AD5293 Analog Devices, AD5293 Datasheet - Page 12

• Manufacturer Part Number: AD5293
• Description: Digital Potentiometer
• Manufacturer: Analog Devices

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AD5293
potentiometer. The data bits (Dx) are the values that are loaded
into the decoded register. The AD5293 has an internal counter
that counts a multiple of 16 bits (a frame) for proper operation.
For example, the AD5293 works with a 32-bit word, but it
cannot work properly with a 31-bit or 33-bit word. The AD5293
does not require a continuous SCLK and dynamic power can be
saved by only transmitting clock pulses during a serial write. All
interface pins should be operated at close to the supply rails to
minimize power consumption in the digital input buffers.
DAISY-CHAIN OPERATION
The serial data output pin (SDO) serves two purposes. It can be
used to read the contents of the wiper setting using Command 2
(Table 7) or it can be used for daisy chaining multiple devices.
The remaining instructions are valid for daisy-chaining
multiple devices in simultaneous operations. Daisy-chaining
minimizes the number of port pins required from the
controlling IC. The SDO pin contains an open-drain N-Ch FET
that requires a pull-up resistor, if this function is used. As
shown in Figure 6, users need to tie the SDO pin of one package
Table 7. Command Operation Truth Table
Command
Number
0
1
2
3
4
5
6
Table 8. Control Register and special function codes
Register Name
Control
B13
C3
0
0
0
0
0
0
1
Command
C2
0
0
0
1
1
1
0
Data Byte
D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
X
C1
0
0
1
0
1
1
0
X X
C0
0
1
0
0
0
1
0
X
B9
D9
X
D9
X
X
X
X
X
X
D8
X
D8
X
X
X
X
X
X
X C2 C1 X
D7
X
D7
X
X
X
X
X
B8
D6
X
D6
X
X
X
X
X
Rev. PrA | Page 12 of 15
B7
D5
X
D5
X
X
X
X
X
Data
D4
X
D4
X
X
X
X
X
Operation
C1 = RDAC Register Write Protect.
C2 = Calibration Enable.
D3
X
D3
X
X
X
X
X
to the DIN pin of the next package. Users might need to
increase the clock period, because the pull-up resistor and the
capacitive loading at the SDO–DIN interface might require
additional time delay between subsequent devices.
When two AD5293s are daisy-chained, 32 bits of data are
required. The first 16 bits go to U2, and the second 16 bits go to
U1. The SYNC pin should be kept low until all 32 bits are
clocked into their respective serial registers. The SYNC pin is
then pulled high to complete the operation.
0 = Wiper position frozen to Midscale(Default)
1 = Allow update of wiper position through Digital Interface
0 = RDAC Resistor Tolerance Calibration enabled(Default)
1 = RDAC Resistor Tolerance Calibration enabled
D2
X
D2
X
X
D2
X
X
D1
X
D1
X
X
D1
X
X
Figure 6. Daisy-Chain Configuration Using SD
B0
D0
X
D0
X
X
D0
X
D0
Operation
NOP: Do nothing.
Write contents of Serial Register Data to
RDAC.
Read RDAC wiper setting from SDO
output in the next frame.
Reset: Refresh RDAC with midscale code
Write Contents of Serial Register Data to
Control Register
Read Control Register from SDO output in
the next frame.
Software Powerdown
D0 = 0; Normal Mode
D0 = 1; Device placed in powerdown
mode
Preliminary Technical Data