In our last episode we discussed some of the attributes of Linear Technology’s new LTC3108 energy-scavenging boost converter, which operates on as little as 20 mV from TEGs (thermo-electric generators, thermopiles, or small photo-voltaic cells. Although many energy-scavenging transducers produce small output voltages like those mentioned—on the order of a few millivolts—one in particular presents the opposite problem: Piezo-electric transducers tend to produce outputs larger than most electronic systems can use. Capturing the energy from a piezo and buck-regulating the voltage to something IC friendly is the job of Linear Technology’s second device for energy harvesting.

The LTC3588-1 operates with low-energy transducers with outputs in the range from 2.7 V to 20 V characterized by high output impedances. This includes piezo-electric transducers operating with ambient-vibrational excitation. The buck converter is pin-programmable to one of four output potentials: 1.8 V, 2.5 V, 3.3 V, or 3. 6V. Like the ‘3108, the ‘3588-1 makes do with little operating current—about 950 nA in regulation and 450 nA in ULVO (under-voltage lockout) mode.

In the ULVO mode, the converter accumulates charge on a storage capacitor until it can transfer energy to its output. In full regulation mode, the ‘3588-1 can source as much as 100 mA of output current.

Now piezos can and do get a bit snippy when suitably excited. Think of that satisfying thwack… wooosh sound from a piezo-electric ignition system in a backyard grill. The thwack is a spring –loaded toggle striking a piezo-electric element. The wooosh is what happens when you let the several hundred volts that the piezo develops in that application arc across an air gap in the presence of a flammable gas.

Of course most energy harvesting applications do not subject piezo-electric elements to spring-loaded toggle thwackers. On the other hand, a 20 V maximum can be a risky limit in the presence of an otherwise unconstrained piezo output. So the LTC3588-1 includes a protective shunt zener capable of sinking as much as 25 mA. The zener, which operates in concert with the piezo’s large source impedance limits the converters input differential to a safe maximum.

Prices start at $2.95 (1000). A version of the part suitable for the industrial temperature range starts at $3.47 (1000). Both versions are available in MSOP-10 and 3 mm x 3 mm DFN packages.