ADS-946 ETC, ADS-946 Datasheet - Page 3

• Manufacturer Part Number: ADS-946
• Description: ADS-946 14-Bit/ 8MHz Sampling A/D Converters
• Manufacturer: ETC

TECHNICAL NOTES
1. Obtaining fully specified performance from the ADS-946
2. The ADS-946 achieves its specified accuracies without the
DYNAMIC PERFORMANCE (Cont.)
S/H Acquisition Time
Overvoltage Recovery Time
A/D Conversion Rate
DIGITAL OUTPUTS
Logic Levels
Output Coding
POWER REQUIREMENTS
Power Supply Ranges
Power Supply Currents
Power Dissipation
Power Supply Rejection
Footnotes:
requires careful attention to pc card layout and power
supply decoupling. The device’s analog and digital ground
systems are connected to each other internally. For optimal
performance, tie all ground pins (14, 19 and 24) directly to a
large analog ground plane beneath the package.
Bypass all power supplies to ground with 4.7µF tantalum
capacitors in parallel with 0.1µF ceramic capacitors. Locate
the bypass capacitors as close to the unit as possible.
need for external calibration. If required, the device’s small
initial offset and gain errors can be reduced to zero using
the adjustment circuitry shown in Figures 2 and 3. When
using this circuitry, or any similar offset and gain calibration
hardware, make adjustments following warmup. To avoid
interaction, always adjust offset before gain.
Logic "1"
Logic "0"
Logic Loading "1"
Logic Loading "0"
+5V Supply
–5V Supply
+5V Supply
–5V Supply
®
All power supplies should be on before applying a start convert pulse. All
supplies and the clock (start convert pulses) must be present during warmup
periods. The device must be continuously converting during this time.
Contact DATEL for other input voltage ranges.
An 8MHz clock with a 20nsec positive pulse width is used for all production
testing. See Timing Diagram, Figure 4, for more details.
( to ±0.003%FSR, 4V step)
®
+4.75
–4.75
+2.4
MIN.
—
—
—
—
—
—
—
—
—
8
+25°C
TYP.
+250
–150
+5.0
–5.0
100
55
—
—
—
—
—
—
2
MAX.
+5.25
±0.05
–5.25
+270
–170
+0.4
125
2.2
60
—
—
–4
+4
3
+4.75
–4.75
+2.4
MIN.
—
—
—
—
—
—
—
—
—
8
3. Applying a start convert pulse while a conversion is in
4. A passive bandpass filter is used at the input of the A/D for
SIGNAL
Effective bits is equal to:
This is the time required before the A/D output data is valid once the analog input
is back within the specified range. This time is only guaranteed if the input does
not exceed ±2.2V (S/H saturation voltage).
The minimum supply voltages of +4.9V and –4.9V for ±V
operating at +125°C
INPUT
–55°C operation only. The minimum limits are +4.75V and –4.75V when
progress (EOC = logic 1) will initiate a new and inaccurate
conversion cycle. Data for the interrupted and subsequent
conversions will be invalid.
all production testing.
Figure 2. Optional ADS-946 Gain Adjust Calibration Circuit
0 to +70°C
+250
TYP.
–150
+5.0
–5.0
100
55
—
—
—
—
—
—
2
Offset Binary
ADJUST
(SNR + Distortion) – 1.76 +
GAIN
50
MAX.
+5.25
–5.25
±0.05
+270
–170
+0.4
125
2.2
+4
60
—
—
–4
1.98k
+2.4
+4.9
–4.9
MIN.
—
—
—
—
—
—
—
—
—
8
–55 to +125°C
6.02
20 log
TYP.
+250
–150
+5.0
–5.0
100
55
—
—
—
—
—
—
2
+5V
2k
–5V
Actual Input Amplitude
Full Scale Amplitude
DD
are required for
ADS-946
MAX.
+5.25
–5.25
±0.05
+270
–170
+0.4
125
2.2
–4
+4
60
—
—
To Pin 21
of ADS-946
%FSR/%V
UNITS
Watts
Volts
Volts
Volts
Volts
MHz
mA
mA
mA
mA
ns
ns