BD8961NV ROHM Co. Ltd., BD8961NV Datasheet - Page 7

• Manufacturer Part Number: BD8961NV
• Description: Low Noise Step-down Switching Regulator
• Manufacturer: ROHM Co. Ltd.

●Switching regulator efficiency
Efficiency ŋ may be expressed by the equation shown below:
η=
Efficiency may be improved by reducing the switching regulator power dissipation factors P
Dissipation factors:
1) ON resistance dissipation of inductor and FET：PD(I
2) Gate charge/discharge dissipation：PD(Gate)
3) Switching dissipation：PD(SW)
4) ESR dissipation of capacitor：PD(ESR)
5) Operating current dissipation of IC：PD(IC)
1)PD(I
current.)
2)PD(Gate)=Cgs×f×V (Cgs[F]：Gate capacitance of FET, f[Hz]：Switching frequency, V[V]：Gate driving voltage of FET)
3)PD(SW)=
4)PD(ESR)=I
5)PD(IC)=Vin×I
・Short-current protection circuit with time delay function
Turns OFF the output to protect the IC from breakdown when the incorporated current limiter is activated continuously for
the fixed time(T
UVLO.
V
Output Short circuit
OUT
2
Vin×Iin
R)=I
Threshold Voltage
×I
OUT
Vin
OUT
RMS
2
2
×(R
CC
I
×C
L
2
×ESR (I
LATCH
V
×100[%]=
Limit
OUT
EN
COIL
RSS
I
Standby
(I
I
DRIVE
L
mode
CC
) or more. The output thus held tuned OFF may be recovered by restarting EN or by re-unlocking
×I
+R
[A]：Circuit current.)
OUT
ON
EN
RMS
Fig.24 Short-current protection circuit with time delay timing chart
) (R
P
×f
OUT
Pin
[A]：Ripple current of capacitor, ESR[Ω]：Equivalent series resistance.)
COIL
×100[%]=
(C
[Ω]：DC resistance of inductor, R
RSS
t1<T
[F]：Reverse transfer capacitance of FET, I
Operating mode
LATCH
P
OUT
P
OUT
2
R)
+P
7/15
D
α
×100[%]
t2=T
LATCH
Timer latch
ON
[Ω]：ON resistance of FET, I
Standby
Output OFF
latch
mode
DRIVE
EN
D
α as follows:
Operating mode
[A]：Peak current of gate.)
OUT
[A]：Output