Datasheet

TPS62175, TPS62177

www.ti.com

SLVSB35B –OCTOBER 2012–REVISED JANUARY 2014

Output Discharge

The output is actively discharged through a 175Ω (typ.) resistor on the VOS pin when the device is turned off by

EN, UVLO or thermal shutdown.

Softstart

The internal soft start circuitry controls the output voltage slope during startup. This avoids excessive inrush

current and ensures a controlled output voltage rise time. It also prevents unwanted voltage drops from high-

impedance power sources or batteries. When EN is set to High and the device starts switching, V

OUT

rises with a

slope of typically 10mV/µs. The internal current limit is reduced to typically 525mA during startup. Thereby the

output current is less than 500mA during that time (see Figure 42). The startup sequence ends, when device

achieves regulation; then, the device runs with the full current limit of typically 1A, providing full output current.

The TPS62175/7 can monotonically start into a pre-biased output.

Current Limit And Short Circuit Protection

The TPS62175/7 devices are protected against heavy load and short circuit events. If a current limit situation is

detected, the device switches off. The off time is maintained longer as the output voltage becomes lower. At

heavy overloads the low side MOSFET stays on until the inductor current returns to zero. Then the high side

MOSFET turns on again (see Figure 51 and Figure 52).

Power Good (PG)

The TPS62175/7 has a built in power good (PG) function to indicate that the output reached regulation. The PG

signal can be used for startup sequencing of multiple rails. The PG pin is an open-drain output that requires a

pull-up resistor (to any voltage below 7V). It can sink 2mA of current and maintain its specified logic Low level of

0.3V. It is held Low when the device is turned off by EN, UVLO or thermal shutdown.

If the PG pin is not used, it may be left floating or connected to AGND.

Under Voltage Lockout (UVLO)

If the input voltage drops, the under voltage lockout function prevents misoperation by turning the device off. The

under voltage lockout threshold is set to 4.6V (typically) for rising V

. To cover for possible input voltage drops,

when using high impedance sources or batteries, the falling threshold is set to typically 2.9V, allowing monotonic

startup sequence under such conditions. For input voltages below the minimum VIN of 4.75V and above the

falling UVLO threshold of 2.9V, the device still functions with a current limit and regulation capability but the

electrical characteristics are no longer specified.

Thermal Shutdown

The junction temperature (Tj) of the device is monitored by an internal temperature sensor. If Tj exceeds 150°C

(typ), the device goes into thermal shutdown. Both the high-side and low-side power FETs are turned off and PG

goes Low. When Tj decreases below the hysteresis amount, the converter resumes normal operation, beginning

with Soft Start. To avoid unstable conditions, a hysteresis of typically 20°C is implemented on the thermal

shutdown temperature.

Product Folder Links: TPS62175 TPS62177