Diodes APM8600 - Manual (Page 9)

APM8600
SINGLE CELL LINEAR LITHIUM BATTERY CHARGER
WITH 28V OVP AND PROGRAMMABLE CHARGE TIMER
APM8600
Document number: DS35140 Rev. 1 - 2
9 of 14
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December 2010
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UC
T
Functional Description (continued)
CT
The Charge Timer input on pin 5 allows selection of how long the system timers for Prequal, Charge and Top-off
states last. They are set by selecting the value of capacitor, C
CT
:
⎟
⎠
⎞
⎜
⎝
⎛
× =
nF 68
CCT
min 334 TCHARGE
⎟
⎠
⎞
⎜
⎝
⎛
× = =
nF 68
CCT
min 34.8 TTOPOFF TPREQUAL
The charge timer will hold its current value if the charging was stopped via the thermistor and continue when the battery is in
a valid temperature range for charging.
OUTPUTS
BAT
Pin 1 is the current-controlled charging output for the battery cell. It should be connected to the positive terminal of
the battery. The chip monitors the voltage on this pin. There should be a 2.2µF capacitor connected from BAT to GND.
POK
The POK flag on pin 10 is pulled low when a valid power input is available on DC. It will go high when no valid
power is available and the device will enter the Disable state.
CHG
The CHG flag at pin 11 is pulled low when the device is in the Charge state. It will be high in Prequal and Top-off
states. If the thermistor trips the circuit into the THM state (from Prequal or Charge states), CHG will hold its previous value.
FLT
The FLT flag on pin 14 indicates a battery fault, as determined by a time-out in either the Prequal or Charge states.
If the battery voltage does not reach 3V after the prequal timer (default 34.8mins), or does not reduce charging current to
7.5% after the charge timer (default 334mins), this indicates that the battery has failed or is failing and this will trigger the
FLT flag. This flag will not automatically reset, and can only be cleared by cycling the power input or the EN pin.