BQ24297 Datasheet, PDF (23/48 Pages) Texas Instruments – I2C Controlled 3A Single Cell USB Charger

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bq24296
bq24297
SLUSBP6A – SEPTEMBER 2013 – REVISED OCTOBER 2013
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 I_VBUS (15µA typical) 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 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 (3.8V typical) when pulling I_BADSRC (30mA 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.
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 3A.
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.
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.
D+
VDP_SRC
VLGC_HI
IDP_SRC
CHG_DET
IDM_SINK
VDAC_REF
D-
RDM_DWN
Figure 25. USB D+/D- Detection
DCD (Data Contact Detection) uses a current source to detect when the D+/D– pins have made contact during
an attach event. The protocol for data contact detect is as follows:
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