MAX1220_12 Datasheet, PDF (40/43 Pages) Maxim Integrated Products – 12-Bit, Multichannel ADCs/DACs with FIFO,Temperature Sensing, and GPIO Ports

12-Bit, Multichannel ADCs/DACs with FIFO,
Temperature Sensing, and GPIO Ports
CS
t_GOD
t_GSU
GPIO INPUT/OUTPUT
Figure 13. GPIO Timing
LDAC
OUT_
t_LDACPWL
t_S
±1 LSB
Figure 14. LDAC Functionality
LDAC Functionality
Drive LDAC low to transfer the content of the input reg-
isters to the DAC registers. Drive LDAC permanently
low to make the DAC register transparent. The DAC
output typically settles from zero to full scale within ±1
LSB after 2µs. See Figure 14.
Layout, Grounding, and Bypassing
For best performance, use PC boards. Ensure that digi-
tal and analog signal lines are separated from each
other. Do not run analog and digital signals parallel to
one another (especially clock signals) or do not run digi-
tal lines underneath the MAX1220/MAX1257/
MAX1258 package. High-frequency noise in the AVDD
power supply may affect performance. Bypass the
AVDD supply with a 0.1µF capacitor to AGND, close to
the AVDD pin. Bypass the DVDD supply with a 0.1µF
capacitor to DGND, close to the DVDD pin. Minimize
capacitor lead lengths for best supply-noise rejection. If
the power supply is very noisy, connect a 10Ω resistor in
series with the supply to improve power-supply filtering.
The MAX1220/MAX1257/MAX1258 thin QFN packages
contain an exposed pad on the underside of the device.
Connect this exposed pad to AGND. Refer to the
MAX1258EVKIT for an example of proper layout.
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 end points of the transfer function,
once offset and gain errors have been nullified. INL for
the MAX1220/MAX1257/MAX1258 is measured using
the end-point method.
Differential Nonlinearity
Differential nonlinearity (DNL) is the difference between
an actual step width and the ideal value of 1 LSB. A
DNL error specification of less than 1 LSB guarantees
no missing codes and a monotonic transfer function.
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