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PDF R1232D Data sheet ( Hoja de datos )

Número de pieza R1232D
Descripción PWM STEP-DOWN DC/DC CONVERTER
Fabricantes RICOH electronics 
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R1232D SERIES
PWM STEP-DOWN DC/DC CONVERTER WITH SYNCHRONOUS RECTIFIER
NO.EA-129-0606
OUTLINE
The R1232D Series are CMOS-based PWM step-down DC/DC converters with synchronous rectifier, low
supply current. As an output capacitor, a 10µF or more ceramic capacitor can be used with the R1232D.
Each of these ICs consists of an oscillator, a PWM control circuit, a voltage reference unit, an error amplifier, a
soft-start circuit, protection circuits, a protection against miss operation under low voltage (UVLO), a chip enable
circuit, a synchronous rectifier, Nch. driver transistor, and so on. A low ripple, high efficiency step-down DC/DC
converter can be easily composed of this IC with only a few kinds of external components, or an inductor and
capacitors. (As for R1232D001x type, divider resistors are also necessary.) In terms of the output voltage, it is
fixed internally in the R1232Dxx1x types. While in the R1232D001x types, the output voltage is adjustable with
external divider resistors.
As protection circuits, current limit circuit which limits peak current of LX at each clock cycle, and latch type
protection circuit exist. The latch protection works if the term of the over-current condition keeps on a certain time.
Latch-type protection circuit works to latch an internal driver with keeping it disable. To release the condition of
protection, after disable this IC with a chip enable circuit, enable it again, or restart this IC with power-on or make
the supply voltage at UVLO detector threshold level or lower than UVLO.
FEATURES
Two choices of Oscillator Frequency ............................ 1MHz, 2.25MHz
(Small inductors can be used. 4.7µH for 1MHz/2.2µH for 2.25MHz)
Built-in Driver ON Resistance ....................................... P-channel 0.2(at VIN=5.0V)
Built-in Soft-start Function............................................. Typ. 1.0ms (fosc=1MHz type)
Output Voltage .............................................................. 0.9V to 3.3V (xx1x Type)
0.8V to VIN (001x Type)
High Accuracy Output Voltage ......................................±2.0%
Built-in Current Limit Circuit .......................................... Typ. 1.4A
Package ........................................................................SON-8 (t=0.9mm)
APPLICATIONS
Power source for portable equipment such as PDA, DSC, Notebook PC.
Power source for HDD
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R1232D pdf
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R1232D
ELECTRICAL CHARACTERISTICS
R1232DxxxA/C
Symbol
Item
Conditions
VIN Operating Input Voltage
VOUT
Step-down Output Voltage
VIN=VCE=5.0V, IOUT=10mA
VFB Feedback Voltage
VOUT/Topt
Step-down Output Voltage
Temperature Coefficient
VIN=VCE=5.0V, IOUT=10mA
40°C <= Topt <= 85°C
fosc
IDD
Istandby
Oscillator Frequency
Supply Current
Standby Current
VIN=VCE =VSET +1.5V
VIN=VCE =5.5V, VOUT=5.5V
VCE=VOUT=0V, VIN= 5.5V
ILXleak
RONP
LX Leakage Current
VIN=5.5V,VCE=0V
VLX=0V/5.5V
ON Resistance of Pch Transistor VIN=5.0V, ILX=200mA
RONN
ON Resistance of Nch Transistor VIN=5.0V, ILX=200mA
Maxduty Oscillator Maximum Duty Cycle
tstart Soft-start Time
VIN=VCE =5.0V, at no load
tprot Protection Delay Time
VIN=VCE =5.0V
ILXlimit Lx Current Limit
VIN=VCE =5.0V
VUVLO1 UVLO Detector Threshold
VIN=VCE =2.6V-> 1.5V
VUVLO2 UVLO Released Voltage
VIN=VCE =1.5V-> 2.6V
ICE
IVOUT
VCEH
VCEL
VTESTL
CE Input Current
VOUT Leakage Current
CE "H" Input Voltage
CE "L" Input Voltage
TEST pin "L" Input Voltage
VIN=5.5V, VCE =5.5V/0V
VIN=5.5V, VCE =0V,
VOUT=5.5V/0V
VIN=5.5V
VIN=3.0V
VIN=3.0V
Topt=25°C
Min. Typ. Max. Unit
2.6 5.5 V
×0.980
×1.020 V
0.784 0.800 0.816 V
±150
ppm/
°C
0.75 1.00 1.25 MHz
70 140 190 µA
0.0 5.0 µA
5.0 0.0 5.0 µA
100
0.5
0.1
1.0
2.10
2.20
0.1
0.20
0.20
1.0
2.0
1.4
2.25
VUVLO1
+0.10
0.0
0.35
0.35
1.4
10.0
2.40
2.50
0.1
0.1 0.0 0.1
%
ms
ms
A
V
V
µA
µA
1.5 V
0.3 V
0.3 V
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R1232D arduino
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R1232D
In the continuous mode, when Equation 1 is solved for ton and assumed that the solution is tonc
tonc=t×VOUT/VIN............................................................................................................. Equation 2
When the ton=tonc, the mode is the continuous mode.
OUTPUT CURRENT AND SELECTION OF EXTERNAL COMPONENTS
When P-channel Tr. of LX is ON:
(Wherein, Ripple Current P-P value is described as IRP, ON resistance of P-channel Tr. and N-channel Tr. of LX
are respectively described as RONP and RONN, and the DC resistor of the inductor is described as RL.)
VIN=VOUT+(RONP+RL)×IOUT+L×IRP/ton .............................................................................. Equation 3
When P-channel Tr. of LX is "OFF"(N-channel Tr. is "ON"):
L×IRP/toff=VF+VOUT+RONN×IOUT ....................................................................................... Equation 4
Put Equation 4 to Equation 3 and solve for ON duty of P-channel transistor, Don=ton/(toff+ton),
DON=(VOUTRONN×IOUT+RL×IOUT)/(VIN+RONN×IOUTRONP×IOUT) ........................................... Equation 5
Ripple Current is as follows;
IRP=(VINVOUTRONP×IOUTRL×IOUT)×DON/fosc/L .............................................................. Equation 6
wherein, peak current that flows through L, and LX Tr. is as follows;
ILmax=IOUT+IRP/2 .......................................................................................................... Equation 7
Consider ILmax, condition of input and output and select external components.
ÌThe above explanation is directed to the calculation in an ideal case in continuous mode.
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