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If you have true Tri-state logic (H+L+Z) ie in bus transceivers were both pull-up or pull-down could be used to prevent floating inputs, pull-up is the prefered solution because of noise margin in TTL compatible circuitry is larger in H state than in L (that's one of the (...)
can any one help me in selecting a pull up/pull down resistor value
Hi,who can tell me why & when use pull up & pull down resistor?
most of sensors and digital ICs have open collector configuration and hence their output voltage doesnt reach the supply... in those cases a pull up resistor is needed which is nothing but a resistor to the supply... this supplies current to the output from the supply effectively reducing the load offered to the output pin...
hello, pull up or pull down RB0 is not the real problem. answer first to this question : what is the source of the signal you apply on RB0 pin ? a passive component, as,a,relay reed contact ? or the ouput of a active component ie output of a 7406 ttl driver or other.. you have to considere booth decide if (...)
Another question,usually,what's the internal pull-up resistor value can be called weak pull-up?
A typical value of a pull-up resistor is 10kΩ .. If you want more details on pull-ups, read this article: I am not aware of typical values of pull-down resistors. This will depend on logic family and circuit configuration. 1. Avoid (...)
Hi all: I download a data of download cable from Altera, I don't find that the 10-pin need connect to pull up resistance and pull down resistance, but somebody tell me that if CPLD has no pull up resistance and (...)
Plz clarify my doubt which is better pull up or pull down
I am new to VLSI , i had doubt on pull-up and pull-down ......can anyone help me?
pull up by nmos and pull down by pmos works??
A pull-up device when energized will pull the ouput to supply(i.e "1") and a pull-down will pull the output to ground (i.e. "0"). Usually PMOS is used for pull-up since it can provide GOOD "1" (HIGH) i.e (...)
Hi, Experts: I am looking at one IO buffer design from other Sr person, he used all N devices for both pull up and pull down, please refer to the schematic of attachment. Everyone says N pull up will reduce swing from VCC to VCC-vth, can anyone explain why he designed (...)
Check IC datasheet. It has reference application circuit that shows if this pin should be pulled high or low, and the pull resistor values. Usually 10k resistor is used for 5V devices, and 4k7 for 3.3V and 2.5V devices. In this way, you do not need to calculate any value.
Is it possible to use internal pull up or pull down resistors and make them appear (or dissapear) only when a certain logic condition is satisfied ?
pull up and pull down resistors is same as pull up and pull down transistors in CMOS. pMOS as pull up and nMOS as pull down.
Hello everyone, I need your help! Thank you in advance. Does anyone know the approximate value for the pull up PMOS, the pull down NMOS driver, and access NMOS transistor for 40nm or 32nm sram cell? I just need a approximate value for reference. We want to do a hspice simulation for a sram cell (...)
pull-up and pull-down resistor is a common mechanism used in basic electronic circuits. pull-up means connection of a line or chip, with supply voltage though a resistor with a value of few kOhms. This kind of connection results in maintaining high state, when the external (...)
What is drive current for a PAD and how to decide drive current for I/O PAD while doing characterization.Also how to calculate the pull-up and pull-down resistance for I/O pad cells. Thanks
bidirectional pull-up(PDU02DGZ from tsmc) and pull-down(PDD02DGZ from tsmc) cells. Help me how to simulate for pulling resistance. I/O pad cells' output always can be disabled (OEN=1 , INPUT state is irrelevant). Run a DC analysis and measure the output impedance.
I want to know about pull Up and pull down Resistor with Applications The main feature achieved on such output topology is the ability to allow connect several outputs in parallel at same bus yielding no effective load conflict. +++
hi fellas, i'm working with non-series-parallel arrangements, something like this: 108977 as you can see, the euler paths in pull-up and pull-down are differents. for example, in pull-up we have "abcde" and in (...)
No, a weak pull-down is a large resistance (or equivalent, i.e. it might be an active device on a chip), as high a resistance as possible which overrides any leakage currents to guarantee a valid logic 0 voltage. Smaller values would waste power when driven high, higher values would not guarantee a logic 0.
Hello, Test pin pull-down is required niks
I want to add a weak pull-down resistor on 3-state output buffers and bidirectional buffers in Xilinx FPGA, I have tried to code it like this: IOBUF KIO_0 (.O(KIO_I), .IO(KIO), .I(KIO_O), .T(!we)); IOBUF KIO_1 (.O(KIO_I), .IO(KIO), .I(KIO_O), .T(!we)); IOBUF KIO_2 (.O(KIO_I), .IO(KIO), .I(KIO_O), .T(!we)); IOBU
For pull ups, look at the leakage current of the pin. For example, the MCLR pin of a pic micro is typically 5uA. Too high a pull up value will result in a voltage drop which might make the micro reset with a little noise on the line. The highest recommended value in this case is 33K.
