ISL22414 Datasheet, PDF (10/16 Pages) Intersil Corporation – Single Digitally Controlled Potentiometer

ISL22414
Typical Performance Curves (Continued)
CS
SCL
WIPER
WIPER UNLOADED,
MOVEMENT FROM 0h to FFh
FIGURE 13. MIDSCALE GLITCH, CODE 7Fh TO 80h
Pin Description
Potentiometer Pins
RH AND RL
The high (RH) and low (RL) terminals of the ISL22414 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 255 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.
Bus Interface Pins
SERIAL CLOCK (SCK)
This is the serial clock input of the SPI serial interface.
SERIAL DATA OUTPUT (SDO)
The SDO is a serial data output pin. During a read cycle, the
data bits are shifted out on the falling edge of the serial clock
SCK and will be available to the master on the following
rising edge of SCK.
The output type is configured through ACR[1] bit for Push-
Pull or Open Drain operation. Default setting for this pin is
Push-Pull. An external pull up resistor is required for Open
Drain output operation. Note, the external pull up voltage not
allowed beyond VCC.
SERIAL DATA INPUT (SDI)
The SDI is the serial data input pin for the SPI interface. It
receives device address, operation code, wiper address and
data from the SPI remote host device. The data bits are
10
FIGURE 14. LARGE SIGNAL SETTLING TIME
shifted in at the rising edge of the serial clock SCK, while the
CS input is low.
CHIP SELECT (CS)
CS LOW enables the ISL22414, placing it in the active
power mode. A HIGH to LOW transition on CS is required
prior to the start of any operation after power up. When CS is
HIGH, the ISL22414 is deselected and the SDO pin is at
high impedance, and (unless an internal write cycle is
underway) the device will be in the standby state.
Principles of Operation
The ISL22414 is an integrated circuit incorporating one DCP
with its associated registers, non-volatile memory and the
SPI serial interface providing direct communication between
host and potentiometer and memory. The resistor array is
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
IVR will be maintained in the non-volatile memory. When
power is restored, the content of the IVR is recalled and
loaded into the WR to set the wiper to the initial position.
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 an 8-bit
volatile Wiper Register (WR). When the WR of a DCP
contains all zeroes (WR[7:0]= 00h), its wiper terminal (RW)
FN6424.1
December 16, 2010