Datasheet

AD5273
Rev. H | Page 16 of 24
CONTROLLING THE AD5273
To control the AD5273, users can program the device with
either computer software or with external I
2
C controllers.
SOFTWARE PROGRAMMING
Because of the OTP feature, users can program the AD5273 in
the factory before shipping it to end users. Therefore, Analog
Devices offers device programming software that can be imple-
mented in the factory on computers running Windows NT,
Windows 2000, and Windows XP platforms. The software,
which can be downloaded from the AD5273 product page at
www.analog.com, is an executable file that does not require any
programming languages or user programming skills. Figure 39
shows the software interface.
03224-040
Figure 39. Software Interface
Write
The AD5273 starts at midscale after power-up prior to any OTP
programming. To increment or decrement the resistance, move
the scrollbar on the left. Once the desired setting is found, click
Program Permanent to lock the setting permanently. To write
any specific values, use the bit pattern control in the upper
section and click
Run. The format of writing data to the device
is shown in Figure 31. Once the desired setting is found, set the
T bit to 1 and click
Run to program the setting permanently.
Read
To read the validation bits and data from the device, click Read.
The user can also set the bit pattern in the upper section and
click
Run. The format of reading data from the device is shown
in Figure 32.
To control the device in both read and write operations, the
program generates the I
2
C digital signals through the parallel
port LPT1 Pin 2, Pin 3, Pin 15, and Pin 25 for SDA_write, SCL,
SDA_read, and DGND, respectively (see Figure 40).
To apply the device programming software in the factory, lay
out the AD5273 SCL and SDA pads on the PCB such that the
programming signals can be communicated to and from the
parallel port (see Figure 40). Figure 41 shows a recommended
AD5273 PCB layout into which pogo pins can be inserted for
factory programming. To prevent damaging the PC parallel
port, 100 Ω resistors should also be put in series to the SCL and
SDA pins. Pull-up resistors on SCL and SDA are also required.
03224-041
13
25
12
24
11
23
10
22
9
21
8
20
7
19
6
18
5
17
4
16
3
15
2
14
1
SCL
R3
100Ω
R1
100Ω
R2
100Ω
SDA
READ
WRITE
R4
10kΩ
R5
10kΩ
V
DD
Figure 40. Parallel Port Connection; Pin 2 = SDA_Write, Pin 3 = SCL,
Pin 15 = SDA_Read, and Pin 25 = DGND
W
V
DD
GND
SCL
A
B
AD0
SDA
03224-042
Figure 41. Recommended AD5273 PCB Layout