27
LTC1417
TYPICAL APPLICATIONS
U
Figure 23 uses the DG408 to select one of eight ±2.048V
bipolar signals and apply it to the LTC1417’s analog input.
The circuit is designed to connect to a 68HC11 µC. The
MUX’s parallel input is connected to the controller’s port
C and the LTC1417’s serial interface is accessed through
the controller’s SPI interface.
The sequence to generate a conversion is shown in sample
program Listing B. The first step selects a MUX channel.
This is followed by initiating a conversion and waiting for
BUSY to go high, signifying end of conversion. Once BUSY
goes low, the SPI is used to retrieve the 14-bit conversion
data. The timing relationships between the various control
signals and data transmission are shown in Figure 24.
Figure 23. With an Input Range of ±2.048V for Each of Eight Inputs,
This Data Acquisition System is Configured for Communication with the 68HC11 µC
1417 F23
1µF
10µF
5V
NC
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
LTC1417
5V – 5V5V –5V
PORT C, BIT 7
PORT C, BIT 6
PORT C, BIT 2
PORT C, BIT 1
PORT C, BIT 0
SS
MISO
CLK
A
IN
+
A
IN
–
V
REF
REFCOMP
AGND
EXTCLKIN
SCLK
CLKOUT
V
DD
V
SS
BUSY
CONVST
RD
SHDN
DGND
D
OUT
DG408
S1
S2
S3
S4
S5
S6
S7
S8
13
3
14
2
V
+
V
–
GND
EN
A2
A1
A0
D
IN1
IN2
IN3
IN4
IN5
IN6
IN7
IN8
1
2
3
4
5
6
7
8
0.1µF
0.1µF
MC68HC11
