AD5220 datasheet(11/16 Pages) AD

11 / 16 page

REV. B

AD5200/AD5201

–11–

CODE – Decimal

100.0

10.0

0.1

032

1.0

128

160

192

224

256

RAB = 10k

RAB = 50k

TPC 31. AD5200 I MAX vs. Code

CODE – Decimal

100.0

10.0

0.1

1.0

812

RAB = 10k

RAB = 50k

TPC 32. AD5201 I MAX vs. Code

OPERATION

The AD5200/AD5201 provide 255 and 33 positions digitally-

controlled variable resistor (VR) devices. Changing the

programmed VR settings is accomplished by clocking in an 8-bit

serial data word for AD5200, and a 6-bit serial data word for

AD5201, into the SDI (Serial Data Input) pins. Table I provides

the serial register data word format. The AD5200/AD5201 are

preset to a midscale internally during power-on condition. In

addition, the AD5200/AD5201 contain power shutdown

SHDN pins that place the RDAC in a zero power consump-

tion state where the immediate switches next to Terminals A and

B are open-circuited. Meanwhile, the wiper W is connected to B

terminal, resulting in only leakage current consumption in the VR

structure. During shutdown, the VR latch contents are maintained

when the RDAC is inactive. When the part is returned from

shutdown, the stored VR setting will be applied to the RDAC.

Table I. AD5200 Serial-Data Word Format

Table II. AD5201 Serial-Data Word Format

*Six data bits are needed for 33 positions.

PROGRAMMING THE VARIABLE RESISTOR

Rheostat Operation

The nominal resistance of the RDAC between Terminals A and

B are available with values of 10 k

Ω and 50 kΩ. The final two

digits of the part number determine the nominal resistance

value, e.g., 10 k

Ω = 10 and 50 kΩ = 50. The nominal resistance

(RAB) of AD5200 has 256 contact points accessed by the wiper

terminal. The 8-bit data word in the RDAC latch of AD5200 is

decoded to select one of the 256 possible settings. In both parts,

the wiper’s first connection starts at the B terminal for data 00H.

This B-terminal connection has a wiper contact resistance of

Ω as long as valid V

DD/VSS is applied, regardless of the nominal

resistance. For a 10 k

Ω part, the second connection of AD5200 is

the first tap point with 89

Ω [RWB = RAB/255 + RW = 39 Ω + 50 Ω]

for data 01H. The third connection is the next tap point representing

78 + 50 = 128

Ω for data 02H. Due to its unique internal structure,

AD5201 has 5-bit + 1 resolution, but needs a 6-bit data word to

achieve the full 33 steps resolution. The 6-bit data word in the

RDAC latch is decoded to select one of the 33 possible settings.

Data 34 to 63 will automatically be equal to Position 33. The

wiper 00H connection of AD5201 gives 50

Ω. Similarly, for a

10 k

Ω part, the first tap point of AD5201 yields 363 Ω for

data 01H, 675

Ω for data 02H. For both AD5200 and AD5201,

each LSB data value increase moves the wiper up the resistor

ladder until the last tap point is reached. Figures 2a and 2b show

the simplified diagrams of the equivalent RDAC circuits.

AD5220 датащи(PDF) 11 Page - Analog Devices

AD5220 датащи(HTML) 11 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

датащи скачать

ссылки URL