I'm trying to debug the DC512B (with the LTC4100).
I prepared the setup:
At the beginning I also connected the SCL and SDA to the smart battery pin. I checked with the oscilloscope that the 0x12 commands (current and voltage) was available on the bus.
After turned on the power supply, the ACP led switched on and also the CHGEN.
But I can ear very clearly a switching noise coming from the board and I saw the power supply current demanding completely not constant.
In the second stage I unconnected the SDA and SCL and I tried a “dry run” also with a load of about 50 ohm connected, but the behaviour was the same. (I read that the charger can work also without configuration)
I think that there is something of wrong, but I cannot understand what it is.
I attach the screenshot form the oscilloscope, where you can see the voltage on the battery (blue), the yellow and purple are the two pins of the coil.
Thnaks for the support
It could just be a hot-swapping issue with a high-voltage battery. Try replacing the FET and adding a 10k pull-down resistor on the gate.
More info in this blurb:
When a battery is inserted…
Zack, The schematic is in the previous post in this thread dated 9/22/2020. I am away from office now, but you may have found the issue. The bottom FET source sure does not look like it is connected to…
I received the DC512B evaluation board, and the circuit worked properly. I ordered the same mosfets as used on the eval board and when they arrived, I began replacing the ones selected in our design with…
The switching looks normal. Does it seem to be receiving the current that it is requesting?
The charging seems to stop after a short time. Did you stop the charging or does that keep happening repeatedly? Try increasing your input power - more voltage or more current. You may be power-limited at startup.
If you have a current probe, maybe take a look at the battery current.
thanks for the answer.
Today I retried with a new test, following your suggestion and in that conditions:
ACP, CHGEN high.
The behaviour is the same of yesterday. I can hear switching glitches from the coil, I can see periodic absorption on the power supply (which didn't enter in limitation, only 3-5 W of peak achieved) .
I never stopped the charging but it is happening repeatedly.I also tried to reduce the cable length, but nothing is changed.
I have not the current probe. Can you suggest other checks?
Sure, a couple more things to check.
Take a look at the INFET signal. Is it steady ON or is it turning off with this function?
Check on SDA/SCL while this happens, is there communication that stops the charging?
today I tried to make the new test that you suggested, but after switched on the setup, the transistor Q11 burned.
I suppose the same problem of this topic:
When a battery is inserted with no other supply present, the battery will pull up the BAT and CSP pins and will begin to charge the inductor which also pulls up the SW node. The CLP and CLN pins will also be pulled up via the body diode of the top FET. The exact speed and order of this sequence depends on many factors largely influenced by parasitics.During these events, the BGATE pin is not driven by the IC (high or low). After a hot plug event, the IC typically requires about a millisecond or so to take active control of BGATE. Without an active pull-down, SW pull-up energy couples through the bottom FET Miller capacitance, turning on the FET if its threshold is exceeded. If the bottom FET turns on for an extended period of time, it can be destroyed by the simultaneous combination of Vds and Ids.We have been unable to replicate FET failure in the lab, but we have been able to initiate bottom FET conduction via the capacitive coupling discussed above. Note — the likelihood of turning on the bottom FET depends on many factors including FET threshold and battery voltage. Given the ratio of Miller capacitance to gate capacitance, it is unlikely that battery voltages below about 10V can cause this problem. Therefore, 1-cell and 2-cell Li-ion applications are probably safe.
Solution: A simple solution to this issue is to ground the BGATE pin with a resistor. 10k seems to work well and has minimal impact on switcher efficiency.