EVAL-AD5259DBZ Analog Devices, EVAL-AD5259DBZ Datasheet - Page 20

• Manufacturer Part Number: EVAL-AD5259DBZ
• Description: Digital Potentiometer Development Tools EVALUATION BOARD I.C.
• Manufacturer: Analog Devices
• Series: AD5259r

Specifications of EVAL-AD5259DBZ

• Rohs: yes
• Product: Evaluation Boards
• Tool Is For Evaluation Of: AD5259
• Resistance: 5 kOhms/10 kOhms/50 kOhms/100 kOhms
• Operating Supply Voltage: 5 V
• Description/function: Nonvolatile, I2C compatible 256-position, digital potentiometer
• Interface Type: I2C
• Maximum Operating Temperature: + 85 C
• Factory Pack Quantity: 1
• For Use With: Sim DAC Web Tool

AD5259
DISPLAY APPLICATIONS
CIRCUITRY
A special feature of the AD5259 is its unique separation of the
V
flexibility in applications that do not always provide needed
supply voltages.
In particular, LCD panels often require a V
range of 3 V to 5 V. The circuit in Figure 46 is the rare excep-
tion in which a 5 V supply is available to power the digital
potentiometer.
1µF
In the more common case shown in Figure 47, only analog
14.4 V and digital logic 3.3 V supplies are available. By placing
discrete resistors above and below the digital potentiometer,
V
chosen resistor values, the voltage at V
V, allowing the wiper to be safely operated all the way up to 4.8
V. The current draw of V
because it is only on the order of microamps. V
the MCU’s 3.3 V digital supply because V
mA which is needed when writing to the EEPROM. It would be
impractical to try and source 35 mA through the 70 kΩ resistor,
therefore, V
C1
LOGIC
DD
VCC (~3.3V)
can now be tapped off the resistor string itself. Based on the
MCU
and V
10kΩ
R6
LOGIC
DD
10kΩ
R5
supply pins. The separation provides greater
Figure 46. V
is not connected to the same node as V
5V
AD5259
V
V
SCL
SDA
GND
DD
LOGIC
DD
COM
14.4V
will not affect that node’s bias
A
B
Adjustment Application
R1
70kΩ
R2
10kΩ
R3
25kΩ
W
DD
–
+
AD8565
in this case equals 4.8
LOGIC
U1
COM
will draw the 35
voltage in the
LOGIC
3.5V < V
is tied to
COM
DD
.
< 4.5V
Rev. C | Page 20 of 24
For this reason, V
supply pins that can either be tied together or treated inde-
pendently; V
and V
flexibility.
1µF
For a more detailed look at this application, refer to the article,
“Simple VCOM Adjustment uses any Logic Supply Voltage” in
the September 30, 2004 issue of EDN magazine.
C1
VCC (~3.3V)
Figure 47. Circuitry When a Separate Supply is Not Available for V
MCU
DD
10kΩ
biasing up the A, B, and W terminals for added
R6
SUPPLIES POWER
TO BOTH THE
MICRO AND THE
LOGIC SUPPLY OF
THE DIGITAL POT
LOGIC
10kΩ
R5
LOGIC
supplying the logic/EEPROM with power,
AD5259
and V
V
V
SCL
SDA
GND
DD
LOGIC
14.4V
A
B
DD
R1
70kΩ
R2
10kΩ
R3
25kΩ
are provided as two separate
W
–
+
AD8565
U1
Data Sheet
3.5V < V
COM
DD
< 4.5V