ISL22316
Pin Description
Potentiometers Pins
RH AND RL
The high (RH) and low (RL) terminals of the ISL22316 are
equivalent to the fixed terminals of a mechanical
potentiometer. RH and RL are referenced to the relative
position of the wiper and not the voltage potential on the
terminals. With WR set to 127 decimal, the wiper will be closest
to RH, and with the WR set to 0, the wiper is closest to RL.
RW
RW is the wiper terminal and is equivalent to the movable
terminal of a mechanical potentiometer. The position of the
wiper within the array is determined by the WR register.
SHDN
The SHDN pin forces the resistor to end-to-end open circuit
condition on RH and shorts RW to RL. When SHDN is returned
to logic high, the previous latch settings put RWi at the same
resistance setting prior to shutdown. This pin is logically AND
with the SHDN bit in the ACR register. The I2C interface is still
available in shutdown mode and all registers are accessible.
This pin must remain HIGH for normal operation.
RH
RW
RL
FIGURE 15. DCP CONNECTION IN SHUTDOWN MODE
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, since it is an open drain
input.
DEVICE ADDRESS (A1, A0)
The address inputs are used to set the least significant 2 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 ISL22316. A
maximum of four ISL22316 devices may occupy the I2C serial
bus.
Principles of Operation
The ISL22316 is an integrated circuit incorporating one DCP
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 array is
comprised of individual resistors connected in 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 IVR
will be maintained in the non-volatile memory. When power is
restored, the contents of the IVR is recalled and loaded into the
WR to set the wiper to the initial value.
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 (RH and RL pins). The RW 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 a 7-bit
volatile Wiper Register (WR). When the WR of a DCP contains
all zeroes (WR<6:0>: 00h), its wiper terminal (RW) is closest to
its “Low” terminal (RL). When the WR register of a DCP
contains all ones (WR<6:0>: 7Fh), its wiper terminal (RW) is
closest to its “High” terminal (RH). As the value of the WR
increases from all zeroes (0) to all ones (127 decimal), the
wiper moves monotonically from the position closest to RL to
the closest to RH. At the same time, the resistance between
RW and RL increases monotonically, while the resistance
between RH and RW decreases monotonically.
While the ISL22316 is being powered up, the WR is reset to
40h (64 decimal), which locates RW roughly at the center
between RL and RH. After the power supply voltage becomes
large enough for reliable non-volatile memory reading, the WR
will be reload with the value stored in a non-volatile Initial Value
Register (IVR).
The WR and IVR can be read or written to directly using the
I2C serial interface as described in the following sections.
Memory Description
The ISL22316 contains one non-volatile 8-bit register, known as
the Initial Value Register (IVR), and two volatile 8-bit registers,
Wiper Register (WR) and Access Control Register (ACR). Table
1 shows the Memory map of the ISL22316. The non-volatile
FN6186 Rev 3.00
August 14, 2015
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