L6699DTR STMicroelectronics, L6699DTR Datasheet - Page 26

• Manufacturer Part Number: L6699DTR
• Description: AC/DC Switching Converters Enhanced High Volt Res CTRL 600V
• Manufacturer: STMicroelectronics

Specifications of L6699DTR

• Product Category: AC/DC Switching Converters

Current sensing, OCP and OLP
26/38
therefore providing the system with immunity to short duration phenomena. If, instead, T
is exceeded, an overload protection (OLP) procedure is activated that shuts down the L6699
and, in case of continuous overload/short-circuit, results in continuous intermittent operation
with a user-defined duty cycle.
This function is realized on pin 2 (DELAY), with a capacitor C
R
comparator, in addition to turning on the switch that discharges C
generator that sources 350 µA for 50 µs from the DELAY pin and charges C
overload/short-circuit the OCP comparator and the internal current source is repeatedly
activated and C
the characteristics of the resonant circuit, and the short-circuit impedance; the discharge
due to R
This operation continues until the voltage on C
the time T
not a simple relationship that links T
experimentally. As a rough indication, using 1 µF for C
case of a dead short on the output.
In the case of an overload lasting less than T
decays with the time constant C
is shorter if this occurs before C
up to 2 V, the internal switch that discharges C
pin is pulled low, and the 350 µA current source is forced continuously on until V(DELAY)
reaches 3.5 V. This phase lasts:
Equation 10
with T
close to f
resonant circuit. As V(DELAY) equals 3.5 V, the L6699 stops switching and the internal 350
µA generator is turned off, so that C
when V(DELAY) falls below 0.3 V, which takes:
Equation 11
The timing diagram of
voltage of the L6699 (V
does not restart immediately after V
higher than 0.3 V. Also the PFC_STOP pin stays low as long as V(DELAY) is greater than
0.3 V.
Delay
MP
connected to ground. As the voltage on the ISEN pin exceeds 0.8 V, the first OCP
Delay
start
expressed in ms and C
SH
, or until the overload/short-circuit disappears, whichever occurs first. There is
(see
is negligible because the associated time constant is typically much longer.
Delay
Section 6.3: Safe-start procedure
T
STOP
is charged with an average current depending essentially on C
Figure 20
CC
=
) falls below the UVLO threshold the IC records the event and
R
Delay
Doc ID 022835 Rev 2
Delay
Delay
Delay
shows this operation. Note that if during TSTOP the supply
·
C
Delay
CC
SH
T
·R
is totally discharged. If, on the other hand, it is charged
Delay
MP
in µF. During this time the L6699 runs at a frequency
Delay
to C
exceeds the startup threshold, if V(DELAY) is still
≈
is slowly discharged by R
·
ln
. Note that the value of T
Delay
. 4
SH
. 0
3
· 3
SS
Delay
5 .
33
, C
, so it is more practical to determine C
C
is continuously turned on, the PFC_STOP
Delay
≈
, V(DELAY), reaches 2 V, which defines
De lay
) to minimize the energy inside the
. 2
Delay
is no longer charged, so its voltage
· 4
, T
R
SH
Delay
Delay
should be around 100 ms in
SS
·
and a parallel resistor
Delay
C
, turns on a current
SH
Delay
for the next overload
. The IC restarts
Delay
. During an
SS
L6699
, R
Delay
SH
SS
,