BQ24296_15 Datasheet, PDF (17/55 Pages) Texas Instruments – bq2429x I2C Controlled 3-A Single Cell USB Charger With Narrow VDC Power Path Management and Adjustable Voltage USB OTG

www.ti.com
bq24296, bq24297
SLUSBP6B – SEPTEMBER 2013 – REVISED NOVEMBER 2014
Feature Description (continued)
9.3.1.3.1 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 TS external resistors. The pull-up rail of STAT and PG (bq24296) can be connected to
REGN as well.
The REGN is enabled when all the conditions are valid.
1. VBUS above V_{VBUS_UVLOZ}
2. VBUS above V_BAT + V_SLEEPZ in buck mode or VBUS below V_BAT + V_SLEEP in boost mode
3. After typical 220-ms delay (100 ms 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 I_VBUS (15 µA typical) from VBUS during HIZ state. The battery powers up the system
when the device is in HIZ.
9.3.1.3.2 Input Source Qualification
After REGN LDO powers up, the device 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 V_ACOV (not in VBUS over-voltage)
2. VBUS voltage above V_BADSRC (3.8 V typical) when pulling I_BADSRC (30 mA typical) (poor source detection)
Once the input source passes all the conditions above, the status register REG08[2] goes high and the PG pin
(bq24296) goes low. An INT is asserted to the host.
If the device fails the poor source detection, it will repeat the detection every 2 seconds.
9.3.1.3.3 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 (100
mA/500 mA in USB 2.0, and 150 mA/900 mA in USB 3.0). If the portable device is attached to a charging port, it
is allowed to draw up to 3 A.
After the PG is LOW (bq24296) or 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 bq24297 follows Battery Charging Specification 1.2 (BC1.2) to detect input source through USB D+/D- lines.
The bq24296 sets input current limit through PSEL and OTG pins. After the input current limit detection is done,
the detection result is reported in VBUS_STAT registers (REG08[7:6]) and input current limit is updated in IINLIM
register (REG00[2:0]). In additon, host can write to REG00[2:0] to change the input current limit.
9.3.1.3.4 D+/D– Detection Sets Input Current Limit (bq24297)
The bq24297 contains a D+/D– based input source detection to program the input current limit. The D+/D-
detection has three steps: data contact detect (DCD), primary detection, and non-standard adapter detection.
When the charging source passes data contact detect, the device would proceed to run primary detection.
Otherwise the charger would proceed to run non-standard adapter detection.
Copyright © 2013–2014, Texas Instruments Incorporated
Product Folder Links: bq24296 bq24297
Submit Documentation Feedback
17