ADM7151

Data Sheet

Rev. B | Page 16 of 24

APPLICATIONS INFORMATION

MODEL SELECTION

The ADM7151 is available in two models to allow the user to

select the best combination of power dissipation and PSRR

performance for a given application.

CAPACITOR SELECTION

Output Capacitor

The ADM7151 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 ADM7151. Output capacitance also affects transient

response to changes in load current. Using a larger value of

output capacitance improves the transient response of the

ADM7151 to large changes in load current. Figure 51 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 a capacitor of at least 1 µF between REF and GND.

Table 6. Model Selection Guide for PSRR

Model

PSRR (dB) at 800 mA, 1.2 V Headroom

PSRR (dB) at 400 mA, 1 V Headroom

10 kHz

100 kHz

1 MHz

10 kHz

100 kHz

1 MHz

ADM7151-02

1.5 to 4.0

91

91

50

94

94

58

ADM7151-04

1.5 to 5.1

84

84

53

94

94

67

Table 7. Model Selection Guide for Input Voltage

Model

ADM7151-02

1.5 to 4.0

4.5 V

4.5 V

ADM7151-04

1.5 to 5.1

6.2 V

6 V

1

N/A = not applicable.