LM2611_05 NSC [National Semiconductor], LM2611_05 Datasheet - Page 12

• Manufacturer Part Number: LM2611_05
• Description: 1.4MHz Cuk Converter
• Manufacturer: NSC [National Semiconductor]

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Application Circuits
Split Supply Operation
The LM2611 may be operated with separate power and bias
supplies. In the circuit shown in Figure 12. V
supply that the regulated voltage is derived from, and V
a low current supply used to bias the LM2611. Conditions for
the supplies are:
As the input voltage increases, the maximum output current
capacbility increases. Using a separate, higher voltage sup-
ply for power conversion enables the LM2611 to provide
higher output currents than it would with a single supply that
is limited in voltage by V
0V ≤ V
2.7V ≤ V
IN
FIGURE 12. LM2611 Operating with Separate Power and Biasing Supplies
IN(MAX)
≤ (36 - IV
DD
.
≤ 14V
OUT
(Continued)
I) V
IN
is the power
DD
is
12
Shutdown/Soft Start
A soft start circuit is used in switching power supplies to limit
the input inrush current upon start-up. Without a soft-start
circuit, the inrush current can be several times the steady-
state load current, and thus apply unnecessary stress to the
input source. The LM2611 does not have soft-start circuitry,
but implementing the circuit in Figure 13 will lower the peak
inrush current. The SHDN pin is coupled to the output
through C
run states while the output slowly decreases to its steady-
state value. The energy required to reach steady-state is
spread over a longer time and the input current spikes
decrease (see Figure 14 and Figure 15).
SS
. The LM2611 is toggled between shutdown and
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