Pin settings

HVLED001

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DocID027333 Rev 1

3

Pin settings

Figure 3. Pin connection

Table 2. Pin description

Symbol Pin

Description

HVSU

1

High voltage start-up and input voltage detection.

The pin, able to withstand 800 V, is to be tied to the input voltage using a low value resistor

(1 k

 typ.). It embeds the internal start-up unit that charges the capacitor connected between the

During the operational mode, the voltage at this pin is used to both measure the input voltage and

detect input overvoltages.

N.C.

2

Not connected pin.

TOFF

3

A blanking time for zero voltage detection can be set applying a voltage to this pin. A minimum

blanking time is obtained leaving the pin unconnected.

FB

4

Input for loop regulation.

The pin is intended to be directly driven by the phototransistor (emitter-grounded) of an optocoupler

and / or to the compensation network related to the output voltage primary side regulation loop.

An upper threshold VOFP detects a failure of the optocoupler.

The burst-mode and disable conditions are also related to the voltage applied to this pin.

CTRL

5

This pin is used to disable the IC and generate the soft-start ramp.

External active circuitry can be used to turn off the application.

ZCD

6

Multiple function pin able to detect the zero current instant, to sense the output voltage for primary

side regulation and the input voltage for brownout detection.

A negative-going edge triggers the MOSFET's turn on, while an internal starter unit is active to

generate the triggering signal when not externally available (e.g.: start-up).

CS

7

Input to the current sense comparator for the power regulation.

A second level overcurrent (OCP) threshold detects abnormal currents (e.g.: due to transformer's

saturation) and, on this occurrence, activates the second level overcurrent protection procedure.

GND

8

Reference pin.