BQ24747 Datasheet, PDF (28/36 Pages) Texas Instruments – SMBus-Controlled Level 2 Multi-Chemistry Battery Charger With Input Current Detect Comparator and Charge Enable Pin

bq24747
SLUS988 – OCTOBER 2009 ............................................................................................................................................................................................. www.ti.com
OPERATING CONDITIONS
The bq24747 has the following operating states:
• Adapter Present: When DCIN is greater than 4 V and ACIN is greater than 2.4 V, the adapter is considered
to be present. In this condition, both the VDDP and VREF function properly and battery charging is allowed:
– Charging: The total bq24747 quiescent current when charging is 1 mA (max) plus the current required to
drive the MOSFETs.
– Not Charging: To disable charging, set either ChargeCurrent() or ChargeVoltage() to zero. When the
adapter is present and charging is disabled, the total adapter quiescent current is less than 1.5 mA and
the total battery quiescent current is less than 200 μA.
• Adapter Absent (Power Fail): When VCSSP is less than VCSON + 150 mV, the bq24747 is in the power-fail
state, since the DC-DC converter is in dropout. The charger does not attempt to charge in the power-fail
state. Typically, this occurs when the adapter is absent. When the adapter is absent, the total bq24747
quiescent battery current is less than 1μA (max).
• VDDSMBus Undervoltage (POR): When VDD is less than 2.5 V, the VDD supply is in an undervoltage state
and the internal registers are in their power-on-reset (POR) state. The SMBus interface does not respond to
commands. When VDD rises above 2.7 V, the bq24747 is in a power-on-reset state. Charging does not occur
until the ChargeVoltage() and ChargeCurrent() commands are sent. When VDD is greater than 2.5 V, SMBus
register contents are preserved.
The bq24747 allows charging under the following conditions:
1. DCIN > 4 V, VDDP > 4 V, VREF > 3.1 V
2. VCSSP > VCSON + 250 mV (15 mV falling threshold)
3. VDDSMBus > 2.5 V
Charge Termination for Li-Ion or Li-Polymer
The primary termination method for Li-Ion and Li-Polymer is minimum current. Secondary temperature
termination also provides additional safety. The host controls the charge initiation and the termination. A battery
pack gas gauge assists the hosts on setting the voltages and determining when to terminate based on the
battery pack state of charge.
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