Datasheet

MAX1253/MAX1254
Stand-Alone, 10-Channel, 12-Bit System Monitors
with Internal Temperature Sensor and V
DD
Monitor
______________________________________________________________________________________ 13
In differential mode, the T/H samples the difference
between two analog inputs, eliminating common-mode
DC offsets and noise. See the Input Configuration
Register section and Tables 5 and 6 for more details on
configuring the analog inputs.
Unipolar/Bipolar
When performing differential conversions, the input
configuration register (Tables 5 and 6) also selects
between unipolar and bipolar operation. Unipolar mode
sets the differential input range from 0 to V
REF.
A nega-
tive differential analog input in unipolar mode causes
the digital output code to be zero. Selecting bipolar
mode sets the differential input range to ±V
REF
/2. The
digital output code is straight binary in unipolar mode
and two’s complement in bipolar mode (see the
Transfer Function section).
In single-ended mode, the MAX1253/MAX1254 always
operate in unipolar mode. The analog inputs are inter-
nally referenced to GND with a full-scale input range
from 0 to V
REF.
Digital Interface
The MAX1253/MAX1254 digital interface consists of
five signals: CS, SCLK, DIN, DOUT, and INT. CS,
SCLK, DIN, and DOUT comprise an SPI™-compatible
serial interface (see the Serial Digital Interface section).
INT is an independent output that provides an indica-
tion that an alarm has occurred in the system (see the
INT Interrupt Output section).
Serial Digital Interface
The MAX1253/MAX1254 feature a serial interface com-
patible with SPI, QSPI™, and MICROWIRE™ devices.
For SPI/QSPI, ensure that the CPU serial interface runs
in master mode so it generates the serial clock signal.
Select a serial clock frequency of 10MHz or less, and
set clock polarity (CPOL) and phase (CPHA) in the µP
control registers to the same value, one or zero. The
MAX1253/MAX1254 support operation with SCLK idling
high or low, and thus operate with CPOL = CPHA = 0 or
CPOL = CPHA = 1.
T
T
TT
H
HH
V
AZ
V
DD
ADC
CHOLDP CHOLD
CHOLDN
8-TO-1
DIFFERENTIAL
MUX
TEMP
DIFFERENTIAL INPUT EQUIVALENT INPUT CIRCUIT
T
T
H
H
V
AZ
V
DD
ADC
8-TO-1
DIFFERENTIAL
MUX
TEMP
SINGLE-ENDED INPUT EQUIVALENT INPUT CIRCUIT
Figure 5. Single-Ended/Differential Input Equivalent Input Circuit
SPI and QSPI are trademarks of Motorola, Inc.
MICROWIRE is a trademark of National Semiconductor Corp.