bd95500muv ROHM Co. Ltd., bd95500muv Datasheet - Page 14

• Manufacturer Part Number: bd95500muv
• Description: Switching Regulator With Mosfet Ddr-sdram Cores
• Manufacturer: ROHM Co. Ltd.

© 2010 ROHM Co., Ltd. All rights reserved.
BD95500MUV
www.rohm.com
6. Setting standard voltage (REF)
5.Setting frequency
R1
R2
VREG
V
V
Outside
voltage
OUT
3000
2500
2000
1500
1000
OUT
500
REF
REF
1200
1000
800
600
400
200
0
0
0
0
VIN=5V
50
50
12V
16V
19V
7V
Resistance [kΩ]
RFS [kΩ]
100
CONTROLLA
CONTROLLA
100
H
H
3
3
Reg
Reg
V
V
IN
VIN=5V
IN
REF=1.8V
150
150
TM
TM
12V
16V
19V
7V
200
200
R
S
R
S
Q
Q
14/20
The On Time (t
resistance value connected to FS pin.
But actually SW rising time and falling time come up
due to influence of the external MOSFET gate capacity
or switching speed and t
The frequency is determined by the following formula
after t
Consequently, total frequency becomes lower than the
formula above.
T
current 0A area in continuous mode.
This frequency becomes lower than setting frequency.
It is recommended to check the steady frequency in
large current area (at the point where the coil current
doesn’t back up).
It is available to synchronize setting the reference
voltage (REF) with outside supply voltage [V] by using
outside power supply voltage.
It is available to set the reference voltage (REF) by the
resistance division value from VREG in case it is not
set REF from an external power supply.
REF=
ON
F=
is also influenced by Dead Time around the output
ON
V
R1+R2
, input current and the REF voltage are fixed.
IN
REF
R2
×t
ON
ON
×VREG [V]・・・(14)
) at steady state is determined by
・・・(13)
ON
is increased.
Technical Note
2010.05 - Rev.C