Datasheet

Typical Application Circuit
Analog ratiometric output configuration (Figure 2) pro-
vides an output that is proportional to the power-supply
voltage. Ratiometricity is an important consideration for
battery-operated instruments, and some industrial appli-
cations.
Detailed Description
The MAX1464 is a highly integrated, low-power, low-
noise multichannel sensor signal processor optimized for
industrial, and process-control applications, such as pres-
sure sensing and compensation, RTD and thermocouple
linearization, weight sensing and classification, and
remote process monitoring with limit indication.
The MAX1464 incorporates a 16-bit CPU, user-program-
mable 4kB of FLASH memory, 128 bytes of FLASH user
information, 16-bit ADC, two 16-bit DACs, two 12-bit
PWM digital outputs, four rail-to-rail op amps, SPI inter-
face, two GPIOs, and one on-chip temperature sensor.
Each sensor signal can be amplified, compensated for
temperature, linearized, and the offset and full scale can
be adjusted to the desired value. The MAX1464 can pro-
vide outputs as analog voltage (DAC) or digital (PWM,
GPIOs), or simple on/off alarm indication (GPIOs). The
uncommitted op amps can be used to implement 4–20mA
current loops or for additional gain and filtering. Each
DAC output is routed to either a small or large op amp.
Large op amps are capable of driving heavier external
loads. The unused circuit functions can be turned off to
save power.
All sensor linearization and on-chip temperature com-
pensation is done by a user-defined algorithm stored
in FLASH memory. The user-defined algorithm is pro-
grammed over the serial interface and stored in 4kB of
integrated FLASH memory.
The MAX1464 uses an internal 4MHz oscillator or an
externally supplied 4MHz clock. CPU code execution and
ADC operation is fully synchronized to minimize the noise
interference of a CPU-based sensor processor system.
The CPU sequentially executes instructions stored in
FLASH memory.
Sensor Input
The MAX1464 provides two differential signal inputs,
INP1-INM1 and INP2-INM2. These inputs can also be
configured as four single-ended signals. Each input can
have a common-mode range from V
DD
to V
SS
and a
0.99V/V to 244V/V programmable-gain range. The dif-
ferential input signals are summed with the output of the
coarse offset DAC (CO DAC) for offset correction prior
to being amplified by the programmable-gain amplifier
(PGA). The resulting signal is applied to the differential
input of the ADC for conversion. The CPU can be pro-
grammed to measure one or two differential inputs plus
the internal temperature sensor defined in user-supplied
algorithm. For example, the differential inputs can be
measured many times while the temperature can be mea-
sured less frequently.
Figure 2. Basic Bridge Sensor Ratiometric Output Configuration
5VDC
V
DD
SENSOR
V
SS
V
DDF
OUTnSM OUT
0.1µF
0.1µF 100pF
INPn
INMn
GND
22Ω
MAX1464
MAX1464 Low-Power, Low-Noise Multichannel
Sensor Signal Processor
www.maximintegrated.com
Maxim Integrated │ 12