Data Sheet

ADA4620-1, ADA4620-2

analog.com

Rev. 0

46 of 49

Figure 136. 20 V Step into ADA4620 in AV = +1. Red is 80 V/µs Input Pulse, Blue is After 330 Ω, 330 pF RC into the +IN Pin, Green

is Well-Behaved Output

Recommended Power Solution

Analog Devices has a wide range of power management products that meet the requirements of most high-

performance signal chains. For a dual-supply application, the ADA4620 may need as high as a ±18 V supply. Low

dropout (LDO) linear regulators such as the LT3042 for the positive supply and the LT3093 for the negative supply

help improve the PSRR at high frequency and generate a low noise power rail. In addition, if a negative supply is

not available, the ADP5070 can generate the negative supply from a positive supply. Table 9 shows the list of the

recommended power management devices for ADA4620.

Table 9. Recommended Power Management Devices

Product

Description

ADP5070

DC-to-DC switching regulator with independent positive and negative outputs

LT3032

Dual 150 mA positive/negative low noise LDO linear regulator

LT3093

−20 V, 200 mA, ultralow noise, ultrahigh PSRR negative linear regulator

LT3042

20 V, 200 mA, ultralow noise, ultrahigh PSRR RF linear regulator

It is recommended to use a low ESR 0.1 μF bypass capacitor close to each power supply pin of the ADA4620 and

ground to reduce errors coupling in from the power supplies. For noisy power supplies, place an additional 10 μF

capacitor in parallel with the 0.1 μF for better performance.

Layout Guidelines

The ADA4620 has extremely high impedance inputs. Shunt impedances from leakage resistance and parasitic

capacitance in the PCB layout can severely degrade the performance of the low bias input in the presence of high

impedance sources. Protect against parasitic leakage currents with guarding techniques to reduce the voltage

gradient seen by the input node. Physically, a guard is a low impedance conductor that surrounds a high

impedance node and is driven to the voltage of that node. It buffers leakage by diverting the leakage from the

sensitive node and into the low impedance guard. Remove the solder mask from the guard traces and leave the

metal exposed so it can shunt rogue surface charges to itself rather than allow them to pass over and reach

sensitive nodes. For more information on guarding techniques, refer to Layout For Precision Op Amps.

Depending on the application circuit, the ADA4620-1 (single) or the ADA4620-2 (dual) may be easier to lay out. For

example, for noninverting applications, the dual has a +IN at pin 5 on the corner, easily protected by the adjacent

TIME (1μs/DIV)

AV = +1