Contents
- 1 Why do we need pull-up resistor in i2c?
- 2 Why are internal pull up resistors necessary for inputs?
- 3 Why is pull-up resistor needed for an open collector gate?
- 4 How do you calculate pull-down resistance?
- 5 Is SPI active low?
- 6 Why use a resistor for pull-up?
- 7 What is the purpose of pullup and pulldown resistors?
- 8 What exactly is a ‘pull-down’ resistor?
- 9 What do you need to know about pull up resistors?
- 10 How does the pull up resistor work on a VCC?
- 11 Can a TTL gate be connected to a pull up resistor?
Why do we need pull-up resistor in i2c?
A pull up resistor is used to provide a default state for a signal line or general purpose input/ouput (GPIO) pin. Typically they are of high resistance thousands or tens of thousands of ohms of resistance.
Why are internal pull up resistors necessary for inputs?
Pull-up resistors are used to define the state of an otherwise “floating” input by pulling the voltage at the pin to a set voltage. The most typical example is a switch – let’s say you have some signal, which is connected to your input through a switch. If the switch is open, the state of your input is “floating”.
What is the value of a pull-down resistor?
Here are some rules of thumb when guessing at a good pullup/down resistor value: For most things, 3.3k to 10k ohms works just fine. For power sensitive circuits, use a higher value. 50k or even 100k ohms can work for many applications (but not all).
Why is pull-up resistor needed for an open collector gate?
A pull-up resistor connects unused input pins (AND and NAND gates) to the dc supply voltage, (Vcc) to keep the given input HIGH. Some open-collector gates, such as the 74LS06 are capable of driving larger loads because their outputs can be connected to supplies of up to 30 volts via an external pull-up resistor.
How do you calculate pull-down resistance?
To calculate the pull-down resistor value, it’s slightly different from the pull-up resistor value. Knowing that current is 100uA, we’ll take 0.5v as our pull-down voltage since the input is 0.8v. Thus, applying our R = V/I once again, but this time we don’t have to minus, so our formula remains constant.
What are the standard resistor values?
The most common series are:
- E6 20% tolerance.
- E12 10%
- E24 5% (also available with 1%)
- E48 2%
- E96 1%
- E192 0.5% (also used for resistors with 0.25% and 0.1%).
Is SPI active low?
SPI interfaces can have only one master and can have one or multiple slaves. This is normally an active low signal and is pulled high to disconnect the slave from the SPI bus. When multiple slaves are used, an individual chip select signal for each slave is required from the master.
Why use a resistor for pull-up?
A pull-up resistor is used to establish an additional loop over the critical components while making sure that the voltage is well-defined even when the switch is open. It is used to ensure that a wire is pulled to a high logical level in the absence of an input signal. It is not a special kind of resistor.
Why do you need pull up resistor?
In electronic logic circuits, a pull-up resistor or pull-down resistor is a resistor used to ensure a known state for a signal. It is typically used in combination with components such as switches and transistors , which physically interrupt the connection of subsequent components to ground or to VCC.
What is the purpose of pullup and pulldown resistors?
A pull-up resistor connects unused input pins (AND and NAND gates) to the dc supply voltage, (Vcc) to keep the given input HIGH . A pull-down resistor connects unused input pins (OR and NOR gates) to ground, (0V) to keep the given input LOW .
What exactly is a ‘pull-down’ resistor?
In electronic logic circuits, a pull-up resistor or pull-down resistor is a resistor used to ensure a known state for a signal . It is typically used in combination with components such as switches and transistors, which physically interrupt the connection of subsequent components to ground or to V CC.
What is the difference between a pull up and pull down resistor?
A pull-up resistor connects unused input pins (AND and NAND gates) to the dc supply voltage, (Vcc) to keep the given input HIGH. A pull-down resistor connects unused input pins (OR and NOR gates) to ground, (0V) to keep the given input LOW.
What do you need to know about pull up resistors?
The short and easy answer is that you want a resistor value on the order of 10kΩ for the pull-up. A low resistor value is called a strong pull-up (more current flows), a high resistor value is called a weak pull-up (less current flows). The value of the pull-up resistor needs to be chosen to satisfy two conditions:
How does the pull up resistor work on a VCC?
When the button is pressed, the input pin is pulled low. The value of resistor R1 controls how much current you want to flow from VCC, through the button, and then to ground. When the button is not pressed, the input pin is pulled high. The value of the pull-up resistor controls the voltage on the input pin.
What is the maximum pull up resistor for a logic gate?
By knowing the information above, we can calculate the maximum pull-up resistor value required for a single TTL 74LS series logic gate as: Then using Ohms Law, the maximum pull-up resistance required to drop 3 volts for a single TTL 74LS series logic gate would be 150kΩ.
Can a TTL gate be connected to a pull up resistor?
Two or more open-collector outputs of TTL gates can be directly connected together and tied through a single external pull-up resistor. The result is that the outputs are effectively AND’ed together as the combination behaves as if the gates were connected to an AND gate. This type of configuration is called wired AND logic.