MAX1284-MAX1285 Datasheet, PDF (13/15 Pages) Maxim Integrated Products – 400ksps/300ksps, Single-Supply, Low-Power, Serial 12-Bit ADCs with Internal Reference

400ksps/300ksps, Single-Supply, Low-Power,
Serial 12-Bit ADCs with Internal Reference
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 DGND 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 effects 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 MAX1284/MAX1285 are mea-
sured 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.
CS
1
SCLK
HIGH-Z
DOUT
8
9
16
D11 D10 D9 D8 D7
D6
D5 D4 D3 D2 D1 D0
HIGH-Z
FIRST BYTE READ
Figure 12. SPI/MICROWIRE Serial Interface Timing (CPOL = CPHA = 0)
CS
SECOND BYTE READ
1
3
14
SCLK
HIGH-Z
DOUT
D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1
D0
Figure 13. QSPI Serial Interface Timing (CPOL = 0, CPHA = 1)
HIGH-Z
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