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PDF ADS805E Data sheet ( Hoja de datos )
| Número de pieza | ADS805E | |
| Descripción | 12-Bit/ 20MHz Sampling ANALOG-TO-DIGITAL CONVERTER | |
| Fabricantes | Burr-Brown Corporation | |
| Logotipo |  |
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® ADS805U
ADS805E
ADS805
12-Bit, 20MHz Sampling
TM
ANALOG-TO-DIGITAL CONVERTER
FEATURES
q HIGH SFDR: 74dB at 9.8MHz f
IN
q HIGH SNR: 68dB
q LOW POWER: 300mW
q LOW DLE: 0.25LSB
q SMALL 28-LEAD SSOP AND SOIC
PACKAGES
DESCRIPTION
The ADS805 is a 20MHz, high dynamic range, 12-bit pipelined
analog-to-digital converter. This converter includes a high-band-
width track/hold that gives excellent spurious performance up to
and beyond the Nyquist rate. This high-bandwidth, linear track/hold
minimizes harmonics and has low jitter, leading to excellent SNR
performance. The ADS805 is also pin-compatible with the 10MHz
ADS804 and the 5MHz ADS803.
The ADS805 provides an internal reference or an external reference
can be used. ADS805 can be programmed for a 2Vp-p input range
which is the easiest to drive with a single op amp and provides the
best spurious performance. Alternatively, the 5Vp-p input range can
be used for the lowest input-referred noise of 0.09 LSBs rms giving
+VS
ADS805
q FLEXIBLE INPUT RANGE
q OVER-RANGE INDICATOR
APPLICATIONS
q STUDIO CAMERAS
q IF AND BASEBAND DIGITIZATION
q COPIERS
q TEST INSTRUMENTATION
superior imaging performance. There is also the capability to set the
input range between 2Vp-p and 5Vp-p, either single-ended or
differential. The ADS805 also provides an overrange flag that
indicates when the input signal has exceeded the converter’s full
scale range. This flag can also be used to reduce the gain of the front
end signal conditioning circuitry.
The ADS805 employs digital error techniques to provide excellent
differential linearity for demanding imaging applications. Its low
distortion and high SNR give the extra margin needed for commu-
nications, medical imaging, video and test instrumentation applica-
tions. The ADS805 is available in 28-lead SSOP and SOIC pack-
ages.
CLK VDRV
Timing Circuitry
VIN IN
T/H
IN
CM
12-Bit
Pipelined
A/D Core
Error
Correction
Logic
3-State
Outputs
D0
•••
D11
Reference Ladder
and Driver
Reference and
Mode Select
OVR
REFT
VREF
SEL REFB
OE
International Airport Industrial Park • Mailing Address: PO Box 11400, Tucson, AZ 85734 • Street Address: 6730 S. Tucson Blvd., Tucson, AZ 85706 • Tel: (520) 746-1111 • Twx: 910-952-1111
Internet: http://www.burr-brown.com/ • FAXLine: (800) 548-6133 (US/Canada Only) • Cable: BBRCORP • Telex: 066-6491 • FAX: (520) 889-1510 • Immediate Product Info: (800) 548-6132
©1997 Burr-Brown Corporation
PDS-1397C
Printed in U.S.A. October, 1998
1 page  
TYPICAL PERFORMANCE CURVES
At TA = full specified temperature range, VS = +5V, specified single-ended input range = 1.5V to 3.5V, sampling rate = 20MHz, unless otherwise specified.
0
–20
–40
–60
–80
–100
–120
0
SPECTRAL PERFORMANCE
fIN = 500kHz
2.0 4.0 6.0 8.0
Frequency (MHz)
10.0
0
–20
–40
–60
–80
–100
–120
0
SPECTRAL PERFORMANCE
fIN = 9.8MHz
2.0 4.0 6.0 8.0
Frequency (MHz)
10.0
FREQUENCY SPECTRUM
0
f7 = 7.7MHz at –7dBFS
–20 f2 = 7.9MHz at –7dBFS
IMD (3) = –70dBc
–40
–60
–80
–100
–120
0
2.5 5.0
Frequency (MHz)
7.5
10.0
1.0
0.5
0
–0.5
–1.0
0
DIFFERENTIAL LINEARITY ERROR
fIN = 9.8MHz
1024
2048
Output Code
3072
4096
4.0
2.0
0
–2.0
–4.0
0
INTEGRAL LINEARITY ERROR
fIN = 500kHz
1024
2048
Output Code
3072
4096
SWEPT POWER SFDR
100
fIN = 9.8MHz
80
dBFS
60
dBc
40
20
0
–60 –50 –40 –30 –20 –10
Input Amplitude (dBFS)
0
®
5 ADS805
5 Page 
SELECTING THE INPUT RANGE AND
REFERENCE
Figures 7 through 9 show a selection of circuits for the most
common input ranges when using the internal reference of
the ADS805. All examples are for single-ended input and
operate with a nominal common-mode voltage of +2.5V.
5V
VIN
0V
IN
ADS805
IN
VREF
+2.5V
SEL
FIGURE 7. Internal Reference with 0V to 5V Input Range.
3.5V
1.5V
VIN
+2.5V ext.
IN
ADS805
IN
VREF
+1V
SEL
FIGURE 8. Internal Reference with 1.5V to 3.5V Input
Range.
4V
VIN
1V
IN
ADS805
+2.5V ext.
VREF = 1V
1 + R1
R2
FSR = 2 x VREF
IN
VREF
SEL
R1
5kΩ
+1.5V
R2
10kΩ
EXTERNAL REFERENCE OPERATION
Depending on the application requirements, it might be
advantageous to operate the ADS805 with an external refer-
ence. This may improve the DC accuracy if the external
reference circuitry is superior in its drift and accuracy. To
use the ADS805 with an external reference, the user must
disable the internal reference (see Figure 10). By connecting
the SEL pin to +VS, the internal logic will shut down the
internal reference. At the same time, the output of the
internal reference buffer is disconnected from the VREF pin,
which now must be driven with the external reference. Note
that a similar bypassing scheme should be maintained as
described for the internal reference operation.
4.5V
0.5V
VIN
REF1004
+2.5V
+
10µF
+2.5V ext.
1.24kΩ
0.1µF
+2VDC
IN
ADS805
IN
VREF SEL
+5V
4.99kΩ
FIGURE 10. External Reference, Input Range 0.5V to 4.5V
(4Vp-p), with +2.5V Common-Mode Voltage.
DIGITAL INPUTS AND OUTPUTS
Over Range (OVR)
One feature of the ADS805 is its ‘Over Range’ digital output
(OVR). This pin can be used to monitor any out-of-range
condition, which occurs every time the applied analog input
voltage exceeds the input range (set by VREF). The OVR
output is LOW when the input voltage is within the defined
input range. It becomes HIGH when the input voltage is
beyond the input range. This is the case when the input
voltage is either below the bottom reference voltage or
above the top reference voltage. OVR will remain active
until the analog input returns to its normal signal range and
another conversion is completed. Using the MSB and its
complement in conjunction with OVR, a simple decode
logic can be built that detects the overrange and underrange
conditions, (see Figure 11). It should be noted that OVR is
a digital output which is updated along with the bit informa-
tion corresponding to the particular sampling incidence of
the analog signal. Therefore, the OVR data is subject to the
same pipeline delay (latency) as the digital data.
FIGURE 9. Internal Reference with 1V to 4V Input Range.
®
11 ADS805
11 Page | ||
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| PDF Descargar | [ Datasheet ADS805E.PDF ] | |
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