A robust energy harvesting system using the LTC3588-1 and LTC4071 is presented that can continuously run a 12.4mA, 1% duty cycle sensor/transmitter without grid power.
The document details the design of a complete energy-harvesting power subsystem for wireless sensor-transmitters. It utilizes a piezoelectric transducer to gather intermittent power, which is stored in Li-Polymer batteries managed by an integrated disconnect switch to prevent over-discharge.
The system operates in two modes: charging-sending and discharging-sending. Key components include the LTC3588-1 buck regulator and two LTC4071 shunt battery chargers, which manage float voltage with temperature compensation and provide low-leakage disconnect circuits to protect battery life.
| Harvested Energy Power Range | about 1mw-10mw |
|---|---|
| Active Sensor-Transmitter Power Requirement | 1comw-250mw |
| Battery Capacity | 8mah |
| Float Voltage Setting | 4.1v |
| Maximum Float Voltage Tolerance | +1% |
| Charging Time from Empty | about 75 hours |
The LTC4071 provides an internal low battery disconnect circuit to ensure the battery voltage never falls below a safe limit (e.g., 2.7v or 3.2V).
The system enters discharging-sending mode, where the batteries supply energy until the disconnect circuit activates to protect them.