R1280D002B
94
92
90
maxduty1(%)
88
Maximum Duty Cycle
86
-60 -40 -20 0 20 40 60 80 100
Temperature Topt
(°C) (°C)
(°C)
VIN=3.3V
94
92
90
(%)
88
Maximum Duty Cycle maxduty2
86
-60 -40 -20 0 20 40 60 80 100
R1280D002B
Temperature Topt
Rev. 1.10 - 17 -
Page 18
6) Feedback Voltage vs. Temperature 7) Input Offset Voltage vs. Temperature
VIN=3.3V
R1280D002A/B/C
1.02
(V)
1.01
FB1
R1280D002A/B/C
10.0
FB2
5.0
1.00
0.0
0.99
0.98
Feedback Voltage V
0.97
-60 -40 -20 0 20 40 60 80 100
Temperature Topt
(°C)
(mV)
-5.0
Input Offset Voltage V
-10.0
-60 -40 -20 0 20 40 60 80 100
Temperature Topt
8) Vrefout Output Voltage vs. Temperature 9) Vrefout Output Voltage vs. Output Current
VIN=3.3V
1.55
1.53
1.51
R1280D002A/B/C
1.8
1.5
1.2
R1280D002A/B/C
0.9
1.49
0.6
Vrefout Voltage(V)
1.47
Vrefout Voltage(V)
0.3
(°C)
1.45
-60 -40 -20 0 20 40 60 80 100
Temperature Topt
(°C)
0
0 102030405060
ROUT
I
(mA)
10) Vrefout Output Voltage vs. Output Current 11) Protection Circuit Delay Time vs. Temperature
1.508
1.506
1.504
1.502
Vrefout Voltage(V)
1.500
1.498
0 5 10 15 20
R1280D002A/B/C
ROUT
(mA)
I
140
120
100
TDLY (ms)
80
Protection Circuit Delay Time
60
-60 -40 -20 0 20 40 60 80 100
R1280D002A/B/C
Temperature Topt
(°C)
VIN=3.3V
Rev.1.10 - 18 -
Page 19
12) Duty Cycle vs. DTC Voltage
VIN=3.3V, EXT=1000pF VIN=3.3V, EXT=1000pF
R1280D002A
100
80
60
40
Duty Cycle Duty(%)
20
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4
DTC
V
(V)
100
80
60
40
Duty Cycle Duty(%)
20
0
0 0.2 0.4 0.6 0.8 1 1.2 1.4
R1280D002C
DTC
(V)
V
13) Output Sink Current vs. Temperature 14) Output Source Current vs. Temperature
VIN=3.3V VIN=3.3V
130
120
(uA)
110
AMPL
I
100
Output Sink Current
90
-60 -40 -20 0 20 40 60 80 100
R1280D002A/C
Temperature Topt
(°C)
0.0
-0.5
(mA)
AMPH
-1.0
-1.5
-2.0
-2.5
Output Sink Current I
-3.0
-60 -40 -20 0 20 40 60 80 100
R1280D002A/C
Temperature Topt
(°C)
15) CE "H" Input Voltage vs. Temperature 16) CE "L" Input Voltage vs. Temperature
VIN=5.5V VIN=2.5V
R1280D002B
1.25
(V)
1.00
CEH
0.75
0.50
CE"H" Input Voltage V
0.25
-50 0 50 100
Temperature Topt
(°C)
1.25
(V)
1
CEL
0.75
0.5
CE"L" Input Voltage V
0.25
-50 0 50 100
R1280D002B
Temperature Topt
(°C)
Rev. 1.10 - 19 -
Page 20
17) Soft Starting Time vs. Capacitance value
VIN=3.3V
40
30
(ms)
SS1
20
10
R1280D002B
Soft Starting Time T
0
0 0.2 0.4 0.6 0.8 1 1.2
Capacitance value for Soft Start(uF)
18) Soft Starting Time vs. Temperature
R1280D002B
20
(ms)
15
SS1
R1280D002B
50
40
(ms)
SS2
30
20
10
Soft Starting Time T
0
00.20.40.60.811.2
CDTC1=0.33µFCDTC2=0.33
Capacitance value for Soft Start(uF)
R1280D002B
VIN=3.3V
µ
F
30
25
(ms)
SS2
20
10
5
Soft Starting Time T
0
-50 0 50 100
Temperature Topt
(°C)
19) Load Transient Response(Step-up Side)
R1280D002A
10.5
10
(V)
9.5
OUT1
9
8.5
8
Output Voltage V
