MP2602 – 28V, 1A LINEAR LI-ION BATTERY CHARGER WITH TRICKLE CHARGE
MP2602 Rev.1.3 www.MonolithicPower.com 8
1/25/2010 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2010 MPS. All Rights Reserved.
Charge Status Indicator (CHG)
The MP2602 has an integrated charge status
pin that remains low while the battery is
charging. Once the charge current has reduced
to the battery full charge current threshold (I
BF
),
the CHG pin will become high impedance.
Under full charge conditions, certain systems
may draw a very narrow current pulse that
exceeds the IBF threshold. The
CHG indicator
may glitch. It is desirable to blank the
CHG glitch so that the system can properly
indicate full charge conditions to the end user.
A simple solution is to add a RC filter on the
CHG pin to filter out the possible CHG glitch,
as shown in Figure 5.
Negative Thermal Coefficient (NTC)
Thermistor
The MP2602 has a built-in NTC resistance
window comparator. If configured as the typical
application circuit as indicated in Figure 1, the
MP2602 will cease charging if R
NTC
<32.3kΩ or
R
NTC
>376.6kΩ. This represents a valid charging
temperature range of 0°C to 50°C for the
TH11-4H104F NTC resistor.
Thermal Protection
The MP2602 has proprietary thermal protection
to prevent the IC from overheating. When in
thermal protection mode, the charge current
becomes a saw-tooth waveform instead of a
DC current. The average current of the saw-
tooth waveform will be lower than the
programmed DC charge current to prevent the
IC from overheating. The frequency and
amplitude of the saw-tooth current waveform
can be altered by changing the capacitance
value connected to the SS pin. Operating in
thermal protection mode will slow down the
charging process. Lowering the input voltage
and enhancing thermal dissipation to the
environment can effectively prevent the IC from
going into thermal protection mode.
MP2602
BATT
ISET
IBF
SS
GND
10
9
8
7
6
IN
CHG
ACOK
EN
NTC
1
2
3
4
5
JP4
JP1 JP2 JP3
VIN
BAT
GND
GND
CHG
ACOK
EN
NTC
Figure 5—Filtered Charge Status with GPIO Connection
