Pin connection

HVLED805

8/29

Doc ID 18077 Rev 1

Table 5.

Pin functions

N.

Name

Function

1, 2

SOURCE

Power section source and input to the PWM comparator. The current flowing in the MOSFET

is sensed through a resistor connected between the pin and GND. The resulting voltage is

compared with an internal reference (0.75V typ.) to determine MOSFET’s turn-off. The pin is

equipped with 250 ns blanking time after the gate-drive output goes high for improved noise

immunity. If a second comparison level located at 1V is exceeded the IC is stopped and

restarted after Vcc has dropped below 5V.

3VCC

Supply Voltage of the device. An electrolytic capacitor, connected between this pin and

ground, is initially charged by the internal high-voltage start-up generator; when the device is

running the same generator will keep it charged in case the voltage supplied by the auxiliary

winding is not sufficient. This feature is disabled in case a protection is tripped. Sometimes a

small bypass capacitor (100nF typ.) to GND might be useful to get a clean bias voltage for the

signal part of the IC.

4GND

Ground. Current return for both the signal part of the IC and the gate drive. All of the ground

connections of the bias components should be tied to a trace going to this pin and kept

separate from any pulsed current return.

5ILED

CC regulation loop reference voltage. An external capacitor will be connected between this

pin and GND. An internal circuit develops a voltage on this capacitor that is used as the

reference for the MOSFET’s peak drain current during CC regulation. The voltage is

automatically adjusted to keep the average output current constant.

6DMG

Transformer’s demagnetization sensing for quasi-resonant operation. Input/output voltage

monitor. A negative-going edge triggers MOSFET’s turn-on. The current sourced by the pin

during MOSFET’s ON-time is monitored to get an image of the input voltage to the converter,

in order to compensate the internal delay of the current sensing circuit and achieve a CC

regulation independent of the mains voltage. If this current does not exceed 50µA, either a

floating pin or an abnormally low input voltage is assumed, the device is stopped and

restarted after Vcc has dropped below 5V. Still, the pin voltage is sampled-and-held right at

the end of transformer’s demagnetization to get an accurate image of the output voltage to be

fed to the inverting input of the internal, transconductance-type, error amplifier, whose non-

current has to not exceed ±2 mA (AMR) in all the Vin range conditions. No capacitor is

allowed between the pin and the auxiliary transformer.

7COMP

Output of the internal transconductance error amplifier. The compensation network will be

placed between this pin and GND to achieve stability and good dynamic performance of the

voltage control loop.

8-11

N.A

Not available. These pins must be left not connected

12

N.C

Not internally connected. Provision for clearance on the PCB to meet safety requirements.

13 to 16

DRAIN

Drain connection of the internal power section. The internal high-voltage start-up generator

sinks current from this pin as well. Pins connected to the internal metal frame to facilitate heat

dissipation.