Microchip Technology ADM00352 Data Sheet
MCP16301/H
DS20005004C-page 14
2011-2013 Microchip Technology Inc.
FIGURE 4-3:
Shunt and External Boost Supply.
Shunt Boost Supply Regulation is used for low output
voltage converters operating from a wide ranging input
source. A regulated 3.0V to 5.5V supply is needed to
provide high-side drive bias. The shunt uses a Zener
diode to clamp the voltage within the 3.0V to 5.5V
range using the resistance shown in
voltage converters operating from a wide ranging input
source. A regulated 3.0V to 5.5V supply is needed to
provide high-side drive bias. The shunt uses a Zener
diode to clamp the voltage within the 3.0V to 5.5V
range using the resistance shown in
To calculate the shunt resistance, the boost drive
current can be estimated using
current can be estimated using
.
I
BOOST_TYP
for 3.3V Boost Supply = 0.6 mA
I
BOOST_TYP
for 5.0V Boost Supply = 0.8 mA
EQUATION 4-1:
BOOST CURRENT
C
B
V
OUT
V
IN
C
IN
C
OUT
SW
EN
FB
L
R
TOP
V
IN
FW Diode
2V
12V
VZ = 5.1V
C1
R
SH
C
B
V
OUT
V
IN
C
IN
C
OUT
SW
BOOST
GND
EN
FB
L
R
TOP
R
BOT
V
IN
Boost Diode
FW Diode
2V
12V
3.0V to 5.5V External Supply
R
BOT
MCP16301/H
MCP16301/H
Boost Diode
BOOST
GND
I
BOOST
I
BOOST_TYP
1.5
mA
=