Other Parts Discussed in Thread: LM66200
Tool/software:
Hello,
in our electronics we use a Bluetooth Low Energy Module and some sensors running at 1,8 VDC. These 1,8 VDC are generated by a DC/DC converter; the input of this converter is connected to U_SUP (see schematics below). The Reed contact S1 is a 'normally closed' type and does not make any troubles.
In our system we have an energy harvester which generates energy when our tool runs; the principle is like a bycicle dynamo - at very low speed there is not enough energy generated, so a CR2032 battery has to deliver the needed energy. When increasing the speed a DC/DC-converter generates an output voltage of max. 3,6 VDC, connected to U_GEN. The speed is selected by the customer due to its application. If the speed is high enough that U_GEN achieves at least 3.5 VDC a Supercap is charged from 0 to about 3.5V, this voltage is used by a TPS61099YFF to generate 3.3VDC which are connected to U_CAP.
With Y1 closed I see a correct supply function: At standstill of the motor I see that U_SUP equals the battery voltage. When the motor starts to turn U_GEN is increasing and at high RPMs U_GEN (and U_SUP) achieve 3.6 VDC and the SuperCap starts to be charged. When the voltage at the SuperCap exceeds 1.0V the TPS61099YFF generates an output of 3.3VDC. If I stop the motor the harvester voltage (was running at high RPMs) U_GEN breaks down, then the system is supplied by the 3.3VDC from the TPS61099YFF until the SuperCap voltage goes less than 1.0 VDC and then the battery supplies the system. This works fine, but:
When the motor runs at high RPMs I see the 3.6VDC not only at U_GEN and U_SUP, but also at the battery! And when the motor stops and the SuperCap was charged I see after the 3.6 VDC the 3.3VDC at U_SUP (which is correct), but also at the battery (which is not correct).
The needed current at U_SUP is between some µAmps (when the BLE module is in sleep mode) and can reach up to 30 mA when the SuperCap is loaded and a new firmware is transmitted and flashed; mostly it turns at about 1 mA.
Is there an error iny my schematics or what can I do to avoid these voltages at the battery? If a hardware change is recommended - would the LM66200 be a better choice?
Best regards,
Matthias
