TPS2480PW datasheet(27/60 Pages) TI2

27 / 60 page

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RETRY

TMRHI(NOM)

TMRLO(NOM)

SOURCE(NOM)

SINK(NOM)

RETRY

21 56

TPS2480

TPS2481

www.ti.com

SLUS939B – APRIL 2010 – REVISED DECEMBER 2010

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 varying 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 since every setup differs.

Applications using the retry feature (TPS2481)

Applications using the retry feature may want to estimate fault retry time. The TPS2481 will retry (enable M1 to

attempt turn on) once for every 16 timer charge/discharge cycles (15 cycles between 1 V and 4 V, 1 cycle

between 0 V and 4 V).

(28)

(29)

NOTE

Equation 29 simplified - assumes no error.

Layout Considerations

Good layout practice places the power devices D1, RS, M1, and CO so power flows in a sequential, linear

fashion. A ground plane under the power and the TPS2480/81 is desirable. The TPS2480/81 should be placed

close to the sense resistor and MOSFET using a Kelvin type connection to achieve accurate current sensing

across RS. A low-impedance GND connection is required because the TPS2480/81 can 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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