TPS20xxC

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SLVSAU6A –JUNE 2011–REVISED JULY 2011

DETAILED DESCRIPTION

The TPS20xxC are current-limited, power-distribution switches providing between 0.5 A and 2 A of continuous

load current in 5 V circuits. These parts use N-channel MOSFETs for low resistance, maintaining voltage

regulation to the load. They are designed for applications where short circuits or heavy capacitive loads will be

encountered. Device features include enable, reverse blocking when disabled, output discharge pulldown,

overcurrent protection, over-temperature protection, and deglitched fault reporting.

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 drop from large

current surges. FLT is high impedance when the TPS20xxC is in UVLO.

ENABLE

The logic enable input (EN, or EN), controls the power switch, bias for the charge pump, driver, and other

circuits. The supply current is reduced to less than 1 µA when the TPS20xxC is disabled. Disabling the

TPS20xxC will immediately clear an active FLT indication. The enable input is compatible with both TTL and

CMOS logic levels.

are internally controlled. The rise time is controlled by both the TPS20xxC and the external loading (especially

An output load consisting of only a resistor will experience a fall time set by the TPS20xxC. An output load with

parallel R and C elements will experience a fall time determined by the (R × C) time constant if it is longer than

The enable should not be left open, and may be tied to VIN or GND depending on the device.

INTERNAL CHARGE PUMP

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 gate driver circuit and provides the necessary voltage to pull

the gate of the MOSFET above the source. The driver incorporates circuitry that controls the rise and fall times of

the output voltage to limit large current and voltage surges on the input supply, and provides built-in soft-start

functionality. The MOSFET power switch will block current from OUT to IN when turned off by the UVLO or

disabled.

CURRENT LIMIT

Characteristics table. When an overload condition is present, the device maintains a constant output current, with

The first overload condition occurs when either: 1) input voltage is first applied, enable is true, and a short circuit

circuit. The output voltage is held near zero potential with respect to ground and the TPS20xxC ramps the output

begins to thermal cycle. This is demonstrated in Figure 11 where the device was enabled into a short, and

subsequently cycles current off and on as the thermal protection engages.

The second condition is when an overload occurs while the device is enabled and fully turned on. The device

Characteristics table) is applied. The response speed and shape will vary with the overload level, input circuit,

condition is removed or the device begins to thermal cycle. This is demonstrated by Figure 12, Figure 13, and

Figure 14.

Copyright © 2011, Texas Instruments Incorporated

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