LTC2255/LTC2254
10
22554fa
UU
U
PI FU CTIO S
AIN+ (Pin 1): Positive Differential Analog Input.
AIN- (Pin 2): Negative Differential Analog Input.
REFH (Pins 3, 4): ADC High Reference. Short together and
bypass to pins 5, 6 with a 0.1
F ceramic chip capacitor as
close to the pin as possible. Also bypass to pins 5, 6 with
an additional 2.2
F ceramic chip capacitor and to ground
with a 1
F ceramic chip capacitor.
REFL (Pins 5, 6): ADC Low Reference. Short together and
bypass to pins 3, 4 with a 0.1
F ceramic chip capacitor as
close to the pin as possible. Also bypass to pins 3, 4 with
an additional 2.2
F ceramic chip capacitor and to ground
with a 1
F ceramic chip capacitor.
VDD (Pins 7, 32): 3V Supply. Bypass to GND with 0.1F
ceramic chip capacitors.
GND (Pin 8): ADC Power Ground.
CLK (Pin 9): Clock Input. The input sample starts on the
positive edge.
SHDN (Pin 10): Shutdown Mode Selection Pin. Connect-
ing SHDN to GND and OE to GND results in normal
operation with the outputs enabled. Connecting SHDN to
GND and OE to VDD results in normal operation with the
outputs at high impedance. Connecting SHDN to VDD and
OE to GND results in nap mode with the outputs at high
impedance. Connecting SHDN to VDD and OE to VDD
results in sleep mode with the outputs at high impedance.
OE (Pin 11): Output Enable Pin. Refer to SHDN pin
function.
D0 – D13 (Pins 12, 13, 14, 15, 16, 17, 18, 19, 22, 23, 24,
25, 26, 27): Digital Outputs. D13 is the MSB.
OGND (Pin 20): Output Driver Ground.
OVDD (Pin 21): Positive Supply for the Output Drivers.
Bypass to ground with 0.1
Fceramicchipcapacitor.OVDD
can be 0.5V to 3.6V.
OF (Pin 28): Over/Under Flow Output. High when an over
or under flow has occurred.
MODE (Pin 29): Output Format and Clock Duty Cycle
Stabilizer Selection Pin. Connecting MODE to GND selects
offset binary output format and turns the clock duty cycle
stabilizer off. 1/3 VDD selects offset binary output format
and turns the clock duty cycle stabilizer on. 2/3 VDD selects
2’s complement output format and turns the clock duty
cycle stabilizer on. VDD selects 2’s complement output
format and turns the clock duty cycle stabilizer off.
SENSE (Pin 30): Reference Programming Pin. Connecting
SENSE to VCM selects the internal reference and a ±0.5V
input range. VDD selects the internal reference and a ±1V
input range. An external reference greater than 0.5V and
less than 1V applied to SENSE selects an input range of
±VSENSE. ±1V is the largest valid input range.
VCM (Pin 31): 1.5V Output and Input Common Mode Bias.
Bypass to ground with 2.2
F ceramic chip capacitor.
GND (Exposed Pad) (Pin 33): ADC Power Ground. The
exposed pad on the bottom of the package needs to be
soldered to ground.