Author Topic: Identifying the value / type of a diode  (Read 585 times)

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Offline arobyTopic starter

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Identifying the value / type of a diode
« on: September 27, 2023, 09:14:53 pm »
How can I go about identifying the value of the diode with the CA marking in this photo? There are 4 of them on the board, testing with a meter shows 0.14v across 3 of them and the 4th has failed.  They are tiny - I think an 0802 size. 

Their use is in the circuit with the 1362 LED driver.  I'm not sure if this is a zener or a Schottky diode, the datasheet for the 1362 makes no mention of it, it just shows it on the circuit diagram!
 

Offline Kim Christensen

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Re: Identifying the value / type of a diode
« Reply #1 on: September 27, 2023, 09:54:47 pm »
The symbol on the datasheet diagram is for a Schottky diode. Maybe it's a PMEG6010CEH or similar.

From page 20 of the datasheet:
Quote
Diode Selection
For maximum efficiency and performance, the rectifier (D1) should be a fast low capacitance Schottky diode* with low reverse leakage at the
maximum operating voltage and temperature.
They also provide better efficiency than silicon diodes, due to a combination of lower forward voltage and reduced recovery time.
It is important to select parts with a peak current rating above the peak coil current and a continuous current rating higher than the maximum
output load current. It is very important to consider the reverse leakage of the diode when operating above +85°C. Excess leakage will increase
the power dissipation in the device and if close to the load may create a thermal runaway condition.
The higher forward voltage and overshoot due to reverse recovery time in silicon diodes will increase the peak voltage on the LX output. If a
silicon diode is used, care should be taken to ensure that the total voltage appearing on the LX pin including supply ripple, does not exceed the
specified maximum value.
*A suitable Schottky diode would be PDS3100.
« Last Edit: September 27, 2023, 10:04:23 pm by Kim Christensen »
 
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Offline fzabkar

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Re: Identifying the value / type of a diode
« Reply #2 on: September 27, 2023, 10:01:08 pm »
From the same page in the datasheet ...

Quote
*A suitable Schottky diode would be PDS3100.

https://www.diodes.com/assets/Datasheets/ds30487.pdf
« Last Edit: September 27, 2023, 10:03:22 pm by fzabkar »
 
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Offline arobyTopic starter

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Re: Identifying the value / type of a diode
« Reply #3 on: September 28, 2023, 02:28:16 pm »
Thanks all, I completely missed the paragraph in the datasheet!  The suggested diode isn't the one (wrong form factor), but I did find a candidate - Nexperia PMEG2020EJ - that seems to have suitable parameters, is available in the SOD323F form factor and has the CA marking.  Hopefully this gets me back in action!

Thanks again.
 


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