MAX1084/MAX1085
400ksps/300ksps, Single-Supply, Low-Power,
Serial 10-Bit ADCs with Internal Reference
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Figure 14 shows the recommended system ground con-
nections. Establish a single-point analog ground (“star”
ground point) at GND, separate from the logic ground.
Connect all other analog grounds and GND to this star
ground point for further noise reduction. No other digital
system ground should be connected to this single-point
analog ground. The ground return to the power supply for
this ground should be low impedance and as short as
possible for noise-free operation.
High-frequency noise in the V
DD
power supply may affect
the ADC’s high-speed comparator. Bypass this supply to
the single-point analog ground with 0.1µF and 10µF
bypass capacitors. Minimize capacitor lead lengths for
best supply-noise rejection. To reduce the effect of sup-
ply noise, a 10Ω resistor can be connected as a lowpass
filter to attenuate supply noise (Figure 14).
Definitions
Integral Nonlinearity
Integral nonlinearity (INL) is the deviation of the values
on an actual transfer function from a straight line. This
straight line can be either a best-straight-line fit or a line
drawn between the endpoints of the transfer function,
once offset and gain errors have been nullified. The
static linearity parameters for the MAX1084/MAX1085
are measured using the endpoints method.
Differential Nonlinearity
Differential nonlinearity (DNL) is the difference between
an actual step width and the ideal value of 1LSB. A
DNL error specification of 1LSB or less guarantees no
missing codes and a monotonic transfer function.
Aperture Jitter
Aperture jitter (t
AJ
) is the sample-to-sample variation in
the time between the samples.
Aperture Delay
Aperture delay (t
AD
) is the time defined between the
falling edge of CS and the instant when an actual sam-
ple is taken.
Signal-to-Noise Ratio
For a waveform perfectly reconstructed from digital
samples, signal-to-noise ratio (SNR) is the ratio of full-
scale analog input (RMS value) to the RMS quantization
error (residual error). The theoretical minimum analog-
to-digital noise is caused by quantization error and
results directly from the ADC’s resolution, (N bits):
