The sense lines must be connected to a point on the resistor that is not shared with the main current path, as shown in Figure 7-2 above. For lowest drift, the amplifier must be mounted away from any heat generating devices, which can include the sense resistor. The traces must be one continuous trace of copper from the sense resistor pad to the amplifier input pin pad, and ideally on the same copper layer with minimal vias or connectors. This can be important around the sense resistor if the resistor is generating any significant heat gradients. Vias in the sense lines must be formed from continuous plated copper and routing through connectors must be avoided. Extending the sense lines is better than to place the amplifier in a hostile environment.

To minimize noise pickup and thermal errors, the input traces must be treated like a high-speed differential signal pair and routed tightly together with a direct path to the input pins on the same copper layer. The input traces do not need to be "impedance matched", but must follow the same matching rules about vias, spacing and equal lengths. The input traces must be run away from noise sources, such as digital lines, switching supplies or motor drive lines. Remember that these input traces can contain high voltage, and must have the appropriate trace routing clearances to other traces and layers. Since the sense traces only carry the amplifier bias current (typically about 12µA per input at room temp), the connecting input traces can be thin traces running close together. This can help with routing or creating the required spacings.

Note that, due to the nature of the device topology, the positive input bias current varies with V_SENSE with an extra current approximately equivalent to V_SENSE / 4kΩ on top of the typical 12µA bias current. The negative input bias current is not in the feedback path and does not change over V_SENSE. High or miss-matched source impedances must be avoided as this imbalance creates an additional error over input voltage.