BD9528MUV ROHM [Rohm], BD9528MUV Datasheet - Page 14

• Manufacturer Part Number: BD9528MUV
• Description: Main Power Supply ICs for Note PC(Linear Regulator Integrated)
• Manufacturer: ROHM [Rohm]

●Explanation of Operation
H
(Normal operation)
(VOUT drops due to a rapid load change)
(when VIN drops)
If VIN voltage drops because of the battery voltage fall, ontime t
t
if VIN still drops and
more, as a result output voltage drops. In
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BD9528MUV
ON
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3
Reg
The BD9528MUV is a 2ch synchronous buck regulator controller incorporating ROHM’s proprietary H
control system. Because controlling of output voltage by a comparator, high response is realized with not relying on the
switching frequency. And, when VOUT drops due to a rapid load change, the system quickly restores VOUT by extending
the TON time interval. Thus, it serves to improve the regulator’s transient response. Activating the Light Load Mode will also
exercise Simple Light Load Mode (SLLM) control when the load is light, to further increase efficiency.
=VOUT/VIN×I/f and t
REF
HG
REF
LG
FB
FB
HG
TM
LG
Io
control
VIN
HG
LG
FB
REF
FB
reference
Internal
t
voltage
OFF equals to
REF
t
ON
1
t
OFF
OFF
1
Comparator for
output voltage
=(VIN-VOUT)/VIN×f so that
control
t
minoff (tminoff：Minimum OFF time, regulated inside IC) , because t
H
t
3
ON
t
Reg
ON
2
+α
t
OFF
TM
2
system, lengthening t
A
B
Transient
Vout/Vin
Circuit
Circuit
t
ON
3
t
t
ON lengthen and tOFF shorten to keep output voltage constant. However,
OFF
14/33
3
ON and offtime tOFF
ON time than regulated tON (lengthen tON time until
When FB falls to a reference voltage (REF), the drop is
detected, activating the H
system.<Route A>
（
When V
voltage remains below reference voltage after the
programmed t
comparator for output voltage control =H), the system
quickly restores V
improving the transient response.<Route B> After VOUT
restores (FB=REF), HG turns to be OFF, and it goes back
to a normal operation.
HG output is determined by the formula above.
After the status of HG is OFF, LG go on outputting until
output voltage become FB=REF.
t
t
ON
ON
4
=
Driver
t
OUT
OFF
4
VOUT
=
VIN
drops due to a rapid load change, and the
t
Output voltage drops
OFF
is determined by the following formula:
ON
HG
SW
LG
3
time interval has elapsed (Output of a
VIN
OUT
× 1
H
by extending the t
3
Reg
f
3
REG CONTROLLA
TM
[sec]・・・(1)
FB=REF
t
ON
VOU
OFF cannot shorten any
T
4+α
）
t
OFF
Technical Note
2010.03 - Rev.A
3
REG CONTROLLA
ON
4
=
t
time,
OFF
FB＞REF)
3