MAX174ACPI Просмотр технического описания (PDF) - Maxim Integrated
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MAX174ACPI Datasheet PDF : 18 Pages
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MAX174/MX574A/MX674A
Industry-Standard, Complete 12-Bit ADCs
Stand-Alone Operation
For systems which do not use or require full bus interfac-
ing, the MAX174/MX574A/MX674A can be operated in
a stand-alone mode directly linked through dedicated
input ports.
When configured in the stand-alone mode, conversion is
controlled by R/C. In addition, CS and A0 are wired low;
CE and 12/8 are wired high. To enable the three-state
buffers, set R/C low. A conversion starts when R/C is set
high. This allows either a high- or a low-pulse control sig-
nal. Shown in Figure 6 is the operation with a low pulse. In
this mode, the outputs, in response to the falling edge of
R/C, are forced into the high-impedance state and return
to valid logic-levels after the conversion is complete. The
STS output goes high following the R/C falling edge and
returns low when the conversion is complete.
A high-pulse conversion initiation is illustrated in Figure 7.
When R/C is high, the data lines are enabled. The next con-
version starts with the falling edge of R/C. The data lines
return and remain in high impedance state until another
R/C high pulse.
Analog Considerations
Application Hints
Physical Layout
For best system performance, PCBs should be used for
the MAX174/MX574A/MX674A. Wirew rap boards are not
recommended. The layout of the board should ensure
that digital and analog signal lines are kept separated
from each other as much as possible. Care should be
taken not to run analog and digital lines parallel to each
other or digital lines underneath the MAX174/MX574A/
MX674A.
Grounding
The recommended power-supply grounding practice is
shown in Figure 8. The ground reference point for the on-
chip reference is AGND. It should be connected directly
to the analog reference point of the system. The analog
and digital grounds should be connected together at the
package in order to gain all of the accuracy possible
from the MAX174/MX574A/MX674A in high digital noise
environments. In situations permitting, they can be con-
nected to the most accessible ground-reference point.
The preference is analog power return.
tHRL
R/C
tDS
tC
STS
tHDR
tHS
D0–11
HIGH IMPEDANCE
Figure 6. Low Pulse for R//C in Stand-Alone Mode
R/C
STS
D0–11
tHRH
tDS
tDDR
tHDR
HIGH IMPEDANCE
Figure 7. High Pulse for R//C in Stand-Alone Mode
ANALOG SUPPLY
-15V
GND +15V
DIGITAL SUPPLY
+5V GND
VEE GND VCC
S/H AND
ANALOG
CIRCUITRY
VEE AGND VCC VL DGND
MAX174
MX574A
MX674A
+5V DGND
DIGITAL
CIRCUITRY
Figure 8. Power-Supply Grounding Practice
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