ADA4938-2ACPZ-R2 Analog Devices Inc, ADA4938-2ACPZ-R2 Datasheet - Page 23

• Manufacturer Part Number: ADA4938-2ACPZ-R2
• Description: IC ADC DRIVER DUAL DIFF 24LFCSP
• Manufacturer: Analog Devices Inc
• Type: ADC Driverr

Specifications of ADA4938-2ACPZ-R2

• Applications: Data Acquisition
• Mounting Type: Surface Mount
• Package / Case: 24-LFCSP
• No. Of Amplifiers: 2
• Input Offset Voltage: 4mV
• Bandwidth: 1GHz
• Slew Rate: 4700V/µs
• Supply Voltage Range: 4.5V To 11V
• Supply Current: 37mA
• Amplifier Case Style: LFCSP
• No. Of Pins: 24
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LAYOUT, GROUNDING, AND BYPASSING
As a high speed device, the ADA4938-x is sensitive to the
PCB environment in which it operates. Realizing its superior
performance requires attention to the details of high speed
PCB design.
The first requirement is a solid ground plane that covers as much of
the board area around the ADA4938-x as possible. However, the
area near the feedback resistors (R
and the input summing nodes should be cleared of all ground
and power planes (see Figure 66). 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. The exposed pad
is electrically isolated from the device; therefore, it can be con-
nected to a ground plane using vias. Examples of the thermal
attach pad and via structure for the ADA4938-1 are shown in
Figure 67 and Figure 68.
Figure 66. Ground and Power Plane Voiding in Vicinity of R
Figure 68. Cross-Section of a 4-Layer PCB (ADA4938-1) Showing a Thermal Via Connection to the Buried Ground Plane (Dimensions in mm)
JA
, is specified for the device, including
GROUND PLANE
BOTTOM METAL
POWER PLANE
TOP METAL
F
), input gain resistors (R
F
and R
G
G
),
Rev. A | Page 23 of 28
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. It is recommended that two parallel bypass capa-
citors (1000 pF and 0.1 μF) be used for each supply with the
1000 pF capacitor placed closer to the device; if further away,
provide low frequency bypassing using 10 μF tantalum capacitors
from each supply to ground.
Signal routing should be 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, keep
PCB traces close together and twist any differential wiring to
minimize loop area. Doing this reduces radiated energy and
makes the circuit less susceptible to interference.
Figure 67. Recommended PCB Thermal Attach Pad (ADA4938-1)
1.30
0.80
(Dimensions in mm)
ADA4938-1/ADA4938-2
1.30
0.80