L6566ATR View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6566ATR' PDF : 51 Pages View PDF
L6566A
Application information
the converter works intermittently, which is very safe. In case of overload the system has a
power capability lower than that at nominal load but the output current may be quite high
and overstressing the output rectifier. In the case of FF operation the capability is almost
unchanged and both short-circuit and overload conditions are more critical to handle.
The L6566A, regardless of the operating option selected, makes it easier to handle such
conditions: the 2 V clamp on the SS pin is removed and a second internal current generator
ISS2 = ISS1 /4 keeps on charging Css. As the voltage reaches 5 V, the device is disabled, if it
is allowed to reach 2 VBE over 5 V, the device is latched off. In the former case the resulting
behavior is identical to that under short-circuit illustrated in Figure 6; in the latter case the
result is identical to that of Figure 20. See Section 5.9 for additional details.
A diode, with the anode to the SS pin and the cathode connected to the VREF pin (10) is the
simplest way to select either auto-restart mode or latch-mode behavior upon overcurrent. If
the overload disappears before the Css voltage reaches 5 V, the ISS2 generator is turned off
and the voltage gradually brought back down to 2 V. Refer to Section 6 (Figure 7) for
additional hints.
If latch-mode behavior is desired also for converter short-circuit, make sure that the supply
voltage of the device does not fall below the UVLO threshold before activating the latch.
Figure 21 shows soft-start pin behavior under different operating conditions and with
different settings (latch-mode or auto-restart).
Figure 21. Soft-start pin operation under different operating conditions and settings
Vcc
(pin 5)
SS 5V+2Vbe
(pin 14) 5V
2V
COMP
(pin 9)
Vcc falls below UVLO
before latching off
here the IC
shuts down
here the IC
latches off
UVLO
t
t
GD
(pin 4)
t
Vcc_PFC
(pin 6)
t
START-UP
NORMAL
OPERATION
TEMPORARY
OVERLOAD
NORMAL
OPERATION
OVERLOAD
SHUTDOWN
LATCHED
AUTORESTART
t
RESTART
Note:
Unlike other PWM controllers provided with a soft-start pin, in the L6566A, grounding the SS
pin does not guarantee that the gate-driver is disabled.
Doc ID 13794 Rev 4
33/52
Share Link: 