7.5
0 0.0005 0.001 0.0015 0.002
Time (sec)
15
10
5
Soft Starting Time T
0
-50 0 50 100
L1=6.8µH L1=6.8µH
Temperature Topt
R1280D002A
(°C)
VIN=3.3V
11.5
11
(mA)
OUT
(V)
10.5
OUT1
(mA)
OUT
10
100
Output Current I
0.1
9.5
Output Voltage V
9
8.5
100
Output Current I
0.1
0 0.01 0.02 0.03 0.04 0.05
Time (sec)
Rev.1.10 - 20 -
Page 21
L1=6.8µH L1=6.8µH
R1280D002B
10.5
10
(V)
9.5
OUT1
9
8.5
Output Voltage V
8
7.5
0 0.0005 0.001 0.0015 0.002
Time (sec)
R1280D002C
10.5
10
(V)
9.5
OUT1
9
8.5
Output Voltage V
8
7.5
0 0.0005 0.001 0.0015 0.002
Time (s)
20) Load Transient Response (Inverting Side)
R1280D002B
11.5
11
(mA)
OUT
(V)
10.5
OUT1
(mA)
OUT
10
100
Output Current I
0.1
9.5
Output Voltage V
9
8.5
100
Output Current I
0.1
0 0.01 0.02 0.03 0.04 0.05
Time (sec)
L1=22µH L1=22µH
R1280D002C
11.5
11
(mA)
OUT
(V)
10.5
OUT1
10
100
Output Curren I
0.1
9.5
Output Voltage V
9
8.5
100
0.1
0 0.01 0.02 0.03 0.04 0.05
Time (sec)
VIN=3.3V
L2=6.8µH L2=6.8µH
(mA)
OUT
Output Current I
R1280D002A
-9
-9.5
(V)
OUT2
-10
-10.5
-11
Output Voltage V
-50
-0.1
(mA)
OUT
Output Current I
-11.5
0.00000.00010.00020.00030.00040.00050.000
Time (sec)
6
Rev. 1.10 - 21 -
R1280D002A
-9.5
-10
(V)
OUT2
-10.5
-11
-11.5
Output Voltage V
-12
0.000 0.005 0.010 0.015 0.020
Time (sec)
(mA)
OUT
-50
-0.1
Output Current I
Page 22
L2=6.8µH L2=6.8µH
R1280D002B
-9
-9.5
(V)
OUT2
-10
-10.5
-11
Output Voltage V
-11.5
0.00000.00010.00020.00030.00040.00050.000
Time (sec)
R1280D002C
-9.5
(V)
OUT2
-10
-9
R1280D002B
-9.5
-10
(V)
OUT2
-10.5
-11
-11.5
Output Voltage V
-50
-0.1
-50
-0.1
(mA)
OUT
Output Current I
-12
6
0.000 0.005 0.010 0.015 0.020
Time (sec)
L2=22µH L2=22µH
R1280D002C
-9.5
-10
(V)
(mA)
OUT
OUT2
-10.5
(mA)
OUT
Output Current I
(mA)
OUT
-10.5
-11
Output Voltage V
-11.5
0.0000 0.0001 0.0002 0.0003 0.0004 0.0005 0.0006
Time(s)
-50
-0.1
-11
-11.5
Output Current I
Output Voltage V
-12
0.000 0.005 0.010 0.015 0.020
Time(s)
-50
-0.1
Output Current I
Rev.1.10 - 22 -
Page 23
TYPICAL APPLICATION AND TECHNICAL NOTES
V
V
V
V
■
●
R1280D002A/C
L1
NMOS
C9
R11
C3
C4
R7
R8
EXT1
GND
AMPOUT
DTC1
FB1
EXT2
V
IN
1
refout
DTC2
FB2
V
C5
R9
C7
PMOS
C8
L2
R3
R10
Diode
R4
C1
OUT1
R1
R2
C6
R5
OUT2
R6
External Components
Inductor L1,2: 6.8µH, LDR655312T(TDK) for A type, 22µH 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≤100kΩ or R3+R4≤100k
R5=43kΩ, R6=10kΩ, R7=R9=22kΩ, R8=R10=43kΩ, R11=220k
Capacitors: Ceramic Capacitor
(Example)
R1280D002A: C1=C2=10µF, C3=4.7µF, C4=0.22µF, C5=0.47µF, C6=120pF, C7=50pF, C8=1µF, C9=1000pF
R1280D002C: C1=C2=10µF, C3=4.7µF, C4=0.22µF, C5=0.47µF, C6=220pF, C7=330pF, C8=1µF, C9=1000pF
Note: Maximum voltage tolerance of each component should be considered. W ith the transistor shown above is
appropriate to set up to ±15V as output voltage.
