AD5273

–13–

disturbances during the programming as shown in Figure 6a. Once

the programming is completed, the supply voltage can be reduced

to 2.7 V with supply current of less than 1 µA.

AD5273

SCL

SDA

C

10 F

5V

5%

100mA

Figure 6a. OTP Power Supply Requirement

AD5273

SCL

SDA

C

10 F

5V

5%

100mA

3V

(REMOVED AFTER OTP PROGRAMMING)

Figure 6b. External Power Supply Applied for Programming

For users who have an on-board 3 V supply for portable appli-

cations, a separate 5 V supply must be applied one time in the

factories for programming and a low VF Schoktty Diode should

be designed with the AD5273 to isolate the supply voltages.

Once the programming is done, the 5 V supply can be removed

shows one such implementation.

CONTROLLING THE AD5273

There are two ways of controlling the AD5273. Users can either

program the device with computer software or with external I

controllers.

Software Programming

Due to the advantage of the one-time-programmable feature, most

systems using the AD5273 will program the devices in the facto-

ries before shipping to the end users. As a result, ADI offers device

programming software that can be implemented in the factory on

computers running Windows NT, 2000, and XP platforms. The

software can be downloaded from the AD5273 product folder at

www.analog.com and is an executable file that does not require

any programming languages or user programming skills. Figure 7

shows the software interface.

Write

The AD5273 starts at midscale after power up prior to any OTP

programming. To increment or decrement the resistance, the user

may simply move the scrollbar on the left. Once the desired set-

ting is found, the user may press the Program Permanent button

to lock the setting permanently. To write any specific values, the

user should use the bit pattern control in the upper screen and

press the Run button. The format of writing data to the device

is shown in Table I. Once the desired setting is found, the user

may turn the T bit to 1 and press the Run button to program the

setting permanently.

Read

To read the validation bits and data out from the device, the user

may simply press the Read button. The user may also set the bit

pattern in the upper screen and press the Run button. The format

of reading data out from the device is shown in Table II.

Figure 7. Computer Software

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