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PDF R1282D002A Data sheet ( Hoja de datos )
| Número de pieza | R1282D002A | |
| Descripción | 2CH PWM DC/DC CONTROLLER | |
| Fabricantes | RICOH electronics devices division | |
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2CH PWM DC/DC CONTROLLER
R1282D002A SERIES
NO. EA-086-0502
OUTLINE
The R1282D002A is a CMOS-based 2-channel PWM Step-up (as Channel 1)/Step-down (as Channel 2)
DC/DC converter controller.
The R1282D002A 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/Step-down DC/DC converter can be composed of this IC with inductors, diodes, power MOSFETs,
resisters, and capacitors. Each output voltage and maximum duty cycle can be adjustable with external resistors,
while soft-start time can be adjustable with external capacitors and resistors.
As for a protection circuit, if Maximum duty cycle of either Step-up DC/DC converter side or Step-down DC/DC
converter side is continued for a certain time, the R1280D002A latches 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).
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
• High Accuracy Voltage Reference ....................±1.5%
• U.V.L.O. Threshold............................................Typ. 2.2V (Hysteresis: Typ. 0.2V)
• 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.
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R1282D002A
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.
VIN
GND
<Basic Circuit>
Inductor
Diode
i2
i1 Lx Tr CL
IOUT
VOUT
<Current through L>
Discontinuous Mode
IL IL
ILxmax
Continuous Mode
ILxmax
ILxmin
Tf
t
Ton
T=1/fosc
Toff
ILxmin
Iconst
Ton
T=1/fosc
t
Toff
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.
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R1282D002A
EXT1
OSCILLOSCOPE
EXT1
C1
GND
VIN
C2
Vrefout
OSCILLOSCOPE
C1
GND
VIN
C2
Vrefout
DTC1 DTC2
VFB1
VFB2
DTC1 DTC2
VFB1
VFB2
Test Circuit 7
Test Circuit 8
EXT2
OSCILLOSCOPE
C1
GND
VIN
C1
Vrefout
DTC1 DTC2
C2
VFB1
VFB2
GND
VIN
A AMPOUT1
Vrefout
DTC1 DTC2
VFB1
VFB2
C2
Test Circuit 9
Test Circuit 10
Typical Characteristics shown in the following pages are obtained with test circuits shown above.
Test Circuit 1,2 :
Test Circuit 3 :
Test Circuit 4 :
Test Circuit 5 :
Test Circuit 6 :
Test Circuit 7 :
Test Circuit 8 :
Test Circuit 9 :
Test Circuit 10 :
Typical Characteristic 4)
Typical Characteristic 5)
Typical Characteristic 5)
Typical Characteristic 6)
Typical Characteristics 7) 8)
Typical Characteristic 9)
Typical Characteristic 10)
Typical Characteristics 10)
Typical Characteristics 11) 12)
Note) Capacitors' values of test circuits
Capacitors: Ceramic Type:
C1=4.7µF, C2=1.0µF
Efficiency η(%) can be calculated with the next formula:
η=(VOUT1×IOUT1+VOUT2×IOUT2)/(VIN×IIN)×100
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| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet R1282D002A.PDF ] | |
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