Low-side I/V sensing IC, with internal power calculation
Instantaneous power is calculated internally by multiplying the load current and a fraction of the load voltage set by an external resistive divider. All three outputs are scaled to a full-scale current of 100 µA. An additional output current of 100 µA is available at the reference (REF) output; this current can be used to create a reference voltage for the ADC that is being used to measure the power, voltage, and current signals.
By providing the ADC with both the measured signals and the input reference voltage, the ADC can make a ratiometric measurement, allowing improved accuracy. The use of currents, rather than voltage, to convey the measured signals to the ADC eliminates any errors caused by voltage drops across the parasitic resistance of PCB, which can be significant for high-current systems. To allow full-system calibration, the CAL bump provides a way to calibrate gain and offset for the ADC.
The device measures load current by using a precision, auto-zeroed current-sense amplifier (CSA), which due to its ultra-low offset voltage allows precise measurement of full-scale voltages of 5 mV, 10 mV, and 20 mV. The load voltage is measured via a user-selectable resistive network, dividing the input voltage down to a full scale of 1.00V.
The wide supply voltage range of 3V to 5.5V allows the simple sharing of supplies with either the ADC or a microcontroller. The device can be powered down and the outputs will then go high impedance. The device is available in a 2.4 x 2.4 mm, 16-bump wafer-level package (WLP) and is specified for the 0°C to +85°C temperature range.
MAX44298 is a very similar product with a choice of 50 µA output current and alternate pinout. An evaluation kit (EV kit) provides a proven design to evaluate the MAX44299 current, voltage, and power monitor. The EV kit PCB is preconfigured with the CSA full-scale input voltage range (VSENSE) of 10 mV and 100 µA of output current ranges, but can be reconfigured to 10 mV/5 mV of FS VSENSE or 50 µA of output current by changing a few jumpers. The EV kit comes with a MAX44299EWE+ and a voltage divider to provide a forced full-scale VSENSE of 10 mV range at the CSA inputs installed.
Maxim Integrated; www.maximintegrated.com/en/products/analog/amplifiers/MAX44299.html
next page; feature listing
High accuracy improves measurement quality
Accurate power measurement: < 1.1% of reading total error
Zero thermal drift current-sense input
High Integration saves cost and space
Power, current, and voltage monitoring plus reference
5 mV, 10 mV, and 20 mV programmable current-sensing full-scale voltage
Calibration point at 10 μA upon command
Single-supply range and low power simplify power-supply design
Current output signals overcome trace output voltage drops and noise
3V to 5.5V single supply
Power-down mode with high-impedance output
0°C to +85°C temperature range
16-bump, 2.4 x 2.4 mm WLP