DEMO CIRCUIT 1459B LTC3588EMSE-1/-2 QUICK START GUIDE LTC3588EMSE-1 LTC3588EMSE-2 Piezoelectric Energy Harvesting Power Supply DESCRIPTION Demonstration Circuit 1459B is an energy harvesting produces a logic high referenced to VOUT on the power supply featuring the LTC3588-1/LTC3588-2. PGOOD pin when the converter reaches the pro- The LTC3588 integrates a low-loss full-wave bridge grammed VOUT, signaling that the output is in regula- with a high efficiency buck converter to form a com- tion. plete energy harvesting solution optimized for high The LTC3588EMSE-1/LTC3588EMSE-2 are available output impedance energy sources such as piezoelec- in a 10-lead (3mm 3mm) MSE surface mount pack- tric transducers. An ultralow quiescent current under- age with exposed pad. voltage lockout mode with a wide hysteresis window L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered allows charge to accumulate on an input capacitor trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy Drive, FilterCAD, Hot Swap, LinearView, Module, Micropower SwitcherCAD, Multimode until the buck converter can efficiently transfer a por- Dimming, No Latency , No Latency Delta-Sigma, No R , Operational Filter, PanelProtect, SENSE tion of the stored charge to the output. Four output PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT, UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names voltages are pin selectable with up to 100mA of con- may be trademarks of the companies that manufacture the products. tinuous output current. A power good comparator TABLE 1 PERFORMANCE SUMMARY LTC3588EMSE-1 Specifications are at T = 25C A SYMBOL PARAMETER CONDITIONS MIN MAX UNITS VIN Input Voltage Range 4.3 18.0 V VOUT 1.8V Output Voltage Range D0 = 0, D1=0 1.71 to 1.89 V VOUT 2.5V Output Voltage Range D0 = 1, D1=0 2.425 to 2.575 V VOUT 3.3V Output Voltage Range D0 = 0, D1=1 3.201 to 3.399 V VOUT 3.6V Output Voltage Range D0 = 1, D1=1 3.491 to 3.708 V PERFORMANCE SUMMARY LTC3588EMSE-2 Specifications are at T = 25C A SYMBOL PARAMETER CONDITIONS MIN MAX UNITS VIN Input Voltage Range 14.0 18.0 V VOUT 3.45V Output Voltage Range D0 = 0, D1=0 3.346 to 3.554 V VOUT 4.1V Output Voltage Range D0 = 1, D1=0 3.977 to 4.223 V VOUT 4.5V Output Voltage Range D0 = 0, D1=1 4.365 to 4.635 V VOUT 5.0V Output Voltage Range D0 = 1, D1=1 4.850 to 5.150 V 1 LTC3588EMSE-1/-2 OPERATING PRINCIPLE Refer to the block diagram within the LTC3588-1/-2 nected to the CAP and VIN2 pins to serve as energy data sheet for its operating principle. reservoirs for driving the buck switches. The buck regulator uses a hysteretic voltage algo- The LTC3588 is an ultralow quiescent current power rithm to control the output through internal feedback supply designed specifically for energy harvesting from the VOUT sense pin. The buck converter charges and/or low current step-down applications. The part an output capacitor through an inductor to a value is designed to interface directly to a piezoelectric or slightly higher than the regulation point. It does this alternative A/C energy source, rectify and store the by ramping the inductor current up to 250mA harvested energy on an external capacitor, bleed off through an internal PMOS switch and then ramping it any excess energy via an internal shunt regulator, down to 0mA through an internal NMOS switch. and maintain a regulated output voltage by means of When the buck brings the output voltage into regula- a nano-power high efficiency synchronous buck reg- tion the converter enters a low quiescent current ulator. sleep state that monitors the output voltage with a The LTC3588 has an internal full-wave bridge recti- sleep comparator. During this operating mode load fier accessible via PZ1 and PZ2 that rectifies AC in- current is provided by the buck output capacitor. puts such as those from a piezoelectric element. The When the output voltage falls below the regulation rectified output is stored on a capacitor at the VIN pin point the buck regulator wakes up and the cycle re- and can be used as an energy reservoir for the buck peats. This hysteretic method of providing a regu- converter. The bridge is capable of carrying up to lated output reduces losses associated with FET 50mA. switching and maintains an output at light loads. The When the voltage on VIN crosses the UVLO rising buck delivers a minimum of 100mA average load threshold the buck converter is enabled and charge current when it is switching. is transferred from the input capacitor to the output A power good comparator produces a logic high ref- capacitor. A wide (~1V) UVLO hysteresis window is erenced to VOUT on the PGOOD pin the first time the employed with a lower threshold approximately converter reaches the programmed VOUT, signaling 200mV above the selected regulated output voltage that the output is in regulation. The PGOOD pin will to prevent short cycling during buck power-up. remain high until VOUT falls to 92% of the desired When the input capacitor voltage is depleted below regulated voltage. the UVLO falling threshold the buck converter is dis- abled. Two internal rails, CAP and VIN2, are generated from VIN and are used to drive the high side PMOS and low side NMOS of the buck converter, respectively. Additionally the VIN2 rail serves as logic high for out- put voltage select bits D0 and D1. The VIN2 rail is re- gulated at 4.8V above GND while the CAP rail is regu- lated at 4.8V below VIN. These are not intended to be used as external rails. Capacitors should be con- 2