EVAL-ADN2850-25EBZ Analog Devices Inc, EVAL-ADN2850-25EBZ Datasheet - Page 24

• Manufacturer Part Number: EVAL-ADN2850-25EBZ
• Description: BOARD EVALUATION FOR ADN2850-25
• Manufacturer: Analog Devices Inc

Specifications of EVAL-ADN2850-25EBZ

• Main Purpose: Digital Potentiometer
• Utilized Ic / Part: ADN2850-35
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Secondary Attributes: -
• Embedded: -
• Primary Attributes: -
• Lead Free Status / Rohs Status: Supplier Unconfirmed

ADN2850
RESISTANCE TOLERANCE, DRIFT, AND
TEMPERATURE COEFFICIENT MISMATCH
CONSIDERATIONS
In operation, such as gain control, the tolerance mismatch
between the digital resistor and the discrete resistor can cause
repeatability issues among various systems (see Figure 42).
Because of the inherent matching of the silicon process, it is
practical to apply the dual-channel device in this type of
application. As such, R1 can be replaced by one of the channels
of the digital resistor and programmed to a specific value. R2 can
be used for the adjustable gain. Although it adds cost, this approach
minimizes the tolerance and temperature coefficient mismatch
between R1 and R2. This approach also tracks the resistance
drift over time. As a result, these less than ideal parameters
become less sensitive to system variations.
Figure 42. Linear Gain Control with Tracking Resistance Tolerance,
* REPLACED WITH ANOTHER
CHANNEL OF RDAC
R1*
Drift, and Temperature Coefficient
V
i
–
AD8601
+
B
W
C1
R2
U1
V
O
Rev. C | Page 24 of 28
RDAC CIRCUIT SIMULATION MODEL
The internal parasitic capacitances and the external capacitive
loads dominate the ac characteristics of the RDACs. A parasitic
simulation model is shown in Figure 43.
The following code provides a macro model net list for the
25 kΩ RDAC:
.PARAM D = 1024, RDAC = 25E3
*
.SUBCKT DPOT ( W, B)
*
CW
RWB W
CB
*
.ENDS DPOT
W
B
Figure 43. RDAC Circuit Simulation Model (RDAC = 25 kΩ)
0
B
0
80E-12
{D/1024 * RDAC + 50}
11E-12
RDAC
25kΩ
W
80pF
C
11pF
B
B