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PDF R5212D Data sheet ( Hoja de datos )
| Número de pieza | R5212D | |
| Descripción | Step-down DC/DC Converter | |
| Fabricantes | RICOH electronics devices division | |
| Logotipo |  |
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R5212D SERIES
Step-down DC/DC Converter with VR and Reset
NO.EA-128-0510
OUTLINE
The R5212D is CMOS-based PWM step-down DC/DC converter combined with a voltage regulator (VR) and
a voltage detector (VD), with low supply current.
Each of these ICs consists of an oscillator, a PWM control circuit, a voltage reference unit, an error amplifier, a
soft-start circuit, a current limit circuit, a phase compensation circuit, a resistor net for voltage detect circuit, an
output driver transistor, and so on. A low ripple, high efficiency step-down DC/DC converter can be easily
composed of this IC with some external components, or an inductor, a diode, and capacitors.
The oscillator frequency is 1.2MHz, therefore small inductor and capacitor can be used with this IC. Further,
this IC equips the under voltage lockout function (UVLO). If the input voltage becomes equal or less than 2.35V
(Typ.), the output of DC/DC converter turns off. However, in the A/B version, embedded voltage regulator and
detector continue to operate. In the C/D version, LDO output also turns off and only the voltage detector is
working.
The voltage regulator consists of a voltage reference unit, a resistor net for voltage detect circuit, an error
amplifier, an output driver transistor, and so on.
The input source voltage of the built-in voltage regulator is VIN pin (A/B version) or VOUT1 pin, the output of
DC/DC converter (C/D version).
The built-in voltage detector supervises the input voltage and the output is N-channel open drain.
Power-on reset delay time is also included and internally set typically at 12ms (A/C version) or 50ms(B/D
version).
FEATURES
• Range of Input Voltage ............................. 3.0V~5.5V
• Built-in Soft-start Function (Typ. 1ms) and built-in power-on reset delay (Typ. 12ms or 50ms)
• Maximum Output Current...........................500mA (DC/DC), 200mA (VR)
• Accuracy Output Voltage .......................... ±2.0% (DC/DC and Voltage Regulator Output)
• Accuracy of voltage detector .................... ±2.5%
• Output Voltage (VR)(A/B Version) ............ Stepwise Setting with a step of 0.1V in the range of 2.0V to 3.6V
(C/D Version) ............ Stepwise Setting with a step of 0.1V in the range of 1.2V to 3.0V
• Output Voltage (DC/DC) (A/B Version) ..... Stepwise Setting with a step of 0.1V in the range of 1.2V to 3.6V
(C/D Version) ..... Stepwise Setting with a step of 0.1V in the range of 2.5V to 3.6V
• Output Voltage (VD).................................. Stepwise Setting with a step of 0.1V in the range of 3.0V to 4.5V
• Package .................................................... HSON-6 (t=0.9mm)
APPLICATIONS
• Power source for hand-held communication equipment, CD or DVD drives.
• Power source for battery-powered equipment.
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R5212D
ELECTRICAL CHARACTERISTICS
• R5212DxxxA
Symbol
VIN
IDD
VUVLO2
VUVLOHYS
Item
Operating Input Voltage
Supply Current
UVLO Release Voltage
UVLO Detector Threshold
Voltage Hysteresis
Conditions
VIN=5.0V, VOUT1=0V
Min.
3.0
2.35
0.05
• DC/DC Part
Symbol
Item
VOUT1 DC/DC Output Voltage
∆VOUT1/
∆Topt
fosc
RLX
ILXleak
ILXLIM
Maxduty
tstart
DC/DC Output Voltage
Temperature Coefficient
Oscillator Frequency
Lx on Resistance
Lx Leakage Current
Lx Current Limit
Maximum duty cycle
Soft-start Time
Conditions
VIN=5.0V, at no load
OPEN LOOP
40°C <= Topt <= 85°C
VIN=5.0V
VIN=5.0V, ILX=100mA
VIN=VOUT1=5.5V, VLX=0V
VIN=5.0V
VIN=5.0V
Min.
VOUT1
×0.98
960
600
100
0.35
• VR Part
Symbol
Item
VOUT2 VR Output Voltage
IOUT2 Maximum Output Current of VR
VREG2 VR Load Regulation
VDIF2
ILIM2
∆VOUT2/
∆Topt
Dropout Voltage
Short Current Limit
VR Output Voltage
Temperature Coefficient
Conditions
VIN=5.0V, IOUT2=10mA
VIN=5.0V
VIN−VOUT2=0V
1mA <= IOUT2 <= 80mA
IOUT2=100mA
VOUT2=0V
40°C <= Topt <= 85°C
Min.
VOUT2
×0.98
200
• VD Part
Symbol
Item
−VDET VD Detector Threshold
∆−VDET/ VD Detector Threshold
∆Topt Temperature Coefficient
Conditions
40°C <= Topt <= 85°C
Min.
−VDET
×0.975
VHYS Hysteresis Range
tPLH
IDOUTL
VD Output Delay Time for Release
VDOUT “L” Output Current
VIN=VDOUT=−VDET×0.9 to 5.0
VIN=2.0V, IOUT=0.1V
3
2
Typ.
400
2.50
0.15
Typ.
±100
1200
0.4
0.01
800
1.00
Typ.
20
0.2
50
±100
Typ.
±100
−VDET
×0.05
12
7
Topt=25°C
Max. Unit
5.5
800
2.65
V
µA
V
0.25 V
Topt=25°C
Max.
VOUT1
×1.02
1440
0.8
5.00
3.00
Unit
V
ppm
/°C
kHz
Ω
µA
mA
%
ms
Topt=25°C
Max.
VOUT2
×1.02
Unit
V
mA
60 mV
0.3 V
mA
ppm
/°C
Topt=25°C
Max.
−VDET
×1.025
Unit
V
ppm
/°C
V
30 ms
20 mA
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R5212D
OPERATION of step-down DC/DC converter and Output Current
The step-down DC/DC converter charges energy in the inductor when Lx transistor is ON, and discharges the
energy from the inductor when Lx transistor is OFF and controls with less energy loss, so that a lower output
voltage than the input voltage is obtained. The operation will be explained with reference to the following
diagrams:
<Basic Circuits>
VIN Lx Tr
SD
i1 IOUT
L VOUT
i2 CL
<Current through L>
IL
ILmax
ILxmin
topen
ton
t=1/fosc
toff
Step 1 : Lx Tr. turns on and current IL (=i1) flows, and energy is charged into CL. At this moment,
IL increases from ILmin (=0) to reach ILmax in proportion to the on-time period (ton) of LX Tr.
Step 2 : When Lx Tr. turns off, Schottky diode (SD) turns on in order that L maintains IL at ILmax,
and current IL (=i2) flows.
Step 3 : IL decreases gradually and reaches ILmin after a time period of topen, and SD turns off,
provided that in the continuous mode, next cycle starts before IL becomes to 0 because toff time is not
enough. In this case, IL value is from this ILmin (>0).
In the case of PWM control system, the output voltage is maintained by controlling the on-time period (ton),
with the oscillator frequency (fosc) being maintained constant.
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