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PDF LTC1418C Data sheet ( Hoja de datos )
| Número de pieza | LTC1418C | |
| Descripción | Low Power/ 14-Bit/ 200ksps ADC with Serial and Parallel I/O | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC1418
Low Power, 14-Bit, 200ksps
ADC with Serial and Parallel I/O
FEATURES
s Single Supply 5V or ± 5V Operation
s Sample Rate: 200ksps
s ±1.25LSB INL and ±1LSB DNL Max
s Power Dissipation: 15mW (Typ)
s Parallel or Serial Data Output
s No Missing Codes Over Temperature
s Power Shutdown: Nap and Sleep
s External or Internal Reference
s Differential High Impedance Analog Input
s Input Range: 0V to 4.096V or ±2.048V
s 81.5dB S/(N + D) and – 94dB THD at Nyquist
s 28-Pin Narrow PDIP and SSOP Packages
U
APPLICATIONS
s Remote Data Acquisition
s Battery Operated Systems
s Digital Signal Processing
s Isolated Data Acquisition Systems
s Audio and Telecom Processing
s Medical Instrumentation
DESCRIPTION
The LTC ®1418 is a low power, 200ksps, 14-bit A/D
converter. Data output is selectable for 14-bit parallel or
serial format. This versatile device can operate from a
single 5V or ±5V supply. An onboard high performance
sample-and-hold, a precision reference and internal tim-
ing minimize external circuitry requirements. The low
15mW power dissipation is made even more attractive
with two user selectable power shutdown modes.
The LTC1418 converts 0V to 4.096V unipolar inputs from
a single 5V supply and ±2.048V bipolar inputs from ±5V
supplies. DC specs include ±1.25LSB INL, ±1LSB DNL
and no missing codes over temperature. Outstanding AC
performance includes 82dB S/(N + D) and 94dB THD at the
Nyquist input frequency of 100kHz.
The flexible output format allows either parallel or serial I/O.
The SPI/MICROWIRETM compatible serial I/O port can oper-
ate as either master or slave and can support clock frequen-
cies from DC to 10MHz. A separate convert start input and
a data ready signal (BUSY) allow easy control of conversion
start and data transfer.
, LTC and LT are registered trademarks of Linear Technology Corporation.
MICROWIRE is a trademark of National Semiconductor Corporation.
TYPICAL APPLICATION
Low Power, 200kHz, 14-Bit Sampling A/D Converter
5V
AIN+
AIN–
REFCOMP
10µF
VREF
1µF
LTC1418
10µF
VDD
S/H 14-BIT ADC
4.096V
BUFFER
14 SELECTABLE
SERIAL/
PARALLEL
PORT
8k 2.5V
REFERENCE
TIMING AND
LOGIC
AGND
VSS
(0V OR – 5V)
DGND
SER/PAR
D13
D5
D4 (EXTCLKIN)
D3 (SCLK)
D2 (CLKOUT)
D1 (DOUT)
D0 (EXT/INT)
BUSY
CS
RD
CONVST
SHDN
1418 TA01
Typical INL Curve
1.0
0.5
0
–0.5
–1.0
0
4096
8192
12288
OUTPUT CODE
16384
1418 TA02
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LTC1418
Typical INL Curve
1.0
0.5
0
–0.5
–1.0
0
4096
8192
12288
OUTPUT CODE
16384
1418 TA02
Signal-to-Noise Ratio
vs Input Frequency
90
80
70
60
50
40
30
20
10
0
1k 10k 100k 1M
INPUT FREQUENCY (Hz)
1418 G02
Nonaveraged, 4096 Point FFT,
Input Frequency = 10kHz
0
fSAMPLE = 200kHz
–20
fIN = 9.9609375kHz
SFDR = 99.32
SINAD = 82.4
–40
–60
–80
–100
–120
0 10 20 30 40 50 60 70 80 90 100
FREQUENCY (kHz)
1418 F02a
Differential Nonlinearity
vs Output Code
1.0
0.5
0
– 0.5
– 1.0
0
4096
8192 12288
OUTPUT CODE
16384
1418 G06
Distortion vs Input Frequency
0
–20
–40
–60
–80
–100
3RD
THD
2ND
–120
1k
10k 100k
INPUT FREQUENCY (Hz)
1M
1418 G03
Nonaveraged, 4096 Point FFT,
Input Frequency = 100kHz
0
fSAMPLE = 200kHz
–20
fIN = 97.509765kHz
SFDR = 94.29
SINAD = 81.4
–40
–60
–80
–100
–120
0 10 20 30 40 50 60 70 80 90 100
FREQUENCY (kHz)
1418 F02b
S/(N + D) vs Input Frequency
and Amplitude
90
80 VIN = 0dB
70 VIN = –20dB
60
50
40
30 VIN = –60dB
20
10
0
1k 10k 100k 1M
INPUT FREQUENCY (Hz)
1418 G01
Spurious-Free Dynamic Range
vs Input Frequency
0
–20
–40
–60
–80
–100
–120
10k
100k
INPUT FREQUENCY (Hz)
1M
1418 G04
Intermodulation Distortion Plot
0
fSAMPLE = 200kHz
– 20
fIN1 = 97.65625kHz
fIN2 = 104.248046kHz
– 40
– 60
– 80
– 100
– 120
0 10 20 30 40 50 60 70 80 90 100
FREQUENCY (kHz)
1418 G05
5
5 Page 
LTC1418
APPLICATIONS INFORMATION
Full-Power and Full-Linear Bandwidth
The full-power bandwidth is that input frequency at which
the amplitude of the reconstructed fundamental is
reduced by 3dB for a full-scale input signal.
