TPS65721 datasheet(25/50 Pages) TI

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TPS65720

TPS65721

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SLVS979 – OCTOBER 2009

Under-Voltage Lockout

The under voltage lockout circuit prevents the device from malfunctioning at low input voltages and from

excessive discharge of the battery and disables the converters and LDOs. The under-voltage lockout threshold is

typically 2.2V.

SHORT-CIRCUIT PROTECTION

All outputs are short circuit protected with a maximum output current as defined in the electrical specifications.

THERMAL SHUTDOWN

There are two thermal sensors in TPS6572x located at the main sources of power dissipation - the charger and

the LDO. The maximum temperature of the charger is regulated by reducing its charge current. If the

temperature increases further, the charger is disabled - see details in the charger description.

The second sensor is enabled as soon as the LDO is enabled. As soon as the junction temperature, TJ, exceeds

typically 150°C, the device goes into thermal shutdown. In this mode, the low side and high side MOSFETs are

turned-off. A thermal shutdown for the LDO will disable both, LDO and the DCDC converter simultaneously.

LDO1

The low dropout voltage regulator is designed to operate well with low value ceramic input and output capacitors.

It operates with input voltages down to 1.8V. The LDOs offer a maximum dropout voltage of 160mV at rated

output current. LDO1 supports a current limit feature. Its output voltage is adjustable using a resistor divider at

FB_LDO1 for TPS65721. The LDO1 voltage is fixed to 1.85V for TPS65720.

Default Voltage Setting for LDOs and DCDC1

In TPS65721, both DCDC1 and LDO1 are externally adjustable.

For TPS65720, the output voltage of the DCDC1 converter is externally adjustable and for LDO1 it is fixed to

1.85V per default. The I2C registers do allow changing the default voltage for LDO1 in a range of 0.8V to 3.3V.

For DCDC1, the register also allows setting any voltage in the range from 0.8V to 3.3V, however for the

adjustable version of DCDC1, the change in the I2C register has no effect on the output voltage. The registers

will be set to the default value when the voltage at SYS drops below the undervoltage lockout threshold or by a

reset event (RESET output is actively pulled low). See the register description for more details.

GPIOs, LED Drivers

TPS65720 contains 4 standard input/output pins (GPIOs) named GPIO0 to GPIO3. The output driver/input buffer

is available in register GPIO_SSC while register GPIODIR selects the data direction and additional features.

After RESET, GPIO0 and GPIO1 are pre-defined as general purpose inputs while GPIO2 and GPIO3 are

configured as LED driver outputs which are high impedance. The LED driver outputs are designed to be constant

current sinks to GND, sinking a constant current of 5mA when enabled. The GPIOs do not have internal pull-up

resistors. External pull-up resistors might be required if configured as inputs or outputs.

RESET output

Actively low, open drain reset output. Connect external pull-up resistor. The reset pin will go high impedance

100ms after the reset condition is left. For TPS65720, reset is generated, depending on the power-good signal of

LDO1, when the output voltage is below the threshold or LDO1 is disabled. For TPS65721, reset is generated

depending on the voltage at pin THRESHOLD.

THRESHOLD INPUT (TPS65721 only)

This is an input to the comparator driving the Reset output. If the voltage applied at THRESHOLD is below the

threshold, Reset is pulled actively LOW. If the voltage rises above the threshold + hysteresis, the Reset output is

released after a delay time of 100ms (typically).

ENABLE for DCDC1 and LDO1

The DCDC1 converter and LDO1 are enabled as soon as PB_IN is pulled LOW OR input voltage at pin AC is

detected (<CH_PGOOD>=1).

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