ADN2850BCP250 Analog Devices Inc, ADN2850BCP250 Datasheet - Page 18

• Manufacturer Part Number: ADN2850BCP250
• Description: IC DGTL RHEO DL 1024POS 16LFCSP
• Manufacturer: Analog Devices Inc

Specifications of ADN2850BCP250

• Taps: 1024
• Resistance (ohms): 250K
• Number Of Circuits: 2
• Temperature Coefficient: 35 ppm/°C Typical
• Memory Type: Non-Volatile
• Interface: 4-Wire SPI Serial
• Voltage - Supply: 3 V ~ 5.5 V, ±2.25 V ~ 2.75 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-LFCSP
• Resistance In Ohms: 250K
• Number Of Elements: 2
• # Of Taps: 1024
• Resistance (max): 250KOhm
• Power Supply Requirement: Single/Dual
• Interface Type: Serial (4-Wire/SPI)
• Single Supply Voltage (typ): 5V
• Dual Supply Voltage (typ): ±2.5V
• Single Supply Voltage (min): 3V
• Single Supply Voltage (max): 5.5V
• Dual Supply Voltage (min): ±2.25V
• Dual Supply Voltage (max): ±2.75V
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 16
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• For Use With: EVAL-ADN2850-25EBZ - BOARD EVALUATION FOR ADN2850-25
• Lead Free Status / RoHS Status: Not Compliant, Contains lead / RoHS non-compliant

ADN2850
Using CS to Re-Execute a Previous Command
Another subtle feature of the ADN2850 is that a subsequent CS
strobe, without clock and data, repeats a previous command.
Using Additional Internal Nonvolatile EEMEM
The ADN2850 contains additional user EEMEM registers for
storing any 16-bit data such as memory data for other components,
look-up tables, or system identification information. Table 10 pro-
vides an address map of the internal storage registers shown in the
functional block diagram (see Figure 1) as EEMEM1, EEMEM2,
and 26 bytes (13 addresses × 2 bytes each) of User EEMEM.
Table 10. EEMEM Address Map
EEMEM No.
1
2
3
4
…
15
16
1
2
3
Calculating Actual End-to-End Terminal Resistance
The resistance tolerance is stored in the EEMEM register during
factory testing. The actual end-to-end resistance can, therefore,
be calculated, which is valuable for calibration, tolerance matching,
and precision applications. Note that this value is read only and
the R
0.1%.
The resistance tolerance in percentage is contained in the last
16 bits of data in EEMEM Register 15. The format is the sign
magnitude binary format with the MSB designate for sign
(0 = negative and 1 = positive), the next 7 MSB designate the
integer number, and the 8 LSB designate the decimal number
(see Table 12).
Table 12. Calculating End-to-End Terminal Resistance
Bit
Sign
Mag
Read only.
RDAC data stored in EEMEM locations is transferred to the corresponding
RDAC register at power-on, or when Instruction 1, Instruction 8, and PR are
executed.
USERx are internal nonvolatile EEMEM registers available to store and
retrieve constants and other 16-bit information using Instruction 3 and
Instruction 9, respectively.
WB2
D15
Sign
at full scale matches with R
D14
2
6
Address
0000
0001
0010
0011
…
1110
1111
D13
2
5
7 Bits for Integer Number
D12
2
4
EEMEM Content for …
RDAC1
RDAC2
USER1
USER2
…
USER13
R
WB1
WB1
D11
2
tolerance
3
at full scale, typically
2
1
D10
2
2
3
D9
2
1
Rev. C | Page 18 of 28
D8
2
0
Decimal
Point
.
For example, if R
shows XXXX XXXX 1001 1100 0000 1111, R
be calculated as follows:
RDAC STRUCTURE
The RDAC contains multiple strings of equal resistor segments
with an array of analog switches that acts as the wiper
connection. The number of positions is the resolution of the device.
The ADN2850 has 1024 connection points, allowing it to provide
better than 0.1% setability resolution. Figure 32 shows an
equivalent structure of the connections among the three
terminals of the RDAC. The SW
switches, SW(0) to SW(2
the resistance position decoded from the data bits. Because the
switch is not ideal, there is a 30 Ω wiper resistance, R
resistance is a function of supply voltage and temperature. The
lower the supply voltage or the higher the temperature, the
higher the resulting wiper resistance. Users should be aware of
the wiper resistance dynamics, if accurate prediction of the
output resistance is needed.
Table 11. Nominal Individual Segment Resistor Values
Device Resolution
1024-Step
MSB: 1 = positive
Next 7 LSB: 001 1100 = 28
8 LSB: 0000 1111 = 15 × 2
% tolerance = 28.06%
Therefore, R
D7
2
−1
R
S
D6
2
= R
DIGITAL
CIRCUITRY
OMITTED FOR
CLARITY
−2
REGISTER
DECODER
Figure 32. Equivalent RDAC Structure
WB_RATED
WB
WB_NOMINAL
WIPER
RDAC
AND
at full scale = 320.15 kΩ
D5
2
−3
8 Bits for Decimal Number
N
= 250 kΩ and the data in the SDO
− 1), are on one at a time, depending on
/2
D4
2
N
R
R
R
−4
−8
S
S
S
B
= 0.06
is always on, while the
SW(2
SW(2
25 kΩ
24.4Ω
D3
2
SW
SW
SW
−5
N –
N –
(1)
(0)
B
2)
1)
D2
2
WB
−6
at full scale can
W
B
250 kΩ
244Ω
D1
2
W
−7
. Wiper
D0
2
−8