MAX1253 Datasheet, PDF (19/29 Pages) Maxim Integrated Products – Stand-Alone, 10-Channel, 12-Bit System Monitors with Internal Temperature Sensor and VDD Monitor

Stand-Alone, 10-Channel, 12-Bit System Monitors
with Internal Temperature Sensor and V_DD Monitor
Setup Register
The 8-bit setup register (Table 7) holds configuration
data common to all input channels. At power-up and
after a RESET command, this register defaults to
00000000b.
Setup Register: Sample Wait Bits (B7, B6, B5)
These 3 bits in the setup register (Table 8) set the wait
time between conversion scans. The following are
examples of how the MAX1253/MAX1254 begin a sam-
ple sequence (see the Setup Register: Reference
Selection Bits (B1, B0) section).
Operating in reference mode 00 (external reference for
voltage conversions, internal reference for temperature
conversions):
1) Convert the first-enabled channel. If this channel is a
temperature measurement, power up the internal ref-
erence (this takes 20µs for each enabled tempera-
ture measurement in reference mode 00).
2) Sequence to the next-enabled channel until all chan-
nels have been converted.
3) Wait the sample wait period.
4) Repeat the procedure.
Operating in reference mode 01 (internal reference for all
conversions, can be powered down between scans):
1) Power up the internal reference, if powered down
(this takes 40µs).
2) Convert the first-enabled channel, starting with the
internal temperature sensor, if enabled.
3) Sequence to the next-enabled channel until all
enabled channels have been converted.
4) Wait the sample wait time, and enter internal refer-
ence power-down mode if this period is greater than
80µs.
5) Repeat the above steps.
Operating in reference mode 10 (internal reference for
all conversions, continuously powered up):
1) Convert the first-enabled channel.
2) Sequence to the next-enabled channel until all
enabled channels have been converted.
3) Wait the sample wait time.
4) Repeat the procedure.
Use the sample wait feature to reduce supply current
when measuring slow-changing analog signals. This
power savings occurs when reference mode 00 or 01 is
used in combination with wait times longer than 80µs.
With reference mode 10 or wait times of less than 80µs,
the internal reference system remains powered up, mini-
mizing any power savings. See the Computing Data
Throughput section. Table 8 shows the B7, B6, B5 wait
time encoding.
Setup Register: Interrupt Control (B4, B3)
Bits B3 and B4 in the setup register configure INT and
how it responds to an alarm event (see the Alarm
Register section). Table 9 shows the available INT
options.
Table 7. Setup Register Format
B7 (MSB)
B6
B5
Sample wait bits
B4
Interrupt
active
B3
Interrupt
polarity
B2
Scan
mode
B1
Reference
source B1
B0 (LSB)
Reference
source B2
Table 8. Wait Time Encoding
B7, B6, B5
000
001
010
011
100
101
110
111
WAIT TIME (ms)
0
0.080
0.395
1.310
4.970
19.600
78.200
312.000
Table 9. Interrupt Control
BIT
FUNCTION
BIT
STATE
INT OPERATION
1 Driven high or low at all times
B4
Output
driver type
0
High-Z when inactive, driven (high
or low) when active
B3
Output
polarity
1 Active = high, inactive = low or high-Z
0 Active = low, inactive = high or high-Z
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