Datasheet

Q1
Q2
Q3
Q4
N
P
CS
LM5046
R
F
C
F
R
CS
VIN
AGND
Q1
Q2
Q3
Q4
V
PWR
N
P
N
S1
N
S2
R
F
C
F
R
CS
CS
LM5046
VIN
AGND
NTC
THERMISTOR
OVP
LM5046
1.25V
20 PA
STANDBY
V
PWR
5V
R1
R2
T
LM5046
SNVS703G –FEBRUARY 2011–REVISED MARCH 2013 www.ti.com
Figure 30. Remote Thermal Protection
CURRENT SENSE
The CS pin receives an input signal representative of its transformer’s primary current, either from a current
sense transformer or from a resistor located at the junction of source pin of the primary switches, as shown in
Figure 31 and Figure 32, respectively. In both the cases, the filter components R
F
and C
F
should be located as
close to the IC as possible, and the ground connection from the current sense transformer, or R
SENSE
should be
a dedicated trace to the appropriate GND pin. Please refer to the layout section for more layout tips.
The current sense components must provide a signal > 710mV at the CS pin during an over-load event. Once
the voltage on the CS pin crosses the current limit threshold, the current sense comparator terminates the PWM
pulse and starts to charge the RES pin. Depending on the configuration of the RES pin, the LM5046 will
eventually initiate a hiccup mode restart or be in continuous current limit.
Figure 31. Transformer Current Sense
Figure 32. Resistor Current Sense
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