8 Power Supply Recommendations

The OPA388-Q1 device is specified for operation from 2.5 V to 5.5 V (±1.25 V to ±2.75 V). Parameters that can

exhibit significant variance with regard to operating voltage are presented in Section 6.6.

9 Layout

9.1 Layout Guidelines

Paying attention to good layout practice is always recommended. Keep traces short and, when possible, use a

printed-circuit board (PCB) ground plane with surface-mount components placed as close to the device pins as

possible. Place a 0.1-µF capacitor closely across the supply pins. These guidelines must be applied throughout

the analog circuit to improve performance and provide benefits such as reducing the electromagnetic

interference (EMI) susceptibility.

For lowest offset voltage and precision performance, circuit layout and mechanical conditions must be optimized.

Avoid temperature gradients that create thermoelectric (Seebeck) effects in the thermocouple junctions formed

from connecting dissimilar conductors. These thermally-generated potentials can be made to cancel by assuring

they are equal on both input terminals. Other layout and design considerations include:

• Use low thermoelectric-coefficient conditions (avoid dissimilar metals).

• Thermally isolate components from power supplies or other heat sources.

• Shield operational amplifier and input circuitry from air currents, such as cooling fans.

Following these guidelines reduces the likelihood of junctions being at different temperatures, which can cause

thermoelectric voltage drift of 0.1 µV/°C or higher, depending on materials used.

9.2 Layout Example

+

VIN

VOUT

RG

RF

Figure 9-1. Schematic Representation

N/C

±IN

+IN

V±

V+

OUTPUT

N/C

N/C

VS+

GND

Ground (GND) plane on another layer

VOUT

VIN

GND

Run the input traces

as far away from

the supply lines

as possible

RF

RG

Place components close

to device and to each

other to reduce parasitic

errors

Use low-ESR,

ceramic bypass

capacitors

GND

Figure 9-2. Layout Example

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OPA388-Q1

SBOS989 – AUGUST 2020

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