ADP1650ACPZ-R7 datasheet(27/32 Pages) AD

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ADP1650

Rev. C | Page 27 of 32

The worst-case capacitance accounting for capacitor variation

over temperature, component tolerance, and voltage is calcu-

lated using the following equation:

CEFF = COUT × (1 − TEMPCO) × (1 − TOL)

where:

CEFF is the effective capacitance at the operating voltage.

TEMPCO is the worst-case capacitor temperature coefficient.

TOL is the worst-case component tolerance.

In this example, the 10 μF X5R capacitor has the following

characteristics:

TEMPCO from −40°C to +85°C is 15%.

TOL is 10%.

COUT at VOUT (MAX) = 5 V, is 3 μF, as shown in Figure 44.

–10

–20

–30

–40

–50

–60

–70

–80

–90

6.30

5.04

3.78

2.52

DC BIAS VOLTAGE (V)

1.26

Figure 44. DC Bias Characteristic of a 3 × 6.3 V, 10 μF Ceramic Capacitor

Substituting these values in the equation yields

CEFF = 3 μF × (1 − 0.15) × (1 − 0.1) = 2.29 μF

The effective capacitance needed for stability, which includes

temperature and dc bias effects, is 3.0 μF.

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