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TPS2490

TPS2491

SLVS503 – NOVEMBER 2003

APPLICATION INFORMATION (continued)

Output Clamp Diode

Inductive loads on the output may drive the OUT pin below GND when the circuit is unplugged or during a

current limit. The OUT pin ratings can be maintained with a small diode, such as an S1B, across TPS2490/91

OUT to GND.

Gate Clamp Diode

The TPS2490/91 has a relatively well-regulated gate voltage of 12–16 V, even with low supply voltages. A small

High Gate Capacitance Applications

Gate voltage overstress and abnormally large fault current spikes can be caused by large gate capacitance. An

external gate clamp Zener diode is recommended if the total gate capacitance of M1 exceeds about 4000 pF.

When gate capacitor inrush control is used, a 1-k

Ω resistor in series with C

Output Short Circuit Measurements

Repeatable short-circuit testing results are difficult to obtain. The many details of source bypassing, input leads,

circuit layout and component selection, output shorting method, relative location of the short, and instrumentation

all contribute to obtaining different results. The actual short itself exhibits a certain degree of randomness as it

microscopically bounces and arcs. Care in configuration and methods must be used to obtain realistic results. Do

not expect to see waveforms exactly like those in the data sheet—every setup differs.

Layout Considerations

preferably in a straight line. A ground plane under the power and the TPS2490/91 is desirable. The TPS2490/91

should be placed close to the sense resistor and the MOSFET; a Kelvin connection is recommended to achieve

momentarily sink upwards of 100 mA from the gate of M1. The GATE amplifier has high bandwidth while active,

so keep the gate trace length short. The PROG, TIMER, and EN pins have high input impedances, therefore

keep their input leads short. Oversize power traces and power device connections to assure low voltage drop

and good thermal performance.

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