
91
on: April 19, 2025, 08:45:26 08:45
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Started by Ahmad_k - Last post by Sideshow Bob | ||
This is me just spitballing. But are you sure the inductor is up to snuff current and frequency way. The datasheet mention that saturating the inductor may cause the device going into thermal shutdown mode and the possibility of damaging the inductor. See the datasheet page 7-8
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92
on: April 19, 2025, 07:33:20 07:33
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Started by Ahmad_k - Last post by Ahmad_k | ||
Check waveform voltage on C8. C8 shouldn't be under 100-150nF (C8 is for supply driving circuit in active cycle so it must not be too low). I thougt add to them parallel 1-10nF (I not expect too much from this but try). For inductors you used, what is declared current? (I ask beacuse of possible saturation. Bigger inductance for same size mean lower saturation current...). I suspect on IC, but you check all other (beacuse of very high switshnig freq these ics are sensitive so layout also can cause different problems)... 1A max current coil. So it should be safe. I still suspect the IC as you said because I noticed the switching frequency was 1.75Mhz which is outside the limitation. I will order from trusted reseller and report back in a week or two |
93
on: April 18, 2025, 10:18:51 22:18
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Started by Ahmad_k - Last post by dennis78 | ||
Check waveform voltage on C8. C8 shouldn't be under 100-150nF (C8 is for supply driving circuit in active cycle so it must not be too low). I thougt add to them parallel 1-10nF (I not expect too much from this but try).
For inductors you used, what is declared current? (I ask beacuse of possible saturation. Bigger inductance for same size mean lower saturation current...). I suspect on IC, but you check all other (beacuse of very high switshnig freq these ics are sensitive so layout also can cause different problems)... |
94
on: April 18, 2025, 08:12:19 20:12
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Started by Ahmad_k - Last post by Ahmad_k | ||
For C8 I didn't try any value below 100nF as the datasheet recommended a Cap of 150nF.
For the inductor I tried 22uH, 47uH, 68uH, 220uH. Higher the inductor value, higher falling time. I will check the waveform on C8 tomorrow |
95
on: April 18, 2025, 06:40:41 18:40
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Started by Ahmad_k - Last post by dennis78 | ||
Clone IC's can be problem in most cases (they usualy sell it as LMR14203 but real chip work only for low voltages - many users will use it for 12 to xx converters so no problems
![]() @between SW and GND -> im not sure but...that possible means that conveter work in dcm mode. It can produce problem for bootstrap voltage because C8 can't charge and it produce many other problems for this type of converter (did you try for C8: 10nF + 0.1uF-1uF?). 1. Check with scope voltage on C8. 2. What inductor you use? Did you try with inductor for much bigger current (22-47uH, 1A or etc...)? |
96
on: April 18, 2025, 06:25:29 18:25
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Started by Ahmad_k - Last post by Ahmad_k | ||
I think for fixed voltage output you need to recalculate the swicthing ferquency CAP (CB ) and L1 or use values that used in demonstration board user guide. I did follow the datasheet and the application note, those values in the schematic are just for reference, I did try a lot of different pairs or Cboost and Inductorhttps://www.ti.com/lit/ug/snva502b/snva502b.pdf?ts=1744980548862&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLMR14203 sadman 1) Under what conditions (Vin, Vout, Iout...) is waveform? 2) waveform you show is voltage at U5.6 - GND or U5.5 - U5.6? 3) Is your IC's genuine (many asian clones can be problematic)? @sadman about swicthing ferquency CAP (CB ) - I think CB(8?) isn't swicthing ferquency CAP, it's bootstrap cap for driving internal mosfet? Vin was 10v, Vout 5.1V I=50mA Only. Now I start believing that maybe it could be a clone. I spent all the day trying different values. I will order another batch from different seller. Those chips I have now can be used for input below 13v without any issue. First I thought that my ceramic capacitor was 16v only and I said that's it, but it was 50v Posted on: April 18, 2025, 06:24:19 18:24 - Automerged 2) waveform you show is voltage at U5.6 - GND or U5.5 - U5.6? between SW and GND@sadman about swicthing ferquency CAP (CB ) - I think CB(8?) isn't swicthing ferquency CAP, it's bootstrap cap for driving internal mosfet? |
97
on: April 18, 2025, 02:30:33 14:30
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Started by Ahmad_k - Last post by dennis78 | ||
1) Under what conditions (Vin, Vout, Iout...) is waveform?
2) waveform you show is voltage at U5.6 - GND or U5.5 - U5.6? 3) Is your IC's genuine (many asian clones can be problematic)? @sadman about swicthing ferquency CAP (CB ) - I think CB(8?) isn't swicthing ferquency CAP, it's bootstrap cap for driving internal mosfet? |
98
on: April 18, 2025, 01:55:19 13:55
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Started by Ahmad_k - Last post by sadman | ||
I am developing a tiny device that can handle DC input from 8 to 30V 100mA max, so my choice went to LMR14203 as I see it a lot of devices and it is working great. I replicated the same PCB mentioned in their application note but I have weird result. The falling time of switching signal is high. That's not a problem when my input is below 13V. Increasing it will make my signal near SAW TOOTH format and the chip starts heating even on 50mA load. Does anyone know what factor am I missing ? can be saturated coil or what ? The falling time on a working LMR14203 is so small compared to my result I think for fixed voltage output you need to recalculate the swicthing ferquency CAP (CB ) and L1 or use values that used in demonstration board user guide. https://www.ti.com/lit/ug/snva502b/snva502b.pdf?ts=1744980548862&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FLMR14203 sadman |
99
on: April 18, 2025, 06:51:15 06:51
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Started by Ahmad_k - Last post by Ahmad_k | ||
I am developing a tiny device that can handle DC input from 8 to 30V 100mA max, so my choice went to LMR14203 as I see it a lot of devices and it is working great.
I replicated the same PCB mentioned in their application note but I have weird result. The falling time of switching signal is high. That's not a problem when my input is below 13V. Increasing it will make my signal near SAW TOOTH format and the chip starts heating even on 50mA load. Does anyone know what factor am I missing ? can be saturated coil or what ? The falling time on a working LMR14203 is so small compared to my result |
100
on: April 17, 2025, 08:59:41 08:59
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Started by alexut4 - Last post by alexut4 | ||||||
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