Datasheet

bq24616
SLUSA49B –APRIL 2010– REVISED OCTOBER 2011 www.ti.com
Power Up
The bq24616 uses a SLEEP comparator to determine the source of power on the VCC pin, because VCC can be
supplied either from the battery or the adapter. If the VCC voltage is greater than the SRN voltage, the bq24616
enables the ACFET and disables BATFET. If all other conditions are met for charging, the bq24616 then
attempts to charge the battery (see Enable and Disable Charging Enable and Disable Charging). If the SRN
voltage is greater than VCC, indicating that the battery is the power source, the bq24616 enables BATFET, and
enters a low-quiescent-current (<15-μA) SLEEP mode to minimize current drain from the battery.
If VCC is below the UVLO threshold, the device is disabled, ACFET turns of, and BATFET turns on.
Enable and Disable Charging
The following conditions must be valid before charge is enabled:
• CE is HIGH.
• The device is not in UVCCLOWV mode.
• The device is not in SLEEP mode.
• The VCC voltage is lower than the ac overvoltage threshold (VCC < V
ACOV
)
• 30-ms delay is complete after initial power up.
• The REGN LDO and VREF LDO voltages are at the correct levels.
• Thermal shut (TSHUT) is not valid.
• TS fault is not detected.
Any of the following conditions stops on-going charging:
• CE is LOW.
• Adapter is removed, causing the device to enter VCCLOWV or SLEEP mode.
• Adapter is over voltage.
• The REGN or VREF LDOs are overloaded.
• TSHUT IC temperature threshold is reached (145°C on rising edge with 15°C hysteresis).
• TS voltage goes out of range, indicating the battery temperature is too hot or too cold.
• TTC safety timer times out.
System Power Selector
The bq24616 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. The battery is disconnected from the system and
then the adapter is connected to the system 30 ms after exiting SLEEP. An automatic break-before-make logic
prevents shoot-through currents when the selectors switch.
ACDRV is used to drive a pair of back-to-back p-channel power MOSFETs between the adapter and ACP with
sources connected together and to VCC. The FET connected to the adapter prevents reverse discharge from the
battery to the adapter when turned off. The p-channel FET with the drain connected to the adapter input provides
reverse battery discharge protection when off, and also minimizes system power dissipation with its low r
DS(on)
compared to a Schottky diode. The other p-channel FET connected to ACP separates the battery from the
adapter, and provides a limited dI/dt when connecting the adapter to the system by controlling the FET turnon
time. The BATDRV controls a p-channel power MOSFET placed between BAT and the system.
When the adapter is not detected, ACDRV is pulled to VCC to keep ACFET off, disconnecting the adapter from
the system. BATDRV stays at ACN-6V to connect the battery to the system.
Approximately 30 ms after the device comes out of SLEEP mode, the system begins to switch from battery to
adapter. The break-before-make logic keeps both ACFET and BATFET off for 10 µs before ACFET turns on.
This prevents shoot-through current or any large discharging current from going into the battery. BATDRV is
pulled up to ACN and the ACDRV pin is set to VCC-6V by an internal regulator to turn on p-channel ACFET,
connecting the adapter to the system.
When the adapter is removed, the system waits until VCC drops back to within 200 mV above SRN to switch
from the adapter back to the battery. The break-before-make logic still keeps 10-μs dead time. The ACDRV is
pulled up to VCC and the BATDRV pin is set to ACN-6V by an internal regulator to turn on p-channel BATFET,
connecting the battery to the system.
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