C2
Ω
Ω
●
R1280D002B
V
OUT1
C1
R1
R2
C6
R5
L1
L1
NMOS
C3
C4
EXT2
EXT1
GND
V
IN
CE
DTC1DTC2
V
FB1
V
FB2
C5
C7
R6
PMOS
C8
L2
R3
Diode
R4
Rev. 1.10 - 23 -
Page 24
External Components
A
Inductor L1,2: 6.8µH, 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≤100kΩ or R3+R4≤100k
R5=43kΩ, R6=10k
Capacitors: Ceramic Capacitor
(Example)
C1=C2=10µF, C3=4.7µF, C4=0.33µF, C5=0.33µF, C6=120pF, C7=50pF, C8=1µF
Note: Maximum voltage tolerance of each component should be considered. W ith the transistor shown above is
appropriate to set up to ±15V as output voltage.
APPLICATION EXAMPLE
■
●
R1280D002A/C
Ω
VOUT3
Ω
C3
C4
C11
R7
R8
EXT2
EXT1
GND
MPOUT1
Vrefout
DTC2
DTC1
V
PMOS
V
C8
R9
L2
R3
R10
C5
V
Diode
VOUT1
C1
R1
R2
C10
L1
NMOS
C6
C9
R5
R11
R4
C7
VOUT2
OUT1
C2
-Vf
R6
External Components
Inductor L1,2: 6.8µH, LDR655312T(TDK) for A version, 22µH 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≤100kΩ or R3+R4≤100k
R5=43kΩ, R6=10kΩ, R7=R9=22kΩ, R8=R10=43kΩ, R11=220k
Capacitors: Ceramic Capacitor
(Example)
R1280D002A: C1=C2=10µF, C3=4.7µF, C4=0.22µF, 5=0.47µF,C6=120pF,C7=50pF,C8=C10=C11=1µF,C9=1000pF
R1280D002C:C1=C2=10µF,C 3=4 .7µF, C4=0.22µF,C 5=0 .4 7µF,C6=220pF,C7=330pF,C8=C10=C11=1µF,C9=1000pF
This IC can be used 3 Output TFT Bias Circuit as shown above. V
OUT3
Ω
=2×V
Ω
Note: Maximum voltage tolerance of each component should be considered. W ith the transistor shown above is
OUT1
appropriate to set up to +15V as V
Rev.1.10 - 24 -
, -15V as V
OUT2,
30V as V
OUT3.
Page 25
●
R1280D002B
VOUT3
C11
VOUT1
C10
L1
C1
C3
EXT2
R1
R2
C6
R5
NMOS
C4
EXT1
V
GND
IN
CE
Vrefout
DTC1DTC2
V
FB1
V
FB2
C5
C7
C8
R3
R4
PMOS
L2
Diode
VOUT2
R6
External Components
Inductor L1,2: 6.8µH, 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≤100kΩ or R3+R4≤100k
R5=43kΩ, R6=10k
Capacitors: Ceramic Capacitor
(Example)
R1280D002B: C1=C2=10µF, C3=4.7µF, C4=0.33µF, 5=0.33µF, C6=120pF,C7=50pF,C8=C10=C11=1µF
Ω
Ω
This IC can be used 3 Output TFT Bias Circuit as shown above. V
Note: Maximum voltage tolerance of each component should be considered. W ith the transistor shown above is
OUT1
appropriate to set up to +15V as V
EXTERNAL COMPONENTS
■
1. How to set the output voltages
FB1
FB1
: R2
SS2
As for step-up side, feedback (V
OUT1
: R1+R2=V
V
SS1
≅
OUT1=VFB1
OUT2
RS1×C4, T
Thus, V
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
Thus, |-V
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
Soft starting time can be described as in next formula. (Topt=25°C)
T
In the above formulas, RS1 value is TYP. 32kΩ, while RS2 value is TYP. 45kΩ. 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
×
(R1+R2)/R2
OUT2
|:R4
|=Vrefout×R4/R3
SS1
and T
SS2
≅
RS2×C5
, -15V as V
) pin voltage is controlled to maintain 1V, therefore,
are adjustable. Soft starting time can be set with the time constant of RC.
OUT2,
30V as V
OUT3
OUT3
=2×V
OUT1
-Vf
Rev. 1.10 - 25 -
Page 26
and capacitor.
TECHNICAL NOTES on EXTERNAL COMPONENTS
■
●
External components should be set as close to this IC as possible. Especially, wiring of the capacitor connected
IN
pin should be shortest.
to V
●
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.
●
Recommended capacitance value of C3 is equal or more than 4.7µF. 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.
●
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 10kΩ to 50kΩ as R5 and try to reduce the noise level. In the case of
OUT2
, use the resistor as much as 10kΩ as R6.
V
●
Select an inductor with low D.C. current, large permissible current, and uneasy to cause magnetic saturation. If
LX
the inductance value is too small, I
●
Select a Schottky diode with fast switching speed and large enough permissible current.
●
Recommended capacitance value of C1 and C2 is as much as Ceramic 10µF. In case that the operation with the
might be beyond the absolute maximum rating at the maximum load.
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.
●
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.
●
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.
●
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.
Rev.1.10 - 26 -
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