BD91361MUV_12 Datasheet, PDF (13/23 Pages) Rohm – 2.7V to 5.5V, 4A 1ch Synchronous Buck Converter Integrated FET

BD91361MUV
Datasheet
Advantage 3 : ・Supplied in smaller package due to small-sized power MOS FET incorporated.
・Output capacitor Co required for current mode control: 22µF ceramic capacitor
・Inductance L required for the operating frequency of 1 MHz: 2.2µH inductor
・Incorporates FET + Boot strap diode
Reduces a mounting area required.
V CC
EN
VID<0>
VID<1>
VREF
SELECTOR
Gm Amp
+
Soft
Start
Current Comp
+
SLOPE
VCC ^CLK
RQ
S
UVLO
TSD
SCP
Current
Sense/
Protect
+
Driver
Logic
PVCC
VCC
BST
PVCC
Input
SW
Output
PGND
GND
20mm
15mm
Rf
Cf _{C BST} CIN
L
R1
R2
R ITH
CITH
Co
ADJ
R2
R1
ITH
RITH CITH
Fig.29 Example application
●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 PDα 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×V² (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.)
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02.MAR.2012 Rev.001