L6566B STMicroelectronics, L6566B Datasheet - Page 39

• 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
Figure 26. Voltage sensing techniques to implement brownout protection with the
It is typically convenient to use a single divider to bias both the AC_OK and the VFF pins, as
shown in
is lower than that on the AC_OK pin. Once R
and k
Equation 18
Circuit a) senses the input voltage bus (across the bulk capacitor, downstream the bridge
rectifier); in this case, for a proper operation of the brownout function, Vsen
than the peak voltage at minimum mains and Vsen
the input bulk capacitor at minimum mains and maximum load considering, in case, holdup
requirements during mains missing cycles as well. Brownout level will be load-dependent. In
case of latched shutdown, when the input source is removed it is necessary to wait until the
bulk capacitor voltage falls below the start voltage of the HV generator V
the unit to restart, which may take even several seconds.
Circuit b) senses the mains voltage directly, upstream the bridge rectifier. It can be
configured either for half-wave sensing (only the line/neutral wire is sensed) or full-wave
sensing (both neutral and line are sensed); in the first case, assuming C
the sensed voltage will be equal to 1/
will be equal to 2/
to have small residual ripple superimposed on the dc level; as a rule-of-thumb, use a time
constant R
sensing, 2-3 times in case of full-wave sensing. Then fine tune if needed, considering also
transient conditions such as mains missing cycles. Brownout level will not depend on the
load. When the input source is removed C
circuit is suitable to have a quick restart after a latched shutdown.
The AC_OK pin is a high impedance input connected to high value resistors, thus it is prone
to pick up noise, which might alter the OFF threshold when the converter is running or give
origin to undesired switch-off of the device during ESD tests. It is possible to bypass the pin
to ground with a small film capacitor (e.g. 1-10 nF) to prevent any malfunctioning of this kind.
The voltage on the pin is clamped upwards at about 3.15 V; then, if the function is not used
the pin has to be connected to Vcc through a resistor (220 to 680 kΩ).
R
HV Input bus
L
opt
R
H
, either calculated from (6) or (8) or experimentally found, R
R
R
Figure 26
L1
L2
L
AC_OK
·C
L6566B
VFF
F
at least 4-5 times the maximum line cycle period in case of half-wave
π
16
15
a)
: this is possible because in all practical cases the voltage on the VFF pin
the peak mains voltage. C
OVPsettings
Optionalfor
L6566B
R
L
2
=
k
opt
(
R
π
L
the peak mains voltage, while in the second case it
+
AC mains (N/L)
R
F
H
will be discharged after some ten ms then this
H
)
F
and R
needs to be quite a big capacitor (in the uF)
;
OFF
R
R
L
H
L
have been found as suggested above,
1
AC mains (L/N)
R
lower than the minimum voltage on
=
L
R
R
H
L
−
R
R
L1
L2
R
b)
L
AC_OK
2
C
F
Application information
VFF
L
will be split as:
16
15
F
HVstart
is large enough,
ON
OVP settings
Optionalfor
L6566B
must be lower
in order for
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