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Can a Zener diode be used for 5V level shifting?
Upon looking at the data sheet for the max31850, it looks like you want to connect an open-drain 3.3V output (or input) to a 5V input (or output when low). I don’t think this is a good idea to use a zener- the knee is too soft, and the output driver of the max31850 is too wimpy (4mA) to make this work reliably.
How are resistors used to reduce voltage in circuit?
You know from the introductory electronics notes that two resistors in series can form a voltage divider (Figure 1). This is one way to reduce the voltage of a circuit. You need to calculate the ratio of the resistors based on the ratio of the input voltage to the output voltage. Here’s a handy calculator for working those values out.
How does level shifting work with a voltage divider?
Level Shifting With a Voltage Divider. You know from the introductory electronics notes that two resistors in series can form a voltage divider. This is one way to reduce the voltage of a circuit. You need to calculate the ratio of the resistors based on the ratio of the input voltage to the output voltage.
What kind of circuitry is used for level shifting?
This is a typical circuit for 5V-to-3.3V level shifting. If Vin is 5V, then V out will be 3.3V with this circuit. If you’ve got several of I/O pins to shift, then you can use a level shifter IC. These chips contain all the circuitry to shift from one level to another for you automatically.
What is the voltage drop from 5V to 3.3V?
The input of the 3.3V system is pulled up to 3.3V through R1. Then the 5V-system outputs 0V, the diode is forward biased, so the voltage at the 3.3V input will be the forward voltage drop of the diode: about 0.6-0.7V for silicon diodes, or 0.35V for Schottky diodes.
What happens when 5V is fed through a diode?
When a 5V is fed through the resistor to the input, the diode will turn on: the resistor limits the current that flows into the pin, protecting the input. The maximum current into pin is sometimes indicated in the datasheet, and it should be kept low for two reasons: Normally, except the leakage current, no current would flow into a pin.
How to level shift 5V to 3.3V?
Using 2 resistors and an input voltage, we can create an output voltage that is a fraction of the input. Below you can see the formula that you need to use to calculate the resistors that you need in your circuit: Solving the formula above with Vin=5V, R1=1000ohms and Vout=3.3V. We get R2~=2000ohms.