BQ24400_16 Datasheet, PDF (14/27 Pages) Texas Instruments – Programmable NiCd/NiMH Fast-Charge Management IC

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
Charge qualification (including battery conditioning and charge suspended)
Fast charge (current regulation)
Top-off charge
Trickle maintenance charge (after fast charge)
Charge complete
Battery absent
Sleep mode
LED STATUS
1 Hz flash
Low
High impedance
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_IN needs to be high enough such that when V_IN 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_IN at which point the
bq24400 re-enters sleep mode. During sleep mode, the RC pin will be at V_SS potential. A typical sleep mode
waveform is shown in Figure 17.
14
Submit Documentation Feedback
Product Folder Link(s): bq24400
Copyright © 2001–2010, Texas Instruments Incorporated