RV5VH Datasheet, PDF (20/47 Pages) RICOH electronics devices division – DC/DC CONVERTER CONTROLLER

• DC/DC Converter 2
RV5VH1××/RV5VH2××
OSC
Error Amp.2
VFM2
RV5VH1××/RV5VH2××
CSW
1
FB
7
VOUT1
C2
PMOS
EXT2
SBD
6
L
R1
R2
VOUT2
C1
The DC/DC2 can operate by a voltage of “VOUT1”. A change in the VOUT2 will feed back to the internal error amplifier
through external voltage setting resistors. The reference voltage should be provided from externally fixed power supply
such as VOUT1.
When the feed back voltage to the cmp2 is higher than the ground voltage the error amplifier enables oscillation or other-
wise 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 becomes smaller temporarily at light load current. The output of “EXT2” is driven by CMOS
buffer operated VOUT1 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 “H”, 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 High while the DC/DC2 is disabled.
• Set output voltage DC/DC Converter2
VOUT2 is described as follows:
VOUT1:R1=|–VOUT2| : R2 / The FB voltage is controlled to 0V and VOUT1 is provided externally
|–VOUT2|=VOUT1 × R2/R1
thus, any output voltage of DC/DC2 can be set by changing R1 or/and R2.
Certain temperature coefficient of VOUT2 can be set by using R1,R2 having such temperature characteristics.
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