STMicroelectronics 19 V - 75 W SMPS using the L6563 and the L6566A EVL6566A-75WES4 EVL6566A-75WES4 Data Sheet

Doc ID 16116 Rev 4

9/43

7

PFC_OK

PFC pre-regulator output voltage monitoring/disable function. This pin senses the output 
voltage of the PFC pre-regulator through a resistor divider and is used for protection purposes. 

If the voltage on the pin exceeds 2.5 V the IC stops switching and restarts as the voltage on the 
pin falls below 2.4 V. However, if at the same time the voltage of the INV pin falls below 1.66V, a 
feedback failure is assumed. In this case the device is latched off and the pin PWM_LATCH (#8) 
is asserted high. Normal operation can be resumed only by cycling Vcc bringing its value lower 
than 6V before to move up the Turn on threshold.

If the voltage on this pin is brought below 0.23 V the IC is shut down. To restart the IC the 
voltage on the pin must go above 0.27 V. This can be used as a remote on/off control input.

8

PWM_LATCH

Output pin for fault signaling. During normal operation this pin features high impedance. If a 
feedback failure is detected (PFC_OK > 2.5 V and INV< 1.66V) the pin is asserted high. 
Normally, this pin is used to stop the operation of the dc-dc converter supplied by the PFC pre-
regulator by invoking a latched disable of its PWM controller. If not used, the pin will be left 
floating. 

9

PWM_STOP

Output pin for fault signaling. During normal operation this pin features high impedance. If the 
IC is disabled by a voltage below 0.8 V on pin RUN (#10) the voltage on the pin is pulled to 
ground. Normally, this pin is used to temporarily stop the operation of the dc-dc converter 
supplied by the PFC pre-regulator by disabling its PWM controller. A typical usage of this 
function is brownout protection in systems where the PFC pre-regulator is the master stage. If 
not used, the pin will be left floating.

10

RUN

Remote ON/OFF control. A voltage below 0.8V shuts down (not latched) the IC and brings its 
consumption to a considerably lower level. PWM_STOP is asserted low. The IC restarts as the 
voltage at the pin goes above 0.88 V. Connect this pin to pin VFF (#5) either directly or through 
a resistor divider to use this function as brownout (AC mains undervoltage) protection.

11

ZCD

Boost inductor’s demagnetization sensing input for transition-mode operation. A negative-going 
edge triggers MOSFET’s turn-on.

12

GND

Ground. Current return for both the signal part of the IC and the gate driver.

13

GD

Gate driver output. The totem pole output stage is able to drive power MOSFET’s and IGBT’s 
with a peak current of 600 mA source and 800 mA sink. The high-level voltage of this pin is 
clamped at about 12 V to avoid excessive gate voltages. 

14

Vcc

Supply voltage of both the signal part of the IC and the gate driver. Sometimes a small bypass 
capacitor (0.1 µF typ.) to GND might be useful to get a clean bias voltage for the signal part of 
the IC.