BQ24196_17 Datasheet, PDF (14/50 Pages) Texas Instruments – I2C Controlled 2.5-A Single Cell USB/Adapter Charger with Narrow VDC Power Path Management and USB OTG

bq24196
SLUSB98A – OCTOBER 2012 – REVISED DECEMBER 2014
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Feature Description (continued)
1. VBUS voltage below 18 V (not in ACOV)
2. VBUS voltage above 3.8 V when pulling 30 mA (poor source detection)
Once the input source passes all the conditions above, the status register REG08[2] goes high and the PG pin
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.
8.3.1.3.3 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 1.5 A.
After the PG is LOW 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 bq24196 sets input current limit through PSEL and OTG pins.
After the input current limit detection is done, the host can write to REG00[2:0] to change the input current limit.
8.3.1.3.4 PSEL/OTG Pins Set Input Current Limit
The bq24196 has PSEL. It directly takes the USB PHY device output to decide whether the input is USB host or
charging port.
Table 2. bq24196 Input Current Limit Detection
PSEL
HIGH
HIGH
LOW
OTG
LOW
HIGH
—
INPUT CURRENT LIMIT
100 mA
500 mA
3A
REG08[7:6]
01
01
10
8.3.1.3.5 HIZ State wth 100mA USB Host
In battery charging spec, the good battery threshold is the minimum charge level of a battery to power up the
portable device successfully. When the input source is 100-mA USB host, and the battery is above bat-good
threshold (V_BATGD), the device follows battery charging spec and enters high impedance state (HIZ). In HIZ state,
the device is in the lowest quiescent state with REGN LDO and the bias circuits off. The charger device sets
REG00[7] to 1, and the VBUS current during HIZ state will be less than 30 µA. The system is supplied by the
battery.
Once the charger device enters HIZ state in host mode, it stays in HIZ until the host writes REG00[7] = 0. When
the processor host wakes up, it is recommended to first check if the charger is in HIZ state.
In default mode, the charger IC will reset REG00[7] back to 0 when input source is removed. When another
source plugs in, the charger IC will run detection again, and update the input current limit.
8.3.1.3.6 Force Input Current Limit Detection
The host can force the charger device to run input current limit detection by setting REG07[7] = 1. After the
detection is complete, REG07[7] will return to 0 by itself.
8.3.1.4 Converter Power-Up
After the input current limit is set, the converter is enabled and the HSFET and LSFET start switching. If battery
charging is disabled, BATFET turns off. Otherwise, BATFET stays on to charge the battery.
The bq24196 provides soft-start when ramp up the system rail. When the system rail is below 2.2 V, the input
current limit is forced to 100 mA. After the system rises above 2.2 V, the charger device sets the input current
limit set by the lower value between register and ILIM pin.
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