Datasheet

LM5032
CS1
OUT1
GND1
VIN
Q1
R1
Power
Transformer
R
F
C
F
V
PWR
LM5032
CS1
OUT1
GND1
VIN
R1
Power
Transformer
Current
Sense
Q1
V
PWR
C
F
R
F
LM5032
www.ti.com SNVS344A –MARCH 2005–REVISED APRIL 2013
If the LM5032 is to be synchronized to an external clock, that signal must be coupled into the RT/SYNC pin
through a 100 pF capacitor. The external synchronizing frequency must be at least 4% higher than the free
running frequency set by the R
T
resistor and no higher than twice the free running frequency. The RT/SYNC pin
voltage is nominally regulated at 2.0V and the external pulse amplitude should lift the pin to between 3.8V and
5.0V on the low-to-high transition. The synchronization pulse width should be between 15 and 150 ns. The R
T
resistor is always required, whether the oscillator is free running or externally synchronized.
VOLTAGE FEEDBACK, COMP1, COMP2
Each COMP pin is designed to accept a voltage feedback signal from the respective regulated output via an
error amplifier and (typically) an opto-coupler. A typical configuration is shown in Figure 18. V
OUT
is compared to
a reference by the error amplifier which has an appropriate frequency compensation network. The amplifier’s
output drives the opto-coupler, which in turn drives the COMP pin.
When the LM5032’s two controller channels are configured to provide a single high current output, COMP1 and
COMP2 are typically connected together, and to the feedback signal from the optocoupler.
CURRENT SENSE, CS1, CS2
Each CS pin receives an input signal representative of its transformer’s primary current, either from a current
sense transformer or from a resistor in series with the source of the primary switch, as shown in Figure 28 and
Figure 29. In both cases the sensed current creates a ramping voltage across R1, and the R
F
/C
F
filter
suppresses noise and transients. R1, R
F
and C
F
should be as physically close to the LM5032 as possible, and
the ground connection from the current sense transformer, or R1, should be a dedicated track to the appropriate
GND pin. The current sense components must provide >0.5V at the CS pin when an over-current condition
exists.
Figure 28. Current Sense Using a Current Sense Transformer
Figure 29. Current Sense Using a Source Sense Resistor (R1)
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