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Low cost logic analyzer probe for Rigol MSO5000 EasyEDA project

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S. Petrukhin:
Friends, I found that the output voltage of 4.5V to power the circuit supplied from the oscilloscope was weak and dropped to 4V at load. It seems that the LVDS driver consumes a little, but there are 16 of them and the total current consumption was about 86mA. It turned out that the drivers due to the voltage drop on the LDO does not receive 3.3V, only 3.0V. But the scheme works steadily. 3V is the permissible supply voltage of the LVDS driver.

Gandalf_Sr:
The voltage regulator you used, the LM1117 has a dropout voltage (Vin - Vout) of about 1100 mV at 100 mA supply which would explain your not being able to get to 3.3V out.

I used a MC33375ST-3.3T3G which has a WAY lower dropout voltage, around 115 mV at 100 mA and never more than 500 mV, worst case at full load.

I chose my LDOs because they needed to have very low dropout voltages - sorry I missed that aspect when looking over your design.

S. Petrukhin:

--- Quote from: Gandalf_Sr on August 31, 2020, 03:20:00 pm ---The voltage regulator you used, the LM1117 has a dropout voltage (Vin - Vout) of about 1100 mV at 100 mA supply which would explain your not being able to get to 3.3V out.

I used a MC33375ST-3.3T3G which has a WAY lower dropout voltage, around 115 mV at 100 mA and never more than 500 mV, worst case at full load.

I chose my LDOs because they needed to have very low dropout voltages - sorry I missed that aspect when looking over your design.

--- End quote ---

Thank you, sir!
I changed the design to use MC33375ST-3.3T3G in the new version 2.1 now.

Gandalf_Sr:
You're welcome.

S. Petrukhin:

--- Quote from: Gandalf_Sr on September 01, 2020, 12:27:34 am ---You're welcome.

--- End quote ---

I started making an amplifier for built-in generators. The amplitude of 2.5V is very small, I think to make the gain by 2 or 10.
I sometimes need to emulate the sensor signal in industrial 24V equipment.

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