adc16061ccvt National Semiconductor Corporation, adc16061ccvt Datasheet - Page 20

• Manufacturer Part Number: adc16061ccvt
• Description: Self-calibrating 16-bit, 2.5 Msps, 390 Mw A/d Converter
• Manufacturer: National Semiconductor Corporation

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Applications Information
faulty or erratic operation. It is not uncommon for high speed
digital circuits (e.g., 74F and 74AC devices) to exhibit under-
shoot that goes more than a volt below ground. A resistor of
about 50 to 100Ω in series with the offending digital input will
eliminate the problem.
Do not allow input voltages to exceed the supply voltage
during power up.
Be careful not to overdrive the inputs of the ADC16061 with
a device that is powered from supplies outside the range of
the ADC16061 supply. Such practice may lead to conversion
inaccuracies and even to device damage.
Attempting to drive a high capacitance digital data bus.
The more capacitance the output drivers must charge for
each conversion, the more instantaneous digital current
flows through V
current spikes can couple into the analog circuitry of the
ADC16061, degrading dynamic performance. Adequate by-
passing and maintaining separate analog and digital ground
planes will reduce this problem. The digital data outputs
should be buffered (with 74ACQ541, for example). Dynamic
performance can also be improved by adding series resis-
tors at each digital output, close to the ADC16061, which
reduces the energy coupled back into the converter output
pins by limiting the output current. A reasonable value for
these resistors is 100Ω.
Using an inadequate amplifier to drive the analog input.
As explained in Section 1.3, the capacitance seen at the
D
I/O and DGND I/O. These large charging
(Continued)
20
input alternates between 12 pF and 28 pF, depending upon
the phase of the clock. This dynamic load is more difficult to
drive than is a fixed capacitance.
If the amplifier exhibits overshoot, ringing, or any evidence of
instability, even at a very low level, it will degrade perfor-
mance. Amplifiers that have been used successfully to drive
the analog inputs of the ADC16061 include the LMH6550,
LM6152, LM6154, LM6181 and the LM6182. A small series
resistor at each amplifier output and a capacitor across the
analog inputs (as shown in Figure 7) will improve perfor-
mance.
Operating with the reference pins outside of the speci-
fied range. As mentioned in section 1.2, V
the range of
with V
lead to excessive distortion or noise.
Using a clock source with excessive jitter, using an
excessively long clock signal trace, or having other
signals coupled to the clock signal trace. This will cause
the sampling interval to vary, causing excessive output noise
and a reduction in SNR performance.
Connecting pins marked "NC" to any potential. Some of
these pins are used for factory testing. They should all be left
floating. Connecting them to ground, power supply, or some
other voltage could result in a non-functional device.
REF
−
IN
≤ 1.0V. Operating outside of these limits could
1.8V ≤ V
REF
≤ 2.2V
REF
should be in