Help Needed with Circuit Design: TPL5110 Timer and MOSFET Not Functioning as Int - Page 1
Forum section: electronics / beginners

author: Dicko
author_rank: Contributor
timestamp: March 15, 2023, 07:05:28 pm
content: Greetings everyone,I am reaching out for some assistance with a circuit that I have designed, which is not functioning as intended. This is rather perplexing since the circuit was previously working flawlessly, but suddenly stopped working as expected. Allow me to elaborate.I have an Arduino connected to several sensors that take measurements. To reduce sleep current, I decided to create a circuit employing a TPL5110 Nano-Power System Timer and a MOSFET. The timer circuit is powered by a 3.7V LiPo battery, with external resistors selecting the timer duration. Following a certain amount of time, the timer outputs a drive signal to a MOSFET, which in turn provides the supply voltage to the Arduino, powering it. Once the Arduino sends a done signal to the timer circuit (a digital pin that transitions from Low to High), power to the Arduino is cut off until the designated time has elapsed. Previously, the circuit, as shown in Figure 1, worked perfectly and performed its intended function. However, it suddenly stopped functioning, and I am uncertain as to whether a component has become damaged or what the problem could be.I suspected that the Done signal might be floating high, so I added a pull-down resistor to the board. However, the circuit is now behaving unpredictably; it starts intermittently, and at other times it does not power up at all. I have spent the last two days investigating this issue but have made no progress.I should add that the done signal comes from a potential divider circuit (one of my sensors is resistive), two digital pins are used for power. One high 3.3V the other LOW 0V. I use the LOW pins as the done signal to the timer circuit. Once the Arduino has taken a measurement in the potential divider, I toggle the LOW pin high to give a done signal to the timer circuit, scribble shown attached.I would greatly appreciate any suggestions or assistance with identifying what could be going wrong with the circuit or how to go about fault-finding.MOSFET:https://uk.farnell.com/nexperia/nx3008pbk-215/mosfet-p-ch-30v-230ma-sot23/dp/2069547?ost=2069547TPL511-:https://www.ti.com/lit/ds/symlink/tpl5110.pdf?ts=1678869240894&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTPL5110%252Fpart-details%252FTPL5110DDCTArduino:https://docs.arduino.cc/hardware/mkr-wan-1310

author: drvtech
author_rank: Regular Contributor
timestamp: March 16, 2023, 09:37:40 pm
content: On your third picture (the green, hand drawn one) you show DONE connected to ground. What's really connected to DONE?It would help if you post the full schematic, especially since it sounds as if you're doing something slightly unconventional.

author: Dicko
author_rank: Contributor
timestamp: March 16, 2023, 11:01:40 pm
content: Apologies, the Done signal is not connected to ground. There is a potential divider powered by two digital pins, one set high to 3.3V, the other set Low 0V (I mistakenly called it ground when I put 0V) it is this pin that is connected to the done signal. Because a done signal is a transition from low to high. It starts low because as I said this pin is acting as a digital ground for the potential divider. Once the Arduino is finished measuring the potential divider I turn the pin from Low to High, therefore giving the Low-High transition to the done pin, which turns the timer circuit off.

author: Kim Christensen
author_rank: Super Contributor
timestamp: March 16, 2023, 11:37:47 pm
content: Whatexactlyare Vin1 and Vout1 connected to?

author: Dicko
author_rank: Contributor
timestamp: March 17, 2023, 08:45:05 am
content: Vin 1 comes from a LiPo battery and Vout it the output voltage to a microcontroller.

author: Kim Christensen
author_rank: Super Contributor
timestamp: March 17, 2023, 03:43:20 pm
content: Quote from: Dicko on March 17, 2023, 08:45:05 amPost a proper schematic. The Arduino board can be powered in more than one way.

author: CountChocula
author_rank: Unknown
timestamp: March 17, 2023, 04:14:09 pm
content: A schematic would, indeed, be helpful, as would a photo of your setup (for example: Is this on a breadboard? If so, my money is on some kind of connection problem).Other things to consider without knowing more:Is your battery sufficiently charged and able to provide enough power to your circuit?Breadboard or not, did you double-check all your connections?If you have access to an oscilloscope, can you observe the various lines for the expected behaviour?