11.5 EVM and Layout Recommendations

The THS4531 EVM (SLOU334) should be used as a reference when designing the circuit board. It is recommended to follow the EVM layout of the external components near to the amplifier, ground plane construction, and power routing as closely as possible. General guidelines are:

1. Signal routing should be direct and as short as possible into and out of the op amp.
2. The feedback path should be short and direct avoiding vias if possible.
3. Ground or power planes should be removed from directly under the amplifier’s input and output pins.
4. A series output resistor is recommended to be placed as near to the output pin as possible. See Figure 77Recommended Series Output Resistor vs. Capacitive Load for recommended values given expected capacitive load of design.
5. A 2.2 µF power supply decoupling capacitor should be placed within 2 inches of the device and can be shared with other op amps. For split supply, a capacitor is required for both supplies.
6. A 0.1 µF power supply decoupling capacitor should be placed as near to the power supply pins as possible. Preferably within 0.1 inch. For split supply, a capacitor is required for both supplies.
7. The PD pin uses TTL logic levels referenced to the negative supply voltage (V_S-). When not used it should tied to the positive supply to enable the amplifier. When used, it must be actively driven high or low and should not be left in an indeterminate logic state. A bypass capacitor is not required, but can be used for robustness in noisy environments.