LTC1609I View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1609I' PDF : 24 Pages View PDF
LTC1609
APPLICATIO S I FOR ATIO
Table 1c. LTC1609 Output Codes for Ideal Input Voltages
DESCRIPTION
ANALOG INPUT
TWO’S COMPLEMENT STRAIGHT BINARY
(SB/BTC LOW)
(SB/BTC HIGH)
Full-Scale Range
±10V
±5V
±3.34 0V to 10V 0V to 5V 0V to 4V
Least Significant Bit
305µV 153µV
102µV
153µV
76µV
61µV
+Full Scale (FS – 1LSB) 9.999695V 4.999847V 3.339898V 9.999847V 4.999924V 3.999939V 0111 1111 1111 1111 1111 1111 1111 1111
Midscale
0V
0V
0V
5V
2.5V
2V 0000 0000 0000 0000 1000 0000 0000 0000
1LSB Below Midscale – 305µV –153µV –102µV 4.999847V 2.499924V 1.999939V 1111 1111 1111 1111 0111 1111 1111 1111
– Full Scale
– 10V
– 5V – 3.340000V 0V
0V
0V 1000 0000 0000 0000 0000 0000 0000 0000
011...111
011...110
000...001
000...000
111...111
111...110
BIPOLAR
ZERO
100...001
100...000
–FSR/2
FSR = +FS – –FS
1LSB = FSR/65536
–1 0V 1 FSR/2 – 1LSB
LSB LSB
INPUT VOLTAGE (V)
1609 F04a
Figure 4a. LTC1609 Bipolar Transfer Characteristics
The ideal ± FS value for the ±3.3V range is 3.340000V – 1LSB
and – 3.340000V, respectively. The external 33.2k resistor
that is connected between the CAP pin and the R2IN pin,
slightly attenuates the input signal applied to R2IN. With-
out the 33.2k resistor the ±FS value would be 3.333333V
– 1LSB and – 3.333333V (zero volt offset), respectively.
DC Performance
One way of measuring the transition noise associated with
a high resolution ADC is to use a technique where a DC
signal is applied to the input of the ADC and the resulting
output codes are collected over a large number of conver-
sions. For example in Figure 5 the distribution of output
code is shown for a DC input that has been digitized 4096
times. The distribution is Gaussian and the RMS code
transition is about 0.9LSB.
12
111...111
111...110
100...001
100...000
011...111
011...110
000...001
000...000
1LSB = FS/65536
0V
FS – 1LSB
INPUT VOLTAGE (V)
1609 F04b
Figure 4b. LTC1609 Unipolar Transfer Characteristics
2000
1500
1000
500
0
–3 –2 –1 0 1
CODE
23
1609 F05
Figure 5. Histogram for 4096 Conversions
1609fa
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