MAX1202 Datasheet, PDF (17/24 Pages) Maxim Integrated Products – 5v, 8-cHANNEL, sERIAL, 12-bIT adcS WITH 3v dIGITAL iNTERFACE

5V, 8-Channel, Serial, 12-Bit ADCs
with 3V Digital Interface
CS
SCLK
DIN
DOUT
SSTRB
1
8
1
8
1
S CONTROL BYTE 0
S
CONTROL BYTE 1
B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
CONVERSION RESULT 0
S CONTROL BYTE 2
B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
CONVERSION RESULT 1
Figure 11a. External Clock Mode, 15 Clocks/Conversion Timing
CS
SCLK
DIN
DOUT
S CONTROL BYTE 0
S CONTROL BYTE 1
B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B0
CONVERSION RESULT 0
•••
•••
•••
B11 B10 B9 B8 B7 B6 B5 • • •
CONVERSION RESULT 1
Figure 11b. External Clock Mode, 16 Clocks/Conversion Timing
Hardware Power-Down
The SHDN pin places the converter into full power-down
mode. Unlike the software power-down modes, conver-
sion is not completed; it stops coincidentally with SHDN
being brought low. There is no power-up delay if an
external reference, which is not shut down, is used.
SHDN also selects internal or external reference com-
pensation (Table 7).
Power-Down Sequencing
The MAX1202/MAX1203’s automatic power-down
modes can save considerable power when operating
at less than maximum sample rates. The following sec-
tions discuss the various power-down sequences.
Lowest Power at up to
500 Conversions per Channel per Second
Figure 14a depicts MAX1202 power consumption for one
or eight channel conversions using full power-down
mode and internal reference compensation. A 0.01µF
bypass capacitor at REFADJ forms an RC filter with the
internal 20kΩ reference resistor, with a 0.2ms time con-
stant. To achieve full 12-bit accuracy, 10 time constants
(or 2ms in this example) are required for the reference
buffer to settle. When exiting FULLPD, waiting this 2ms in
FASTPD mode (instead of just exiting FULLPD mode and
returning to normal operating mode) reduces power con-
sumption by a factor of 10 or more (Figure 13).
Lowest Power at Higher Throughputs
Figure 14b shows power consumption with external-
reference compensation in fast power-down, with one
and eight channels converted. The external 4.7µF com-
pensation requires a 50µs wait after power-up. This cir-
cuit combines fast multichannel conversion with the
lowest power consumption possible. Full power-down
mode can increase power savings in applications where
the MAX1202/MAX1203 are inactive for long periods of
time, but where intermittent bursts of high-speed conver-
sion are required.
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