Datasheet

bq24400

SLUS498A –SEPTEMBER 2001–REVISED FEBRUARY 2010

www.ti.com

Charge Status Display

The charge status is indicated by open-drain output LED. Table 5 summarizes the display output of the bq24400.

A temperature fault or timer expiring changes the charge state immediately (according to Figure 2) and will thus

change the LED status immediately and accordingly.

Table 5. Charge Status Display

bq24400 CHARGE STATE LED STATUS

Charge qualification (including battery conditioning and charge suspended) 1 Hz flash

Fast charge (current regulation) Low

Top-off charge

Trickle maintenance charge (after fast charge)

Charge complete High impedance

Battery absent

Sleep mode

Sleep Mode

The bq24400 features a sleep mode for low power consumption. This mode is enabled when the voltage at the

BAT pin is above the low-power-mode threshold, V

SLP

. During sleep mode, the bq24400 shuts down all

unnecessary internal circuits, drives the LED output to high-impedance state, and drives the MOD pin low.

Restoring BAT below the V

MCV

threshold initiates the IC and starts a fast-charge cycle. Normally, the bq24400

only enters sleep mode when there is no battery connected on the output and the charger is idling with nothing to

charge. In addition, V

needs to be high enough such that when V

is present on the output, V

BAT

would be

greater than V

SLP

. In sleep mode, the output voltage will decay to V

MCV

at which point the bq24400 turns on and

pulses the MOD pin several times. With no battery connected, the output will rise to near V

at which point the

bq24400 re-enters sleep mode. During sleep mode, the RC pin will be at V

potential. A typical sleep mode

waveform is shown in Figure 17.

Product Folder Link(s): bq24400