LM25010EVAL National Semiconductor, LM25010EVAL Datasheet - Page 14

• Manufacturer Part Number: LM25010EVAL
• Description: BOARD EVALUATION LM25010
• Manufacturer: National Semiconductor

Specifications of LM25010EVAL

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 5V
• Current - Output: 1A
• Voltage - Input: 6 ~ 42V
• Regulator Topology: Buck
• Frequency - Switching: 200kHz
• Board Type: Fully Populated
• Utilized Ic / Part: LM25010
• Lead Free Status / RoHS Status: Not applicable / Not applicable
• Power - Output: -

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MINIMUM LOAD CURRENT
The LM25010 requires a minimum load current of 500 µA. If
the load current falls below that level, the bootstrap capacitor
(C4) may discharge during the long off-time, and the circuit
FIGURE 7. Efficiency vs Load Current and V
C4, C6
Item
R
C1
C2
C3
C5
D1
R1
R2
R3
U1
L1
ON
FIGURE 8. Frequency vs V
Circuit of Figure 6
Circuit of Figure 6
IN
National Semi LM25010
Ceramic Capacitor
Ceramic Capacitor
Ceramic Capacitor
Ceramic Capacitor
Ceramic Capacitor
20172737
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Schottky Diode
Description
Resistor
Resistor
Resistor
Resistor
Inductor
IN
14
will either shutdown, or cycle on and off at a low frequency. If
the load current is expected to drop below 500 µA in the ap-
plication, R1 and R2 should be chosen low enough in value
so they provide the minimum required current at nominal
V
LOW OUTPUT RIPPLE CONFIGURATIONS
For applications where low output voltage ripple is required
the output can be taken directly from the low ESR output ca-
pacitor (C2) as shown in Figure 9. However, R3 slightly
degrades the load regulation. The specific component values,
and the application determine if this is suitable.
Where the circuit of Figure 9 is not suitable, the circuits of
Figure 10 or Figure 11 can be used.
In Figure 10, Cff is added across R1 to AC-couple the ripple
at V
to be reduced, in some cases considerably, by reducing R3.
In the circuit of Figure 6, the ripple at V
mVp-p at V
OUT
FIGURE 10. Low Output Ripple Using a Feedforward
OUT
.
directly to the FB pin. This allows the ripple at V
IN
= 6V to 285 mVp-p at V
FIGURE 9. Low Ripple Output
Capacitor
(2) 2.2 µF, 50V
0.022 µF, 16V
0.47 µF, 16V
0.1 µF, 50V
22 µF, 16V
60V, 2A
100 µH
200 kΩ
1.0 kΩ
1.0 kΩ
Value
1.5 Ω
IN
OUT
= 40V. By adding a
ranged from 50
20172748
20172715
OUT