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AD5293

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RESET

A low-to-high transition of the hardware RESET pin loads the

RDAC register with midscale. The AD5293 can also be reset

through software by executing Command 3 (see

). The

control register is restored with default settings (see

Table 8

Table 10

RESISTOR PERFORMANCE MODE

This mode activates a new, patented 1% end-to-end resistor

tolerance that ensures a ±1% resistor tolerance on each code,

that is, code = half scale, RWB = 10 kΩ ± 100 Ω. See Table 2 to

verify which codes achieve ±1% resistor tolerance. The resistor

performance mode is activated by programming Bit C2 of the

control register (see Table 9 and Table 10). The typical settling

time is shown in Figure 23.

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

(see Table 8), 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-channel FET that requires

a pull-up resistor, if this function is used. As shown in Figure 32,

the SDO pin of one package must be tied to the DIN pin of the

next package. Users may need to increase the clock period because

the pull-up resistor and the capacitive loading at the SDO/DIN

interface may require an additional time delay between subsequent

devices.

When two AD5293 devices 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 held low until all 32 bits are clocked into

their respective serial registers. The SYNC pin is then pulled high

to complete the operation.

DIN

SDO

SCLK

2.2kΩ

DIN

SDO

AD5293

SYNC

VLOGIC

MICRO-

CONTROLLER

SCLK

MOSI

SYNC

Figure 32. Daisy-Chain Configuration Using SDO

Table 8. Command Operation Truth Table

Command

Command Bits[B13:B10]

Data Bits[B9:B0]1

Operation

NOP command. 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 power-down.

D0 = 0 (normal mode).

D0 = 1 (device placed in shutdown

mode).

1 X = don’t care.

Table 9. Control Register Bit Map

1 X = don’t care.

Table 10. Control Register Bit Descriptions

Bit Name

Description

Control

Calibration enable.

0 = Resistor Performance Mode (default).

1 = Normal Mode.

RDAC register write protect.

0 = locks the wiper position through the digital interface (default).

1 = allows update of wiper position through digital interface.

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