Other Parts Discussed in Thread: LM46001
Hello!
I read similar questions. And my problems in common with them.
I have some problems with the LM5017 device. I need to get 2 outs. 12V unisolated source and 3.3V isolated. Total output current is less than 10 mA. My input is unstable voltage in range 20-80 V. It can change during work. I use the scheme as recommended in datasheet. I used YA8864-BLD transformer.
Problems:
1. Large noise at IN and OUT points. Even when working from a laboratory power source. But after the transformer the isolated output is OK.
2. Output voltage instability. When the input voltage changes from 20 to 50 V, the output voltage varies from 8 to 12 volts. Although setting the divider to 12 V. Can it keep a stable output voltage at a non-constant input level?
3. Frequent fails. Internal protections do not cope with situations:
a) I connect the device to a charged capacitor (In the process of debugging I have to connect different blocks separately. LM5017 was turned off. But the input capacitor was in the circuit. I connect the device to capacitor - it is damaged. Without load).
b) I connect the output capacitor when the device is turned on or I add one else capacitor 1 uF to the output of the operating device. As a result - it is damaged. I added a capacitor to check, if the noise level would decrease.
c) The device is turned on at idle, connect the load - it is damaged. Can I add load or change load on a running device? (In my case the load was one emitter follower. Very high resistance.)
I previously used LM46001. It worked much more stable. But it has an input limit of up to 60V.
I understand that I am describing not regular modes of operation, but also not dangerous, in my opinion. And the load can be connected in jumps. It is permissible.
In total, about 10 devices failed. What can you recommend? Can you recommend alternative for LM5017?
Best regards.
Valeriy Mikhailichenko
