Application information

HVLED001A

18/30

DocID029000 Rev 2

7.1.2

Active mode

It is the normal operational mode. During this state the external MOSFET is driven

accordingly to signals coming from the application in order to regulate the desired output

parameter in the closed loop (peak current control method).

Vcc,su threshold. The HVSU is inactive during the active mode.

7.1.3

Stop mode

This state is intended to stop the switching activity without turning off the entire function set,

to quickly restart when abnormal or disabling conditions end. During this state the power

consumption is not minimized and the soft-start procedure is not enabled.

7.1.4

Low consumption mode

This state is intended to stop the switching activity reducing the power consumption to

a minimum level. The soft-start procedure is set to be performed when abnormal or

disabling condition is removed.

During this state the VCC is kept between VCC,su and VCC,on by the high voltage startup

unit (HVSU) delivering Icharge to the output capacitor.

Note:

IMPORTANT: The HVSU charges the VCC so any other external voltage (including

auxiliary winding) must be decoupled using a diode (e.g.: 1N4148).

7.1.5

Soft-start

The soft-start phase is entered after the startup and every time the IC exits from the low

consumption mode. This phase lasts until the voltage at the CTRL pin reaches the “end of

soft-start” level (Veoss).

The current sense maximum limit is derived from this voltage, therefore the charging time of

a capacitor placed between the CTRL pin and GND defines the soft-start time.

During this phase some protections [optocoupler failure protection (OFP), brownout (BO)

and analog disable (AN_DIS)] are ignored.