Diodes APM8601 - Manual (Page 10)

APM8601
DUAL CHANNEL SINGLE CELL LINEAR LITHIUM BATTERY
CHARGER WITH 28V OVP and PROGRAMMABLE CHARGE
TIMER
APM8601
Document number: DS35138 Rev. 1 - 2
10 of 14
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December 2010
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UC
T
Functional Description (continued)
CHARGING PROCESS DESCRIPTION
The charging process is as follows, working through the state diagram.
The device will begin in the Disable state as the input power supply ramps from 0V. Once the input power supply has got into
the valid range (4.15V – 7V), and the device is enabled then it will enter the Prequal state. This state allows for slow charging
of a severely discharged battery. If the battery is already partially charged then the condition to move into the Charge state is
met. If it is not then the slow charge will increase the battery voltage until it can enter the Charge state, or if the voltage does
not rise sufficiently before the charge timer runs out (set using the capacitor on the CT pin) then the device will go into the
Fault
state, indicating that the battery cell may be damaged or has failed and is not taking charge. In the Prequal state the
battery temperature can be monitored with a 10k NTC thermistor connected to the THM pin, and if the battery temperature
goes out of range (above ~50°C or below ~0°C, depending on thermistor choice) then charging will be suspended with the
device going into the THM state.
Once the battery has charged to a level of 3V, the device enters the Charge state, allowing faster charging of the battery in
its normal voltage range, with 10 times the current used in the Prequal state. For information on setting the charge currents,
see the functional description of the SETI pin. Again, the battery temperature is monitored and charging will be suspended if
the temperature goes out of range. The Charge state will last until the current drawn by the battery drops to 7.5% of the full
charge current. The device will then enter the Top-Off state, maintaining battery voltage and providing top-off charging
current for the time defined by the C
T
value. Once that timer completes, the device will enter the Done state, with zero battery
current. If the battery voltage falls below 4.05V then the device will automatically return to the Charge state.
DONE TOP-OFF CHARGE PREQUAL DISABLE
EN
CHG
V
BAT
I
BAT
t
0V
I
PREQUAL
150/R
SETI
0A
I
CHARGE
1500/R
SETI
3V
4.2V
I
TOPOFF
112.5/R
SETI