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BD95242MUV_10 Datasheet, PDF (9/21 Pages) Rohm – 2ch Switching Regulator for Desktop PC | |||
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Technical Note
â Explanation of Operation
The BD95242MUV is a 2ch synchronous buck regulator controller incorporating ROHMâs proprietary H3RegTM CONTROLLA
control system. 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 regulatorâs 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.
H3RegTM control
(Normal operation)
VOUT
2ÃREF
When VOUT falls to a reference voltage (2ÃREF), the
drop is detected, activating the H3RegTM CONTROLLA
system.
HG
tON= 2ÃREF à 1 [sec]ã»ã»ã»(1)
VIN
f
HG output is determined by the formula above.
LG
(VOUT drops due to a rapid load change)
VOUT
Io
tON+α
When VOUT drops due to a rapid load change, and the
voltage remains below reference voltage after the
programmed tON time interval has elapsed, the system
quickly restores VOUT by extending the tON time, improving
the transient response.
HG
LG
Light Load Control
(SLLM)
VOUT
2ÃREF
HG
LG
In SLLM (MCTL=âHigh voltageâ), when the status of LG is OFF and
the coil current is within 0A (it flows to SW from VOUT.),
SLLM function is operated to prevent output next HG. The status
of HG is ON, when VOUT falls below reference voltage again.
0A
(QLLM)
VOUT
2ÃREF
HG
LG
0A
In QLLM (MCTL=âHiz or Middle voltageâ), when the status
of LG is OFF and the coil current is within 0A (it flows to
SW from VOUT.), QLLM function is operated to prevent
output next HG.
Then, VOUT falls below the output programmed voltage
within the programmed time (typ.=40µs), the status of HG
is ON. In case VOUT doesnât fall in the programmed time,
the status of LG is ON forcedly and VOUT falls. As a result,
he status of next HG is ON.
ï¼Attention: H3RegTM CONTROLLA monitors the supplying current
from capacitor to load, using the ESR of output
capacitor, and realize the rapid response. Bypass
capacitor used at each load (Ex. Ceramic capacitor)
COUT
Load
exercise the effect with connecting to each load side. Do
not put a ceramic capacitor on COUT side of power
supply.
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© 2010 ROHM Co., Ltd. All rights reserved.
9/20
2010.03 - Rev.C
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