bd8962muv ROHM Co. Ltd., bd8962muv Datasheet - Page 7

• Manufacturer Part Number: bd8962muv
• Description: 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
2)PD(Gate)=Cgs×f×V (Cgs[F]：Gate capacitance of FET, f[H]：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
Standby mode
V
OUT
2
Vin×Iin
V
Limit
R)=I
OUT
EN
I
×I
L
OUT
Vin
OUT
RMS
LATCH
2
2
EN
×(R
CC
×C
2
×ESR (I
×100[%]=
) or more. The output thus held tuned OFF may be recovered by restarting EN or by re-unlocking UVLO.
I
COIL
RSS
(I
DRIVE
Output Current in non-control
CC
×I
+R
[A]：Circuit current.)
OUT
ON
RMS
Fig.24 Short-current protection circuit with time delay timing chart
) (R
P
×f
OUT
Pin
Operated mode
[A]：Ripple current of capacitor, ESR[Ω]：Equivalent series resistance.)
Output Current in control by limit value
(With fall of the output voltage, limit value goes down)
COIL
×100[%]=
(C
[Ω]：DC resistance of inductor, R
RSS
[F]：Reverse transfer capacitance of FET, I
1/2V
P
OUT
OUT
P
OUT
2
R)
+P
D
α
7/15
1msec
×100[%]
Timer Latch
Standby mode
ON
Output voltage OFF Latch
[Ω]：ON resistance of FET, I
EN
DRIVE
Until output voltage goes up the half of Vo or over,
timer latch is not operated.
(No timer latch, only limit to the output current)
Operated mode
D
α as follows:
[A]：Peak current of gate.)
OUT
[A]：Output current.)