AD5204/AD5206 Data Sheet
Rev. D | Page 12 of 20
OPERATION
The AD5204 provides a 4-channel, 256-position digitally
controlled VR device, and the AD5206 provides a 6-channel,
256-position digitally controlled VR device. Changing the pro-
grammed VR settings is accomplished by clocking an 11-bit
serial data-word into the SDI pin. The format of this data-word
is three address bits, MSB first, followed by eight data bits, MSB
first. Table 6 provides the serial register data-word format.
Table 6. Serial Data-Word Format
Address Data
B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0
MSB LSB MSB LSB
2
10
2
8
2
7
2
0
See Table 10 for the AD5204/AD5206 address assignments to
decode the location of the VR latch receiving the serial register
data in Bit B7 through Bit B0. The VR outputs can be changed
one at a time in random sequence. The AD5204 presets to
midscale by asserting the
PR
pin, simplifying fault condition
recovery at power up. Both parts have an internal power-on
preset that places the wiper in a preset midscale condition at
power on. In addition, the AD5204 contains a power shutdown pin
(
SHDN
) that places the RDAC in a zero power consumption
state, where terminals Ax are open circuited and wipers Wx are
connected to terminals Bx, resulting in only leakage currents
being consumed in the VR structure. In shutdown mode, the
VR latch settings are maintained so that the VR settings return
to their previous resistance values when the device is returned
to operational mode from power shutdown.
D7
D6
D5
D4
D3
D2
D1
D0
RDAC
LATCH
AND
DECODER
Ax
Wx
Bx
R
S
HDN
R
S
R
S
R
S
06884-044
Figure 21. AD5204/AD5206 Equivalent RDAC Circuit
