Pin Settings

L6599

4/36

2

Pin Settings

2.1

Connection

Figure 1.

Pin Connection (Top view)

2.2

Functions

GND

Css

DELAY

STBY

ISEN

LINE

LVG

VBOOT

HVG

N.C.

Vcc

PFC_STOP

OUT

DIS

CF

RFmin

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

Table 1.

Pin functions

N.

Name

Function

Soft start. This pin connects an external capacitor to GND and a resistor to RFmin (pin 4)

that set both the maximum oscillator frequency and the time constant for the frequency shift

that occurs as the chip starts up (soft-start). An internal switch discharges this capacitor

1.5V, DELAY > 3.5V) to make sure it will be soft-started next, and when the voltage on the

current sense pin (ISEN) exceeds 0.8V, as long as it stays above 0.75V.

2DELAY

Delayed shutdown upon overcurrent. A capacitor and a resistor are connected from this pin

to GND to set both the maximum duration of an overcurrent condition before the IC stops

switching and the delay after which the IC restarts switching. Every time the voltage on the

ISEN pin exceeds 0.8V the capacitor is charged by an internal 150µA current generator and

is slowly discharged by the external resistor. If the voltage on the pin reaches 2V, the soft

start capacitor is completely discharged so that the switching frequency is pushed to its

maximum value and the 150µA is kept always on. As the voltage on the pin exceeds 3.5V

the IC stops switching and the internal generator is turned OFF, so that the voltage on the

pin will decay because of the external resistor. The IC will be soft-restarted as the voltage

drops below 0.3V. In this way, under short circuit conditions, the converter will work

intermittently with very low input average power.

3CF

Timing capacitor. A capacitor connected from this pin to GND is charged and discharged by

internal current generators programmed by the external network connected to pin 4 (RFmin)

and determines the switching frequency of the converter.