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LTC4062

4062f

APPLICATIO S I FOR ATIO

charge the battery until the internal timer reaches 3 hours

(as set by CTIMER). During recharge cycles, the LTC4062

charges the battery until the internal timer reaches

1.5 hours. Figure 3 describes the operation of the LTC4062

charger when charge time termination is used.

Charge Current Termination

Connecting the TIMER pin to ground selects charge cur-

rent termination. With this method, the timer is disabled

and a resistor (RDET) must be connected from the IDET pin

to ground. IDETECT is programmed using the same equa-

tion stated in the previous section. The charge cycle

terminates when the charge current falls below IDETECT.

This condition is detected using an internal filtered com-

parator to monitor the IDET pin. When the IDET pin falls

below 100mV for longer than tTERM (typically 1.5ms),

charging is terminated.

When charging, transient loads on the BAT pin can cause

the IDET pin to fall below 100mV for short periods of time

before the DC current has dropped below the IDETECT

VCC

CHRG

PROG

IDET

CTIMER

0.1µF

VIN

4062 F02

BAT

500mA

TIMER

RDET

RPROG

LTC4062

GND

C/5

Figure 2. Time Termination Mode.

The Charge Cycle Ends After 3 Hours

Figure 3. State Diagram of a Charge Cycle

Using Charge Time Termination

CHARGE MODE

FULL CURRENT

CHRG STATE:

PULL-DOWN IF IBAT > IDETECT

Hi-Z IF IBAT < IDETECT

CHARGE TIME

ELAPSES

1/4 CHARGE TIME

ELAPSES

BAT < 4.1V

4062 F03

TRICKLE CHARGE MODE

1/10TH FULL CURRENT

BAT > 2.9V

BAT < 2.9V

2.9V < BAT < 4.1V

BAT > 4.1V

EN = 5V

UVLO CONDITION

STANDBY MODE

NO CHARGE CURRENT

CHRG STATE: Hi-Z

SHUTDOWN MODE

ICC DROPS TO 20µA

CHRG STATE: Hi-Z

CHRG STATE: PULL-DOWN

DEFECTIVE BATTERY

FAULT MODE

NO CHARGE CURRENT

CHRG STATE: PULSING

RECHARGE MODE

FULL CURRENT

CHRG STATE:

PULL-DOWN IF IBAT > IDETECT

Hi-Z IF IBAT < IDETECT

1/2 CHARGE

TIME ELAPSES

POWER ON

EN = 0V

OR UVLO

CONDITION

STOPS

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