LTC2489
8
2489fb
For more information www.linear.com/LTC2489
f
O
(Pin 1): Frequency Control Pin. Digital input that controls
the internal conversion clock rate. When f
O
is connected
to GND, the converter uses its internal oscillator running
at 307.2kHz. The conversion clock may also be overrid
-
den by driving the f
O
pin with an external clock in order to
change the output rate and the digital filter rejection null.
CA0, CA1 (Pins 2, 3): Chip Address Control Pins. These
pins are configured as a three-state (LOW, HIGH, Floating)
address control bits for the device’s I
2
C address.
SCL (Pin 4): Serial Clock Pin of the I
2
C Interface. The
LTC2489 can only act as a slave and the SCL pin only
accepts an external serial clock. Data is shifted into the
SDA pin on the rising edges of the SCL clock and output
through the SDA pin on the falling edges of the SCL clock.
SDA (Pin 5): Bidirectional Serial Data Line of the I
2
C Inter-
face. In the transmitter mode (Read), the conversion result
is output through the SDA pin, while in the receiver mode
(Write), the device channel select bits are input through the
SDA pin. The pin is high impedance during the data input
mode and is an open drain output (requires an appropri
-
ate pull-up device to V
CC
) during the data output mode.
GND (Pin 6): Ground. Connect this pin to a common ground
plane through a low impedance connection.
COM (Pin 7): The Common Negative Input (IN
–
) for All
Single-Ended Multiplexer Configurations. The voltage
on CH0-CH3 and COM pins can have any value between
GND – 0.3V to V
CC
+ 0.3V. Within these limits, the two
selected inputs (IN
+
and IN
–
) provide a bipolar input
range (V
IN
= IN
+
– IN
–
) from –0.5 • V
REF
to 0.5 • V
REF
.
Outside this input range, the converter produces unique
over-range and under-range output codes.
CH0 to CH3 (Pin 8-Pin 11): Analog Inputs. May be pro
-
grammed for single-ended or differential mode.
V
CC
(Pin 12): Positive Supply Voltage. Bypass to GND with
a 10µF tantalum capacitor in parallel with a 0.1µF ceramic
capacitor as close to the part as possible.
REF
+
, REF
–
(Pin 13, Pin 14): Differential Reference Input.
The voltage on these pins can have any value between
GND and V
CC
as long as the reference positive input, REF
+
,
remains more positive than the negative reference input,
REF
–
, by at least 0.1V. The differential voltage (V
REF
= REF
+
– REF
–
) sets the full-scale range for all input channels.
Exposed Pad (Pin 15): Ground. This pin is ground and
must be soldered to the PCB ground plane. For prototyping
purposes, this pin may remain floating.
pin FuncTions
