Julian Straub

creations and thoughts

Posted at — Jan 1, 0001

Analog Devices: - LTC3105 doesnt do battery management for you. The LDO output is ony on when power is present on the input. This means you would have to build another it has 10uA Iq for Vout which means the energy storage device can be drained once input power is lost (higher leakage than bq series from TI!)

TI https://www.ti.com/lit/ml/slpt026a/slpt026a.pdf?ts=1590849932113 - bq25504 ($4.44) seems great for charging and maintaining a battery/super cap charged from harvested energy. Lower quiescent power than LTC3105. Low Ubat leakage of <1uA - bq25505 adds functionality to have a primary non-rechargeable power source (not needed) - TPS6273x ($4.5 at mouser)low power switching power supply down to 10uA the “6” version goes to 50mA output and the “7” version to 200mA. - bq25570 seems like bq25504 + TPS6273x ($6.71 at mouser.com) this means it is cheaper to get this IC if harvesting + buck output regulation are desired. The buck output voltage is slave to the harvester being enabled. So buck output can only happen if the harvester is enabled. In this circuit we would want to have the microcontroller be powered directly from the battery and the parts of the circuit that need regulated voltage powered from the buck. That way the microcontroller can turn of buck as needed between bursts of needed regulated output power (the buck only has <50% efficiency in the realm of 10uA output).

Leakage in shutdown: LTC3105: 10uA into Vout in shutdown, 1uA into LDO in shutdown -> put in shutdown when the sunlight is gone; could add Shottky into supercap to remove BQ25504: Vbat leakage <100nA, Vstor quiescent <1uA in shutdown

For the LED blinker we dont need regulated output voltage. For something like a wireless module we may need it. It would be good to have a constant current LED boost driver to drive the LED from the unregulated battery voltage.

So: - 1.2V solar cell MPP - 2.7V Ubat (since that seems to be higher efficiency than 5.5V output (3V output 80% vs 5V output 60% at 10uA input current) - Ubat to drive the ATtiny

LED driver boost: - TPS61043 soft start (cheaper!) this means though that I have to have 2 LEDs since Vout > Vin (up to 5V) - LT1932 no soft start but allows for output voltage < input voltage both have low <1uA shutdown current

Solderable solar cells monocrystaline: - https://www.digikey.com/product-detail/en/SM111K04L/SM111K04L-ND/9990435/?itemSeq=327961547

Low voltage low power OpAmp: - http://ww1.microchip.com/downloads/en/DeviceDoc/22257C.pdf seems better -> MSOP 2 - lower power consumption and fA bias current! https://www.ti.com/lit/ds/symlink/tlv8812.pdf?HQS=TI-null-null-mousermode-df-pf-null-wwe&ts=1593388087225&ref_url=https%253A%252F%252Fwww.mouser.com%252F - https://www.ti.com/lit/ds/symlink/tlv2401.pdf?ts=1590876183201

LDO enable low quiescent - ADP121 11uA: https://www.mouser.com/ProductDetail/Analog-Devices/ADP121-AUJZ18R7?qs=BpaRKvA4VqHDGKZoNijD0g%3D%3D - STLQ50 3uA: https://www.mouser.com/datasheet/2/389/stlq50-1851022.pdf - STLQ020 0.3uA https://www.mouser.com/datasheet/2/389/stlq020-1374949.pdf - TPS783 500nA http://www.ti.com/lit/ds/symlink/tps783.pdf - MCP1810 50nA + <0.5uA: http://ww1.microchip.com/downloads/en/DeviceDoc/20005623B.pdf - *TPS7A02 <100nA: https://www.ti.com/lit/ds/symlink/tps7a02.pdf?ts=1590951403597

Reduce power consumption: - analog switches are super low power (nA) and can also increase number of readable sensors - high side load switch https://www.vishay.com/docs/66597/sip32431.pdf - low leakage MOSFETs https://assets.nexperia.cn/documents/application-note/AN90009.pdf