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PDF ADS5221 Data sheet ( Hoja de datos )
| Número de pieza | ADS5221 | |
| Descripción | ANALOG-TO-DIGITAL CONVERTER | |
| Fabricantes | Burr-Brown Corporation | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de ADS5221 (archivo pdf) en la parte inferior de esta página. Total 19 Páginas | ||
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ADS5221
ADS5221
SBAS262A – APRIL 2003 – REVISED DECEMBER 2003
12-Bit, 65MSPS Sampling, +3.3V
ANALOG-TO-DIGITAL CONVERTER
FEATURES
q HIGH SNR: 70dB
q HIGH SFDR: 88dBFS
q LOW POWER: 285mW
q INTERNAL/EXTERNAL REFERENCE OPTION
q SINGLE-ENDED OR
FULLY DIFFERENTIAL ANALOG INPUT
q FLEXIBLE DUTY CYCLE ADJUST CIRCUITRY
q LOW DNL: 0.5LSB
q SINGLE +3.3V SUPPLY OPERATION
q TQFP-48
APPLICATIONS
q WIRELESS LOCAL LOOP
q COMMUNICATIONS
q MEDICAL IMAGING
q PORTABLE INSTRUMENTATION
AVDD
ADS5221
DESCRIPTION
The ADS5221 is a pipeline, CMOS Analog-to-Digital Con-
verter (ADC) that operates from a single +3.3V power
supply. This converter provides excellent performance with a
single-ended input and can be operated with a differential
input for added spurious performance. This high-perfor-
mance converter includes a 12-bit quantizer, high bandwidth
track-and-hold, and a high accuracy internal reference; it
also allows for the user to disable the internal reference and
utilize external references, providing excellent gain and off-
set matching in multi-channel applications or in applications
where full-scale range adjustment is required.
The ADS5221 employs digital error correction techniques to
enable excellent differential linearity for demanding imaging
applications. Its low distortion and high SNR give the extra
margin needed for medical imaging, communications, video,
and test instrumentation. The ADS5221 offers power dissi-
pation of 285mW and also provides two power-down modes.
The ADS5221 is specified at a maximum sampling fre-
quency of 65MHz and a differential input range of 1V to 2V.
The ADS5221 is available in a TQFP-48.
CLK VDRV
Timing/Duty Cycle
Adjust
Circuitry
IN
VIN
IN
S/H
12-Bit
Pipelined
ADC
Error
Correction
Logic
3-State
Output
D0
•••
D11
Internal
Reference
OVR
STPD QPD
REFT REFB
RSEL VREF
OE
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
www.ti.com
Copyright © 2003, Texas Instruments Incorporated
1 page  
TIMING DIAGRAM
Analog In N
Clock
N+1
N+2
tD tCONV
N+3
N+4
tL tH
N+5
N+6
N+7
Data Out
5 Clock Cycles
N–5
N–4
Data Invalid
N–3
N–2
N–1
t2
N
t1
N+1
N+2
SYMBOL
DESCRIPTION
MIN
tCONV
tL
tH
tD
t1
t2
Convert Clock Period
Clock Pulse LOW
Clock Pulse HIGH
Aperture Delay
Data Hold Time, CL = 0pF
Propagation Delay Time, CL = 5pF max
15.4ns
6.7
6.7
6.0
TYP
7.7
7.7
3
MAX
100µs
6.5
UNITS
ns
ns
ns
ns
ns
ADS5221
SBAS262A
www.ti.com
5
5 Page 
ANALOG INPUT DRIVEN BY OP AMPLIFIER
The ADS5221 can be driven by an operational amplifier with
DC or AC signal coupling, as shown in Figure 4 and Figure
5. In Figure 4, the THS4503, a differential amplifier, is used
to convert a single-ended input to differential output with a
gain of 2. The THS4503 provides an output common-mode
voltage set by VOCM pin, and is DC-coupled to the input of
ADS5221. A low-pass filter can be created by adding small
capacitors (for example, 10pF) in parallel with the feedback
resistors of the THS4503 as needed for some applications.
Due to the THS4503 driving a capacitive load, small series
resistors in the output ensure stable operation. Further de-
tails of this and other functions of the THS4503 may be found
in its product datasheet, located on the Texas Instruments
web site (www.ti.com). In general, differential amplifiers pro-
vide a higher performance driver solution as compared to a
single-ended amplifier.
As shown in Figure 5, an AC-coupled, single-ended input
configuration is realized with TI’s OPA695 for wideband
applications. For narrowband applications, the OPA2822 can
be used. In Figure 5, the OPA695 is configured at single
supply +5V and noninverting operation. The AC gain of the
amplifier is 2 and the DC offset of the amplifier is +2.5V, set
by the voltage divider from the op amp power supply. The
output of the amplifier can provide maximum full-scale volt-
age range for the ADS5221. The OPA695 is a very high
bandwidth, current-feedback op amp that combines 4200V/
µs slew rate and low input voltage noise. It is optimized for
high gain operation. Further details of the OPA695 can be
found in the OPA695 data sheet. The common-mode voltage
at the ADS5221 input is +1.25V, set by a voltage divider from
+3.3V power supply. The +3.3V power supply must be
decoupled, as shown in Figure 11.
+5V
10pF(1)
187Ω
50Ω 60.4Ω
0.1µF
392Ω
24.9Ω
VCM THS4503 24.9Ω
392Ω
3.3V
1.7kΩ
215Ω
1.5V 1.5kΩ
–5V
10pF(1)
IN
22pF
ADS5221
IN
AVDD
FIGURE 4. Using the THS4503 Differential Amplifier (Gain = 2) to Drive the ADS5221 in a DC-Coupled Configuration.
+5V
0.1µF 6.8µF
0.1µF
806Ω
+5V
50Ω 57.6Ω
806Ω
OPA695
0.1µF
487Ω
487Ω
1.6kΩ
3.3V
1kΩ
0.1µF 30Ω
IN
47pF
ADS5221
0.1µF
IN
47pF
3.3V
1.6kΩ 1.25V 1kΩ
AVDD
FIGURE 5. Single-Ended Input of ADS5221 Driven by OPA695 with Gain = 2.
ADS5221
SBAS262A
www.ti.com
11
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet ADS5221.PDF ] | |
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