Datasheet

MCP73113/4
DS20002183E-page 22  2009-2013 Microchip Technology Inc.
6.1.1.2 Thermal Considerations
The worst-case power dissipation in the battery
charger occurs when the input voltage is at the
maximum and the device has transitioned from the
Preconditioning mode to the Constant-Current mode.
In this case, the power dissipation is:
Power dissipation with a 5V, ±10% input voltage
source, 500 mA ±10% and preconditioning threshold
voltage at 2.7V is:
EQUATION 6-1:
This power dissipation with the battery charger in the
DFN-10 package will result approximately 63C above
room temperature.
6.1.1.3 External Capacitors
The MCP73113/4 are stable with or without a battery
load. In order to maintain good AC stability in the
Constant-Voltage mode, a minimum capacitance of
1 µF is recommended to bypass the V
BAT
pin to V
SS
.
This capacitance provides compensation when there is
no battery load. In addition, the battery and
interconnections appear inductive at high frequencies.
These elements are in the control feedback loop during
Constant-Voltage mode. Therefore, the bypass
capacitance may be necessary to compensate for the
inductive nature of the battery pack.
A minimum of 1 µF, is recommended for both the output
capacitor and the input capacitor for typical applica-
tions.
TABLE 6-1: MLCC CAPACITOR EXAMPLE
Virtually any good quality output filter capacitor can be
used, independent of the capacitor’s minimum
Effective Series Resistance (ESR) value. The actual
value of the capacitor (and its associated ESR)
depends on the output load current. A 1 µF ceramic,
tantalum or aluminum electrolytic capacitor at the
output is usually sufficient to ensure stability.
6.1.1.4 Reverse-Blocking Protection
The MCP73113/4 provide protection from a faulted or
shorted input. Without the protection, a faulted or
shorted input would discharge the battery pack through
the body diode of the internal pass transistor.
PowerDissipation V
DDMAX
V
PTHMIN
–I
REGMAX
=
Where:
V
DDMAX
= the maximum input voltage
I
REGMAX
= the maximum fast charge current
V
PTHMIN
= the minimum transition threshold
voltage
PowerDissipation 5.5V 2.7V–550mA  1.54W==
MLCC
Capacitors
Temperature
Range
Tolerance
X7R -55C to +125C±15%
X5R -55C to +85C ±15%