TPS65721 datasheet(18/50 Pages) TI

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TPS65720

TPS65721

SLVS979 – OCTOBER 2009

www.ti.com

POWER-ON RESET MODE

The charger enters power-on reset mode when the input voltage at AC is within the valid range: VAC > UVLO

and VAC > VBAT + VIN(DT) and VAC < VOVP, and the Bits <AC input current1, AC input current0> indicate that

the USB suspend mode is not enabled [<AC input current1, AC input current0>

≠ (0,0)]. During power-on reset

mode, all internal timers and other circuit blocks are activated. The device checks for short-circuits at the ISET

pin. If no short conditions exists, the device switches on the input FET Q1 with a 100-mA current limit to check

for a short circuit at SYS. If VOUT rises above VSC, the FET Q1 switches to the current-limit threshold set by

<AC input current1, AC input current0>, and the device enters into the Idle mode.

IDLE MODE

In the Idle mode, the system is powered by the input source (Q1 is on), and the device continuously monitors the

status of the host commands. It also continuously monitors the input voltage conditions. Q2 is turned on

whenever the input source cannot deliver the required load current (supplement mode). The device also enters

Idle mode whenever <CH_EN> =0 while the input voltage is in the valid range of operation.

POWER-PATH MANAGEMENT

The current at the input pin AC of the power path manager is shared between charging the battery and powering

the system load on the SYS pin. Priority is given to the system load. The input current is monitored continuously.

If the sum of the charging and system load currents exceeds the preset maximum input current (programmed

internally by I2C), the charging current is reduced automatically. The default value for the current limit is 500mA

for the AC pin.

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TPS65721 Datasheet(PDF) 18 Page - Texas Instruments