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

www.diodes.com

December 2010

© Diodes Incorporated

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. If the battery voltage falls below 4.05V then the device will automatically return to the Charge state.

EN

CHG

t

0V

0A

3V

4.2V