Hello,
I would like to make sure I understood something about my level shifter circuit that I made.
Basically, I have a 0/5VDC digital signal coming out of a TSOP4838 IR sensor which needs to be connected to a 3.3VDC CPLD input. So, when the TSOP is outputing 0VDC, I need 0VDC to my CPLD input. When the TSOP is outputing 5VDC, I need 3.3 VDC to my CPLD input.
Please view what I did in the attachment!
QUESTIONS:
A) In sketch #1, when point A is 0VDC, using a conventional current anolagy, the current from the 3.3 source (point C) will want to go down through R1 and seek groung, but because of the diode, it will be blocked and therefore, point B will see 0 volts DC. Is this assumption correct?
B) In sketch #2, when point A is 5VDC, using a conventional current anolagy, the current from the 5.0 volt source (point A) will want to go up through R1 and seek the lower voltage at point C, but because of the diode and voltage source at point C, the total potential difference across R1 will be 5VDC - (3.3 + 0.7) which will make VR1 equal to 1V. Is this assumption correct?
C) No mater what resistance I put as R1, VR1 will always be 1V... and therefore the only thing that will change is the the current across R1. Is this assumption correct?
D) In the present circuit, when point A = 0 VDC, point B is 0 volts DC. However, when point A = 5VDC, point B be is approximately 3.7 to 3.8 VDC. My question is, what can I do to make point B 3.3VDC when point A is 5VDC without using an off the shelf level shifter?
All feedback appreciated!
PS. I apologize for the smugy sketch... if it needs to, I can redo it much neater.
r
I would like to make sure I understood something about my level shifter circuit that I made.
Basically, I have a 0/5VDC digital signal coming out of a TSOP4838 IR sensor which needs to be connected to a 3.3VDC CPLD input. So, when the TSOP is outputing 0VDC, I need 0VDC to my CPLD input. When the TSOP is outputing 5VDC, I need 3.3 VDC to my CPLD input.
Please view what I did in the attachment!
QUESTIONS:
A) In sketch #1, when point A is 0VDC, using a conventional current anolagy, the current from the 3.3 source (point C) will want to go down through R1 and seek groung, but because of the diode, it will be blocked and therefore, point B will see 0 volts DC. Is this assumption correct?
B) In sketch #2, when point A is 5VDC, using a conventional current anolagy, the current from the 5.0 volt source (point A) will want to go up through R1 and seek the lower voltage at point C, but because of the diode and voltage source at point C, the total potential difference across R1 will be 5VDC - (3.3 + 0.7) which will make VR1 equal to 1V. Is this assumption correct?
C) No mater what resistance I put as R1, VR1 will always be 1V... and therefore the only thing that will change is the the current across R1. Is this assumption correct?
D) In the present circuit, when point A = 0 VDC, point B is 0 volts DC. However, when point A = 5VDC, point B be is approximately 3.7 to 3.8 VDC. My question is, what can I do to make point B 3.3VDC when point A is 5VDC without using an off the shelf level shifter?
All feedback appreciated!
PS. I apologize for the smugy sketch... if it needs to, I can redo it much neater.
r
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