MAX1275 Maxim Integrated Products, MAX1275 Datasheet - Page 16

• Manufacturer Part Number: MAX1275
• Description: (MAX1274 / MAX1275) 12-Bit ADCs
• Manufacturer: Maxim Integrated Products

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For best performance, use PC boards. Wire-wrap
boards are not recommended. Board layout should
ensure that digital and analog signal lines are separat-
ed from each other. Do not run analog and digital
(especially clock) lines parallel to one another, or digital
lines underneath the ADC package.
1.8Msps, Single-Supply, Low-Power,
True-Differential, 12-Bit ADCs
Figure 18. DSP Interface—Single-Conversion, Continuous/Burst Clock
Figure 20. Power-Supply Grounding Condition
16
Figure 19. Interfacing to the ADSP21_ _ _
______________________________________________________________________________________
CNVST
DOUT
SCLK
V
DD
MAX1274
MAX1275
Layout, Grounding, and Bypassing
0.1µF
10µF
MAX1274
MAX1275
CNVST
DOUT
SCLK
1
GND RGND
0
V
L
GND
0
SUPPLIES
0.1µF
10µF
0
D11
V
L
VDDINT
TCLK
RCLK
TFS
RFS
DR
D10
ADSP21_ _ _
D9
CIRCUITRY
DGND
DIGITAL
D8
V
V
L
L
D7
D6
D5
Figure 20 shows the recommended system ground
connections. 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. 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
affect the ADC’s high-speed comparator. Bypass this
supply to the single-point analog ground with 0.01µF
and 10µF bypass capacitors. Minimize capacitor lead
lengths for best supply-noise rejection.
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 end points of the transfer function,
once offset and gain errors have been nullified. The static
linearity parameters for the MAX1274/MAX1275 are mea-
sured using the end-points method.
Differential nonlinearity (DNL) is the difference between
an actual step width and the ideal value of 1 LSB. A DNL
error specification of 1 LSB or less guarantees no missing
codes and a monotonic transfer function.
Aperture jitter (t
the time between the samples.
Aperture delay (t
falling edge of CNVST and the instant when an actual
sample is taken.
D4
D3
D2
D1
AJ
AD
) is the sample-to-sample variation in
D0
) is the time defined between the
0
Differential Nonlinearity
Integral Nonlinearity
DD
power supply can
Aperture Delay
Aperture Jitter
Definitions
1
0
0