AS1419A AUSTIN [Austin Semiconductor], AS1419A Datasheet - Page 11

• Manufacturer Part Number: AS1419A
• Description: 14 Bit, 800ksps Sampling A/D Converter with Shutdown
• Manufacturer: AUSTIN [Austin Semiconductor]

100Ω source resistor to limit the input bandwidth to 1.6MHz.
The 1000pF capacitor also acts as a charge reservoir for the
input sample-and-hold and isolates the ADC input from
sampling glitch sensitive circuitry. High quality capacitors and
resistors should be used since these components can add
distortion. NPO and silver mica type dielectric capacitors have
excellent linearity. Carbon surface mount resistors can also
generate distortion from self heating and from damage that may
occur during soldering. Metal film surface mount resistors are
much less susceptible to both problems.
Input Range
noise and low distortion. Most op amps also perform well over
this same range, allowing direct coupling to the analog inputs
and eliminating the need for special translation circuitry.
AS1419 differential inputs and reference circuitry can
accommodate other input ranges often with little or no
additional circuitry. The following sections describe the
reference and input circuitry and how they affect the input
range.
Internal Reference
curvature corrected, bandgap reference that is factory trimmed
to 2.500V. It is connected internally to a reference amplifier and
is available at V
with the output so that it can be easily overdriven by an exter-
nal reference or other circuitry, see Figure 8b. The reference
amplifier gains the voltage at the V
required internal reference voltage. This provides buffering
between the V
reference amplifier compensation pin (REFCOMP, Pin 4) must
be bypassed with a capacitor to ground. The reference
amplifier is stable with capacitors of 1µF or greater. For the best
noise performance, a 10µF ceramic or 10µF tantalum in parallel
with a 0.1µF ceramic is recommended.
shown in Figure 9. This is useful in applications where the peak
input signal amplitude may vary. The input span of the ADC
can then be adjusted to match the peak input signal, maximizing
the signal-to-noise ratio. The filtering of the internal AS1419
reference amplifier will limit the bandwidth and settling time of
this circuit. A settling time of 5ms should be allowed for after a
reference adjustment.
AS1419 & AS1419A
Rev. 1.5 08/09
The ±2.5V input range of the AS1419 is optimized for low
Some applications may require other input ranges. The
The AS1419 has an on-chip, temperature compensated,
The V
REF
REF
pin can be driven with a DAC or other means
REF
pin and the high speed capacitive DAC. The
(Pin 3) see Figure 8a. A 2k resistor is in series
Austin Semiconductor, Inc.
REF
pin by 1.625 to create the
11
FIGURE 8b:
FIGURE 8a:
FIGURE 9:
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
Using an External Reference
AS1419 Reference Circuit
Driving V
REF
with a DAC
AS1419A
AS1419
ADC
ADC
ADC
ADC
ADC