L6590A

16/19

At turn-on, there are large current spikes due to the discharge of parasitic capacitances and, in case of Contin-

uos Conduction Mode operation, to secondary diode reverse recovery as well, which could falsely trigger the

OCP comparator. To increase noise immunity the output of the OCP comparator is blanked for a short time

(about 120 ns) just after the MOSFET is turned on, so that any disturbance within this time slot is rejected (Lead-

ing Edge Blanking).

Figure 31. OCP internal schematic

Thermal Shutdown

Overheating of the device due to an excessive power throughput or insufficient heatsinking is avoided by the

Thermal Shutdown function. A thermal sensor monitors the junction temperature close to the power MOSFET

and, when the temperature exceeds 150 °C (min.), sets an alarm signal that stops the operation of the device.

This is a not-latched funtion and the power MOSFET is re-enabled as the temperature falls about 40 °C.

Clock

+

-

DRAIN

GND

1

1/100

S

R

Q

Max. Duty cycle

OSCILLATOR

PWM

Driver

Rsense

OCP

+

-

0.5 V

LEB

Clock