BD9D321EFJ Datasheet, PDF (17/28 Pages) Rohm – 4.5V to 18V Input, 3.0A Integrated MOSFET 1ch Synchronous Buck DC/DC Converter

BD9D321EFJ
Datasheet
(2) Output Voltage Setting
The output voltage value can be set by the feedback resistance ratio.
V_OUT
R1
V_OUT
=
R₁ + R₂
R₂
× 0.765
[V]
FB Voltage
Reference
R2
Figure 31. Feedback Resistor Circuit
BD9D321EFJ can operate under the condition which satisfies
the following equation.
0.07 ≤ ^VOUT ≤ 0.65
V_IN
(3) Soft Start Setting
Turning the EN terminal signal High activates the soft start function. This causes the output voltage to rise gradually while
the current at startup is placed under control. This allows the prevention of output voltage overshoot and inrush current.
The rise time depends on the value of the capacitor connected to the SS terminal.
T_d = (C_SS × V_TH ) I_SS
T_SS  (C_SS  V_FB 1.15) I _SS
Td : Soft Start Delay Time
Tss : Soft Start Time
Css : Capacitor connected to Soft Start Time Terminal
VFB : FB Terminal Voltage (0.765V Typ)
VTH : Internal MOS threshold voltage (0.7V Typ)
Iss : Soft Start Terminal Source Current (2.0µA Typ)
With Css = 3300pF,
Td = ( 3300 pF x 0.7 V ) / 2.0 µA
= 1.16msec
Tss= ( 3300 pF x 0.765 V x 1.15 ) / 2.0 µA
= 1.45 msec
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TSZ22111•15•001
17/25
TSZ02201-0J3J0AC00490-1-2
07.Aug.2013 Rev.001