BQ24600_1 Datasheet, PDF (13/31 Pages) Texas Instruments – Stand-Alone Synchronous Switch-Mode Li-Ion or Li-Polymer Battery Charger with Low Iq

bq24600
www.ti.com
SLUS891 – FEBRUARY 2010
Precharge
On power-up, if the battery voltage is below the V_LOWV threshold, the bq24600 applies the precharge current to
the battery. This feature is intended to revive deeply discharged cells. If the V_LOWV threshold is not reached within
30 minutes of initiating precharge, the charger turns off and a FAULT is indicated on the status pins.
The precharge current is fixed 1/10^th of the programmed charge current, which is determined by the voltage on
the ISET pin according Equation 3:
I_PRECHARGE
I_CHARGE
= ₁₀ =
V_ISET
200 ´ R_SR
(3)
The minimum precharge current is clamped to be around 125mA with default 10mΩ sensing resistor.
Charge Termination, Recharge, and Safety Timer
The bq24600 monitors the charging current during the voltage regulation phase. Termination is detected while
the voltage on the VFB pin is higher than the V_RECH threshold AND the charge current is less than the I_TERM
threshold, which is is fixed 1/10^th of the programmed charge current, as calculated in Equation 4:
I_TERM
=
V_ISET
200 ´ R_SR
(4)
As a safety backup, the bq24600 also provides an internal 5 hour safety timer for fast charge.
A new charge cycle is initiated and safety timer is reset when one of the following conditions occur:
• The battery voltage falls below the recharge threshold
• A power-on-reset (POR) event occurs
• CE is toggled
Power Up
The bq24600 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, bq24600 exits
the SLEEP mode. If all other conditions are met for charging, bq24600 will then attempt to charge the battery
(See Enabling and Disabling Charging). If the SRN voltage is greater than VCC, bq24600 enters a low quiescent
current (<15mA) SLEEP mode to minimize current drain from the battery.
If VCC is below the UVLO threshold, the device is disabled.
Enable and Disable Charging
The following conditions have to be valid before charge is enabled:
• CE is HIGH
• The device is 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 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
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