ADN2860-EVAL AD [Analog Devices], ADN2860-EVAL Datasheet - Page 16

• Manufacturer Part Number: ADN2860-EVAL
• Description: 3-Channel Digital Potentiometer with Nonvolatile Memory
• Manufacturer: AD [Analog Devices]

ADN2860
USING ADDITIONAL INTERNAL
NONVOLATILE EEPROM
The ADN2860 contains additional internal user EEPROM for
saving constants and other data. The user EEPROM I
word follows the same format as the general-purpose EEPROM
memory shown in Figure 19 and Figure 20. User EEPROM
memory addresses are shown in Table 6.
To support the use of multiple EEPROM modules on a single
I
Pins 21 and 22 (A1_EE and A0_EE), to manually set the address
of the EEPROM included with the ADN2860. This feature
ensures that the correct EEPROM memory is accessed when
using multiple memory modules on a single I
DIGITAL INPUT/OUTPUT CONFIGURATION
All digital inputs are ESD protected. Digital inputs are high
impedance and can be driven directly from most digital
sources. The RESET digital input pin does not have an internal
pull-up resistor. Therefore, the user should place a pull-up
resistor from RESET to V
WP pin has an internal pull-down resistor. If not driven by an
external source, the ADN2860 defaults to a write-protected
state. ESD protection of the digital inputs is shown in Figure 27.
MULTIPLE DEVICES ON ONE BUS
Figure 28 shows four ADN2860 devices on the same serial bus.
Each has a different slave address because the state of their AD0
and AD1 pins are different. This allows independent reading
and writing to each RDAC within each device.
2
C bus, the ADN2860 features two external addressing pins,
MASTER
Figure 28. Multiple ADN2860 Devices on a Single Bus
AD1
AD0
SDA
WP
SCL
Figure 27. Equivalent WP ESD Protection
R
P
V
INPUTS
DD
R
P
AD1
AD0
SDA
DD
GND
+5V
if the function is not used. The
SCL
V
DD
AD1
AD0
SDA
V
DD
SCL
2
V
C bus.
DD
AD1
AD0
SDA
2
SCL
C data-
SDA
SCL
Rev. A | Page 16 of 20
LEVEL SHIFT FOR BIDIRECTIONAL
COMMUNICATION
While most legacy systems operate at one voltage, adding a new
component might require a different voltage. When two
systems transmit the same signal at two different voltages, use a
level shifter to allow the systems to communicate.
For example, a 3.3 V microcontroller (MCU) can be used along
with a 5 V digital potentiometer. A level shifter is required to
enable bidirectional communication.
Figure 29 shows one of many possible techniques to properly
level-shift signals between two devices. M1 and M2 are
N-channel FETs (2N7002). If V
threshold N-channel FETs (FDV301N) for M1 and M2.
TERMINAL VOLTAGE OPERATION RANGE
The ADN2860 positive V
inputs define the boundary conditions for proper 2-terminal
programmable resistance operation. Supply signals on
Terminals W and B that exceed V
internal forward-biased diodes of the ADN2860.
The ground pin of the ADN2860 is used as a digital ground
reference and needs to be tied to the common ground of the
PCB. Reference the digital input control signals to the
ADN2860 ground pin and satisfy the logic levels defined in
Table 1 and Table 2.
V
SDA1
SCL1
DD1
Figure 29. Level Shifting for Different Voltage Devices on an I
= 3.3V
Figure 30. Maximum Terminal Voltages Set by V
MCU
3.3V
R
P
R
S
P
DD
G
M1
and negative V
D
S
DD
G
DD
falls below 2.5 V, use low
M2
or V
R
D
P
SS
V
A
W
B
V
DD
SS
are clamped by the
SS
power supply
ADN2860
R
P
DD
5V
and V
V
2
DD2
SS
C Bus
SDA2
= 5V
SCL2