EVAL-AD5246EBZ Analog Devices Inc, EVAL-AD5246EBZ Datasheet - Page 14

• Manufacturer Part Number: EVAL-AD5246EBZ
• Description: EVALUATION BOARD I.C.
• Manufacturer: Analog Devices Inc

Specifications of EVAL-AD5246EBZ

• Main Purpose: Digital Potentiometer
• Embedded: No
• Utilized Ic / Part: AD5246
• Primary Attributes: 1 Channel, 128 Position
• Secondary Attributes: I²C Interface
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD5246
A repeated write function gives the user flexibility to update the
RDAC output a number of times after addressing the part only
once. For example, after the RDAC has acknowledged its slave
address in write mode, the RDAC output updates on each succes-
sive byte. If different instructions are needed, the write/read mode
has to start again with a new slave address and data byte.
Similarly, a repeated read function of the RDAC is also allowed.
LEVEL SHIFTING FOR BIDIRECTIONAL INTERFACE
While most legacy systems may be operated at one voltage,
a new component may be optimized at another. When two
systems operate the same signal at two different voltages, proper
level shifting is needed. For instance, one can use a 1.8 V
E
shifting scheme is needed to enable a bidirectional communi-
cation so that the setting of the digital potentiometer can be
stored to and retrieved from the E
one of the implementations. M1 and M2 can be any N channel
signal FETs, or if V
threshold FETs such as the FDV301N.
ESD PROTECTION
All digital inputs are protected with a series input resistor
and parallel Zener ESD structures, as shown in Figure 31.
This applies to the digital input pins SDA and SCL.
TERMINAL VOLTAGE OPERATING RANGE
The AD5246 V
conditions for proper 3-terminal digital potentiometer
operation. Supply signals present on Terminal B and
Terminal W that exceed V
the internal forward biased diodes (see Figure 32).
2
PROM to interface with a 5 V digital potentiometer. A level
V
SDA1
SCL1
DD1
Figure 30. Level Shifting for Operation at Different Potentials
= 1.8V
E
2
PROM
1.8V
DD
Figure 31. ESD Protection of Digital Pins
R
P
and GND power supply defines the boundary
DD
falls below 2.5 V, M1 and M2 can be low
R
P
S
340Ω
DD
G
M1
GND
or GND are clamped by
D
S
LOGIC
2
G
M2
PROM. Figure 30 shows
D
R
P
AD5246
R
P
5V
V
DD2 =
5V
SDA2
SCL2
Rev. B | Page 14 of 16
MAXIMUM OPERATING CURRENT
At low code values, the user should be aware that due to low
resistance values, the current through the RDAC may exceed
the 5 mA limit. In Figure 33, a 5 V supply is placed on the
wiper, and the current through Terminal W and Terminal B is
plotted with respect to code. A line is also drawn denoting the
5 mA current limit. Note that at low code values (particularly
for the 5 kΩ and 10 kΩ options), the current level increases
significantly. Care should be taken to limit the current flow
between W and B in this state to a maximum continuous
current of 5 mA and a maximum pulse current of no more than
20 mA. Otherwise, degradation or possible destruction of the
internal switch contacts can occur.
POWER-UP SEQUENCE
Since the ESD protection diodes limit the voltage compliance
at Terminal B and Terminal W (see Figure 32), it is important
to power V
and Terminal W; otherwise, the diode is forward biased such
that V
the user’s circuit. The ideal power-up sequence is in the follow-
ing order: GND, V
relative order of powering V
is not important, providing they are powered after V
DD
0.01
100
Figure 32. Maximum Terminal Voltages Set by V
0.1
10
1
is powered unintentionally and may affect the rest of
0
DD
/GND before applying any voltage to Terminal B
16
Figure 33. Maximum Operating Current
DD
, digital inputs, and then V
32
5mA CURRENT LIMIT
48
CODE (Decimal)
B
and V
64
W
R
and the digital inputs
AB
80
= 10k Ω
R
AB
V
B
W
GND
DD
= 100k Ω
R
96
R
AB
DD
AB
B
/V
= 5k Ω
and GND
= 50k Ω
112
W
. The
DD
/GND.
128