TPS2140, TPS2141

TPS2150, TPS2151

SLVS399A − JANUARY 2002 − REVISED MAY 2006

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detailed description (continued)

LDO_OUT

LDO_OUT is the output of the internal LDO. It has an output voltage range of 0.9 V to 3.3 V.

LDO_EN

LDO_EN is used to enable or disable the internal LDO and is compatible with CMOS and TTL logic. LDO_EN

is an active high input.

ADJ

ADJ is used to adjust the LDO output voltage (LDO_OUT) anywhere between 0.9 V and 3.3 V by connecting

a resistor divider from LDO_OUT to ground (ADJ connects to the center point of the resistor divider).

LDO_PG

LDO_PG signals the presence of an undervoltage condition on LDO_OUT. LDO_PG is an open-drain output

and is pulled low during an undervoltage condition. To minimize erroneous LDO_PG responses from transients

on the voltage rail, the voltage sense circuit incorporates a 150-

µs falling deglitch filter. When the LDO_OUT

voltage is lower than 94% of a threshold voltage (set by an external resistor divider), LDO_PG goes low to

indicate an undervoltage condition. A pullup resistor from LDO_PG to a power rail is required for proper

operation.

LDO_PLDN

LDO_PLDN is an open drain output incorporated to provide a discharge path. When the LDO is on, this pin is

open; otherwise, it is pulled down to ground. When this pin is connected to LDO_OUT, the output voltage fall

time is reduced but the rise time remains unaffected.

current sense

Both the power switch and the LDO have integrated current sense circuits. When an overload or short circuit

is encountered, the current-sense circuitry sends a control signal to the driver. The driver reduces the gate

voltage until the current drops back to the limiting value.

thermal sense

A dual-threshold thermal trip is implemented to protect the device. The lower thermal trip point is used to protect

the device during an overcurrent condition. The higher thermal trip point is used to protect the device when the

junction temperature rises but not due to an overcurrent condition.

undervoltage lockout

A voltage sense circuit monitors both input voltages on SW_IN and LDO_IN. When the input voltage is below

its respective threshold, a control signal turns off the related channel (the power switch or the LDO).