Datasheet

DS3906
Triple NV Low Step Size Variable
Resistor Plus Memory
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Detailed Description
The DS3906 contains three variable resistors plus a
user EEPROM. The block diagram illustrates these in
addition to the registers that control the resistors. The
following sections provide detailed information about
the DS3906.
Memory Organization
The DS3906 contains 16 bytes of User EEPROM plus 3
NV resistor registers. Refer to Table 1. Communication
with the memory/registers is achieved through the I
2
C-
compatible serial interface and is described in subse-
quent sections.
Resistor Registers/Settings
Each of the three resistors in the DS3906 has its own
control register used to set the resistor position. Refer
to the block diagram and Table 2. Each resistor has 64
positions plus a high impedance state. The nominal
resistance values for each position is listed in Table 3.
Resistors 0 and 1 have the same full-scale resistance,
which is different than resistor 2. As shown in Table 3,
the resistors have a pseudo-log response (resistance
vs. position) when used without an external parallel
resistor. Valid resistor settings are 00h to 3Fh. Writing a
value greater than 3Fh to any of the resistor registers
Pin Description
PIN NAME FUNCTION
1A1I
2
C Address Input. Inputs A0, A1, and A2 determine the I
2
C slave address of the device.
2 SDA I
2
C Serial Data Open-Drain Input/Output
3 SCL I
2
C Serial Clock Input
4V
CC
Power Supply Voltage
5 GND Ground
6H2High Terminal of Resistor 2
7H1High Terminal of Resistor 1
8H0High Terminal of Resistor 0
9A0
10 A2
I
2
C Address Input. Inputs A0, A1, and A2 determine the I
2
C slave address of the device.
Block Diagram
I
2
C
INTERFACE
USER
EEPROM
16 BYTES
(00h-0Fh)
RHIZ CONTROL
EEPROM
RES 0
2.54k
Ω
H0
F8h
MSB
6
LSB
GND
SCL
SDA
A0
V
CC
V
CC
DS3906
RESISTOR 0
RHIZ CONTROL
RES 1
2.54k
Ω
H1
F9h
MSB LSB
RESISTOR 1
RHIZ CONTROL
RES 2
1.45k
Ω
H2
FAh
MSB LSB
RESISTOR 2
6
6
A1
A2