bd9132muv ROHM Co. Ltd., bd9132muv Datasheet - Page 5

• Manufacturer Part Number: bd9132muv
• Description: Step-down Switching Regulator
• Manufacturer: ROHM Co. Ltd.

●Operation
Current
RESET
Comp
V
SET
BD9132MUV is a synchronous rectifying step-down switching regulator that achieves faster transient response by employing
current mode PWM control system. It utilizes switching operation in PWM (Pulse Width Modulation) mode for heavier load,
while it utilizes SLLM (Simple Light Load Mode) operation for lighter load to improve efficiency.
○Synchronous rectifier
It does not require the power to be dissipated by a rectifier externally connected to a conventional DC/DC converter IC, and its
P.N junction shoot-through protection circuit limits the shoot-through current during operation, by which the power dissipation of
the set is reduced.
○Current mode PWM control
Synthesizes a PWM control signal with a inductor current feedback loop added to the voltage feedback.
・PWM (Pulse Width Modulation) control
・SLLM (Simple Light Load Mode) control
SW
OUT
The oscillation frequency for PWM is 1 MHz. SET signal form OSC turns ON a highside MOS FET (while a lowside MOS FET
is turned OFF), and an inductor current I
feedback control signal (SENSE: Voltage converted from I
signal if both input signals are identical to each other, and turns OFF the highside MOS FET (while a lowside MOS FET is turned
ON) for the rest of the fixed period. The PWM control repeat this operation.
When the control mode is shifted from PWM for heavier load to the one for lighter load or vise versa, the switching pulse is
designed to turn OFF with the device held operated in normal PWM control loop, which allows linear operation without voltage
drop or deterioration in transient response during the mode switching from light load to heavy load or vise versa.
I
Although the PWM control loop continues to operate with a SET signal from OSC and a RESET signal from Current Comp, it is
so designed that the RESET signal is held issued if shifted to the light load mode, with which the switching is tuned OFF and
the switching pulses are thinned out under control. Activating the switching intermittently reduces the switching dissipation
and improves the efficiency.
L
Fig.22 PWM switching timing chart
V
OUT
Gm Amp.
Level
Shift
ITH
Fig.21 Diagram of current mode PWM control
FB
L
SENSE
increases. The current comparator (Current Comp) receives two signals, a current
Current
Comp
PVCC
GND
GND
GND
I
V
RESET
L
(AVE)
OUT
OSC
SET
(AVE)
FB
SENSE
R Q
S
L
) and a voltage feedback control signal (FB), and issues a RESET
5/15
Current
RESET
Comp
Driver
Logic
V
SET
SW
OUT
I
L
Fig.23 SLLM
SW
I
L
TM
Not switching
switching timing chart
Load
V
OUT
FB
PVCC
SENSE
GND
GND
GND
0A
V
OUT
(AVE)