BD9528AMUV Datasheet, PDF (15/30 Pages) Rohm – High Performance Regulators for PCs Main Power Supply for Notebook PCs(With Built-in Linear Regulator)

BD9528AMUV
Technical Note
Notes when waking up with CTL pin or VIN pin
If EN pin is High or short (or pull up resistor) to REG1 pin, IC starts up by switching CTL pin, the IC might fail to start
up (SCP function) with the reason below, please be careful of SS pin and REF pin capacitor capacity.
REG1 REG2
VIN
CTL
Inner
reference
circuit
REF
FB
BG
SCP circuit
Delay
SCP_REF
1ms(typ.)
SCP
SCP
SS
PWM
(Switching control signal)
CTL
(Vin)
REG1(5V)
REG2(3.3V)
SS
Inclination of REF is influenced
by the external condenser connected to REF.
SCP invalid for
SS has not reached 1.5V.
about 1.5V
SCP_REF
FB
REF
FB
SCP becomes valid from the point
SS reached 1.5V.
FB
FB
SCP is effective at SCP_REF>FB condition.
SCP protection (function) activates when output shorts
and FB falls below the activation standard of SCP.
SCP valid area
SCP is valid here,
because this is SCP valid
area and also because FB
fall below SCP_REF.
SCP will be effective with
EN=ON at this section.
SCP is valid here,but with FB
exceeding SCP_REF it is normally
activate-able area.
EN
Start up NG
SW
SCP
EN
Start up OK
SW
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© 2011 ROHM Co., Ltd. All rights reserved.
15/29
※ To be accurate,Delay occurs after SCP activating.
But this shows the relationship of each signals briefly.
2011.11 - Rev.A