ADN2850 Analog Devices, Inc., ADN2850 Datasheet - Page 12

• Manufacturer Part Number: ADN2850
• Description: Nonvolatile Memory, Dual 1024 Position Programmable Resistors
• Manufacturer: Analog Devices, Inc.

ADN2850
for data 001
ing R
LSB data value increase moves the wiper up the resistor ladder
until the last tap point is reached at R
Figure 9 for a simplified diagram of the equivalent RDAC circuit.
WB
(2) = 48.8 + 50 = 98.8 Ω for data 002
25
20
15
10
5
0
0
H
. The third connection is the next tap point represent-
R
WB_FS
Figure 10. R
256
= 25k
CODE – Decimal
WB
512
(D) vs. Code
WB
(1023) = 25026 Ω. See
768
H
and so on. Each
1023
–12–
The general equation that determines the programmed output
resistance between Wx and Bx is:
where D is the decimal equivalent of the data contained in the
RDAC register, R
W and B, and R
For example, the following output resistance values will be set for
the following RDAC latch codes with V
R
D
(DEC)
1023
512
1
0
Note that in the zero-scale condition a finite wiper resistance of
50 Ω is present. In this state, care should be taken to limit the
current flow between W and B to no more than 20 mA to avoid
degradation or possible destruction of the internal switches.
Channel-to-channel R
scale. The change in R
temperature coefficient.
WB_FS
R
Table VIII. R
WB
= 25 kΩ programmable resistors):
( )
D
R
( )
25026
12550
74.4
50
=
WB
1024
W
(D)
D
WB_FS
is the wiper resistance.
WB
×
WB
is the full-scale resistance between terminals
WB
at Selected Codes (R
R
WB FS
matching is well within 1% at full-
with temperature has a 35 ppm/°C
Output State
Full-Scale
Mid Scale
1 LSB
Zero-Scale (Wiper contact resistance)
_
+
R
W
DD
= 5 V (applies to
WB_FS
= 25 k )
REV. B
(1)