ISL22323 Datasheet, PDF (12/18 Pages) Intersil Corporation – Dual Digitally Controlled Potentiometer XDCP

ISL22323
Pin Description
Potentiometers Pins
RHI AND RLi
The high (RHi) and low (RLi) terminals of the ISL22323 are
equivalent to the fixed terminals of a mechanical
potentiometer. RHi and RLi are referenced to the relative
position of the wiper and not the voltage potential on the
terminals. With WRi set to 255 decimal, the wiper will be
closest to RHi, and with the WRi set to 0, the wiper is closest
to RLi.
RWi
RWi is the wiper terminal, and it is equivalent to the movable
terminal of a mechanical potentiometer. The position of the
wiper within the array is determined by the WRi register.
Bus Interface Pins
SERIAL DATA INPUT/OUTPUT (SDA)
The SDA is a bidirectional serial data input/output pin for I²C
interface. It receives device address, operation code, wiper
address and data from an I²C external master device at the
rising edge of the serial clock SCL, and it shifts out data after
each falling edge of the serial clock.
SDA requires an external pull-up resistor, since it is an open
drain input/output.
SERIAL CLOCK (SCL)
This input is the serial clock of the I²C serial interface. SCL
requires an external pull-up resistor.
DEVICE ADDRESS (A2, A1, A0)
The address inputs are used to set the least significant 3 bits
of the 7-bit I²C interface slave address. A match in the slave
address serial data stream must match with the Address
input pins in order to initiate communication with the
ISL22323. A maximum of eight ISL22323 devices may
occupy the I²C serial bus (See Table 3).
Principles of Operation
The ISL22323 is an integrated circuit incorporating two
DCPs with its associated registers, non-volatile memory and
an I²C serial interface providing direct communication
between a host and the potentiometer and memory. The
resistor arrays are comprised of individual resistors
connected in a series. At either end of the array and
between each resistor is an electronic switch that transfers
the potential at that point to the wiper.
The electronic switches on the device operate in a “make
before break” mode when the wiper changes tap positions.
When the device is powered down, the last value stored in
IVRi will be maintained in the non-volatile memory. When
power is restored, the contents of the IVRi are recalled and
loaded into the corresponding WRi to set the wipers to their
initial positions.
DCP Description
The DCP is implemented with a combination of resistor
elements and CMOS switches. The physical ends of each
DCP are equivalent to the fixed terminals of a mechanical
potentiometer (RHi and RLi pins). The RWi pin of the DCP is
connected to intermediate nodes, and is equivalent to the
wiper terminal of a mechanical potentiometer. The position
of the wiper terminal within the DCP is controlled by an 8-bit
volatile Wiper Register (WRi). When the WRi of a DCP
contains all zeroes (WRi[7:0]= 00h), its wiper terminal (RWi)
is closest to its “Low” terminal (RLi). When the WRi register
of a DCP contains all ones (WRi[7:0] = FFh), its wiper
terminal (RWi) is closest to its “High” terminal (RHi). As the
value of the WRi increases from all zeroes (0) to all ones
(255 decimal), the wiper moves monotonically from the
position closest to RLi to the position closest to RHi. At the
same time, the resistance between RWi and RLi increases
monotonically, while the resistance between RHi and RWi
decreases monotonically.
While the ISL22323 is being powered up, the WRi is reset to
80h (128 decimal), which locates RWi roughly at the center
between RLi and RHi. After the power supply voltage
becomes large enough for reliable non-volatile memory
reading, the WRi will be reloaded with the value stored in
corresponding non-volatile Initial Value Register (IVRi).
The WRi and IVRi can be read or written to directly using the
I²C serial interface as described in the following sections.
Memory Description
The ISL22323 contains two non-volatile 8-bit Initial Value
Register (IVRi), thirteen General Purpose non-volatile 8-bit
registers and three volatile 8-bit registers: two Wiper Registers
(WRi) and Access Control Register (ACR). Memory map of
ISL22323 is in Table 1. The non-volatile registers (IVRi) at
address 0 and 1, contain initial wiper position and volatile
registers (WRi) contain current wiper position.
TABLE 1. MEMORY MAP
ADDRESS
(hex)
NON-VOLATILE
VOLATILE
10
N/A
ACR
F
Reserved
E
General Purpose
N/A
D
General Purpose
N/A
C
General Purpose
N/A
B
General Purpose
N/A
A
General Purpose
N/A
9
General Purpose
N/A
8
General Purpose
N/A
12
FN6422.1
March 13, 2008