Pin Settings
L6599
2
Pin Settings
2.1
Connection
Figure 1. Pin Connection (Top view)
VBOOT
HVG
Css
DELAY
CF
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
OUT
RFmin
STBY
ISEN
LINE
N.C.
Vcc
LVG
GND
DIS
PFC_STOP
2.2
Functions
Table 1.
N.
Pin functions
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
every time the chip turns OFF (VCC < UVLO, LINE < 1.25V or > 6V, DIS > 1.85V, ISEN >
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.
1
CSS
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.
2
DELAY
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.
3
CF
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STMICROELECTRONICS [ ST ]
