LTC1408-12
PI FU CTIO S
SDO (Pin 1):
Three-State Serial Data Output. Each set of
six output data words represent the six analog input
channels at the start of the previous conversion. Data for
CH0 comes out first and data for CH5 comes out last. Each
data word comes out MSB first.
OGND (Pin 2):
Ground Return for SDO Currents. Connect
to the solid ground plane.
OV
DD
(Pin 3):
Power Supply for the SDO Pin. OV
DD
must
be no more than 300mV higher than V
DD
and can be
brought to a lower voltage to interface to low voltage logic
families. The unloaded high state at SDO is at the potential
of OV
DD
.
CH0
+
(Pin 4):
Non-Inverting Channel 0. CH0
+
operates
fully differentially with respect to CH0
–
with a 0V to 2.5V,
or
±1.25V
differential swing and a 0V to V
DD
absolute
input range.
CH0
–
(Pin 5):
Inverting Channel 0. CH0
–
operates fully
differentially with respect to CH0
+
with a –2.5V to 0V,
or
±1.25V
differential swing and a 0V to V
DD
absolute
input range.
GND (Pins 6, 9, 12, 13, 16, 19):
Analog Grounds. These
ground pins must be tied directly to the solid ground plane
under the part. Analog signal currents flow through these
connections.
CH1
+
(Pin 7):
Non-Inverting Channel 1. CH1
+
operates
fully differentially with respect to CH1
–
with a 0V to 2.5V,
or
±1.25V
differential swing and a 0V to V
DD
absolute
input range.
CH1
–
(Pin 8):
Inverting Channel 1. CH1
–
operates fully
differentially with respect to CH1
+
with a –2.5V to 0V,
or
±1.25V
differential swing and a 0V to V
DD
absolute
input range.
CH2
+
(Pin 10):
Non-Inverting Channel 2. CH2
+
operates
fully differentially with respect to CH2
–
with a 0V to 2.5V,
or
±1.25V
differential swing and a 0V to V
DD
absolute
input range.
CH2
–
(Pin 11):
Inverting Channel 2. CH2
–
operates fully
differentially with respect to CH2
+
with a –2.5V to 0V, or
±1.25V
differential swing and a 0V to V
DD
absolute
input range.
CH3
+
(Pin 14):
Non-Inverting Channel 3. CH3
+
operates
fully differentially with respect to CH3
–
with a 0V to 2.5V,
or
±1.25V
differential swing and a 0V to V
DD
absolute
input range.
CH3
–
(Pin 15):
Inverting Channel 3. CH3
–
operates fully
differentially with respect to CH3
+
with a –2.5V to 0V, or
±1.25V
differential swing and a 0V to V
DD
absolute
input range.
CH4
+
(Pin 17):
Non-Inverting Channel 4. CH4
+
operates
fully differentially with respect to CH4
–
with a 0V to 2.5V,
or
±1.25V
differential swing and a 0V to V
DD
absolute input
range.
CH4
–
(Pin 18):
Inverting Channel 4. CH4
–
operates fully
differentially with respect to CH4
+
with a –2.5V to 0V, or
±1.25V
differential swing and a 0V to V
DD
absolute input
range.
CH5
+
(Pin 20):
Non-Inverting Channel 5. CH5
+
operates
fully differentially with respect to CH5
–
with a 0V to 2.5V,
or
±1.25V
differential swing and a 0V to V
DD
absolute input
range.
CH5
–
(Pin 21):
Inverting Channel 5. CH5
–
operates fully
differentially with respect to CH5
+
with a –2.5V to 0V, or
±1.25V
differential swing and a 0V to V
DD
absolute input
range.
GND (PIN 22):
Analog Ground for Reference. Analog
ground must be tied directly to the solid ground plane
under the part. Analog signal currents flow through this
connection. The 10µF reference bypass capacitor should
be returned to this pad.
V
REF
(Pin 23):
2.5V Internal Reference. Bypass to GND
and a solid analog ground plane with a 10µF ceramic
capacitor (or 10µF tantalum in parallel with 0.1µF ce-
ramic). Can be overdriven by an external reference voltage
between 2.55V and V
DD
, V
CC
.
V
CC
(Pin 24):
3V Positive Analog Supply. This pin supplies
3V to the analog section. Bypass to the solid analog
ground plane with a 10µF ceramic capacitor (or 10µF
tantalum) in parallel with 0.1µF ceramic. Care should be
taken to place the 0.1µF bypass capacitor as close to
Pin 24 as possible. Pin 24 must be tied to Pin 25.
140812f
U
U
U
7
LINER [ LINEAR TECHNOLOGY ]
