SC4612 データシートの表示（PDF） - Semtech Corporation
部品番号
コンポーネント説明
メーカー
SC4612 Datasheet PDF : 24 Pages
| |||
SC4612
POWER MANAGEMENT
Applications Information (Cont.)
Gate Drive/Control
The SC4612 also provides integrated high current gate
drives for fast switching of large MOSFETs. The high side
and low side MOSFET gates could be switched with a peak
gate current of 1.7A. The higher gate current will reduce
switching losses of the larger MOSFETs.
The low side gate drives are supplied directly from the DRV.
The high side gate drives could be provided with the clas-
sical bootstrapping technique from DRV.
Cross conduction prevention circuitry ensures a non over-
lapping (30ns typical) gate drive between the top and bot-
tom MOSFETs. This prevents shoot through losses which
provides higher efficiency. Typical total minimum off time
for the SC4612 is about 30ns which will cause the maxi-
mum duty cycle at higher frequencies to be limited to lower
than 100%.
where,
VIN – Input voltage
L – Output inductance
RL – Load resistance
C – Output capacitance
ESRC – Output capacitor ESR
VS – Peak to peak ramp voltage
The classical Type III compensation network can be built
around the error amplifier as shown below:
C3
C2 R3
R2
C1
R1
-
OVERVOLTAGE PROTECTION
If the FB pin ever exceeds 600mV, the top side driver is
latched OFF, and the low side driver is latched ON. This
mode can only be reset by power supply cycling.
ERROR AMPLIFIER DESIGN
The SC4612 is a voltage mode buck controller that utilizes
an externally compensated high bandwidth error amplifier
to regulate output voltage. The power stage of the
synchronous rectified buck converter control-to-output
transfer function is as shown below:
GVD(s)
=
VIN
VS
×
1+
1+ s
sESRCC
L
RL
+ s2LC
+
Vref
Figure 1. Voltage mode buck converter compensation
network
The transfer function of the compensation network is as
follows:
(1+ s )(1+ s )
GCOMP (s)
=
ωI
s
⋅
(1 +
ωZ1
s )(1+
ωZ2
s
)
ωP1
ωP2
where,
ωZ1
=
1
R2C1
,
ωZ2
=
(R1
1
+ R3 )C2
,
ωo =
1
Lout × Cout
ωI
=
1
R1(C1 +
C3 ) ,
ωP1
=
1
R3C2
,
1
ωP2
=
R2
C1C3
C1 + C3
2007 Semtech Corp.
12
www.semtech.com
Share Link: 