參數(shù)資料
型號(hào)： R1234D261B
廠商： Ricoh Co., Ltd.
英文描述： PWM/VFM Step-Down DC/DC CONVERTER with Synchronous Rectifier
中文描述： 脈寬調(diào)制/ VFM的降壓型DC / DC同步整流變換器
文件頁(yè)數(shù)： 1/26頁(yè)
文件大小： 876K
代理商： R1234D261B
R1234D SERIES
PWM/VFM Step-Down DC/DC CONVERTER with Synchronous Rectifier
NO.EA-137-070221
OUTLINE
1
The R1234D Series are CMOS-based PWM step-down DC/DC Converters with synchronous rectifier, low
supply current.
Each of these ICs consists of an oscillator, a PWM control circuit, a reference voltage unit, an error amplifier, a
soft-start circuit, protection circuits, a protection against miss operation under low voltage (UVLO), PWM/VFM
alternative circuit, a chip enable circuit, and a driver transistor. 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 R1234D001C/D types, divider resistors are also necessary.) In terms of Output Voltage, it is
fixed internally in the R1234Dxx1A/B types. While in the R1234D001C/D types, Output Voltage is adjustable with
external divider resistors.
PWM/VFM alternative circuit is active with Mode Pin of the R1234D Series. Thus, when the load current is
small, the operation can be switching into the VFM operation from PWM operation by the logic of MODE pin and
the efficiency at small load current can be improved. As protection circuits, Current Limit circuit which limits peak
current of Lx at each clock cycle, and Latch type protection circuit which works if the term of Over-current
condition keeps on a certain time in PWM mode exist. 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
Supply Current..................................................Typ. 230
μ
A (R1234Dxx1A/C)
Typ. 250
μ
A (R1234Dxx1B/D)
Standby Current................................................Typ. 0
μ
A
Input Voltage Range ........................................ 2.4V to 5.5V (ABSOLUTE MAXIMUM : 6.5V)
Output Voltage Range.......................................2.2V to 3.3V (R1234Dxx1A/B)
0.8V to V
IN
(R1234Dxx1C/D)
Output Voltage Accuracy...................................
±
2.0% (R1234DxxA/B)
Oscillator Frequency.........................................Typ. 500kHz (R1234Dxx1A/C)
Typ. 800kHz (R1234Dxx1B/D)
Built-in Driver ON Resistance...........................Pch 0.4
,Nch 0.6
(V
IN
=
3V)
Control mode switch .........................................MODE pin
=
”L”: PWN
MODE pin
=
”H”: VFM
Efficiency...........................................................Typ. 90%
Package............................................................SON-8
Built-in Soft-start Function.................................Typ. 1.5ms
Latch-type Protection Function.........................Typ. 1.5ms
Built-in Current Limit Circuit
APPLICATIONS
Power source for portable equipment.
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