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INA302, INA303

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SBOS775C – SEPTEMBER 2016 – REVISED MARCH 2019

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9 Power Supply Recommendations

The device input circuitry accurately measures signals on common-mode voltages beyond the power-supply

voltage, VS. For example, the voltage applied to the VS power-supply pin can be 5 V, whereas the load power-

supply voltage being monitored (VCM) can be as high as 36 V. At power-up, for applications where the common-

mode voltage (VCM) slew rate is greater than 6 V/μs with a final common-mode voltage greater than 20 V, the VS

supply is recommended to be present before VCM. If the use case requires VCM to be present before VS with VCM

under these same slewing conditions, then a 331-Ω resistor must be added between the VS supply and the VS

pin bypass capacitor.

Power-supply bypass capacitors are required for stability, and must be placed as close as possible to the supply

and ground pins of the device. A typical value for this supply bypass capacitor is 0.1 µF. Applications with noisy

or high-impedance power supplies may require additional decoupling capacitors to reject power-supply noise.

During slow power-up events, current flow through the sense resistor or voltage applied to the REF pin can result

in the output voltage momentarily exceeding the voltage at the LIMITx pins, resulting in an erroneous indication

of an out-of-range event on the ALERTx output. When powering the device with a slow ramping power rail where

an input signal is already present, all alert indications should be disregarded until the supply voltage has reached

the final value.

10 Layout

10.1 Layout Guidelines

•

Apply connections to the current-sense resistor, RSENSE, on the inside of the resistor pads to avoid additional

voltage losses incurred by the high current traces to the resistor. Route the traces from the current-sense

resistor symmetrically and side-by-side back to the input of the INA to minimize common-mode errors and

noise pickup.

•

Place the power-supply bypass capacitor as closely as possible to the supply and ground pins. The

recommended value of this bypass capacitor is 0.1 µF. Additional decoupling capacitance can be added to

compensate for noisy or high-impedance power supplies.

•

Make the connection of RLIMIT to the ground pin as direct as possible to limit additional capacitance on this

node. Routing this connection must be limited to the same plane if possible to avoid vias to internal planes. If

the routing can not be made on the same plane and must pass through vias, make sure that a path is routed

from RLIMIT back to the ground pin, and that RLIMIT is not simply connected directly to a ground plane.

•

Routing to the delay capacitor must be short and direct. Keep the routing trace from the DELAY pin to the

delay capacitor away from the ALERT2 trace (or any other noisy signals) to minimize any coupling effects. If

no delay capacitor is used do not have any connection to the DELAY pin. Long trace lengths on the DELAY

pin can cause noise to couple to the device, resulting in false trips.

•

Pull up the open-drain output pins to the supply voltage rail; a 10-kΩ pullup resistor is recommended.