Datasheet

Test Procedures

2-3

Test Summary

The bq24001/2/3/7 enters preconditioning mode if the battery is below the

LowV threshold. In this mode, the bq24001/2/3/7 trickle-charges with

approximately 65 mA for approximately 23 minutes. If the battery does not

reach the LowV threshold during this period, then the charge current is

terminated and the bq24001/2/3/7 enters fault mode. The red LED flashes

when in fault mode. This feature may be tested by removing input power,

replacing the battery with a 30–40-Ω, 0.25-W resistor from BAT+ to DC–, and

applying power (Vin) for more than 23 minutes. Fault mode is reset by toggling

input power or enable pin.

Once the battery charges to the LowV-stop threshold, the battery enters fast-

charge mode and charges at the programmed 1-A level. Program charge level

may be changed by adjusting R3

R3 +

0.10 V

chg

The battery remains at the fast-charge mode until either the selected time

expires or the battery charges to the selected regulation voltage. The bq24007

IC’s 3/4.5/6 hour timer can be disabled which disables termination.

The time-out feature is tested by using a 10–14-Ω, 3-W resistor in place of the

battery. Apply the resistor after the unit is powered.

If the battery discharges down to the HighV threshold, the charger starts fast

charging. The refresh feature may be tested by charging a battery to

completion (I

term

+ 23 minutes) and, without disconnecting the battery,

installing a 3–5-Ω, 10-W resistor in parallel with the battery. The regulator

should start charging once the HIGHV threshold is reached. Note that battery

is still charging for another 23 minutes after the LED turns off. If a load (>Iterm)

is applied before the 23 minutes has timed out then the load will reset the 23

minute timer.

The circuit has an overvoltage comparator for added protection. If the battery

voltage exceeds this threshold for 330 ms, then the charger goes into fault

mode. This may be tested by connecting an external power supply in place of

the battery and adjusting the voltage above the threshold.