X9440 datasheet(2/21 Pages) INTERSIL

2 / 21 page

FN8200.0

March 28, 2005

PIN DESCRIPTIONS

Host Interface Pins

Serial Output (SO)

SO is a push/pull serial data output pin. During a read

cycle, data is shifted out on this pin. Data is clocked

out by the falling edge of the serial clock.

Serial Input (SI)

SI is the serial data input pin. All opcodes, byte

addresses and data to be written to the pots and pot

registers are input on this pin. Data is latched by the

rising edge of the serial clock.

Serial Clock (SCK)

The SCK input is used to clock data into and out of the

X9440.

Chip Select (CS)

When CS is HIGH, the X9440 is deselected and the

SO pin is at high impedance, and (unless an internal

write cycle is underway) the device will be in the

standby state. CS LOW enables the X9440, placing it

in the active power mode. It should be noted that after

a power-up, a HIGH to LOW transition on CS is

required prior to the start of any operation.

Hold (HOLD)

HOLD is used in conjunction with the CS pin to select

the device. Once the part is selected and a serial

sequence is underway, HOLD may be used to pause

the serial communication with the controller without

resetting the serial sequence. To pause, HOLD must

be brought LOW while SCK is LOW. To resume com-

munication, HOLD is brought HIGH, again while SCK

is LOW. If the pause feature is not used, HOLD should

be held HIGH at all times.

Device Address (A0-A1)

The address inputs are used to set the least significant

2 bits of the 8-bit slave address. A match in the slave

address serial data stream must be made with the

Address input in order to initiate communication with

the X9440. A maximum of 4 devices may share the

same SPI serial bus.

Potentiometer Pins

VH (VH0-VH3), VL (VL0-VL3)

The VH and VL inputs are equivalent to the terminal con-

nections on either end of a mechanical potentiometer.

VW (VW0-VW1)

The wiper output VW is equivalent to the wiper output

of a mechanical potentiometer and is connected to the

inverting input of the voltage comparator.

Comparator and Device Pins

Voltage Input VNI0, VNI1

VNI0 and VNI1 are the input voltages to the plus (non-

inverting) inputs of the two comparators.

Buffered Voltage Outputs VOUT0, VOUT1

VOUT0 and VOUT1 are the buffered voltage comparator

outputs controlled by bits in the volatile analog control

Hardware Write Protect Input WP

The WP pin when low prevents non volatile writes to

the wiper counter and analog control registers.

Analog Supplies V+, V-

The Analog Supplies V+, V- are the supply voltages for

the XDCP analog section and the voltage comparators.

System Supply VCC and Ground VSS

The system supply, VCC and its reference VSS is used

to bias the interface and control circuits.

X9440

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