General Description

The MAX12900 is an ultra-low-power, highly integrated

4-20mA sensor transmitter. The MAX12900 integrates

ten building blocks in a small package: a wide input supply

voltage LDO, two conditioner circuits for pulse-widthmodulated

(PWM) inputs, two low-power, low-drift, generalpurpose

operational amplifiers (op amp) one wide bandwidth,

zero-offset drift operational amplifier; two diagnostic

comparators, a power-up sequencer with power good

output to allow for a smooth power-up, and a low-drift

voltage reference.

The MAX12900 converts PWM data from a microcontroller

into current over a 4-20mA loop with two, three, or fourwire

configurations.

The equivalent to an ultra-low-power, high-resolution,

digital-to-analog converter is realized with the combination

of two-PWM signals received from a microcontroller, the

two conditioner circuits, and an active filter built with the

integrated low-power op amp. The outputs of the two

conditioner circuits provide a stable PWM amplitude over

voltage supply and temperature variation. The wide bandwidth

amplifier, in combination with a discrete transistor,

converts a voltage input into a current output and allows

HART and Foundation Fieldbus H1 signal modulation.

The zero-offset operational amplifier and the low-drift

voltage reference provide negligible error over wide

temperature. The low-power operational amplifier and

comparators provide building blocks for enhanced

diagnostic features. Supply rail monitoring, output

current readback, open circuit and failure detection are a

few examples of diagnostic features. All these features,

as well as ultra-low-power and high accuracy make the

MAX12900 ideal for loop-powered smart sensor transmitters

for industrial application.

The MAX12900 is available in 5mm x 5mm 32-pin TQFN

package and operates over a wide industrial temperature

range of -40°C to +125°C.

Benefits and Features

● Wide Input Supply Range: 4.0V to 36V

● Ultra-Low-Power Consumption: 170μA (typ)

● High Linearity: 0.01% (Max Error)

● High Resolution: Up to 16 Bit

● Low Drift Voltage Reference: 10ppm/°C max

● Wide Temperature Range: -40°C to +125°C

● Small Package: 5mm x 5mm x 0.8mm 32-pin TQFN

Applications

● Loop-Powered 4-20mA Current Transmitter

● Smart Sensors

● Remote Instrumentation

● Industrial Automation and Process Control