Datasheet

EVM Description

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4 EVM Description

4.1 Application Changes

Components may be changed for operation at other voltages, current or start-up conditions. See the

design example in the TPS2394 datasheet (TI Literature Number SLVSAA9) to assist with component

selection.

4.2 Floating System

As the schematic is drawn, the EVM and power supply are floating with respect to GND. Therefore, a

GND may be placed on any single point in the system. The GND is shown on the -48-V terminal so that

UV, OV, etc, can be calculated, and viewed on the scope like positive voltage signals.

4.3 Reverse Voltage

Reverse voltage is often desired with negative voltage systems. Do not test reverse voltage directly with

the TPS2394EVM. The input has an electrolytic capacitor since the EVM is used in labs with long leads to

power supplies. The capacitor should be removed before attempting reverse voltage input.

NOTE: There is a series diode in the RTN line of the TPS2394. This is not strictly needed but is a

good design practice.

The load is not protected form reverse voltage. There is a capacitor on the load side that should be

removed in addition to removing the load for reverse voltage testing.

4.4 Output Status Logic Levels

The fault signal, FLT, is a low true signal with the LED indicator and current limiting resistor between RTN

and the lower rail. The signal output at the FLT test point covers the full range of the power supply.

The PG signal is high true and is connected between the LED indicator and the current limiting resistor.

When the PG signal is false, it is at the negative rail. When PG is true, it is only about 1.5 V above the

negative rail, the LED forward voltage drop.

The logic levels should be considered if they are used to interface remote equipment.

4.5 UV, OV

The EVM is set up to operate from 10 V to 56 V. The TPS2394 internal under voltage setting is 9 V.

4.6 Retry Controller

The TPS2394 is a retry controller. After a fault, the controller will attempt to turn the FET back on again. It

turns the FET fully on when the fault is cleared

TPS2394 Hot Swap Controller System SLUU456–October 2010

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