ADC14161 datasheet(19/20 Pages) NSC

19 / 20 page

Applications Information (Continued)

put alternates between 12 pF and 28 pF, depending upon the

phase of the clock. This dynamic loaad 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 sucessfully to dirve

the analog inputs of the ADC14161 include the CLC427,

CLC440, LM6152, LM6154, LM6181 and the LM6182. A

small series reistor at each amplifier output and a capacitor

across the analog inputs (as shown in

Figure 7) will often im-

prove performance.

Operating with the reference pins outside of the speci-

fied range. As mentioned in section 1.1, V

REF should be in

the range of

1.8V

≤ V

REF ≤ 2.2V

with V

REF− IN ≤ 1.0V. Operating outside of these limits could

lead to signal distortion.

Using a clock source with excessive jitter, using exces-

sively long clock signal trace, or having other signals

coupled to the clock signal trace. This will cause the sam-

pling 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.

ADC14161 Datasheet(PDF) 19 Page - National Semiconductor (TI)