ADM7150

Data Sheet

APPLICATIONS INFORMATION

CAPACITOR SELECTION

Output Capacitor

The ADM7150 is designed for operation with ceramic capacitors

but functions with most commonly used capacitors as long as

care is taken with regard to the effective series resistance (ESR)

value. The ESR of the output capacitor affects the stability of the

LDO control loop. A minimum of 10 µF capacitance with an

ESR of 0.2 Ω or less is recommended to ensure the stability of the

ADM7150. Output capacitance also affects transient response to

changes in load current. Using a larger value of output capacitance

improves the transient response of the ADM7150 to large changes

in load current. Figure 53 shows the transient responses for an

output capacitance value of 10 µF.

A CH1

200mA

1

2

T

Input and VREG Capacitor

Connecting a 10 µF capacitor from VIN to GND reduces the

circuit sensitivity to PCB layout, especially when long input

traces or high source impedance are encountered.

To maintain the best possible stability and PSRR performance,

connect a 10 µF capacitor from VREG to GND. When more

than 10 µF of output capacitance is required, increase the input

and VREG capacitors to match it.

REF Capacitor

The REF capacitor is necessary to stabilize the reference amplifier.

Connect at least a 1 µF capacitor between REF and GND.

BYP Capacitor

The BYP capacitor is necessary to filter the reference buffer. A

1 µF capacitor is typically connected between BYP and GND.

Capacitors as small as 0.1 µF can be used; however, the output

noise voltage of the LDO increases as a result.

In addition, the BYP capacitor value can be increased to reduce

the noise below 1 kHz at the expense of increasing the start-up

the noise below 10 Hz. Tantalum capacitors are recommended for

capacitors larger than approximately 33 µF. A 1 μF ceramic

capacitor in parallel with the larger tantalum capacitor is required

to retain good noise performance at higher frequencies. Solid

tantalum capacitors are less prone to microphonic noise issues.

FREQUENCY (Hz)

1M

0.1

1

10

100

1k

10k

100k

1

100k

100

1k

10k

10

1000

1

10

100

1

10k

100

1k

10

1Hz

10Hz

100Hz

400Hz

3Hz

30Hz

300Hz

1kHz

Different Frequencies

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