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PDF LTC1275ACS Data sheet ( Hoja de datos )
| Número de pieza | LTC1275ACS | |
| Descripción | 12-Bit/ 300ksps Sampling A/D Converters with Reference | |
| Fabricantes | Linear Technology | |
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FEATURES
s Single Supply 5V or ±5V Operation
s 300ksps Sample Rate
s 75mW (Typ) Power Dissipation
s On-Chip 25ppm/°C Reference
s Internal Synchronized Clock; No Clock Required
s High Impedance Analog Input
s 70dB S/(N + D) and 77dB THD at Nyquist
s ±1/2LSB INL and ±3/4LSB DNL Max (A Grade)
s ESD Protected On All Pins
s 24-Pin Narrow DIP and SOL Packages
s Variety of Input Ranges:
0V to 5V (LTC1273)
±2.5V (LTC1275)
±5V (LTC1276)
APPLICATI S
s High Speed Data Acquisition
s Digital Signal Processing
s Multiplexed Data Acquisition Systems
s Audio and Telecom Processing
s Spectrum Analysis
LTC1273
LTC1275/LTC1276
12-Bit, 300ksps Sampling
A/D Converters with Reference
DESCRIPTIO
The LTC1273/LTC1275/LTC1276 are 300ksps, sampling
12-bit A/D converters that draw only 75mW from single
5V or ±5V supplies. These easy-to-use devices come
complete with 600ns sample-and-holds, precision refer-
ences and internally trimmed clocks. Unipolar and bipo-
lar conversion modes provide flexibility for various appli-
cations. They are built with LTBiCMOSTM switched ca-
pacitor technology.
These devices have 25ppm/°C (max) internal references.
The LTC1273 converts 0V to 5V unipolar inputs from a
single 5V supply. The LTC1275/LTC1276 convert ±2.5V
and ±5V respectively from ±5V supplies. Maximum DC
specifications include ±1/2LSB INL, ±3/4LSB DNL and
25ppm/°C full scale drift over temperature. Outstanding
AC performance includes 70dB S/(N + D) and 77dB THD
at the Nyquist input frequency of 150kHz.
The internal clock is trimmed for 2.7µs maximum conver-
sion time. The clock automatically synchronizes to each
sample command eliminating problems with asynchro-
nous clock noise found in competitive devices. A high
speed parallel interface eases connections to FIFOs, DSPs
and microprocessors.
LTBiCMOSTM is a trademark of Linear Technology Corporation
TYPICAL APPLICATI
Single 5V Supply, 300ksps, 12-Bit Sampling A/D Converter
2.42V
VREF
OUTPUT
+
10µF
ANALOG INPUT 1
(0V TO 5V) 2
0.1µF
3
4
5
6
7
8
9
8- OR 12-BIT
PARALLEL BUS
10
11
12
LTC1273
AIN
VREF
AGND
D11
D10
D9
D8
D7
D6
D5
D4
DGND
VDD
NC
BUSY
CS
RD
HBEN
NC
NC
D0/8
D1/9
D2/10
D3/11
24
23
22
21
20
19
18
17
16
15
14
13
5V
+
10µF
0.1µF
µP CONTROL
LINES
LTC1273/75/76 • TA01
Effective Bits and Signal to (Noise + Distortion)
vs Input Frequency
12 74
11 68
10 NYQUIST 62
9 FREQUENCY 56
8 50
7
6
5
4
3
2
1 fSAMPLE = 300kHz
0
10k 100k
1M 2M
INPUT FREQUENCY (Hz)
LTC1273/75/76 • TA02
1
1 page  
LTC1273
LTC1275/LTC1276
WU
TI I G CHARACTERISTICS See Timing Characteristics Figures (Note 5)
SYMBOL PARAMETER
t7 Bus Relinquish Time
t8 HBEN to RD Setup Time
t9 HBEN to RD Hold Time
t10 Delay Between RD Operations
t11 Delay Between Conversions
t12 Aperture Delay of Sample-and-Hold
CONDITIONS
Commercial
Military
(Note 10)
Commercial
Military
LTC1273A/LTC1275A/LTC1276A
LTC1273B/LTC1275B/LTC1276B
MIN TYP MAX UNITS
20 30
75
q 20
85
q 20
90
ns
ns
ns
q0
ns
q0
ns
q 40
ns
500
q 600
q 1000
ns
ns
ns
25 ns
The q indicates specifications which apply over the full operating
temperature range; all other limits and typicals TA = 25°C.
Note 1: Absolute maximum ratings are those values beyond which the life
of a device may be impaired.
Note 2: All voltage values are with respect to ground with DGND and
AGND wired together (unless otherwise noted).
Note 3: When these pin voltages are taken below VSS (ground for
LTC1273) or above VDD, they will be clamped by internal diodes. This
product can handle input currents greater than 60mA below VSS (ground
for LTC1273) or above VDD without latch-up.
