LM25011MY-EVAL/NOPB National Semiconductor, LM25011MY-EVAL/NOPB Datasheet - Page 15

• Manufacturer Part Number: LM25011MY-EVAL/NOPB
• Description: EVAL BOARD FOR LM25011
• Manufacturer: National Semiconductor

Specifications of LM25011MY-EVAL/NOPB

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

FIGURE 7. Frequency vs V
FIGURE 6. Efficiency (Circuit of
IN
(Circuit of
Figure
Figure
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FIGURE 5. Example Circuit
5)
5)
15
OUTPUT RIPPLE CONTROL (LM25011A)
The LM25011A most likely will require more ripple voltage
than is generated across the RS resistor. Additional ripple can
be supplied to the FB pin, in phase with the switching wave-
form at the SW pin, for proper operation. The required ripple
can be supplied from ripple generated at V
feedback resistors, as described in Option A below. Options
B and C provide for lower output ripple with one or two addi-
tional components.
The amount of additional ripple voltage needed at the FB pin
is typically in the range of 30-150mV. Higher switching fre-
quencies or higher inductor values (less ripple current) re-
quire more ripple voltage injected on FB. Insufficient ripple
voltage will result in frequency jitter. For a particular applica-
tion, add only as much ripple as needed to stabilize the
switching frequency over the required input voltage.
Option A) Lowest Cost Configuration: In this configuration
R1 is installed in series with the output capacitor (C
shown in Figure 8. The inductor’s ripple current passes
through R1, generating a ripple voltage at V
value for R1 is:
where ΔI is the minimum ripple current amplitude, which oc-
curs at minimum Vin.
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OUT
OUT
. The minimum
, through the
www.national.com
OUT
) as