MAX1153_10 datasheet(10/30 Pages) MAXIM

10 / 30 page

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

with Internal Temperature Sensor and VDD Monitor

______________________________________________________________________________________

DGND

a) VOL TO VOH

CLOAD = 100pF

100

μA

DOUT

DGND

VDD

b) HIGH-Z TO VOL AND VOH TO VOL

CLOAD = 100pF

100

μA

DOUT

Figure 1. Load Circuits for DOUT Enable Time and SCLK to

DOUT Delay Time

DGND

a) VOH TO HIGH-Z

CLOAD = 100pF

100

μA

DOUT

DGND

VDD

b) VOL TO HIGH-Z

CLOAD = 100pF

100

μA

DOUT

Figure 2. Load Circuit for DOUT Disable Time

Detailed Description

The MAX1153/MAX1154 are precision-monitoring inte-

grated circuit systems specifically intended for stand-

alone operation. They can monitor diverse types of

inputs, such as those from temperature sensors and

voltage signals from pressure, vibration, and accelera-

tion sensors, and digitize these input signals. The digi-

tal values are then compared to preprogrammed

thresholds and, if the thresholds are exceeded, the

processor is alerted by an interrupt signal. No interac-

tion by the CPU or microcontroller (µC) is required until

one of the programmed limits is exceeded (Figures 3

and 4).

Voltages on all the inputs are converted to 10-bit values

sequentially and stored in the current data registers.

Note that eight of these inputs are external and two are

internal. One of the internal inputs monitors the VDD

voltage supply, while the other monitors the internal IC

temperature. AIN0 to AIN7 can be configured as either

single ended (default) or differential. In addition, these

inputs can be configured for single-ended or differen-

tial temperature measurements. In the temperature

configuration, the device provides the proper bias nec-

essary to measure temperature with a diode-connected

transistor sensor. The user enables which inputs are

measured (both external and internal) and sets the

delay between each sequence of measurements dur-

ing the initial setup of the device.

The values stored in the current data registers are com-

pared to the user-preprogrammed values in the thresh-

old registers (upper and lower thresholds) and, if

exceeded, activate the interrupt output and generate an

alarm condition. If desired, the device can be pro-

grammed to average the results of many measurements

before comparing to the threshold value. This reduces

the sensitivity to external noise in the measured signal.

In addition, the user can set the number of times the

threshold is exceeded (fault cycles) before generating

an interrupt. This feature reduces falsely triggered

alarms caused by undesired, random spurious impulses.

When the fault cycle criterion is exceeded, an alarm

condition is created. The device writes the fault condi-

tion into the alarm register to indicate the alarmed input

channel.

Converter Operation

The MAX1153/MAX1154 ADCs use a fully differential

successive-approximation register (SAR) conversion

technique and an on-chip track-and-hold (T/H) block to

convert temperature and voltage signals into a 10-bit

digital result. Both single-ended and differential config-

urations are supported with a unipolar signal range for

single-ended mode and bipolar or unipolar ranges for

differential mode. Figure 5 shows the equivalent input

circuit for the MAX1153/MAX1154. Configure the input

channels according to Tables 5 and 6 (see the

Input

Configuration Register section).

In single-ended mode, the positive input (IN+) is con-

nected to the selected input channel and the negative

input (IN-) is connected to GND. In differential mode,

IN+ and IN- are selected from the following pairs:

AIN0/AIN1, AIN2/AIN3, AIN4/AIN5, and AIN6/AIN7.

Once initiated, voltage conversions require 10.6µs (typ)

to complete.

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