BD9132MUV Datasheet, PDF (7/17 Pages) Rohm – Output 2A or More High Efficiency Step-down Switching Regulator with Built-in Power MOSFET

・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(TLATCH) or more. The output thus held tuned OFF may be recovered by restarting EN or by re-unlocking
UVLO.
EN
VOUT
Limit
IL
1msec
Output Current in non-control
1/2VOUT
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)
Output voltage OFF Latch
Output Current in control by limit value
(With fall of the output voltage, limit value goes down)
Standby mode
EN
Operated mode
Standby mode
Operated mode
Timer Latch
EN
Fig.25 Short-current protection circuit with time delay timing chart
●Switching regulator efficiency
Efficiency ŋ may be expressed by the equation shown below:
η= ^VOUT×IOUT ×100[%]= ^POUT ×100[%]=
POUT
×100[%]
Vin×Iin
Pin
POUT+PDα
Efficiency may be improved by reducing the switching regulator power dissipation factors P_Dα as follows:
Dissipation factors:
1) ON resistance dissipation of inductor and FET：PD(I²R)
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(I²R)=IOUT²Ã—(RCOIL+RON) (RCOIL[Ω]：DC resistance of inductor, RON[Ω]：ON resistance of FET, IOUT[A]：Output
current.)
2)PD(Gate)=Cgs×f×V (Cgs[F]：Gate capacitance of FET、f[H]：Switching frequency、V[V]：Gate driving voltage of FET)
Vin²Ã—CRSS×IOUT×f
3)PD(SW)=
IDRIVE
(CRSS[F]：Reverse transfer capacitance of FET、IDRIVE[A]：Peak current of gate.)
4)PD(ESR)=IRMS²Ã—ESR (IRMS[A]：Ripple current of capacitor、ESR[Ω]：Equivalent series resistance.)
5)PD(IC)=Vin×ICC (ICC[A]：Circuit current.)
7/16