BQ24610 Datasheet, PDF (17/33 Pages) Texas Instruments – Stand-Alone Synchronous Switch-Mode Li-Ion or Li-Polymer Battery Charger with System Power Selector and Low Iq

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bq24610
bq24617
SLUS892 – DECEMBER 2009
Power Up
The bq24610/7 uses a SLEEP comparator to determine the source of power on the VCC pin, since VCC can be
supplied either from the battery or the adapter. If the VCC voltage is greater than the SRN voltage, bq24610/7
will enable the ACFET and disable BATFET. If all other conditions are met for charging, bq24610/7 will then
attempt to charge the battery (See Enabling and Disabling Charging). If the SRN voltage is greater than VCC,
indicating that the battery is the power source, bq24610/7 enables the BATFET, and enters a low quiescent
current (<15μA) SLEEP mode to minimize current drain from the battery.
If VCC is below the UVLO threshold, the device is disabled, ACFET turns off and BATFET turns on.
Enable and Disable Charging
The following conditions have to be valid before charge is enabled:
• CE is HIGH
• The device is not in Under-Voltage-Lockout (UVLO) and not in VCCLOWV mode
• The device is not in SLEEP mode
• The VCC voltage is lower than the AC over-voltage threshold (VCC < V_ACOV)
• 30ms 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
One of the following conditions will stop on-going charging:
• CE is LOW;
• Adapter is removed, causing the device to enter UVLO, 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 out
System Power Selector
The bq24610/7 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 30ms 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 p-channel power MOSFETs between adapter and ACP with
sources connected together and to VCC. The FET connected to 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_DSON,
compared to a Schottky diode. The other p-channel FET connected to ACP separates battery from adapter, and
provides a limited dI/dt when connecting the adapter to the system by controlling the FET turn-on time. The
BATDRV controls a p-channel power MOSFET placed between BAT and system.
When adapter is not detected, the ACDRV is pulled to VCC to keep ACFET off, disconnecting the adapter from
system. BATDRV stays at ACN-6V to connect battery to system.
Approximately 30ms 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 10us before ACFET turns on. This
prevents shoot-through current or any large discharging current from going into the battery. The 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 200mV above SRN to switch from
adapter back to battery. The break-before-make logic still keeps 10μs 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.
Copyright © 2009, Texas Instruments Incorporated
Product Folder Link(s): bq24610 bq24617
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