Datasheet

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Stability Considerations

value of C6 and C7. Figure 7 shows the stability of the LM22670INVEVAL evaluation board taken with a

1.5A load current and a 12 V input voltage. At input voltages below 6 V, the phase margin decreases

significantly. To increase the phase margin for applications using low input voltages, select a higher

capacitance value for C6 and C7. It can be helpful to plot the loop transfer function by taking a Bode plot

using a network analyzer.

For details on how to take a Bode plot measurement using only an oscilloscope and a function generator,

see AN-1889 How to Measure the Loop Transfer Function of Power Supplies (SNVA364).

Table 1. LM22670INVEVAL Bill of Materials (BOM) for V

OUT

= -5 V, Designed for 1.5A Output Current

Ref # Value Supplier Part Number

C1, C8 2.2 µF 50 V ceramic TDK C3225X7R1H225K

C2 22 µF 63 V electrolytic Panasonic EEEFK1J220XP

C3 10 nF 50 V ceramic TDK C1608X7R1H103K

C4 120 µF 6.3 V 24 mΩ ESR Nippon Chemi-Con APXE6R3ARA121ME61G

C5 Not Populated -

C6, C7 4.7 µF 50 V ceramic TDK C4532X7R1H475M

D1 60 V, 5A Central Semiconductor CMSH5-60

L1 10 µH 4.09A Wurth WE-PD L 74477110

Coilcraft MSS1260-103MLD

R1 2.55 kΩ Vishay/Dale CRCW06032K55FKEA

R2 7.32 kΩ Vishay/Dale CRCW06037K32FKEA

R3 Not Populated -

U1 Texas Instruments LM22670MR-ADJ

SNVA363E–September 2008–Revised April 2013 AN-1888 LM22670 Evaluation Board Inverting Topology

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