BD9109FVM-LB Datasheet, PDF (3/23 Pages) Rohm – Synchronous Buck Converter Integrated FET

BD9109FVM-LB
Description of Block
BD9109FVM-LB 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^TM (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
The oscillation frequency for PWM is 1 MHz. SET signal form OSC turns ON a P-channel MOS FET (while a
N-channel MOS FET is turned OFF), and an inductor current IL increases. The current comparator (Current Comp)
receives two signals, a current feedback control signal (SENSE: Voltage converted from IL) and a voltage feedback
control signal (FB), and issues a RESET signal if both input signals are identical to each other, and turns OFF the
P-channel MOS FET (while a N-channel MOS FET is turned ON) for the rest of the fixed period. The PWM control
repeat this operation.
Conventional product (VOUT of which is 3.3 volts)
BD9109FVM-LB (Load response IO=100mA→600mA)
VOUT
228mV
VOUT
110mV
IOUT
IOUT
Voltage drop due to sudden change in load was reduced by about 50%.
Figure 4. Comparison of transient response
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21.Feb.2014 Rev.002