No. The pull-up resistor only acts as a "weak" pull-up source. So when slave drives low, the net will be pulled-down to '0'. -------------------------------------------------------------------------------- You can also refer to the open-drain circuit.
pull ups depend values depend on the technology used ,Bipolar or cmos .but also the FAN OUT ..which means how many inputs that signal feeds .The more inputs connected to that signal the lower the resistor the higher the current needed to sustain the logical level
Jebakumar Samuel, If you know the value of the capacitive load on the output, you can calculate the maximum allowable resistance of pullup resistor by solving the equation. Vo = Vin(1-exp(-t/RC)) for R, where Vin is the minimum steady-state "1" output. t is the maximum allowable rise time fro the output to reach Vo. Vo is the minimum acceptabl
it depends on the resistor or active network you use for pull up.... what r u planning on.... active network or passive network....
I'm not sure whether this is an analog or digital question. I know that for an I2C line, you have to pull up SDA and SCL. What other lines do you have to pull up? Someone told me that you have to pull up lines that come from open drains. In general, what are guidelines for (...)
I made a simple program on PIC, in which as long as I press the push button the LED would glow and as I remove my finger from push button it would stop glowing.I choose R0(Pin) for input and B0(Pin) for output. #include<16f877a.h> #use delay(clock=20000000) #fuses NODEBUG void main() { set_tris_b(0x00); while(true) {
In PIC18F4550, only PORTB has internal weak pull-ups, the other ports don't. Hope this helps. Tahmid.
Hey, With FPGAs, specifically the Xilinx Spartan-3E I'm using, I know that you have the ability to set unused pins to have an internal pull up or down resistor. However, would there be pull up/down resistors on a used I/O pin that you have set to Z, or high impedance? I've looked through (...)
1) im using the circuit below and when im connecting pull-up or pull down resistor the system not working ! , i know that PORTB in PIC18F4550 has internal resistors but even when i connect resistors to PORTD system in not working as it should be. "Not working" is in fact a vague information. I understand, (...)
I'm reverse engineering NMOS chips from the early eighties (just for fun and historical reasons, eh). In a NOR gate with many inputs (part of a PLA) I found a pull-up circuit as shown below. What is the reason for T215? A friend guessed that it is working like a bootstrap circuit, to lift and drop the gate voltage of T216 whenever the source vol
Hello. I have a switch which pulls down (to ground) a pin of a PIC18F65K22 Micro to give a logic low. If the switch is open then the pin is pulled up to the 5V rail via a 47K resistor. Do you think I need a 10n (or thereabouts) capacitor connected to the pin to reduce noise at the pin? When (...)
I use pull-down resistors at MCU output lines several time but in my new design i will use TPS25200. According to datasheet it recommends user to use pull-up resistor at enable pin I see no relation between both statements.
Hi, I wonder if @lter@ family has internal pull-up, just like CoolRunner? Best Regards, ltg
:D some ICs require their output pins to be connected with a pull-up resistor. i wonder what this is for. another Q, what does open drains mean? 8O pull up resistors are used for open collector or open drain outputs. Usually, a logic gate output have two switching elements (either bipolar or mos), one which produce "1" l
Nothing will happend. PIC has his internal pull up resistors (they can be switched ON/OFF by software), so in case when pull ups are switched off everything is same as in 8051 case. If they are switched on and you connect additional extern pull you will just boost (...)
For me I think 10k pull up is enough, soemtimes I use 1k.
Hello all, I found there are several values of pull-up resistor, for example 1k, 3.3k, 4.7k. Is the value of resistor proportional to the VCC? Or it related to other parameters, such as current? Regards, DAVY
This discussion assumes 5 V Vcc. TTL output levels must only drive 2.0 volts or greater for a logic high level. In addition, many TTL drivers source less current than they sink, meaning that while they may be rated for 4 mA drive for logic high, they might be rated at 12 mA for a logic low. As the output voltage increases, the drive current dr
pull up resistor shifts output level of circuit toward Vcc ( supply voltage). If NPN transistor's emiter is connected to GND, base to previous stage ( drive circuit), and collector is open, you shoud connect pull resistor between Vcc and collector. In that way when transistor is "open" ( current flows trough collector (...)
hello how can i setup internal pull-up resistors for ports of atmega16? for example how can i setup pull-up resistors for portA? only i must set ddra to 1 or it needs other wthings too? thank you
Hi, This question has been asked a lot of time here. See for example this old post try a seach Replace * by t
Hi I wanted to created a top-level block that contains two 8-bit tristate buffers ,one is connected to the input of a register and the other is connected to the output ...I got this warning : WARNING:Xst:2042 - Unit zreg: 8 internal tristates are replaced by logic (pull-up yes): into1<0>, into1<1>, into1<2>, into1<3>, into1<4>, into1<5>, into1<6
I don't think it is possible to disable the weak pullups on this micro. It is basically an 80C32, where the pullups are always on, to allow the I/O pins to function as both inputs and outputs, simply by clearing the port latch; there is no data direction register. Is it really that important to have the (...)
Is it always better to use a pull up resistor on the CS active low input of an IC? Does it make a difference if the CS input is open drain/collector or not?