Corentin
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Hi everyone,
I hope I am posting in the right section.
I have been facing a problem with the latest design of my board and I need your help to understand where this is coming from. Please, find attached the schematics.
View attachment board_v22.pdf
Problem
The problem concerns the line EN_REGULATOR which goes from the MSP's digital output P6.5 to the diode's anode D1 (double diode in common cathode). It looks the digital output of the MSP gets destroyed on many the boards we manufactured (about 30% of them) and randomly in time (right after manufacture, 1 days after, 2 or 3 days after or more).
When I say "destroyed", I mean that the program requires to set P6.5 output high, but the ouput remains low. When I enter debug mode, I manually set P6.5 output high but it remains low. However, it works with any other pin.
Below is the description of how the circuit should work:
1./ Pad1 and Pad2 are contacts. They are put into water so that they are connected together (some kind of switch), so WETCONT_IN goes high. It goes through the diode D1 and enables the regulator.
2./ When the regulator is enabled, the MSP430 starts, its program runs.
3./ The MSP430 drives its output pin P6.5 (Enable_Regulator) High which also goes to D1. As long as WETCONT_IN is high, EN_REGULATOR doesn't 'drive through' D1 (because WETCONT_IN is at the level of the battery whereas EN_REGULATOR is at the level of the output of the voltage regulator).
4./ When PAD1 and PAD2 are disconnected (out of water and dry), WETCONT_IN goes low. Then EN_REGULATOR immediately drives through D1 to keep the regulator enabled.
5./ The MSP430 decides by itself when it "wants" to shutdown. When it drives EN_REGULATOR low, the regulator is disabled. The regulator stops driving current.
Main components
Battery: single Li-Po cell, 360mAh
D1: Double diode, common cathode. **broken link removed**
REG1: Regulator, TPS79533 (3.3V - 500mA). See datasheet
C3: Tantalum 6.3V 22µF, low ESR, placed next to output of REG1
C7: Tantalum 6.3V 47µF, next to RNXV.
RNXV: WiFi module, using current up to 240mA (in short periods of time). See datasheet
MSP430F233
Questions
Despite the numerous boards we manufactured and met the problem with, we cannot identify the exact time the pin gets "destroyed". We cannot either understand why.
1./ Is the pin P6.5 really "destroyed"? Or is there something I am missing? I would like to mention that when P6.5 is "destroyed", I wire another digital output (P5.4) to P6.5 and modify the program and the board works again (but P6.5 is still probably destroyed). I suppose that this way, P5.4 will sooner or later be destroyed as well.
2./ Is there anything wrong, a big mistake in the design of the schematics? How would you have done it yourself?
3./ Can you identify the reason why the pin is destroyed?
4./ Is there any quick modification I can bring to the PCBs to easily remove the problem? How would you advise to me to do for my next designs? I was thinkings or putting a resistor (1k ?) between the MSP's pin and the diode.
Thanks in advance for your help,
Corentin
I hope I am posting in the right section.
I have been facing a problem with the latest design of my board and I need your help to understand where this is coming from. Please, find attached the schematics.
View attachment board_v22.pdf
Problem
The problem concerns the line EN_REGULATOR which goes from the MSP's digital output P6.5 to the diode's anode D1 (double diode in common cathode). It looks the digital output of the MSP gets destroyed on many the boards we manufactured (about 30% of them) and randomly in time (right after manufacture, 1 days after, 2 or 3 days after or more).
When I say "destroyed", I mean that the program requires to set P6.5 output high, but the ouput remains low. When I enter debug mode, I manually set P6.5 output high but it remains low. However, it works with any other pin.
Below is the description of how the circuit should work:
1./ Pad1 and Pad2 are contacts. They are put into water so that they are connected together (some kind of switch), so WETCONT_IN goes high. It goes through the diode D1 and enables the regulator.
2./ When the regulator is enabled, the MSP430 starts, its program runs.
3./ The MSP430 drives its output pin P6.5 (Enable_Regulator) High which also goes to D1. As long as WETCONT_IN is high, EN_REGULATOR doesn't 'drive through' D1 (because WETCONT_IN is at the level of the battery whereas EN_REGULATOR is at the level of the output of the voltage regulator).
4./ When PAD1 and PAD2 are disconnected (out of water and dry), WETCONT_IN goes low. Then EN_REGULATOR immediately drives through D1 to keep the regulator enabled.
5./ The MSP430 decides by itself when it "wants" to shutdown. When it drives EN_REGULATOR low, the regulator is disabled. The regulator stops driving current.
Main components
Battery: single Li-Po cell, 360mAh
D1: Double diode, common cathode. **broken link removed**
REG1: Regulator, TPS79533 (3.3V - 500mA). See datasheet
C3: Tantalum 6.3V 22µF, low ESR, placed next to output of REG1
C7: Tantalum 6.3V 47µF, next to RNXV.
RNXV: WiFi module, using current up to 240mA (in short periods of time). See datasheet
MSP430F233
Questions
Despite the numerous boards we manufactured and met the problem with, we cannot identify the exact time the pin gets "destroyed". We cannot either understand why.
1./ Is the pin P6.5 really "destroyed"? Or is there something I am missing? I would like to mention that when P6.5 is "destroyed", I wire another digital output (P5.4) to P6.5 and modify the program and the board works again (but P6.5 is still probably destroyed). I suppose that this way, P5.4 will sooner or later be destroyed as well.
2./ Is there anything wrong, a big mistake in the design of the schematics? How would you have done it yourself?
3./ Can you identify the reason why the pin is destroyed?
4./ Is there any quick modification I can bring to the PCBs to easily remove the problem? How would you advise to me to do for my next designs? I was thinkings or putting a resistor (1k ?) between the MSP's pin and the diode.
Thanks in advance for your help,
Corentin
