Stand-Alone, 10-Channel, 10-Bit System Monitors

24

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where:

n = ideality factor (slightly greater than 1)

The temperature measurement process is fully auto-

mated in the MAX1153/MAX1154. All steps are

sequenced and executed by the MAX1153/MAX1154

each time an input channel (or an input channel pair)

configured for temperature measurement is scanned.

The resulting 10-bit, two’s complement number repre-

sents the sensor temperature in degrees Celsius, with

1 LSB = +0.5

°C.

The MAX1153/MAX1154 support both single-ended

and differential temperature measurements.

Applications Information

Setting Up the

MAX1153/MAX1154 Subsystem

The MAX1153/MAX1154 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

configures the input channels, enables the chan-

nels to be used, sets the sample wait time between

scans, configures the interrupt output INT, selects

the reference mode, and starts the automatic scan

mode. See the Write Global Configuration Registers

Command section, Table 2, and Tables 5–10.

Immediately after the global configuration register is

loaded, the MAX1153/MAX1154 begin to update the

current data registers. Acquire conversion data from

the MAX1153/MAX1154 by issuing a command to read

a specific channel with the Read Current Data Register

for Selected Channel command. Read all current data

register at once with the Read Current Data Registers

for All Channels command.

For more complex applications, the monitoring and

interrupt generation features of the MAX1153/MAX1154

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 MAX1153/MAX1154 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

MAX1153/MAX1154 are configured as follows:

•

Sample wait time is 0µs.

•

INT output is open drain and outputs an active-low

signal to signify an alarm.

Table 15. Power-Up/Reset Defaults Summary

REGISTER

BIT RANGE

POWER-UP/RESET STATE

COMMENT

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