Datasheet

 2014 Microchip Technology Inc. DS20005308B-page 17
MCP16331
To calculate the shunt resistance, the maximum I
BOOST
and I
Z
current are used at the minimum input voltage
(
Equation 4-2).
EQUATION 4-2: SHUNT RESISTANCE
V
Z
and I
Z
can be found on the Zener diode
manufacturer’s data sheet. Typically, I
Z
= 1 mA.
FIGURE 4-4: Series Regulator Boost Supply.
Series regulator applications use a Zener diode to drop
the excess voltage. The series regulator bias source
can be input or output voltage derived, as shown in
Figure 4-4. The boost supply must remain between
3.0V and 5.5V at all times for proper circuit operation.
R
SH
V
INMIN
V
Z
–
I
Boost
I
Z
+
------------------------------=
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
12V
15V to 50V
C
B
V
IN
C
IN
SW
BOOST
GND
EN
FB
L
V
IN
Boost Diode
FW Diode
2V
12V
VZ = 7.5V
VZ = 7.5V
V
OUT
R
TOP
R
BOT
C
OUT
MCP16331
MCP16331