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PDF LCD1863 Data sheet ( Hoja de datos )
| Número de pieza | LCD1863 | |
| Descripción | 12-/16-Bit / 8-Channel 200ksps ADCs | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC1863/LTC1867
12-/16-Bit, 8-Channel
200ksps ADCs
FEATURES
s Sample Rate: 200ksps
s 16-Bit No Missing Codes and ±2LSB Max INL
s 8-Channel Multiplexer with:
Single Ended or Differential Inputs and
Unipolar or Bipolar Conversion Modes
s SPI/MICROWIRETM Serial I/O
s Signal-to-Noise Ratio: 89dB
s Single 5V Operation
s On-Chip or External Reference
s Low Power: 1.3mA at 200ksps, 0.76mA at 100ksps
s Sleep Mode
s Automatic Nap Mode Between Conversions
s 16-Pin Narrow SSUOP Package
APPLICATIO S
s Industrial Process Control
s High Speed Data Acquisition
s Battery Operated Systems
s Multiplexed Data Acquisition Systems
s Imaging Systems
DESCRIPTIO
The LTC®1863/LTC1867 are pin-compatible, 8-channel
12-/16-bit A/D converters with serial I/O, and an internal
reference. The ADCs typically draw only 1.3mA from a
single 5V supply.
The 8-channel input multiplexer can be configured for
either single-ended or differential inputs and unipolar
or bipolar conversions (or combinations thereof). The
automatic nap and sleep modes benefit power sensitive
applications.
The LTC1867’s DC performance is outstanding with a
±2LSB INL specification and no missing codes over tem-
perature. The signal-to-noise ratio (SNR) for the LTC1867
is typically 89dB, with the internal reference.
Housed in a compact, narrow 16-pin SSOP package, the
LTC1863/LTC1867 can be used in space-sensitive as well
as low-power applications.
, LTC and LT are registered trademarks of Linear Technology Corporation.
MICROWIRE is a trademark of National Semiconductor Corp.
BLOCK DIAGRA
CH0
CH1
CH2
CH3
CH4
CH5
CH6
CH7/COM
1
2
3
4
5
6
7
8
ANALOG
INPUT
MUX
LTC1863/LTC1867
16
15
VDD
GND
14 SDI
+ 12-/16-BIT SERIAL 13 SDO
–
200ksps
ADC
PORT
12 SCK
11 CS/CONV
INTERNAL
10 VREF
2.5V REF
9
REFCOMP
18637 BD
Integral Nonlinearity vs Output Code
(LTC1867)
2.0
1.5
1.0
0.5
0
– 0.5
– 1.0
– 1.5
– 2.0
0
16384 32768 49152
OUTPUT CODE
65536
18637 GO1
18637f
1
1 page  
LTC1863/LTC1867
TYPICAL PERFOR A CE CHARACTERISTICS (LTC1867)
Integral Nonlinearity vs
Output Code
2.0
1.5
1.0
0.5
0
– 0.5
– 1.0
– 1.5
– 2.0
0
16384 32768 49152
OUTPUT CODE
65536
18637 GO1
4096 Points FFT Plot (fIN = 1kHz)
0
SNR = 88.8dB
–20
SINAD = 87.9dB
THD = 95dB
fSAMPLE = 200ksps
–40 INTERNAL REFERENCE
–60
–80
–100
–120
–140
0
25 50 75
FREQUENCY (kHz)
100
18637 G04
Signal-to-Noise Ratio vs
Frequency
100
90
80
70
60
50
40
30
20
1
10
INPUT FREQUENCY (kHz)
100
18637 G07
Differential Nonlinearity vs
Output Code
2.0
1.5
1.0
0.5
0
– 0.5
– 1.0
– 1.5
– 2.0
0
16384 32768 49152
OUTPUT CODE
65536
18637 GO2
4096 Points FFT Plot (fIN = 1kHz,
REFCOMP = External 5V)
0
SNR = 90dB
–20
SINAD = 88.5dB
THD = 94dB
fSAMPLE = 200ksps
–40 VREF = 0V
REFCOMP = EXT 5V
–60
–80
–100
–120
–140
0
25 50 75
FREQUENCY (kHz)
100
18637 G05
Signal-to-(Noise + Distortion) vs
Input Frequency
100
90
80
70
60
50
40
30
20
1
10
INPUT FREQUENCY (kHz)
100
18637 G08
Histogram for 4096 Conversions
2500
2152
2000
1500
1000
935
579
500
276
1 26
0
–4 –3 –2 –1
0
122
5
12 3
CODE
0
4
18637 GO3
Crosstalk vs Input Frequency
–80
–90
–100
–110
ADJACENT PAIR
–120
–130
NONADJACENT PAIR
–140
1
10 100 1000
ACTIVE CHANNEL INPUT FREQUENCY (kHz)
18637 G06
Total Harmonic Distortion vs
Input Frequency
–20
–30
–40
–50
–60
–70
–80
–90
–100
1
10
INPUT FREQUENCY (kHz)
100
18637 G09
18637f
5
5 Page 
LTC1863/LTC1867
APPLICATIO S I FOR ATIO
ANALOG
INPUT
50Ω
2000pF
CH0
LTC1863/
LTC1867
GND
10µF
REFCOMP
1867 F01a
Figure 1a. Optional RC Input Filtering for Single-Ended Input
DIFFERENTIAL
ANALOG
INPUTS
50Ω
50Ω
1000pF
1000pF
1000pF
CH0
LTC1863/
LTC1867
CH1
10µF
REFCOMP
1867 F01b
Figure 1b. Optional RC Input Filtering for Differential Inputs
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 2 the distribution of output
codes is shown for a DC input that had been digitized 4096
times. The distribution is Gaussian and the RMS code
transition noise is about 0.74LSB.
2500
2000
2152
1500
1000
935
579
500
276
1 26
0
–4 –3 –2 –1
0
122
5
12 3
CODE
0
4
18637 GO3
Figure 2. LTC1867 Histogram for 4096 Conversions
Dynamic Performance
FFT (Fast Fourier Transform) test techniques are used to
test the ADC’s frequency response, distortion and noise at
the rated throughput. By applying a low distortion sine
wave and analyzing the digital output using an FFT algo-
rithm, the ADC’s spectral content can be examined for
frequencies outside the fundamental.
Signal-to-Noise Ratio
The Signal-to-Noise and Distortion Ratio (SINAD) is the
ratio between the RMS amplitude of the fundamental input
frequency to the RMS amplitude of all other frequency
components at the A/D output. The output is band limited
to frequencies from above DC and below half the sampling
frequency. Figure 3 shows a typical SINAD of 87.9dB with
a 200kHz sampling rate and a 1kHz input. When an
external 5V is applied to REFCOMP (tie VREF to GND), a
signal-to-noise ratio of 90dB can be achieved.
0
SNR = 88.8dB
–20
SINAD = 87.9dB
THD = 95dB
fSAMPLE = 200ksps
–40 INTERNAL REFERENCE
–60
–80
–100
–120
–140
0
25 50 75
FREQUENCY (kHz)
100
18637 G04
Figure 3. LTC1867 Nonaveraged 4096 Point FFT Plot
Total Harmonic Distortion
Total Harmonic Distortion (THD) is the ratio of the RMS
sum of all harmonics of the input signal to the fundamental
itself. The out-of-band harmonics alias into the frequency
band between DC and half the sampling frequency. THD is
expressed as:
THD = 20log V22 + V32 + V42... + VN2
V1
18637f
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LCD1863.PDF ] | |
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