BD9540EFV Datasheet, PDF (12/18 Pages) Rohm – 2ch Switching Regulators for Desktop PC

BD9540EFV
Technical Note
6. Output Voltage Setting
The IC will try to maintain output voltage such that REF≒VFB.
However, the actual output voltage will also reflect the average ripple voltage value.
The output voltage is set via a resistive voltage divider between the output and the FB pin. The formula for output voltage
is given in (13) below:
Output voltage=
R1+R2 _{× REF +} 1 _{×ΔIL×ESR・・・(13)}
R2
2
VIN
REF
FB
H³Reg^TM
CONTROLLA
RQ
S
Driver
Circuit
Radd (for Low Ripple)
Output voltage
R1 ^C1
ESR
R2
Cadd (for Low Ripple)
It is recommended that R1 and C1 be connected in parallel to the FB pin.
In low output ripple applications (ΔV < 20 mV), add Radd and Cadd as shown in the above application circuit.
For value settings, refer to the tool provided separately.
REF voltage (for 2ch) is fixed at 0.750 V; however, REF voltage (for 1ch) can be adjusted via the CTL input conditions.
REF1 voltage setting table
CTL1
L
H
L
H
CTL2
L
L
H
H
REF1
0.781V
0.814V
0.851V
0.750V
www.rohm.com
© 2009 ROHM Co., Ltd. All rights reserved.
12/17
2009.04 - Rev.B