L6566B STMicroelectronics, L6566B Datasheet - Page 30

• Manufacturer Part Number: L6566B
• Description: IC CTRLR OVP OTP UVLO HV 16SOIC
• Manufacturer: STMicroelectronics

Specifications of L6566B

• Output Isolation: Isolated
• Frequency Range: 10 ~ 300kHz
• Voltage - Input: 8 ~ 23 V
• Power (watts): 750mW
• Operating Temperature: -40°C ~ 150°C
• Package / Case: 16-SOIC (0.154", 3.90mm Width)
• Output Current: 800 mA
• Output Power: 750 mW
• Input Voltage: 8 V to 23 V
• Operating Temperature Range: - 40 C to + 150 C
• Mounting Style: SMD/SMT
• Duty Cycle (max): 75 %
• Selectable Multi-mode Operation: fixed frequency or quasi-resonant
• For Use With: 497-6452 - BOARD EVAL FOR L6566B497-6451 - BOARD EVAL FOR L6566B497-6450 - BOARD EVAL FOR L6566B497-6449 - BOARD EVAL FOR L6566A
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application information
5.7
30/51
Equation 8
where Lp is the inductance of the primary winding. In case a constant maximum power
capability vs. the input voltage is not required, the VFF pin can be grounded, directly or
through a resistor (see
setpoint at 1 V, or biased at a fixed voltage through a divider from VREF to get a lower
setpoint.
It is possible to bypass the pin to ground with a small film capacitor (e.g. 1-10 nF) to ensure
a clean operation of the IC even in a noisy environment.
The pin is internally forced to ground during UVLO, after activating any latched protection
and when pin COMP is pulled below its low clamp voltage (see
block on page 26
Hiccup-mode OCP
A third comparator senses the voltage on the current sense input and shuts down the device
if the voltage on the pin exceeds 1.5 V, a level well above that of the maximum overcurrent
setpoint (1 V). Such an anomalous condition is typically generated by either a short circuit of
the secondary rectifier or a shorted secondary winding or a hard-saturated flyback
transformer.
Figure 18. Hiccup-mode OCP: timing diagram
To distinguish an actual malfunction from a disturbance (e.g. induced during ESD tests), the
first time the comparator is tripped the protection circuit enters a “warning state”. If in the
next switching cycle the comparator is not tripped, a temporary disturbance is assumed and
the protection logic will be reset in its idle state; if the comparator will be tripped again a real
malfunction is assumed and the L6566B will be stopped. Depending on the time relationship
OCP latch
Vcc_OK
(pin 5)
(pin 7)
(pin 4)
Vcc
Vcc
V
GD
Vcc
Vcc
CS
restart
OFF
ON
1.5 V
).
Section 5.11: OVP block on page 35
Secondary diode is shorted here
k
opt
=
3
Rs
Td
Lp
), hence fixing the overcurrent
Section 5.5: PWM control
L6566B
t
t
t
t
t