vne147
Member
Hello everyone.
I’ve been experimenting with different current monitoring options for a project I’m working. Along the way I discovered the MAX9611/12 which has a built in 12-bit ADC. It seemed like the perfect solution for my needs, so I hooked up a test circuit and wrote some code to interface the IC. Everything seemed to be working fine, that is until I totally fried the part.
I’m still scratching my head about why exactly this happened, so I thought I’d ask ETO to give me a sanity check. I’ve attached a schematic of my test setup.
When the failure occurred, I was supplying the circuit with the **broken link removed**switching power supply. I set the voltage and current limits to 48V, and 3.2A respectively. The load was a 2Ω 50W power resistor which was connected to the supply through a digital multimeter to measure current in the 10A range.
I commanded the power supply on and everything was chugging along. The current and voltage measurements were spot on. Then, I unplugged the DMM- lead from the multimeter. I was expecting the measured current to drop to zero and the voltage to jump to 48V. Instead, the IC caught fire and vaporized the RS+ and RS- pins, in the process allowing the mythical magic smoke to escape.
So, what did I do wrong? Can anyone help me solve this mystery?
Any questions or requests for clarification, don’t hesitate to ask. Thanks in advance for any insight you can provide.
Note: The 3.3V supply to the MAX9611 is referenced to GND, not AGND. But I measured the test circuit and there is less than 100 mV difference between the two ground planes. This isn’t how I plan to connect everything in the final circuit. I just did it this way because it was easier to modify my test setup. I don’t think this contributed to the failure, but for the sake of completeness I depicted it in the schematic and since I don’t know what caused the failure, I’m keeping it in my list of possibilities.
I’ve been experimenting with different current monitoring options for a project I’m working. Along the way I discovered the MAX9611/12 which has a built in 12-bit ADC. It seemed like the perfect solution for my needs, so I hooked up a test circuit and wrote some code to interface the IC. Everything seemed to be working fine, that is until I totally fried the part.
I’m still scratching my head about why exactly this happened, so I thought I’d ask ETO to give me a sanity check. I’ve attached a schematic of my test setup.
When the failure occurred, I was supplying the circuit with the **broken link removed**switching power supply. I set the voltage and current limits to 48V, and 3.2A respectively. The load was a 2Ω 50W power resistor which was connected to the supply through a digital multimeter to measure current in the 10A range.
I commanded the power supply on and everything was chugging along. The current and voltage measurements were spot on. Then, I unplugged the DMM- lead from the multimeter. I was expecting the measured current to drop to zero and the voltage to jump to 48V. Instead, the IC caught fire and vaporized the RS+ and RS- pins, in the process allowing the mythical magic smoke to escape.
So, what did I do wrong? Can anyone help me solve this mystery?
Any questions or requests for clarification, don’t hesitate to ask. Thanks in advance for any insight you can provide.
Note: The 3.3V supply to the MAX9611 is referenced to GND, not AGND. But I measured the test circuit and there is less than 100 mV difference between the two ground planes. This isn’t how I plan to connect everything in the final circuit. I just did it this way because it was easier to modify my test setup. I don’t think this contributed to the failure, but for the sake of completeness I depicted it in the schematic and since I don’t know what caused the failure, I’m keeping it in my list of possibilities.