ADA4896-2ACP-EBZ AD [Analog Devices], ADA4896-2ACP-EBZ Datasheet - Page 24

• Manufacturer Part Number: ADA4896-2ACP-EBZ
• Description: 1 nV/?Hz, Low Power
• Manufacturer: AD [Analog Devices]

ADA4896-2/ADA4897-1/ADA4897-2
LAYOUT CONSIDERATIONS
To ensure optimal performance, careful and deliberate attention
must be paid to the board layout, signal routing, power supply
bypassing, and grounding.
Ground Plane
It is important to avoid ground in the areas under and around the
input and output of the ADA4896-2/ADA4897-1/ADA4897-2.
Stray capacitance created between the ground plane and the
input and output pads of a device is detrimental to high speed
amplifier performance. Stray capacitance at the inverting input,
along with the amplifier input capacitance, lowers the phase
margin and can cause instability. Stray capacitance at the output
creates a pole in the feedback loop, which can reduce phase margin
and can cause the circuit to become unstable.
Power Supply Bypassing
Power supply bypassing is a critical aspect in the performance
of the ADA4896-2/ADA4897-1/ADA4897-2. A parallel connec-
tion of capacitors from each power supply pin to ground works
best. Smaller value capacitor electrolytics offer better high
frequency response, whereas larger value capacitor electrolytics
offer better low frequency performance.
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B
Paralleling different values and sizes of capacitors helps to ensure
that the power supply pins are provided with a low ac impedance
across a wide band of frequencies. This is important for minimiz-
ing the coupling of noise into the amplifier—especially when the
amplifier PSRR begins to roll off—because the bypass capacitors
can help lessen the degradation in PSRR performance.
The smallest value capacitor should be placed on the same side
of the board as the amplifier and as close as possible to the amp-
lifier power supply pins. The ground end of the capacitor should
be connected directly to the ground plane.
It is recommended that a 0.1 μF ceramic capacitor with a 0508
case size be used. The 0508 case size offers low series inductance
and excellent high frequency performance. A 10 μF electrolytic
capacitor should be placed in parallel with the 0.1 μF capacitor.
Depending on the circuit parameters, some enhancement to
performance can be realized by adding additional capacitors.
Each circuit is different and should be analyzed individually for
optimal performance.
Data Sheet