V

DT

*

t

R

DT

C

DT

(2)

TL5001/A

DTC

6

UNDERVOLTAGE-LOCKOUT (UVLO) PROTECTION

SHORT-CIRCUIT PROTECTION (SCP)

Q1

12 k

Ω

185 k

Ω

Q2

SCP

Comparator 2

SCP

Comparator 1

1.5 V

From Error

Amp

To Output

Drive Logic

SCP

5

2.5 V

TL5001A-Q1

soft start, the voltage at DTC is derived by the following equation:

Figure 2. Soft-Start Circuit

UVLO or SCP becomes active.

The undervoltage-lockout circuit turns the output transistor off and resets the SCP latch whenever the supply

voltage drops too low (approximately 3 V at 25°C) for proper operation. A hysteresis voltage of 200 mV

eliminates false triggering on noise and chattering.

The TL5001A includes short-circuit protection (see Figure 3), which turns the power switch off to prevent damage

when the converter output is shorted. When activated, the SCP prevents the switch from being turned on until

the internal latching circuit is reset. The circuit is reset by reducing the input voltage until UVLO becomes active

or until the SCP terminal is pulled to ground externally.

When a short circuit occurs, the error-amplifier output at COMP rises to increase the power-switch duty cycle in

an attempt to maintain the output voltage. SCP comparator 1 starts an RC timing circuit when COMP exceeds

1.5 V. If the short is removed and the error-amplifier output drops below 1.5 V before time out, normal converter

operation continues. If the fault is still present at the end of the time-out period, the timer sets the latching circuit

and turns off the TL5001/A output transistor.

Figure 3. SCP Circuit

4

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