®
®
ADS-946
+25°C
DYNAMIC PERFORMANCE
(Cont.)
S/H Acquisition Time
( to ±0.003%FSR, 4V step)
Overvoltage Recovery Time
A/D Conversion Rate
DIGITAL OUTPUTS
Logic Levels
Logic "1"
Logic "0"
Logic Loading "1"
Logic Loading "0"
Output Coding
POWER REQUIREMENTS
Power Supply Ranges
+5V Supply
–5V Supply
Power Supply Currents
+5V Supply
–5V Supply
Power Dissipation
Power Supply Rejection
+4.75
–4.75
—
—
—
—
+5.0
–5.0
+250
–150
2
—
+5.25
–5.25
+270
–170
2.2
±0.05
+4.75
–4.75
—
—
—
—
+2.4
—
—
—
—
—
—
—
—
+0.4
–4
+4
+2.4
—
—
—
MIN.
—
—
8
TYP.
55
100
—
MAX.
60
125
—
MIN.
—
—
8
0 to +70°C
TYP.
55
100
—
MAX.
60
125
—
MIN.
—
—
8
–55 to +125°C
TYP.
55
100
—
MAX.
60
125
—
UNITS
ns
ns
MHz
—
—
—
+0.4
—
–4
—
+4
Offset Binary
+2.4
—
—
—
—
—
—
—
—
+0.4
–4
+4
Volts
Volts
mA
mA
+5.0
–5.0
+250
–150
2
—
+5.25
–5.25
+270
–170
2.2
±0.05
+4.9
–4.9
—
—
—
—
+5.0
–5.0
+250
–150
2
—
+5.25
–5.25
+270
–170
2.2
±0.05
Volts
Volts
mA
mA
Watts
%FSR/%V
Footnotes:
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.
Effective bits is equal to:
(SNR + Distortion) – 1.76 +
20 log
6.02
Full Scale Amplitude
Actual Input Amplitude
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
DD
are required for
–55°C operation only. The minimum limits are +4.75V and –4.75V when
operating at +125°C
TECHNICAL NOTES
1. Obtaining fully specified performance from the ADS-946
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.
2. The ADS-946 achieves its specified accuracies without the
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.
3. Applying a start convert pulse while a conversion is in
progress (EOC = logic 1) will initiate a new and inaccurate
conversion cycle. Data for the interrupted and subsequent
conversions will be invalid.
4. A passive bandpass filter is used at the input of the A/D for
all production testing.
2k
Ω
GAIN
ADJUST
+5V
SIGNAL
INPUT
1.98k
Ω
50
Ω
To Pin 21
of ADS-946
–5V
Figure 2. Optional ADS-946 Gain Adjust Calibration Circuit
3
MURATA-PS [ MURATA POWER SOLUTIONS INC. ]
