I have downloaded the service manual from the TTI CPX 200, I don't know if the shematics are the same as CPX 200D
https://elektrotanya.com/tti_cpx200_sm.pdf/download.html
1) it is a SMPS, not a linear power supply....not a good idea to try spare some hundreds of $ when you are testing $ 10.000.00 boards. Also no crowbar protection....Why did you not buy a Keyside power supply ?
2) Output is internally never disconnected from power converter, this is not safe for the circuit connected to the output.
3) Output circuit has very high value capacitors (because it is a SMPS !)...On the schematic, I see 2.200 + 470 + 470 = 3.140µF....That's crazy !!!!!
There are three 1.200R 2W resistors in parallel, to discharge the output capacitors....
But, what probably happened: for some reason, during adjust of current limit, these condensators has been charged to the maximum output voltage.
They don't discharge instantanely, you did not measure the output voltage before connecting the power supply to the board, the output condensators where not still fully discharged, there was still a voltage greater than 1.8V and you killed your board....
The "input never disconnected from the power converter" stuff must be true for this model too, I don't hear any relay clicking when I disconnect the output.
I do not think that we already know the root cause. Several shortcomings of the PS have been found, but the effect has not been definitely linked to one of them under the conditions described.
The assumption with the chargeup during current programming would be possible. Now it would be interesting if the OP could give us a timescale for the actions which he was describing so exactly. This might verify or invalidate the hypothesis.
I do not think that we already know the root cause. Several shortcomings of the PS have been found, but the effect has not been definitely linked to one of them under the conditions described.
The assumption with the chargeup during current programming would be possible. Now it would be interesting if the OP could give us a timescale for the actions which he was describing so exactly. This might verify or invalidate the hypothesis.In addition to the defects and limitations of the design of this power supply, there are many other elements that confirm the explanation that I gave:
1) it was a new power supply, nobody was used to its use: a wrong maneuver could easily have been committed.
"We have just bought a new TTI CPX200D power supply for our lab, and it arrived today. We needed a power supply with remote sense capability to better power an RF board. The supply arrived this morning"
2) the settings were made without load. This make possible the internal 3.140µF to be charged at higher voltage than 1.8V.
"The RF board gets its power from a connector,"
3) The fact that the tantalum capacitor has started to burn proves that a voltage well above 1.8V has been applied to the input of the RF module and that, with enough energy to burn the capacitor .... This is not ESD or leakage current.
"Just when the power connector was starting to mate with its socket in the RF board, a tantalium capacitor connected across the power rail just at the RF board power connector blew up and started burning, and the board is now ruined. "
4) The output voltage of the power supply has not been checked with a multimeter before connecting the RF module. They relied only on the fact that the power was with its output "disabled"
"so we set the current limit to 50mA) and proceeded to connect the power connector to the RF board, all of this with the supply output DISABLED."
Now we need to see if it's possible to somehow trigger the transient with the supply channel disabled.
About 4: yes, it was checked before, a multimeter was always present. We disabled the ouput channel before mating the power connector precisely to avoid hot-plug and the issues it carries. Unfortunately our multimeter can't log and it wasn't set to max hold or anything, so we don't know what peak voltage was applied to the board.
Both my colleague and I are 100% sure that it was off.
Human memory is very unreliable, especially in accurately remembering a shocking/unexpected moments. You may verify something 3x and then accidentally press enable button while connecting wires.
The big mistake in this accident is the choice of the brand and the model of the power supply ....
Watching - I like detective stories
Both my colleague and I are 100% sure that it was off.Human memory is very unreliable, especially in accurately remembering a shocking/unexpected moments. You may verify something 3x and then accidentally press enable button while connecting wires.
Watching - I like detective storiesEnjoy it! But it seems more like a boring comedy...
Maybe the culprit is the material of the power supply feet! Are they of plastic or rubber? We have to analyze this!
From the initial description, it seems that was a user fault. They had to test a sensitive device, so they used a power supply with remote sense. But, instead of having fixed connections for this, they decided to connect it "on fly"! The consequences are known...
The sequence of events was as follows:
-Take power connector from the table, proceed to plug in
-Before connector is mated, BOOM.jpg
-I instinctively disconnect the wire and back off, my colleague backs off too.
-I go check the supply to turn it off, realize it is already off
-Without touching anything, we take picutres of everything
-Pictures show that the channel enable LED was off, and current meter shows set current (50mA) instead of 0, which is what it would show if the channel was ON
That's why I say we're pretty sure it was off. In any case, this was destined to happen. One time we would actually forget to turn the supply off or something like that and it would have blown off anyway.
You could easily forget that you first disabled PSU before disconnecting the wire as a first measure. It's really hard to remember accurately when something like this happens. The only way to be sure would be only if you were taking video during the incident.
If something blows up just as you're plugging it in, your attention isn't going to wander back to the power supply button.
If something blows up just as you're plugging it in, your attention isn't going to wander back to the power supply button.When you plug the wire and 10k board starts burning, the first thing you do is start panicking and loose attention to what you do.
I think we already established that this is a pretty crappy supply.
For one, it can only regulate up, not down. If it is disable it will still rely on the internal bleed resistors to lower the output voltage.
WRT the PWM being disabled by the MCU: Even if the MCU could do this, we don't know if it's actually implemented that way.
Maybe they really just set the VSET voltage to zero and hope for the best.
If you look at the voltage amp in the schematics, you will notice it's a pure integrator. If the Vsense lines are disconnected from the output lines then there is no limit.
You should measure the resistance between The pos output and the pos sense and the neg output and the neg sense to see if the PTCs (why are they using PTCs?) are indeed there.
If there is an open, then your output voltage could be anywhere no matter what it is set to.
You could also test this directly by measuring the output voltage and then introduce a voltage difference on the sense terminal.
As others have said, I would definitely get rid of this supply. It's wrong in so many ways...
I think we already established that this is a pretty crappy supply.
For one, it can only regulate up, not down. If it is disable it will still rely on the internal bleed resistors to lower the output voltage.