AD4884BBCZ datasheet(47/116 Pages) AD

47 / 116 page

Data Sheet

AD4884

APPLICATIONS INFORMATION

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Rev. 0 | 47 of 116

POWER SOLUTION

With such low noise and up to a 20MHz sampling rate, it is

important that careful consideration is taken for the power solution

of applications to ensure that the low noise supplies provided to the

AD4884 do not become a source of performance or accuracy deg-

radation. To aid ease of use and to help reduce external required

components, four internal LDO regulators are integrated within the

AD4884. For more details on these regulators, see the Internally

Regulated Supply Configuration section. Also, note that the internal

supply decoupling capacitors are included for all supply rails (see

Table 8), whether generated internally or externally, reducing exter-

nal component count, simplifying use, and offering huge benefits to

PCB layout, routing, and design density.

For generating the required supplies in the application, excellent

choice LDO regulators are the LT3045 or ADP150 for positive rails,

while ADP7182 or ADP7183 can be used to create a negative rail

for −VS, all of them offer ultra-low noise and excellent power supply

rejection. For high efficiency, step-down switching regulators, the

LT8604C is a good choice that can be used for both positive

and negative rail generation, however, a user must take care in

the design of the switching regulator circuity because switching fre-

quencies are possibly to be within the application signal bandwidth,

and although the AD4884 has high AC power supply rejection on

its supplies, appropriate consideration must be given to the supply

rails.

The AD4884 is fully specified with the nominal FDA supply voltages

of +VS = +5V and −VS = −1V, which allow reaching optimum

performance at very low-power consumption. The voltage span

across ±VS can be increased up to the specified maximum of 10V,

with a penalty paid in the form of increased power consumption.

This enables the reuse of an existing quiet rail in the system (for

example, a −5V rail for −VS) if convenient. Conversely, the FDA

supply span can be lowered down to a minimum of 3V for the

absolute minimum power consumption, but performance degrada-

tion must be expected as FDA supply span decreases (see Figure

7) because the full ADC input range cannot be exercised at the

specified distortion levels.

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