BD95242MUV Datasheet, PDF (9/21 Pages) Rohm – 2ch Switching Regurators for Desktop PC

Technical Note
● Explanation of Operation
The BD95242MUV is a 2ch synchronous buck regulator controller incorporating ROHM’s proprietary H³Reg^TM 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 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.
H³Reg^TM control
(Normal operation)
VOUT
2×REF
When VOUT falls to a reference voltage (2×REF), the
drop is detected, activating the H³Reg^TM CONTROLLA
system.
HG
tON= ^2×REF × ¹ [sec]・・・(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
2×REF
HG
LG
In SLLM (MCTL=”High voltage”), 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
2×REF
HG
LG
0A
In QLLM (MCTL=”Hiz or Middle voltage”), 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 doesn’t 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.
＊Attention: H³Reg^TM CONTROLLA monitors the supplying current
from capacitor to load, using the ESR of output
capacitor, and realize the rapid response. Bpass
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 C_OUT side of power
supply.
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9/20
2009.04 - Rev.B