MCP1624T-I View Datasheet(PDF) - Microchip Technology
Part Name
Description
MFG CO.
'MCP1624T-I' PDF : 30 Pages View PDF
5.0 APPLICATION INFORMATION
5.1 Typical Applications
The MCP1623/24 synchronous boost regulator
operates over a wide input voltage and output voltage
range. The power efficiency is high for several decades
of load range. Output current capability increases with
input voltage and decreases with increasing output
voltage. The maximum output current is based on the
N-Channel peak current limit. Typical characterization
curves in this data sheet are presented to display the
typical output current capability.
5.2 Adjustable Output Voltage
Calculations
To calculate the resistor divider values for the
MCP1623/24, Equation 5-1 can be used, where RTOP
is connected to VOUT, RBOT is connected to GND and
both are connected to the FB input pin.
EQUATION 5-1:
RTOP
=
RBOT
V----O----U---T-
VFB
–
1
EXAMPLE 1:
VOUT = 3.3V
VFB = 1.21V
RBOT = 309 k
RTOP = 533.7 k (Standard Value = 536 k)
EXAMPLE 2:
VOUT = 5.0V
VFB = 1.21V
RBOT = 309 k
RTOP = 967.9 k (Standard Value = 976 k)
There are some potential issues with higher value
resistors. For small surface mount resistors,
environment contamination can create leakage paths
that significantly change the resistor divider that effect
the output voltage. The FB input leakage current can
also impact the divider and change the output voltage
tolerance.
MCP1623/24
5.3 Input Capacitor Selection
The boost input current is smoothed by the boost
inductor reducing the amount of filtering necessary at
the input. Some capacitance is recommended to
provide decoupling from the source. Low ESR X5R or
X7R are well suited since they have a low-temperature
coefficient and small size. For most applications,
4.7 µF of capacitance is sufficient at the input. For
high-power applications that have high source
impedance or long leads, connecting the battery to the
input 10 µF of capacitance is recommended. Additional
input capacitance can be added to provide a stable
input voltage.
Table 5-1 contains the recommended range for the
input capacitor value.
5.4 Output Capacitor Selection
The output capacitor helps provide a stable output
voltage during sudden load transients and reduces the
output voltage ripple. As with the input capacitor, X5R
and X7R ceramic capacitors are well suited for this
application.
The MCP1623/24 is internally compensated so output
capacitance range is limited. See Table 5-1 for the
recommended output capacitor range.
While the N-Channel switch is on, the output current is
supplied by the output capacitor COUT. The amount of
output capacitance and equivalent series resistance
will have a significant effect on the output ripple
voltage. While COUT provides load current, a voltage
drop also appears across its internal ESR that results
in ripple voltage.
EQUATION 5-2:
IOUT
=
COUT
d-d---V-t-
Where:
dV = ripple voltage
dt = On time of the N-Channel switch
(D x 1/FSW)
Table 5-1 contains the recommended range for the
input and output capacitor value.
TABLE 5-1: CAPACITOR VALUE RANGE
Min.
Max.
CIN
4.7 µF
—
COUT
10 µF
100 µF
2010-2016 Microchip Technology Inc.
DS40001420D-page 15
Share Link: 
