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2016-03-0004

PT0489-5

04/29/16

7

PI5PD2560/2561

Dual Channel,

Adjustable Current-Limited Power Switch

Functional Description

Block Diagram

Overview

The PI5PD2560/2561 are a dual-channel, current-limited power-distribution switch using N-channel MOSFETs for applications

where short circuits or heavy capacitive loads will be encountered. This device allows the user to program the current-limit

threshold between 250 mA and 2.8 A (typ) per channel via an external resistor. This device incorporates an internal charge pump

and gate drive circuitry necessary to drive the N-channel MOSFETs. The charge pump supplies power to the driver circuit for

each channel 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. Each channel of the PI5PD2560/2561 limit the output current to the programmed current-

voltage at OUTx because the N-channel MOSFET is no longer fully enhanced.

Over-current Conditions

When an over-current condition is detected, the device maintains a constant output current and reduces the output voltage

accordingly.

The PI5PD2560/2561 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 PI5PD2560/2561 cycles on/off until the overload is

removed.

/FAULTx Response

The /FAULTx open-drain outputs are asserted (active low) on an individual channel during an over-current or Over temperature

condition. The PI5PD2560/2561 assert the FAULTx signal until the fault condition is removed and the device resumes normal

operation on that channel. The PI5PD2560/2561 are designed to eliminate false FAULTx reporting by using an internal delay

"deglitch" circuit (9-ms typ) for over-current 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 over temperature condition but is deglitched after the device has cooled and begins to turn on. This unidrectional deglitch

prevents FAULTx oscillation during an overt temperature event.