RV5VH Datasheet, PDF (40/47 Pages) RICOH electronics devices division – DC/DC CONVERTER CONTROLLER

• DC/DC Converter 2
RV5VH3××
OSC
Error Amp.2
VFM2
RV5VH3××
CSW
1
FB2
7
VDD
C2
PMOS
EXT2
SBD
6
L
VREF
R1
R2
VOUT2
C1
The DC/DC2 can operate by an input voltage to the VDD pin. A change in the VOUT2 will feed back to the internal error
amplifier through external voltage setting resistors. The VREF voltage should be provided from externally fixed power sup-
ply such as VOUT1.
When the feed back voltage to the Error Amp.2 is higher than the ground voltage, the error amplifier enables oscillation
otherwise, it will stop oscillation.
Pulses from the “OSC” circuit have a duty cycle of 50% and it makes VFM operation allowable.
There might be certain cases that the duty cycles become smaller temporarily at light load current. The output of “EXT2”
is driven by CMOS buffer operated VDD and GND.
A PMOS driver will be connected to the “EXT2” pin and its switching operation generates negative output voltage through
energy accumulated in an inductor.
The DC/DC1 can be shut down by CSW pin. When the CSW pin is High, VDD level, the DC/DC1 is enabled and when the
CSW pin is “L”, GND level, the DC/DC1 is disabled. The EXT2 pin outputs “H” while the DC/DC2 is disabled.
• Set Output Voltage DC/DC 2
VOUT2 is described as follows:
VREF : R1=|–VOUT2| : R2 The FB2 voltage is controlled to 0V and VREF is provided externally
|–VOUT2|=VREF×R2/R1,
thus, any output voltage of DC/DC2 can be set by R1 and R2.
Certain temperature coefficient of VOUT2 can be set by using R1, R2 having such temperature characteristics.
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