LTC2493
11
2493fd
pin FuncTions
fO(Pin1):FrequencyControlPin.Digitalinputthatcontrols
the internal conversion clock rate. When fO 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 fO 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 I2C address.
SCL (Pin 4): Serial Clock Pin of the I2C Interface. The
LTC2493 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 I2C 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 and configuration 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 appropriate pull-up device to VCC) during the
data output mode.
GND(Pin6):Ground.Connectthispintoacommonground
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 VCC + 0.3V. Within these limits, the two
selected inputs (IN+ and IN– ) provide a bipolar input
range (VIN = IN+ – IN– ) from –0.5 VREF to 0.5 VREF.
Outside this input range, the converter produces unique
over-range and underrange output codes.
CH0 to CH3 (Pin 8-Pin 11): Analog Inputs. May be pro-
grammed for single-ended or differential mode.
VCC(Pin12):PositiveSupplyVoltage.BypasstoGNDwith
a 10F tantalum capacitor in parallel with a 0.1F 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 VCCaslongasthereferencepositiveinput,REF+,
remains more positive than the negative reference input,
REF–,byatleast0.1V.Thedifferentialvoltage(VREF=REF+
– REF–) sets the full-scale range for all input channels.
When performing an on-chip temperature measurement,
the minimum value of REF = 2V.
Exposed Pad (Pin 15): Ground. This pin is ground and
mustbesolderedtothePCBgroundplane.Forprototyping
purposes, this pin may remain floating.