LTC2401 Linear Technology, LTC2401 Datasheet - Page 9

• Manufacturer Part Number: LTC2401
• Description: 1-/2-Channel 24-Bit uPower No Latency ADC in MSOP-10
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
is alternated. Embedded within the serial data output is a
status bit indicating which channel corresponds to the
conversion result. If the conversion was performed on
CH0, this bit (Bit 30) is LOW and is HIGH if the conversion
was performed on CH1 (see Figure 6).
There are no extra control or status pins required to
perform the alternating 2-channel measurements. The
LTC2402 only requires two digital signals (SCK and SDO).
This simplification is ideal for isolated temperature mea-
surements or systems where minimal control signals are
available.
Pseudo Differential Applications
Generally, designers choose fully differential topologies
for several reasons. First, the interface to a 4- or 6-wire
bridge is simple (it is a differential output). Second, they
require good rejection of line frequency noise. Third, they
SDO
SCK
U
EOC
U
CH1
Figure 7. Pseudo Differential Strain Guage Application
W
Figure 6. Embedded Selected Channel Indicator
CH1 DATA OUT
• • •
350
350
U
350
350
I
I
I
EXCITATION
DC
DC
= 0
= 0
2
3
4
5
FS
CH1
ZS
CH0
SET
SET
LTC2402
GND
V
5V
CC
1
typically look at a small differential signal sitting on a
large common mode voltage; they need accurate
measurements of the differential signal independent of
the common mode input voltage. Many applications
currently using fully differential analog-to-digital con-
verters for any of the above reasons may migrate to a
pseudo differential conversion using the LTC2402.
Direct Connection to a Full Bridge
The LTC2402 interfaces directly to a 4- or 6-wire bridge, as
shown in Figure 7. Like the LTC2401, the LTC2402 in-
cludes a FS
voltage directly across the bridge. This eliminates errors
due to excitation currents flowing through parasitic resis-
tors. The LTC2402 also includes two single ended input
channels which can tie directly to the differential output of
the bridge. The two conversion results may be digitally
subtracted yielding the differential result.
SDO
SCK
CS
F
O
EOC
9
8
7
10
3-WIRE
SPI INTERFACE
CH0
SET
24012 F07
and a ZS
CH0 DATA OUT
• • •
LTC2401/LTC2402
SET
for sensing the excitation
24012 F06
9