BD9329AEFJ Datasheet, PDF (10/16 Pages) Rohm – Simple Step-down Switching Regulator with Built-in Power MOSFET

BD9329AEFJ
(3) Design of Feedback Resistance constant
Set the feedback resistance as shown below.
V_OUT
R1
R2
0.9V
＋_ERR
－
FB
Fig.22
●Soft Start Function
COMP
ERRAMP
+
+_-
↓ ^{ISS 10µA}
↓ _SS
C_SS
Fig.23
●EN Function
VIN
EN
66 kΩ(typ.)
91 kΩ(typ.)
REN
EN
ON/OFF
Signal
Technical Note
VOUT =
R1 + R2
R2
 0.9
[V]
An adjustable soft-start function to prevent high inrush current
during start-up is available.
The soft-start time is set by the external capacitor connected to
SS pin.
The soft start time is given by;
TSS [s] = 2.2 x Css / ISS
Setting CSS= 0.1µF;
TSS= 2.2 x 0.1µ / 10µ = 22 [ms]
Please confirm the overshoot of the output voltage and inrush
current when deciding the SS capacitor value.
The EN terminal control IC’s shut down.
Leaving EN terminal open makes IC shutdown.
To start the IC, EN terminal should be connected to VIN or the
other power source output.
When the EN voltage exceed 1.2V (typ.), the IC start operating.
(Attention)
Chattering happens if standing lowering speed is slow
when standing of EN pin is lowered.
The reverse current in which the input side and the
pressure operation are done from the output side is
generated when chattering operates with the output
voltage remained, and there is a case to destruction.
Please set to stand within 100us when you control
ON/OFF by the EN signal.
This necessity doesn't exist when EN pin is connected
with VIN and EN is not controlled.
The control by open drain MOSFET shown in a left chart
is recommended.
Fig.24
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10/15
2011.02 - Rev.A