LM2937

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SNVS100F – MARCH 2000 – REVISED JULY 2014

8 Application and Implementation

8.1 Application Information

capacitance value of at least 10 µF with an ESR of at least 10 m

Ω, but no more than 3 Ω. The minimum

capacitance value, and the ESR requirements apply across the entire expected operating ambient temperature

range.

8.2 Typical Application

Figure 18. LM2937 Typical Application

*Required if the regulator is located more than 3 inches from the power-supply-filter capacitors.

located as close as possible to the regulator. The equivalent series resistance, ESR, of this capacitor may be

as high as 3

Ω.

8.2.1 Design Requirements

For this design example, use the parameters listed in Table 1:

Table 1. Design Parameters

DESIGN PARAMETER

EXAMPLE VALUE

Output voltage

8 V

Input voltage

10 V to 26 V

Characteristics: LM2937-8, Electrical Characteristics: LM2937-10,

Output current requirement

Electrical Characteristics: LM2937-12, Electrical Characteristics:

LM2937-15 for details)

Input capacitor value

0.1 µF

Output capacitor capacitance

10 µF minimum

value

Output capacitor ESR value

0.01

Ω to 3 Ω

8.2.2 Detailed Design Procedure

8.2.2.1 External Capacitors

The output capacitor is critical to maintaining regulator stability, and must meet the required conditions for both

Equivalent Series Resistance (ESR) and minimum amount of capacitance.

Minimum Capacitance:

The minimum output capacitance required to maintain stability is 10

μF. (This value may be increased without

limit.) Larger values of output capacitance will give improved transient response.

ESR Limits:

The ESR of the output capacitor will cause loop instability if it is too high or too low. The acceptable range of

ESR plotted versus load current is shown in the graph below. It is essential that the output capacitor meet

these requirements, or oscillations can result.

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