The full-linear bandwidth is the input frequency at which
the S/(N + D) has dropped to 77dB (12.5 effective bits).
The LTC1418 has been designed to optimize input band-
width, allowing the ADC to undersample input signals with
frequencies above the converter’s Nyquist Frequency. The
noise floor stays very low at high frequencies; S/(N + D)
becomes dominated by distortion at frequencies far
beyond Nyquist.
DRIVING THE ANALOG INPUT
The differential analog inputs of the LTC1418 are easy to
drive. The inputs may be driven differentially or as a single-
ended input (i.e., the AIN– input is grounded). The AIN+ and
AIN– inputs are sampled at the same instant. Any
unwanted signal that is common mode to both inputs will
be reduced by the common mode rejection of the sample-
and-hold circuit. The inputs draw only one small current
spike while charging the sample-and-hold capacitors at
the end of conversion. During conversion, the analog
inputs draw only a small leakage current. If the source
impedance of the driving circuit is low then the LTC1418
inputs can be driven directly. As source impedance
increases so will acquisition time (see Figure 6). For
minimum acquisition time, with high source impedance, a
buffer amplifier must be used. The only requirement is that
the amplifier driving the analog input(s) must settle after
the small current spike before the next conversion starts —
1µs for full throughput rate.
small-signal settling for full throughput rate. If slower op
amps are used, more settling time can be provided by
increasing the time between conversions.
The best choice for an op amp to drive the LTC1418 will
depend on the application. Generally, applications fall into
two categories: AC applications where dynamic specifica-
tions are most critical and time domain applications where
DC accuracy and settling time are most critical. The
following list is a summary of the op amps that are suitable
for driving the LTC1418. More detailed information is
available in the Linear Technology Databooks and on the
LinearViewTM CD-ROM.
LT®1354: 12MHz, 400V/µs Op Amp. 1.25mA maximum
supply current. Good AC and DC specifications. Suitable
for dual supply application.
LT1357: 25MHz, 600V/µs Op Amp. 2.5mA maximum
supply current. Good AC and DC specifications. Suitable
for dual supply application.
LT1366/LT1367: Dual/Quad Precision Rail-to-Rail Input
and Output Op Amps. 375µA supply current per amplifier.
1.8V to ±15V supplies. Low input offset voltage: 150µV.
Good for low power and single supply applications with
sampling rates of 20ksps and under.
LT1498/LT1499: 10MHz, 6V/µs, Dual/Quad Rail-to-Rail
Input and Output Op Amps. 1.7mA supply current per
100
10
Choosing an Input Amplifier
Choosing an input amplifier is easy if a few requirements
are taken into consideration. First, choose an amplifier that
has a low output impedance (<100Ω) at the closed-loop
bandwidth frequency. For example, if an amplifier is used
in a gain of 1 and has a closed-loop bandwidth of 10MHz,
then the output impedance at 10MHz must be less than
100Ω. The second requirement is that the closed-loop
bandwidth must be greater than 5MHz to ensure adequate
1
0.1
1
10 100 1k 10k 100k
SOURCE RESISTANCE (Ω)
1418 F06
Figure 6. tACQ vs Source Resistance
LinearView is a trademark of Linear Technology Corporation.
11
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| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet LTC1418C.PDF ] | |
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