ADA4530-1ARZ-R7 datasheet(49/52 Pages) AD

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Data Sheet

ADA4530-1

POWER SUPPLY RECOMMENDATIONS

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Rev. C | 49 of 52

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.

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 drop-

out 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 neces-

sary, 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.

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

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

ADA4530-1ARZ-R7 数据表(PDF) 49 Page - Analog Devices

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