BQ24721 Datasheet, PDF (39/48 Pages) Texas Instruments – ADVANCED MULTI-CHEMISTRY AND MULTI-CELL SYNCHRONOUS SWITCH-MODE CHARGER AND SYSTEM POWER SELECTOR

bq24721
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BIT
SBS SPEC
11 THERMISTOR_UR
12 ALARM_INHIBITED
13 POWER_FAIL
14 BATTERY PRESENT
15
(MSB)
AC_PRESENT
SLUS683 – NOVEMBER 2005
bq24721 SBS-Like
BATTERY VOLTAGE LOW (battery depleted)
(Note: Added Feature, Not part of SBS spec.)
This bit goes HI when the sensed BAT voltage is below the Battery Depleted threshold programmed by
the CONTROL register 0x12, bits 9,10, and 11. The programmed voltage is per cell, therefore multiply
by the number of cells set by the programmed battery voltage regulation DAC, register 0x15. [3 cell for
voltages between 12V-14.4V; and 4cell for voltages between 16V-19.2V].
FEATURE: the BATDRV is turned off when the battery voltage falls below the BATDEP threshold, and
the AC DRV is turned on if adapter is connected and had previously been in LEARN Cycle (bit 4 of
CONTROL register, 0x12).
VOR, VOLTAGE OUT OF RANGE (Note: moved function from bit7 of SBS spec) A HI indicates the
voltage DAC value from register 0x15 is out of the valid DAC voltage range. The IC either disables the
charge if below, or stays at the maximum possible programmed voltage (19.2 V) according to the
following: Valid voltage DAC range and effect.
• Valid voltages are 9 V, 12 –14.4 V, and 16 V–19.2 V. Intermediate programmed voltages
between Internal DAC values are truncated to the lower value to avoid over-voltage on battery.
• Programmed Voltages above max 19.2 V → Charger is enabled and the voltage regulation value
is set to the maximum 19.2 V.
• Programmed voltages below 12 V (except 9 V), and between 14.4–16V → Charger is disabled,
VOR bit is triggered, and an alarm sent to host.
• Programmed 9V (9000 mV = 2328 Hex) → Charger will regulate to 9 V output for battery
wake-up.
ADAPTER VOLTAGE BELOW BATTERY PACK VOLTAGE
(Note: Added Feature, Not part of SBS spec.) A HI on this bit indicates the battery voltage is above the
adapter voltage (BAT pin > ACP pin).
FEATURE: If the input falls below 150mV above the Battery voltage, the BYPASS FET immediately
turns off to prevent reverse discharge of the battery into the adapter. There is an 8 ms deglitch and 100
mV to hysteresis before allowing the BYPASS FET to turn-on.
BATTERY DETECTED ( through thermistor pin)
FEATURE: HI indicates a battery is detected through the TS pin. The TS pin voltage threshold is lower
than the TS battery detect threshold when this bit is HI. A LO means the TS voltage is above the TS
battery detect threshold. A resistor to ground inside the battery can be used to distinguish a good
battery from a bad battery as well. Programmed by a voltage divider pulled up to the VREF5 pin.
Note: VREF5 only comes up when ac is detected to conserve battery power, since no charging would
be required.
(Note: Added Feature. This could be used for detecting proper battery connected by selecting the
proper valid resistance. This is need to be ORed for dual battery pack chargers to make feature
optimal. This feature also is used as a safety feature to stop charge immediately when the battery pack
is not detected – this allows a faster response time by autonomously terminating charge when no
battery is detected, as opposed to waiting until the host detects the battery is removed and then
alerting the charger.
AC ADAPTOR DETECTED
This bit is HI when the adapter is detected (ACDET pin voltage is above the acdetect threshold of
2.4V). The voltage can be programmed by an external resistor divider from adapter input to ground.
Charge is not allowed until the ACDET threshold is exceeded. VREF5 LDO output only turns on when
the ACDET threshold is exceeded (adapter detected).
REGN POR and SMBus communication will begin soon after ACDET threshold is above 1.2 V and the
VCC is above 6.5 V.
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