BD9A301MUV-LB Datasheet, PDF (23/35 Pages) Rohm – This is the product guarantees long time support in Industrial market

BD9A301MUV-LB
Datasheet
Charge current to output capacitor I_CAP can be expressed in the following method.
I _CAP
C _OUT
C _LOAD
T_SS
V_{OUT [A]}
Computation with VIN= 5V, VOUT= 3.3V, L= 1.5µH, switching frequency F_OSC= 800kHz(Min), Output capacitor COUT=
44µF, Soft Start time TSS= 0.5ms(Min), load current during soft start IOSS= 2A the method is as below.
C _LOAD max
3.8 ‐ I_OSS ‐ ΔI _L /2
V_OUT
T_{SS ‐ COUT  157.9 μF}
If the value of C_LOAD is large, and cannot meet the above equation,
C _LOAD max
1.5 ‐ I_OSS ‐ ΔI _L /2
V_OUT I _SS
V _FB
C _SS ‐ C _OUT
Adjust the value of the capacitor C_SS to meet the above formula.
(Refer to the following items (3) Soft Start Setting equation of time T_SS and soft-start value of the capacitor to be
connected to the C_SS.)
Computation with VIN = 5V, VOUT = 3.3V, L = 1.5µH, load current during soft start IOSS = 2A, switching frequency FOSC=
800kHz (Min), Output capacitor COUT = 44µF, VFB = 0.792V(Max), ISS = 3.6µA(Max), A capacitor connected to the CSS if
you want to connect the CLOAD = 220uF is the following equation.
C _SS
V_OUT I _SS
3.8 ‐ I_OSS ‐ ΔI _L /2 V _FB
C _LOAD C _OUT
2.97 ^[nF^]
2. Output Voltage Setting
The output voltage value can be set by the feedback resistance ratio.
V_OUT
R1
FB ^{gm Amp}
－
R2
＋
0.8V
VOUT
R1 R2
R2
0.8 ^[V^]
Figure 51. Feedback Resistor Circuit
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_SS C _SS V_FB /I _SS
T_SS : Soft Start Time
C _SS : Capacitor connected to Soft Start Time Terminal
V_FB : FB Terminal Voltage (0.8V (Typ))
I _SS : Soft Start Terminal Source Current (1.8μA(Typ))
with C _SS
T_SS
0.01μF,
0.010 [μF]
4.44 ^[msec ^]
0.8 ^[V^])/1.8 [μA]
Turning the EN terminal signal high with the SS terminal open (no capacitor connected) or with the terminal signal high
causes the output voltage to rise in 1msec (Typ).
www.rohm.com
© 2014 ROHM Co., Ltd. All rights reserved.
TSZ22111 • 15 • 001
23/32
TSZ02201-0J3J0AJ00680-1-2
20.Aug.2014 Rev.001