LTC1282ACN View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1282ACN' PDF : 24 Pages View PDF
LTC1282
APPLICATI S I FOR ATIO
MUXing with CD4051
The high input impedance of the LTC1282 provides an
easy, cheap, fast, and accurate way to multiplex many
channels of data through one converter. Figure 24 shows
a low cost CD4051, one of the most common multiplex-
ers connected to the LTC1282. The LTC1282’s input
draws no DC input current so it can be accurately driven
by the unbuffered MUX. The CD4520 counter increments
the MUX channel after each sample is taken.
100ps Resolution ∆Time Measurement with LTC1282
Figure 25 shows a circuit that precisely measures the
difference in time between two events. It has a 400ns full
scale and 100ps resolution. The start signal releases the
ramp generator made up of the PNP current source and
the 500pF capacitor. The circuit ramps until the stop
signal shuts off the current source. The final value of the
ramp represents the time between the start and stop
events. The LTC1282 digitizes this final value and out-
puts the digital data.
3V
8 INPUT
CHANNELS
±1.25V
INPUT
VARIES
CD4051
NO
BUFFER
REQUIRED
D11
•
•
AIN
•
D0
LTC1282
CS
RD
BUSY
– 3V
µP
OR
DSP
LTC1282 • F24
VSS
A BC
Q2 ENABLE
Q1
CD4520
COUNTER
Q0 RESET
Figure 24. MUXing the LTC1282 with CD4051
65Ω
1N457
LM134
45.3Ω
1N457
45.3Ω
5V
START ↑
74HC74
D
Q
CLK
Q
CLR
5V
STOP↑
D
Q
CLK
Q
CLR
1k
5V
65Ω
2N5771
74HC03
2N2369
200k
430Ω
20k
3.3V
2N2369
10µF
REFOUT
VDD
250pF
POLYSTYRENE
AIN
LTC1282
CS VSS GND RD BUSY
10µF
12-BIT
DATA
OUTPUT
1k 1N4148
10k
5V 1N4148
100pF
1k
0.001µF
100k
10k
10pF
DATA
LATCH
SIGNAL
LTC1282 • F25
Figure 25. ∆ Time Measurement with the LTC1282
21
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