OPA4990IPWR datasheet(36/93 Pages) TI2

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9 Power Supply Recommendations

The OPAx990 is specified for operation from 2.7 V to 40 V (±1.35 V to ±20 V); many specifications apply from

–40°C to 125°C or with specific supply voltages and test conditions. Parameters that can exhibit significant

variance with regard to operating voltage or temperature are presented in the Typical Characteristics section.

CAUTION

Supply voltages larger than 40 V can permanently damage the device; see the Absolute Maximum

Ratings.

Place 0.1-µF bypass capacitors close to the power-supply pins to reduce errors coupling in from noisy or

high-impedance power supplies. For more detailed information on bypass capacitor placement, refer to the

Layout section.

10 Layout

10.1 Layout Guidelines

For best operational performance of the device, use good PCB layout practices, including:

• Noise can propagate into analog circuitry through the power pins of the circuit as a whole and op amp itself.

Bypass capacitors are used to reduce the coupled noise by providing low-impedance power sources local to

the analog circuitry.

– Connect low-ESR, 0.1-µF ceramic bypass capacitors between each supply pin and ground, placed as

close to the device as possible. A single bypass capacitor from V+ to ground is applicable for single-

supply applications.

• Separate grounding for analog and digital portions of circuitry is one of the simplest and most-effective

methods of noise suppression. One or more layers on multilayer PCBs are usually devoted to ground planes.

A ground plane helps distribute heat and reduces EMI noise pickup. Make sure to physically separate digital

and analog grounds paying attention to the flow of the ground current.

• In order to reduce parasitic coupling, run the input traces as far away from the supply or output traces as

possible. If these traces cannot be kept separate, crossing the sensitive trace perpendicular is much better as

opposed to in parallel with the noisy trace.

• Place the external components as close to the device as possible. As illustrated in Figure 10-2, keeping RF

and RG close to the inverting input minimizes parasitic capacitance.

• Keep the length of input traces as short as possible. Always remember that the input traces are the most

sensitive part of the circuit.

• Consider a driven, low-impedance guard ring around the critical traces. A guard ring can significantly reduce

leakage currents from nearby traces that are at different potentials.

• Cleaning the PCB following board assembly is recommended for best performance.

• Any precision integrated circuit may experience performance shifts due to moisture ingress into the plastic

package. Following any aqueous PCB cleaning process, baking the PCB assembly is recommended to

remove moisture introduced into the device packaging during the cleaning process. A low temperature, post

cleaning bake at 85°C for 30 minutes is sufficient for most circumstances.

10.2 Layout Example

VIN

VOUT

Figure 10-1. Schematic Representation

OPA990, OPA2990, OPA4990

SBOS933I – FEBRUARY 2019 – REVISED AUGUST 2021

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