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TPS2560, TPS2561

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SLVS930B – DECEMBER 2009 – REVISED DECEMBER 2015

Product Folder Links: TPS2560 TPS2561

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Copyright © 2009–2015, Texas Instruments Incorporated

Feature Description (continued)

The second condition is when a short circuit, partial short circuit, or transient overload occurs while the device is

current-sense amplifier is overdriven during this time and momentarily disables the internal current-limit

cycle.

The TPS256x thermal cycles if an overload condition is present long enough to activate thermal limiting in any of

the above cases. The device turns off when the junction temperature exceeds 135°C (min) while in current limit.

The device remains off until the junction temperature cools 20°C (typ) and then restarts. The TPS256x cycles

on/off until the overload is removed (see Figure 4).

9.3.2 FAULTx Response

The FAULTx open-drain outputs are asserted (active low) on an individual channel during an overcurrent or

overtemperature condition. The TPS256x asserts the FAULTx signal until the fault condition is removed and the

device resumes normal operation on that channel. The TPS256x is designed to eliminate false FAULTx reporting

by using an internal delay "deglitch" circuit (9-ms typ) for overcurrent conditions without the need for external

circuitry. This ensures that FAULTx is not accidentally asserted due to normal operation such as starting into a

heavy capacitive load. The deglitch circuitry delays entering and leaving current-limited induced fault conditions.

The FAULTx signal is not deglitched when the MOSFET is disabled due to an overtemperature condition but is

deglitched after the device has cooled and begins to turn on. This unidrectional deglitch prevents FAULTx

oscillation during an overtemperature event.

9.3.3 Undervoltage Lockout (UVLO)

The undervoltage lockout (UVLO) circuit disables the power switch until the input voltage reaches the UVLO turn-

on threshold. Built-in hysteresis prevents unwanted on/off cycling due to input voltage droop during turn on.

9.3.4 Enable (ENx or ENx)

The logic enables control the power switches and device supply current. The supply current is reduced to less

than 2-

μA when a logic high is present on ENx or when a logic low is present on ENx. A logic low input on ENx

or a logic high input on ENx enables the driver, control circuits, and power switches. The enable inputs are

compatible with both TTL and CMOS logic levels.

9.3.5 Thermal Sense

The TPS256x self protects by using two independent thermal sensing circuits that monitor the operating

temperature of the power switch and disable operation if the temperature exceeds recommended operating

conditions. Each channel of the TPS256x operates in constant-current mode during an overcurrent conditions,

which increases the voltage drop across the power switch. The power dissipation in the package is proportional

to the voltage drop across the power switch, which increases the junction temperature during an overcurrent

condition. The first thermal sensor (OTSD) turns off the individual power switch channel when the die

temperature exceeds 135°C (min) and the channel is in current limit. Hysteresis is built into the thermal sensor,

and the switch turns on after the device has cooled approximately 20°C.

The TPS256x also has a second ambient thermal sensor (OTSD2). The ambient thermal sensor turns off both

power switch channels when the die temperature exceeds 155°C (min) regardless of whether the power switch

channels are in current limit and will turn on the power switches after the device has cooled approximately 20°C.

The TPS256x continues to cycle off and on until the fault is removed.

9.4 Device Functional Modes

There are no other functional modes.