Datasheet

 2014-2016 Microchip Technology Inc. DS20005308C-page 15
MCP16331
4.2.5 ALTERNATIVE BOOST BIAS
For 3.0V to 5.0V output voltage applications, the boost
supply is typically the output voltage. For applications
with V
OUT
< 3.0V or V
OUT
> 5.0V, an alternative boost
supply can be used.
Alternative boost supplies can be from the input, input
derived, output derived or an auxiliary system voltage.
For low-voltage output applications with unregulated
input voltage, a shunt regulator derived from the input
can be used to derive the boost supply. For applications
with high output voltage or regulated high input voltage,
a series regulator can be used to derive the boost
supply. In case the boost is biased from an external
source while in shutdown, the device will draw slightly
higher current.
FIGURE 4-3: Shunt and External Boost Supply.
C
B
V
OUT
V
IN
C
IN
C
OUT
SW
BOOST
GND
EN
FB
L
R
TOP
V
IN
Boost Diode
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
MCP16331
MCP16331