ADC12062EVAL National Semiconductor, ADC12062EVAL Datasheet - Page 13

• Manufacturer Part Number: ADC12062EVAL
• Description: BOARD EVALUATION FOR ADC12062
• Manufacturer: National Semiconductor

Specifications of ADC12062EVAL

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *ADC12062EVAL

Applications Information
is a good choice for this application due to its speed and its
ability to drive large capacitive loads. Figure 8 shows the
LM6361 driving the ADC IN input of an ADC12062. The
100 pF capacitor at the input of the converter absorbs some
Another benefit of using a high speed buffer is improved
THD performance when using the multiplexer of the
ADC12062. The MUX on-resistance is somewhat non-linear
over input voltage, causing the RC time constant formed by
C
This results in increasing THD with increasing frequency.
Inserting the buffer between the MUX OUT and the ADC IN
terminals as shown in Figure 8 will eliminate the loading on
R
tem.
Correct converter operation will be obtained for input volt-
ages greater than AGND − 50 mV and less than AV
IN
MUX
, R
, significantly reducing the THD of the multiplexed sys-
MUX
, and R
SW
to vary depending on the input voltage.
FIGURE 8. Buffering the Input with an LM6361 High Speed Op Amp
FIGURE 7. Simplified ADC12062 Input Stage
(Continued)
CC
+
13
of the high frequency transients generated by the S/H
switching, reducing the op amp transient response require-
ments. The 100 pF capacitor should only be used with high
speed op amps that are unconditionally stable driving ca-
pacitive loads.
50 mV. Avoid driving the signal source more than 300 mV
higher than AV
analog input pin is forced beyond these voltages, the current
flowing through that pin should be limited to 25 mA or less to
avoid permanent damage to the IC. The sum of all the
overdrive currents into all pins must be less than 50 mA.
When the input signal is expected to extend more than
300 mV beyond the power supply limits for any reason
(unknown/uncontrollable input voltage range, power-on tran-
sients, fault conditions, etc.) some form of input protection,
such as that shown in Figure 9 , should be used.
CC
, or more than 300 mV below AGND. If an
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