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Dears, we are having troubles with the DC/DC step-down regulator. By time to time it stops to regulate correctly the output voltage and it looks like that is going in protection mode for overcurrent.
Here is the schematic:
When it is not properly working the output voltage (+15V) is 3.4 V the voltage on pin 6-IC84 is around 0.3 V and the pin 7-IC84 is almost 0.
I have try to reduced the R271 to 5.6kohm but this is not working.
Some times by replacing the component IC84 with a new one it start to work again, but not always.
Do you see any reason why the LM22679 can be damage by the following use?
Regards
Denis
1) When IC84 was not working and providing only 3.2 V at the output (+15V) and the IC85 was working providing -15V at the output, the Voltage on Pin 1-IC84 and current through the inductor was:
C1: L12 current (100 mV = 180 mA) C2: D52 voltage
2 ) I disconnect the IC85 (so the IC84 was only partially loaded by other components) and test as point 1:
C1: L12 current (100 mV = 180 mA) C2: D52 voltage
3) I replace the IC84 with a new one and now the output is coreclty regulated at 15 V
C1: L12 current (100 mV = 180 mA) C2: D52 voltage
4) I reconnect the IC85 and now all the outputs +/- 15V are working correctly
In my opinion the IC84 was damage and it was not operating well. But this problems rise quite often, and I cannot understand the reason.
Last time that I broke the IC84 I was just measuring the voltage with the oscilloscope probe connected to pin 6-IC84
1) When IC84 was not working and providing only 3.2 V at the output (+15V) and the IC85 was working providing -15V at the output, the Voltage on Pin 1-IC84 and current through the inductor was:
C1: L12 current (100 mV = 180 mA) C2: D52 voltage
2 ) I disconnect the IC85 (so the IC84 was only partially loaded by other components) and test as point 1:
C1: L12 current (100 mV = 180 mA) C2: D52 voltage
3) I replace the IC84 with a new one and now the output is coreclty regulated at 15 V
C1: L12 current (100 mV = 180 mA) C2: D52 voltage
4) I reconnect the IC85 and now all the outputs +/- 15V are working correctly
In my opinion the IC84 was damage and it was not operating well. But this problems rise quite often, and I cannot understand the reason.
Last time that I broke the IC84 I was just measuring the voltage with the oscilloscope probe connected to pin 6-IC84