ADA4940-1 AD [Analog Devices], ADA4940-1 Datasheet - Page 27

• Manufacturer Part Number: ADA4940-1
• Description: Ultralow Power, Low Distortion
• Manufacturer: AD [Analog Devices]

Data Sheet
LAYOUT, GROUNDING, AND BYPASSING
As a high speed device, the
sensitive to the PCB environment in which they operate.
Realizing their superior performance requires attention to
the details of high speed PCB design.
ADA4940-1 LFCSP EXAMPLE
The first requirement is a solid ground plane that covers as
much of the board area around the
However, clear the area near the feedback resistors (R
resistors (R
of all ground and power planes (see Figure 74). Clearing the
ground and power planes minimizes any stray capacitance at
these nodes and prevents peaking of the response of the
amplifier at high frequencies.
The thermal resistance, θ
the exposed pad, soldered to a high thermal conductivity 4-layer
circuit board, as described in EIA/JESD 51-7.
Figure 74. Ground and Power Plane Voiding in Vicinity of R
G
), and the input summing nodes (Pin 2 and Pin 3)
Figure 76. Cross-Section of 4-Layer PCB Showing Thermal Via Connection to Buried Ground Plane (Dimensions in mm)
JA
, is specified for the device, including
GROUND PLANE
BOTTOM METAL
ADA4940-1/ADA4940-2
POWER PLANE
TOP METAL
ADA4940-1
as possible.
are
F
F
), gain
and R
G
Rev. B | Page 27 of 32
VIA HOLE
PLATED
1.30
0.30
Bypass the power supply pins as close to the device as possible
and directly to a nearby ground plane. Use high frequency ceramic
chip capacitors. Use two parallel bypass capacitors (1000 pF and
0.1 µF) for each supply. Place the 1000 pF capacitor closer to the
device. Further away, provide low frequency bypassing using
10 µF tantalum capacitors from each supply to ground.
Ensure that signal routing is short and direct to avoid parasitic
effects. Wherever complementary signals exist, provide a
symmetrical layout to maximize balanced performance. When
routing differential signals over a long distance, ensure that
PCB traces are close together, and twist any differential wiring
such that loop area is minimized. Doing this reduces radiated
energy and makes the circuit less susceptible to interference.
Figure 75. Recommended PCB Thermal Attach Pad Dimensions (mm)
1.30
0.80
ADA4940-1/ADA4940-2
1.30
0.80