BD9528AMUV Datasheet, PDF (14/30 Pages) Rohm – High Performance Regulators for PCs Main Power Supply for Notebook PCs(With Built-in Linear Regulator)

BD9528AMUV
Light Load Control
(SLLM)
FB
HG
LG
0A
Technical Note
In SLLM, 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 FB falls below reference voltage again.
(QLLM)
FB
REF
HG
LG
0A
In QLLM, 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, FB falls below the output programmed voltage within
the programmed time (typ=40μs), the status of HG is ON.
In case FB 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.
MCTL1
L
L
H
MCTL2
L
H
X
Control mode
SLLM
QLLM
PWM
Running
PWM
PWM
PWM
*Attention: H³Reg^TMCONTROLLA 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) exercises the effect with connecting to each
load side. Do not put a ceramic capacitor on COUT side of
power supply.
●Timing Chart
• Soft Start Function
EN
Tss
SS
VOUT
IIN
The BD9528AMUV operates in PWM mode until SS pin
reaches cramp voltage (2.5V), regardless of the control
mode setting, in order to operate stable during the
operation.
COUT
Load
Soft start is exercised with the EN pin set high. Current
control takes effect at startup, enabling a moderate
output voltage “ramping start.” Soft start timing and
incoming current are calculated with formulas (2) and
(3) below.
Soft start time
TSS = ^REF×Css [sec] ・・・(2)
2.3μA(typ)
Incoming current
IIN = ^Co×VOUT [A] ・・・(3)
Tss
(Css: Soft start capacitor; Co: Output capacitor)
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14/29
2011.11 - Rev.A