BQ24170 Datasheet, PDF (20/35 Pages) Texas Instruments – 1.6-MHz Synchronous Switch-Mode Li-Ion and Li-Polymer Stand-Alone Battery Charger

bq24170
bq24172
SLUSAD2A – NOVEMBER 2010 – REVISED NOVEMBER 2010
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Pull TTC pin to AGND to disable both termination and fast charge safety timer (reset timer). Pull TTC pin to
VREF to disable the safety timer, but allow charge termination.
POWER UP
The charge uses a SLEEP comparator to determine the source of power on the AVCC pin, since AVCC can be
supplied either from the battery or the adapter. With the adapter source present, if the AVCC voltage is greater
than the SRN voltage, the charger exits SLEEP mode. If all conditions are met for charging, the charger then
starts charge the battery (see the Enabling and Disabling Charging section). If SRN voltage is greater than
AVCC, the charger enters low quiescent current SLEEP mode to minimize current drain from the battery. During
SLEEP mode, the VREF output turns off and the STAT pin goes to high impedance.
If AVCC is below the UVLO threshold, the device is disabled.
INPUT UNDER-VOLTAGE LOCK-OUT (UVLO)
The system must have a minimum AVCC voltage to allow proper operation. This AVCC voltage could come from
either input adapter or battery, since a conduction path exists from the battery to AVCC through the high side
NMOS body diode. When AVCC is below the UVLO threshold, all circuits on the IC are disabled.
INPUT OVER-VOLTAGE/UNDER-VOLTAGE PROTECTION
ACOV provides protection to prevent system damage due to high input voltage. In bq24170/172, once the
voltage on OVPSET is above the 1.6V ACOV threshold or below the 0.5V ACUV threshold, charge is disabled
and input MOSFETs turn off. The bq24170/172 provides flexibility to set the input qualification threshold.
ENABLE AND DISABLE CHARGING
The following conditions have to be valid before charging is enabled:
• ISET pin above 120mV
• Device is not in Under-Voltage-Lock-Out (UVLO) mode (i.e. V_AVCC > V_UVLO)
• Device is not in SLEEP mode (i.e. V_AVCC > V_SRN)
• OVPSET voltage is between 0.5V and 1.6V to qualify the adapter
• 1.5s delay is complete after initial power-up
• REGN LDO and VREF LDO voltages are at correct levels
• Thermal Shut down (TSHUT) is not valid
• TS fault is not detected
• ACFET turns on (See System Power Selector for details)
One of the following conditions stops on-going charging:
• ISET pin voltage is below 40mV
• Device is in UVLO mode
• Adapter is removed, causing the device to enter SLEEP mode
• OVPSET voltage indicates the adapter is not valid
• REGN or VREF LDO voltage is overloaded
• TSHUT temperature threshold is reached
• TS voltage goes out of range indicating the battery temperature is too hot or too cold
• ACFET turns off
• TTC timer expires or pre-charge timer expires
SYSTEM POWER SELECTOR
The IC automatically switches adapter or battery power to the system load. The battery is connected to the
system by default during power up or during SLEEP mode. When the adapter plugs in and the voltage is above
the battery voltage, the IC exits SLEEP mode. The battery is disconnected from the system and the adapter is
connected to the system after exiting SLEEP. An automatic break-before-make logic prevents shoot-through
currents when the selectors switch.
The ACDRV is used to drive a pair of back-to-back n-channel power MOSFETs between adapter and ACP with
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