Note 4: When these pin voltages are taken below VSS (ground for
LTC1273) they will be clamped by internal diodes. This product can handle
input currents greater than 60mA below VSS (ground for LTC1273)
without latch-up. These pins are not clamped to VDD.
Note 5: VDD = 5V (VSS = – 5V for LTC1275/LTC1276), 300kHz at 70°C and
250kHz at 125°C, tr = tf = 5ns unless otherwise specified.
Note 6: Linearity, offset and full scale specifications apply for unipolar and
bipolar modes.
Note 7: Integral nonlinearity is defined as the deviation of a code from a
straight line passing through the actual endpoints of the transfer curve.
The deviation is measured from the center of the quantization band.
Note 8: Bipolar offset (LTC1275/LTC1276) is the different voltage
measured from – 0.5LSB when the LTC1275/LTC1276 output code flickers
between 0000 0000 0000 and 1111 1111 1111.
Note 9: Guaranteed by design, not subject to test.
Note 10: Recommended operating conditions.
Note11: AIN must not exceed VDD or fall below VSS by more than 50mV for
specified accuracy. Therefore the minimum supply voltage for the
LTC1273 is + 4.95V. The minimum supplies for the LTC1275 are +4.75V
and – 2.45V and the minimum supplies for the LTC1276 are ±4.95V.
WU
TI I G CHARACTERISTICS (Note 5)
Slow Memory Mode, Parallel Read Timing Diagram
ROM Mode, Parallel Read Timing Diagram
CS
RD
BUSY
DATA
HOLD
TRACK
t1
t2
t3
t12
t5
tCONV
t11 t10
OLD DATA
DB11 TO DB0
t6 t7
NEW DATA
DB11 TO DB0
t1
LTC1273/75/76 • TA03
CS
RD
BUSY
DATA
HOLD
TRACK
t1 t4
t5
t2 tCONV
t3 t7
OLD DATA
DB11 TO DB0
t12
t1 t4
t11
t2
t5
tCONV
t3 t7
NEW DATA
DB11 TO DB0
t12
LTC1273/75/76 • TA04
5
5 Page 
LTC1273
LTC1275/LTC1276
APPLICATI S I FOR ATIO
Effective Number of Bits
The Effective Number of Bits (ENOBs) is a measurement of
the resolution of an ADC and is directly related to the
S/(N + D) by the equation:
N = [S/(N + D) – 1.76]/6.02
where N is the Effective Number of Bits of resolution and
S/(N + D) is expressed in dB. At the maximum sampling
rate of 300kHz the LTC1273/LTC1275/LTC1276 maintain
very good ENOBs up to the Nyquist input frequency of
150kHz. Refer to Figure 3.
12 74
11 68
10 62
9 56
8 50
7
6
5
4
3
2
1 fSAMPLE = 300kHz
0
10k 100k
1M 2M
INPUT FREQUENCY (Hz)
LTC1273/75/76 • F03
Figure 3. Effective Bits and Signal to (Noise + Distortion)
vs Input Frequency
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
V1
...
+
VN2
where V1 is the RMS amplitude of the fundamental fre-
quency and V2 through VN are the amplitudes of the
second through Nth harmonics. THD versus input fre-
quency is shown in Figure 4. The LTC1273/LTC1275/
LTC1276 have good distortion performance up to Nyquist
and beyond.
0
fSAMPLE = 300kHz
– 10
– 20
– 30
THD
2nd HARMONIC
3rd HARMONIC
– 40
– 50
– 60
– 70
– 80
– 90
– 100
1k
10k 100k
1M
INPUT FREQUENCY (Hz)
10M
LTC1273/75/76 • F04
Figure 4. Distortion vs Input Frequency
Intermodulation Distortion
If the ADC input signal consists of more than one spectral
component, the ADC transfer function nonlinearity can
produce intermodulation distortion (IMD) in addition to
THD. IMD is the change in one sinusoidal input caused by
the presence of another sinusoidal input at a different
frequency.
If two pure sine waves of frequencies fa and fb are applied
to the ADC input, nonlinearities in the ADC transfer func-
tion can create distortion products at sum and difference
frequencies of mfa ± nfb, where m and n = 0, 1, 2, 3, etc.
For example, the 2nd order IMD terms include (fa + fb) and
(fa – fb) while the 3rd order IMD terms include (2fa + fb),
(2fa – fb), (fa + 2fb), and (fa – 2fb). If the two input sine
waves are equal in magnitude, the value (in decibels) of the
2nd order IMD products can be expressed by the following
formula:
IMD
(fa
±
fb)
=
20log
Amplitude at (fa
Amplitude at
±
fa
fb)
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LTC1275ACS.PDF ] | |
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