AD5293BRUZ-20 Analog Devices Inc, AD5293BRUZ-20 Datasheet - Page 18

• Manufacturer Part Number: AD5293BRUZ-20
• Description: IC DGTL POT 1024POS 20K 14TSSOP
• Manufacturer: Analog Devices Inc

Specifications of AD5293BRUZ-20

• Temperature Coefficient: 35 ppm/°C Typical
• Taps: 1024
• Resistance (ohms): 20K
• Number Of Circuits: 1
• Interface: SPI Serial
• Voltage - Supply: 9 V ~ 33 V, ±9 V ~ 16.5 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 14-TSSOP
• Resistance In Ohms: 20K
• End To End Resistance: 20kohm
• Track Taper: Linear
• No. Of Steps: 256
• Resistance Tolerance: ± 1%
• Control Interface: Serial, SPI
• No. Of Pots: Single
• Potentiometer Ic: RoHS Compliant
• Supply Voltage Range: ± 9V To ± 16.5V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Memory Type: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: AD5293BRUZ-20-U1; AD5293BRUZ-20-U1

AD5293
THEORY OF OPERATION
The AD5293 digital potentiometer is designed to operate as
a true variable resistor for analog signals that remain within
the terminal voltage range of V
±1% resistor tolerance feature helps to minimize the total RDAC
resistance error, which reduces the overall system error by
offering better absolute matching and improved open-loop
performance. The digital potentiometer wiper position is
determined by the RDAC register contents. The RDAC register
acts as a scratchpad register, allowing as many value changes
as necessary to place the potentiometer wiper in the correct
position. The RDAC register can be programmed with any
position setting via the standard serial peripheral interface (SPI)
by loading the 16-bit data-word.
SERIAL DATA INTERFACE
The AD5293 contains a serial interface ( SYNC , SCLK, DIN, and
SDO) that is compatible with SPI standards, as well as most DSPs.
The device allows data to be written to every register via the SPI.
SHIFT REGISTER
The AD5293 shift register is 16 bits wide (see Figure 2). The 16-bit
data-word consists of two unused bits, which are set to 0, followed
by four control bits and 10 RDAC data bits. Data is loaded MSB
first (Bit 15). The four control bits determine the function of the
software command (see Table 11). Figure 3 shows a timing diagram
of a typical write sequence.
The write sequence begins by bringing the SYNC line low. The
SYNC pin must be held low until the complete data-word is loaded
from the DIN pin. When SYNC returns high, the serial data-word
is decoded according to the instructions in
command bits (Cx) control the operation of the digital
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 (per frame) for proper operation.
For example, the AD5293 works with a 32-bit word, but it cannot
work properly with a 31- or 33-bit word. The AD5293 does not
require a continuous SCLK, when
pins should be operated close to the supply rails to minimize
power consumption in the digital input buffers.
RDAC REGISTER
The RDAC register directly controls the position of the digital
potentiometer wiper. For example, when the RDAC register is
loaded with all zeros, the wiper is connected to Terminal B of the
variable resistor. The RDAC register is a standard logic register;
there is no restriction on the number of changes allowed. The RDY
pin can be used to monitor the completion of a write to or read
from the RDAC register. The AD5293 presets to midscale on
power-up.
SS
< V
SYNC is high, and all interface
TERM
Table 11
< V
DD
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WRITE PROTECTION
On power-up, the serial data input register write command for
the RDAC register is disabled. The RDAC write protect bit, C1
of the control register (see Table 12 and Table 13), is set to 0 by
default. This disables any change of the RDAC register content,
regardless of the software commands, except that the RDAC register
can be refreshed to midscale using the software reset command
(Command 3, see Table 11) or through hardware, using the
RESET pin. To enable programming of the variable resistor wiper
position (programming the RDAC register), the write protect bit,
C1 of the control register, must first be programmed. This is
accomplished by loading the serial data input register with
Command 4 (see
BASIC OPERATION
The basic mode of setting the variable resistor wiper position
(programming the RDAC register) is accomplished by loading the
serial data input register with Command 1 (see Table 11) and the
desired wiper position data. The RDY pin can be used to monitor
the completion of this RDAC register write command. Command 2
can be used to read back the contents of the RDAC register (see
Table 11). After issuing the readback command, the RDY pin
can be monitored to indicate when the data is available to be
read out on SDO in the next SPI operation. Instead of monitoring
the RDY pin, a minimum delay can be implemented when
executing a write or read command (see Table 5). Table 9
provides an example listing of a sequence of serial data input
(DIN) words with the serial data output appearing at the SDO
pin in hexadecimal format for an RDAC write and read.
Table 9. RDAC Register Write and Read
DIN
0x1802
0x0500
0x0800
0x0000
1
SHUTDOWN MODE
The AD5293 can be placed in shutdown mode by executing the
software shutdown command (see Command 6 in Table 11), and
setting the LSB to 1. This feature places the RDAC in a special state
in which Terminal A is open-circuited and Wiper W is connected
to Terminal B. The contents of the RDAC register are unchanged
by entering shutdown mode. However, all commands listed in
Table 11 are supported while in shutdown mode.
X = unknown.
SDO
0xXXXX
0x1802
0x0500
0x0100
Table 11
1
Action
Enable update of wiper position.
Write 0x100 to the RDAC register.
Wiper moves to ¼ full-scale position.
Prepare data read from RDAC register.
NOP (Instruction 0) sends a 16-bit word
out of SDO, where the last 10 bits contain
the contents of the RDAC register.
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