MP2605 – 28V, 1A LINEAR BATTERY CHARGER WITH TRICKLE CHARGE AND TIMER
MP2605 Rev. 1.0 www.MonolithicPower.com 10
1/19/2017 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2017 MPS. All Rights Reserved.
Charge Current vs.
1/R
CHG
1000
900
800
700
600
500
400
300
200
CHARGE CURRENT (mA)
0 0.20.1 0.3 0.4 0.6
0.7
0.5
Figure 3—Charge Current vs. 1/R
CHG
Resistance
The recommended resistance for programming
the charge current is 2.3kΩ<R
CHG
<11kΩ. The
open-drain pin
CHG is used to indicate
charging status. When the battery full condition
is met or any other condition prevents the
charger from charging,
CHG status will follow
the Table 2.
Timer Operation
The TMR pin is used to set the internal
oscillator frequency,
OSC
TMR
F
F11Hz
C
. The
on-chip timer will start to count down after initial
power-up or every time it is enabled. This timer
will limit the max trickle-charge time to 32768
internal oscillating cycles. If the charger stays in
trickle mode for longer than 32768 cycles, it will
be terminated and a fault state will be set to
CHG pin. After fault reporting, the charger can
be re-initiated only by recycling the power
supply or SHDN signal. If the charger
successfully goes through trickle charge within
the allowed time limit, it will start CC charging
and then CV charging. If the total charge time
exceeds 262144 cycles and the battery full has
not been qualified, the charger will be
terminated and a fault will also be set by
flashing
CHG pin at the rate of half the internal
oscillation frequency. This function prevents
charging a dead battery for prolonged duration.
The timer function can be disabled by shorting
TMR to ground.
Negative Thermal Coefficient (NTC) Thermistor
The MP2605 has a built-in NTC resistance
window comparator. If configured as the typical
application circuit as indicated in Figure 1, the
MP2605 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 MP2605 has proprietary thermal protection
to prevent the IC from overheating. When in
thermal protection mode, the average charge
current will be reduced to prevent the IC from
overheating. 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.
