L6566B STMicroelectronics, L6566B Datasheet - Page 27

• 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

L6566B
5.6
Figure 15. Externally controlled burst-mode operation by driving pin COMP: timing
PWM comparator, PWM latch and voltage feedforward blocks
The PWM comparator senses the voltage across the current sense resistor Rs and, by
comparing it to the programming signal delivered by the feedforward block, determines the
exact time when the external MOSFET is to be switched off. Its output resets the PWM
latch, previously set by the oscillator or the ZCD triggering block, which will assert the gate
driver output low. The use of PWM latch avoids spurious switching of the MOSFET that
might result from the noise generated (“double-pulse suppression”).
Cycle-by-cycle current limitation is realized with a second comparator (OCP comparator)
that senses the voltage across the current sense resistor Rs as well and compares this
voltage to a reference value V
the circuit schematic in
delivered by the feedforward block and sent to the PWM comparator exceeds V
the OCP comparator to reset first the PWM latch instead of the PWM comparator. The value
of V
The power that QR flyback converters with a fixed overcurrent setpoint (like fixed-frequency
systems) are able to deliver changes with the input voltage considerably. With wide-range
mains, at maximum line it can be more than twice the value at minimum line, as shown by
the upper curve in the diagram of
function available to solve this issue.
It acts on the overcurrent setpoint V
Vin sensed through a dedicated pin (15, VFF): the higher the input voltage, the lower the
csx
, thereby, determines the overcurrent setpoint along with the sense resistor Rs.
0.85 mA
Vcc_OK
Vcc
diagram
Vout
COMP
(pin 9)
(pin 5)
(pin 4)
I
Vcc
charge
Vcc
Vcc
GD
restart
OFF
ON
Figure 17 on page 29
csx
Standby is commanded here
. Its output is or-ed with that of the PWM comparator (see
Figure 16 on page 28
csx
, so that it is a function of the converter’s input voltage
). In this way, if the programming signal
. The device has the line feedforward
Application information
t
t
t
t
t
t
csx
, it will be
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