Pin connections

HVLED007

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DS12866 Rev 1

2

Pin connections

Figure 2. Pin connection (top view)

Table 3. Thermal data

Symbol

Parameter

Value

Unit

Rth j-amb

Max. thermal resistance, junction-to-ambient

150

°C/W

Table 4. Pin functions

N.

Name

Function

1CT

Input current shaper (ICS) circuit. A capacitor connected from this pin to ground

(pin #6) is alternately charged and discharged internally, and the voltage

developed across this capacitor is used as the reference for the current loop.

2

COMP

Control input for PWM regulation. The pin is driven by the phototransistor (emitter-

grounded) of an optocoupler to modulate its voltage by modulating the current

sunk. A capacitor placed between the pin and ground (pin #6), as close to the IC

as possible to reduce noise pick-up, is useful to get a clean control voltage. The

dynamics of the pin are in the 2.5 to 5.5 V range. A voltage lower than 2.5 V

activates burst-mode operation. The voltage at the pin is bottom-clamped at about

2.2 V.

3

MULT

Main input to the multiplier. This pin is connected to the rectified mains voltage via

a resistor divider. A capacitor placed between the pin and ground (pin #6), as close

to the IC as possible is useful to reduce noise pick-up.

4CS

Input to the PWM comparator. The current flowing in the MOSFET is sensed

through a resistor, the resulting voltage is applied to this pin and compared with the

internal reference generated by the ICS circuit, to determine MOSFET's turn-off.

5

ZCD

Transformer demagnetization sensing input for transition-mode (quasi-resonant)

operation. A negative-going edge triggers MOSFET's turn-on. A voltage exceeding

5.5 V during MOSFET's OFF-time forces an internal discharge of the COMP pin

(#2) below the burst-mode threshold. As a consequence, the IC is temporarily

stopped (overvoltage protection). This function is strobed and digitally filtered to

increase noise immunity.

6

GND

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