TPS2552
TPS2553, TPS2552-1, TPS2553-1
www.ti.com........................................................................................................................................ SLVS841A–NOVEMBER 2008–REVISED DECEMBER 2008
DETAILED DESCRIPTION
OVERVIEW
The TPS2552/53 and TPS2552-1/53-1 are current-limited, power-distribution switches using N-channel
MOSFETs for applications where short circuits or heavy capacitive loads will be encountered. These devices
allow the user to program the current-limit threshold between 75 mA and 1.3 A (typ) via an external resistor.
Additional device shutdown features include overtemperature protection and reverse-voltage protection. The
device incorporates an internal charge pump and gate drive circuitry necessary to drive the N-channel MOSFET.
The charge pump supplies power to the driver circuit and provides the necessary voltage to pull the gate of the
MOSFET above the source. The charge pump operates from input voltages as low as 2.5 V and requires little
supply current. The driver controls the gate voltage of the power switch. The driver incorporates circuitry that
controls the rise and fall times of the output voltage to limit large current and voltage surges and provides built-in
soft-start functionality. There are two device families that handle overcurrent situations differently. The
TPS2552/53 family enters constant-current mode while the TPS2552-1/53-1 family latches off when the load
exceeds the current-limit threshold.
OVERCURRENT CONDITIONS
The TPS2552/53 and TPS2552-1/53-1 respond to overcurrent conditions by limiting their output current to the IOS
levels shown in Figure 24. When an overcurrent condition is detected, the device maintains a constant output
current and reduces the output voltage accordingly. Two possible overload conditions can occur.
The first condition is when a short circuit or partial short circuit is present when the device is powered-up or
enabled. The output voltage is held near zero potential with respect to ground and the TPS2552/53 ramps the
output current to IOS. The TPS2552/53 devices will limit the current to IOS until the overload condition is removed
or the device begins to thermal cycle. The TPS2552-1/53-1 devices will limit the current to IOS until the overload
condition is removed or the internal deglitch time (7.5-ms typical) is reached and the device is turned off . The
device will remain off until power is cycled or the device enable is toggled.
The second condition is when a short circuit, partial short circuit, or transient overload occurs while the device is
enabled and powered on. The device responds to the overcurrent condition within time tIOS (see Figure 3). The
current-sense amplifier is overdriven during this time and momentarily disables the internal current-limit
MOSFET. The current-sense amplifier recovers and limits the output current to IOS. Similar to the previous case,
the TPS2552/53 will limit the current to IOS until the overload condition is removed or the device begins to thermal
cycle; the TPS2552-1/53-1 will limit the current to IOS until the overload condition is removed or the internal
deglitch time is reached and the device is latched off.
The TPS2552/53 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 (typ) while in current
limit. The device remains off until the junction temperature cools 10°C (typ) and then restarts. The TPS2552/53
cycles on/off until the overload is removed (see Figure 10 and Figure 12) .
REVERSE-VOLTAGE PROTECTION
The reverse-voltage protection feature turns off the N-channel MOSFET whenever the output voltage exceeds
the input voltage by 135 mV (typ) for 4-ms (typ). This prevents damage to devices on the input side of the
TPS2552/53 and TPS2552-1/TPS2253-1 by preventing significant current from sinking into the input capacitance.
The TPS2552/53 devices allow the N-channel MOSFET to turn on once the output voltage goes below the input
voltage for the same 4-ms deglitch time. The TPS2552-1/53-1 devices keep the device turned off even if the
reverse-voltage condition is removed and do not allow the N-channel MOSFET to turn on until power is cycled or
the device enable is toggled. The reverse-voltage comparator also asserts the FAULT output (active-low) after
4-ms.
Copyright © 2008, Texas Instruments Incorporated
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Product Folder Link(s): TPS2552 TPS2553 TPS2552-1 TPS2553-1
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