L6599AT

Device description

Doc ID 15534 Rev 3

3/31

1

Device description

The L6599AT is a temperature-extended version of the L6599A. It is a double-ended

controller specifically designed for the series-resonant half-bridge topology. It provides a

50% complementary duty cycle: the high-side switch and the low-side switch are driven

ON/OFF at 180° out-of-phase for exactly the same time interval. Output voltage regulation is

obtained by modulating the operating frequency. A fixed dead-time inserted between the

turn-off of one switch and the turn-on of the other guarantees soft-switching and enables

high-frequency operation.

To drive the high-side switch using the bootstrap approach, the IC incorporates a high-

voltage floating structure capable of withstanding more than 600 V with a synchronous-

driven high-voltage DMOS that replaces the external fast-recovery bootstrap diode.

The IC enables the designer to set the operating frequency range of the converter by means

of an externally programmable oscillator.

At start-up, to prevent uncontrolled inrush current, the switching frequency starts from a

programmable maximum value and progressively decays until it reaches the steady-state

value determined by the control loop. This frequency shift is non linear to minimize output

voltage overshoots; its duration is programmable as well.

At light load the IC may enter a controlled burst-mode operation that keeps the converter

input consumption to a minimum.

The device’s functions include a not-latched active-low disable input with current hysteresis

suitable for power sequencing or for brownout protection, a current sense input for OCP with

frequency shift and delayed shutdown with automatic restart. A higher level OCP latches off

the IC if the first-level protection is not sufficient to control the primary current. Their

combination offers complete protection against overload and short-circuits. An additional

latched disable input (DIS) allows easy implementation of OTP and/or OVP.

An interface with the PFC controller is provided that enables the switching off of the pre-

regulator during fault conditions, such as OCP shutdown and DIS high, or during burst-

mode operation.