ADA4530-1ARZ-R7 datasheet(50/51 Pages) AD

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Data Sheet

ADA4530-1

Rev. A | Page 49 of 50

POWER SUPPLY RECOMMENDATIONS

Analog Devices offers a wide range of power management

products to meet the requirements of most high performance

signal chains.

Examples of a single- and dual-supply solution is shown in

Figure 133. The ADP2370 and ADP5075, cascaded with the

ADP7118 or ADM7170, and the ADP7182 generate clean

positive and negative rails. These rails power the ADA4530-1,

electrometer amplifier and/or the precision converter in a

typical signal chain.

+5V

3.3V

INPUT

ADP5070

BOOST AND

INVERTING

REGULATOR

ADP7118

LDO

ADP7182

LDO

ADP2370

BUCK

REGULATOR

+7.5V

OR +5V

+8.5V

OR +6V

ADP7118

LDO

ADP5075

INVERTING

REGULATOR

–8.5V

OR –6V

+6V

–6V

–5V

ADP7182

LDO

15V/12V/6V

INPUT

ADM7170/

ADP7118

LDO

+12V/+10V/+5V

12V

INPUT

–7.5V

OR –5V

Figure 133. Recommended Power Solutions

Table 16. Recommended Power Management Devices

Product

Description

ADP5075

800 mA, dc-to-dc inverting regulator

ADP2370

High voltage, 1.2 MHz/600 kHz, 800 mA, low

quiescent current buck regulator

ADP5070

1 A/0.6 A, dc-to-dc switching regulator with

independent positive and negative outputs

ADM7170

6.5 V, 500 mA, ultralow noise, high PSRR, CMOS LDO

ADP7118

20 V, 200 mA, low noise, high PSRR, CMOS LDO

ADP7182

−28 V, −200 mA, low noise, linear regulator

POWER SUPPLY CONSIDERATIONS

The PSRR of the ADA4530-1 is excellent at dc (approximately

150 dB); however, it decreases as frequency increases. To achieve

the best performance of the ADA4530-1, a low-noise supply is

necessary. If switching supplies are used for input rails, a low

dropout regulator (LDO) is essential to attenuate the switching

spurs to a level that does not affect the ADA4530-1 output.

Switching power supply noise typically spans a frequency range

from 300 kHz and up. The switching spurs can effectively be

attenuated using the LDO. Additional filtering around the LDO

may be necessary, especially when using a switching regulator to

generate an intermediate rail. Switching regulators also generate

high frequency noise content (>100 MHz), even when running

in the 100 kHz range, because of the high dv/dt of the switch

node. In this case, ferrite beads can be used, as described in the

AN-1120 Application Note and the AN-1368 Application Note.

For a single-supply application, the ADA4530-1 typically needs

a 5 V, 10 V, or 12 V supply, although a 4.5 V to 16 V supply can

also be used. An LDO like the ADM7170 or ADP7118 is ideal

to generate the low noise rail.

For a dual-supply application, the ADA4530-1 typically needs a

±5 V supply, although in some applications, a ±2.5 V to ±8 V

supply can be used. LDOs like the ADP7118 or ADM7170 are the

optimum choices for the positive supply, and the ADP7182 for

the negative supply. In addition, if a negative supply is not already

available, the ADP5075 or the ADP5070 can generate the

negative supply from a positive supply, as shown in Figure 133.

Figure 134 shows the combined PSRR of using the ADP7118 to

provide +5 V on +VSY of the ADA4530-1, and the ADP7182 to

provide –5 V on–VSY, from a 9 V battery main supply. Figure 135

shows the maximum allowable ripple at the input so that the

combined PSRR of the LDO and the amplifier can still attenuate

the noise level down to the noise floor.

For example, if the main supply to the ADP7118 and ADA4530-1

has a switching noise of 20 mV p-p at 300 kHz, Figure 135 shows

that it is below the maximum value of 90 mV p-p. Therefore,

the combined PSRR of the system can still attenuate and bring

the noise level down to the noise floor, in effect, the 300 kHz

noise at the input is not seen at the output of the amplifier.

–120

–100

–80

–60

–40

–20

10k

10M

100k

FREQUENCY (Hz)

+PSRR

–PSRR

Figure 134. Positive and Negative PSRR for the ADP7118 and ADP7182

Powering ADA4530-1, ±VSY = ±5 V, +IN = 0 V

100

1000

0.01

0.1

0.01

ADP7118

ADP7182

FREQUENCY (Hz)

Figure 135. Maximum Allowable Ripple at the Input of the LDOs to Bring

Spurs To Noise Floor Level (−120 dB)

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