Datasheet

MAX1253/MAX1254
Stand-Alone, 10-Channel, 12-Bit System Monitors
with Internal Temperature Sensor and V
DD
Monitor
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The temperature measurement process is fully auto-
mated in the MAX1253/MAX1254. All steps are
sequenced and executed by the MAX1253/MAX1254
each time an input channel (or an input channel pair)
configured for temperature measurement is scanned.
The resulting 12-bit, two’s complement number repre-
sents the sensor temperature in degrees Celsius, with
1 LSB = +0.125°C.
The MAX1253/MAX1254 support both single-ended
and differential temperature measurements.
Applications Information
Setting Up the
MAX1253/MAX1254 Subsystem
The MAX1253/MAX1254 are autonomous subsystems,
requiring only initialization to scan, convert, and monitor
the voltage signals or the temperature sensors con-
nected to their input channels.
For simple applications, using any number of the input
channels and any combination of voltage/temperature
and unipolar/differential, with no interrupt generation
required, use the following intitialization procedure:
• Issue a Write Global Configuration Registers com-
mand. This is a single, 5-byte write operation that con-
figures the input channels, enables the channels to be
used, sets the sample wait time between scans, con-
figures the interrupt output INT, selects the reference
mode, and starts the automatic scan mode. See the
Write Global Configuration Registers Command sec-
tion, Table 2, and Tables 5–10.
Immediately after the global configuration register is
loaded, the MAX1253/MAX1254 begin to update the
current data registers. Acquire conversion data from
the MAX1253/MAX1254 by issuing a command to read
a specific channel with the Read Current Data Register
for Selected Channel command. Read all current data
registers at once with the Read Current Data Registers
for All Channels command.
For more complex applications, the monitoring and
interrupt generation features of the MAX1253/MAX1254
require a second step of initialization. Each enabled
channel to be monitored requires configuration using a
Write Configuration Register for Selected Channel com-
mand. Each command is a 5-byte write that sets the
upper and lower fault thresholds, the number of faults for
an alarm before an interrupt is generated, and an aver-
age algorithm parameter if the application requires input
signal filtering.
Applications can read the current data registers and
respond to interrupts signaled by the INT output (see
the Servicing Interrupts at INT section).
All the MAX1253/MAX1254 registers can be verified by
reading back written data, including the configuration
registers. This feature is useful for development and
testing (see Table 2).
Power-Up/Reset Defaults Summary
Setup Register Power-Up/Reset Defaults
At initial power-up or after a RESET command, the
setup register resets to 00 hex. Consequently, the
MAX1253/MAX1254 are configured as follows:
• Sample wait time is 0µs.
• INT output is open drain and outputs an active-low
signal to signify an alarm.
• Manual conversion mode.
• External reference for voltage measurements.
Table 15. Power-Up/Reset Defaults Summary
REGISTER BIT RANGE POWER-UP/RESET STATE COMMENTS
Setup B0 to B7 All 0s See Setup Register Power-Up/Reset Defaults
Channel enable B0 to B11 All 1s All channels (int/ext) enabled
Input configuration B0 to B11 All 0s All single-ended voltage inputs
Alarm register B0 to B23 All 0s No alarms set
Channel configuration B0 to B7 All 0s Faults = 0, no averaging
Upper threshold B0 to B9 All 1s All upper thresholds max range
Lower threshold B0 to B9 All 0s All lower thresholds min range
Current data registers B0 to B9 200hex Set at midrange