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User Guide
EVALUATION BOARD HARDWARE
GAIN SWITCH CONTROL
The ADA4351-2 has two channels, A and B. Each channel is
connected to two feedback paths that can each be accessed by
toggling the switch control pins, SW SEL A (SELA) for Channel A
and SW SEL B (SELB) for Channel B, to either low or high.
The EVAL-ADA4351-2EBZ provides two methods for controlling the
gain switch: through pin headers or through mounted SMA jack
connectors. In addition, the ADA4351-2 has a pull-down feature
that automatically sets the switch control to low when connections
to both switch control methods are open.
feedback path is active based on the state of the switch control.
Switch Control via Pin Headers
The EVAL-ADA4351-2EBZ provides pin headers that, when short-
ed, connects to the DVDD supply to change the switch state from
low to high. The pin header for Channel A is P5 (SELA), as shown
in
Figure
3, while the pin header for Channel B is P4 (SELB).
Switch Control via SMA Jack Connectors
The EVAL-ADA4351-2EBZ comes with a mounted SMA female
jack for each channel; these can connect power supplies or any
other voltage sources, such as pulse generators or batteries, to the
Table 4. Switch Control and Gain Setting
Default Gain Setting
Channel
(Feedback Path)
A
40.2 kΩ (SW0 A)
499 kΩ (SW1 A)
B
40.2 kΩ (SW0 B)
499 kΩ (SW1 B)
analog.com
Table 4
details which
Designator
Gain Switch Control State
R21
SW SEL A = low
R22
SW SEL A = high
R23
SW SEL B = low
R24
SW SEL B = high
EVAL-ADA4351-2
switch control pins. The SMA jack for Channel A is J8 (SELA), and
the SMA jack for Channel B is J7 (SELB)(see
GAIN SETTING
As mentioned, each channel of the
paths accessible by selecting their designated switch state. Each
path, SW0 x and SW1 x (where x equals the channel letter),
contains a resistor that declares the gain of the channel.
By default, the EVAL-ADA4351-2EBZ has both channels populated
with 40.2 kΩ resistors for SW0 x (R21 for Channel A and R23 for
Channel B) and 499 kΩ resistors for SW1 x (R22 for Channel A
and R24 for Channel B). In addition, the 40.2 kΩ resistor of each
channel is compensated with a 3.3 pF capacitor (C11 for Channel A
and C13 for Channel B), as shown in
These resistors can be replaced on the board for different gain
settings by swapping out R21 for the feedback path of SW0 A or
R22 for the feedback path of SW1 A for Channel A, and R23 for
the feedback path of SW0 B or R24 for the feedback path of SW1
B of Channel B. When swapping out the default resistors, be aware
that the compensation capacitors (C11 and C12 for Channel A and
C13 and C14 for Channel B) may require adjustment for optimal
system performance. Refer to
gain setting.
Pin Header Connection
Leave P5 open.
Install jumper at P5.
Leave P4 open.
Install jumper at P4.
Figure
3).
ADA4351-2
has two feedback
Figure
8.
Table 4
on how to access a specific
Switch Setting Methods
SMA Connection
Set the voltage level to less
than DVSS + 0.5 V for J8.
Set the voltage level to greater
than DVDD − 0.7 V for J8.
Set the voltage level to less
than DVSS + 0.5 V for J7.
Set the voltage level to greater
than DVDD − 0.7 V for J7.
Rev. 0 | 4 of 9
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