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TPS2556DRBT Datasheet(PDF) 10 Page - Texas Instruments |
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TPS2556DRBT Datasheet(HTML) 10 Page - Texas Instruments |
10 / 23 page TPS2556 TPS2557 SLVS931A – NOVEMBER 2009 – REVISED FEBRUARY 2012 www.ti.com FAULT RESPONSE The FAULT open-drain output is asserted (active low) during an overcurrent or overtemperature condition. The TPS2556/57 asserts the FAULT signal until the fault condition is removed and the device resumes normal operation. The TPS2556/57 is designed to eliminate false FAULTreporting by using an internal delay "deglitch" circuit for overcurrent (9-ms typ) conditions without the need for external circuitry. This ensures that FAULTis not accidentally asserted due to normal operation such as starting into a heavy capacitive load. The deglitch circuitry delays entering and leaving current-limit induced fault conditions. The FAULTsignal 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 unidirectional deglitch prevents FAULT oscillation during an overtemperature event. 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. ENABLE (EN OR EN) The logic enable controls the power switch and device supply current. The supply current is reduced to less than 2- μA when a logic high is present on EN or when a logic low is present on EN. A logic low input on EN or a logic high input on EN enables the driver, control circuits, and power switch. The enable input is compatible with both TTL and CMOS logic levels. THERMAL SENSE The TPS2556/57 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. The TPS2556/57 device operates in constant-current mode during an overcurrent conditions, which increases the voltage drop across 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 power switch when the die temperature exceeds 135 °C (min) and the part 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 TPS2556/57 also has a second ambient thermal sensor (OTSD2). The ambient thermal sensor turns off the power switch when the die temperature exceeds 155 °C (min) regardless of whether the power switch is in current limit and will turn on the power switch after the device has cooled approximately 20 °C. The TPS2556/57 continues to cycle off and on until the fault is removed. APPLICATION INFORMATION INPUT AND OUTPUT CAPACITANCE Input and output capacitance improves the performance of the device; the actual capacitance should be optimized for the particular application. For all applications, a 0.1 μF or greater ceramic bypass capacitor between IN and GND is recommended as close to the device as possible for local noise decoupling. This precaution reduces ringing on the input due to power-supply transients. Additional input capacitance may be needed on the input to reduce voltage overshoot from exceeding the absolute-maximum voltage of the device during heavy transient conditions. This is especially important during bench testing when long, inductive cables are used to connect the evaluation board to the bench power supply. Output capacitance is not required, but placing a high-value electrolytic capacitor on the output pin is recommended when large transient currents are expected on the output. 10 Submit Documentation Feedback Copyright © 2009–2012, Texas Instruments Incorporated Product Folder Link(s): TPS2556 TPS2557 |
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