BQ24195 Datasheet, PDF (18/41 Pages) Texas Instruments – I2C Controlled 2.5A / 4.5A Single Cell USB/Adapter Charger With 5.1V at 1A / 5.1V at 2.1A Synchronous Boost Operation

bq24195
bq24195L
SLUSB97 – OCTOBER 2012
www.ti.com
Power Up from DC Source
When the DC source plugs in, the bq24195L, bq24195 checks the input source voltage to turn on REGN LDO
and all the bias circuits. It also checks the input current limit before starts the buck converter.
REGN LDO
The REGN LDO supplies internal bias circuits as well as the HSFET and LSFET gate drive. The LDO also
provides bias rail to TS1/TS2 external resistors. The pull-up rail of STAT can be connected to REGN as well.
The REGN is enabled when all the conditions are valid.
1. VBUS above UVLOZ
2. VBUS above battery + V_SLEEPZ in buck mode or VBUS below battery + V_SLEEPZ in boost mode
3. After typical 220ms delay (100ms minimum) is complete
If one of the above conditions is not valid, the device is in high impedance mode (HIZ) with REGN LDO off. The
device draws less than 50µA from VBUS during HIZ state. The battery powers up the system when the device is
in HIZ.
Input Source Qualification
After REGN LDO powers up, the bq24195L, bq24195 checks the current capability of the input source. The input
source has to meet the following requirements to start the buck converter.
1. VBUS voltage below 18V (not in ACOV)
2. VBUS voltage above 3.8V when pulling 30mA (poor source detection)
Once the input source passes all the conditions above, the status register REG08[2] goes high. An INT is
asserted to the host.
If the device fails the poor source detection, it will repeat the detection every 2 seconds.
Input Current Limit Detection
The USB ports on personal computers are convenient charging source for portable devices (PDs). If the portable
device is attached to a USB host, the USB specification requires the portable device to draw limited current
(100mA/500mA in USB 2.0, and 150mA/900mA in USB 3.0). If the portable device is attached to a charging port,
it is allowed to draw up to 1.5A.
After REG08[2] goes HIGH, the charger device always runs input current limit detection when a DC source plugs
in unless the charger is in HIZ during host mode.
The bq24195L, bq24195 follows battery charging specification 1.2 (bc1.2) to detect input source through USB
D+/D– lines. After the input current limit detection is done, the host can write to REG00[2:0] to change the input
current limit.
D+/D– Detection Sets Input Current Limit
The bq24195L, bq24195 contains a D+/D– based input source detection to program the input current limit. The
D+/D- detection has two steps: data contact detect (DCD) followed by primary detection.
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