Called NEH7100BU, it can mediate between a harvesting power source, a USB charger, a battery (or capacitor) and the load.
To maximise power extracted from photovoltaic cells, which have variable output impedance, and embedded hill-climbing algorithm homes-in on the best operating point for the internal dc-dc boost converter – so called maximum power point tracking or MPPT. The IC defaults to running this algorithm once a second.
Other potential power sources are kinetic (electro-magnetic or piezo) or temperature difference.
The load is supplied from the energy store via a linear regulator.
Pads on the IC, or its I2C bus, can be used to set the maximum store voltage to 3.1, 3.5, 4.0 or 4.2V, the main output to various common values between 1.2 and 3.3V, and the max output current to 50, 100 or 200mA. Not all combinations of values are available.
The dc-dc converter is a switched capacitor type (four external capacitors are required) with options of 2x, 4x, 8x and 16x boosting and 32kHz to 1.024MHz switching – Nexperia has been asked if this is correct, so watch this space is this is important to you.
With prior knowledge of the solar cell and load characteristics, power consumption and hill-climbing agility can be improved via the chip’s I2C bus, which allows: Adjusting the MPPT cycle from 1s to between 500ms and 64s, and setting upper and lower boundaries on the dc-dc converter’s multiplication range and operating frequency.
NEH7110BU is a related simplified IC without an I2C bus, that can only MPPT once a second and offers no external control over dc-dc multiplication or frequency.
Up to 5.5V can be applied to the harvesting input, provided that it comes from a photovoltaic cell or other source limited to 140mA (abs max). If it is from a low impedance source such as a bench power supply, maximum applied voltage is 2V.
Harvesting range is between 15μW and 50mW, and up to 200mA can be delivered to the power store if a USB charger is connected.
The battery can be at any voltage up to 4.5V, but some operational modes are restricted until this is above 2.9V (typ). A liner regulator is used to connect the USB charger (when available) to the energy store.
Operation is over -40 to +85°C, and packaging is 4 x 4mm QFN28.
Applications are foreseen in remote controls, key fobs, smart tags, asset trackers, occupancy sensors, environmental monitors, wearables, keyboards and tire pressure monitors.
Find the NEH7100BU product page here
