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A pull-down resistor brings a line down to a voltage (typically ground potential) when the line isn't being driven to a specific voltage. It prevents the line from "floating" with an unknown voltage on it.

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Regarding the practice of including a grounding resistor on the input of a MOSFET gate to prevent float conditions from biasing the MOSFET into the active region... Since the RP2040/RP2350 MCUs ...
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I created a schematic for the MAX3485 with the ESP32, but I have a question about the selection of biasing resistor(R39,R40) values. Some people use 4.7k, 10k, and 20k ohm resistors, but I'm unsure ...
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In Xilinx's 7 Series FPGAs Configuration User Guide (UG470), they say M[2:0] determine the configuration mode. Connect each mode pin either directly, or via a ≤1 kΩ resistor, to VCCO_0 or GND. Adding ...
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While I play with STM32 a lot on the software side, I still miss a lot of hardware knowledge so I want to confirm my thinking before making a test PCB. I use STM32L4R5 GPIO to control LM3800 power ...
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I am trying to make a power up sequence for a sensor that requires 3.3V, 5V and 10V. 5V and 10V power should be applied after 3.3V. My PCB is powered by 12V, and I use STM32L4R5, connected to the EN ...
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I drew a schematic of connecting button to GPIO with input mode with built-in pull up / pull down resistor: Is it a true connection? if it's not, can you fix the problem? The thing I want to do is so ...
omid ghasemi's user avatar
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I’ve been reading the book “Complex Digital Hardware Design” by Istvan Nagy. On page 74 he writes PU [resistors are] typically 3 to 10 times larger resistor value than PD. On 3.3V signals a 10k PU ...
SchematicSavy's user avatar
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I am currently trying to design a circuit that makes it possible to either pull up a line to 5V or pull it down to ground depending on the signal of a microcontroller. The resistor needs to be 1K to ...
Theneka's user avatar
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I am making measurements for the characterization of pull-up and pull-down resistances in microcontrollers GPIO interface. I am currently working on a STM32 microcontroller, and in particular the ...
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Both of my 'Cube-like' SN4-N2 Inductive Sensor (NPN NC) LED go slightly 'Dim' when activated. I need the LED to turn Off/On when activated. I've tried 5K6 and 2K7 resistors with little change in LED ...
GrievousAngel's user avatar
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Regarding this power multiplexer IC's the digital inputs D0 and D1, the input impedance of the D0 and D1 is not given. Only Input current at D0 or D1 is given as 1.4uA. So far I ended with the ...
pnatk's user avatar
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Im using a4988 and are constructing a small pcb carrier for multiple a4988. I have a question on how to connect ms1, ms2, ms3. Do I need pulldown resistors after my DIP switch? Is it necessary? When I ...
acroscene's user avatar
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This is my first project: Do you think that all the pull-up and pull-dwn resistors value are good? Do the capacitor are oversized? Any suggestions about the circuit in general? Thank you :) Updates:
PaoloRos's user avatar
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Like many others I'm in software so apologies in advance if the question sounds dumb. I watched some videos, read some articles and also read some answers here, such as: Pull-up resistor clarification ...
codefast's user avatar
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I'm using the VNQ9080 in a design and am undecided about adding pull-downs to the inputs. The inputs are controlled from a SX1509 I2C I/O expander which has the pins on HI-Z by default. I want to make ...
hiot's user avatar
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I have an ESP32-S3 that is driving a LED from a GPIO, however when there is no firmware flashed yet it seems like the GPIO is floating, thus the LED is not completely on or off. When there is no ...
eidetech's user avatar
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I’m using an ESP32-S3 to communicate with a 5V-only LCD module with an i8080 parallel bus interface. To shift the levels, I’m using the SN74LVC8T245 bidirectional level shifter. This means I can both ...
Emil Sahlén's user avatar
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Good morning everyone, I received help from several members of this page regarding my goal of adding a USB-C connector to a tablet that already has a micro USB connector for charging. After ...
condor12's user avatar
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I have an older tablet, and I plan to replace the charging-only micro USB connector (which does not transmit data) with a USB-C connector. However, upon examining the pinout, I noticed that the two ...
condor12's user avatar
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Good morning, everyone. I am exploring the transition of the receptacle from a micro USB connector to a USB Type-C. Initially, my plan included implementing both sink and source capacity. However, ...
condor12's user avatar
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I'm considering upgrading my dad's old tablet, which currently has a micro USB connector. The issue arises from his habit of frequently misplacing the charger, and I'd prefer not to rely on an ...
condor12's user avatar
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I have a low-pulse triggered latching relay board (datasheet for individual relays, link to board). Whenever I plug-in, or un-plug my Arduino Nano's USB cable the relay changes state (sometimes ...
Goulash's user avatar
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I'm currently working on a circuit and I'm not too familiar with inverting Op-amps therefore I am asking for some help. Below is my circuit, it's the latter half of the circuit and just wondering if I ...
jarred coles's user avatar
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I'm designing a circuit containing a button with a pull-up/pull-down logic depending on whether I'm grounding a header. The button triggers a GPIO that will detect if the header is grounded thanks to ...
Bibibou's user avatar
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I have been working on an Arduino project: 4 LEDs connected on a breadboard, with series-parallel circuits, that are being controlled by push button. The desired behavior is to start in OFF mode, and ...
Dio B.'s user avatar
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I'm feeding a BCD diode matrix of switches with Vcc at 3.3 V and running the BCD outputs into GPIOs on the ESP32-C6. The plan is to set each GPIO input to internal pull-down so I can pull it up ...
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I am integrating a KP236N6165 analog absolute pressure sensor from Infineon. They recommend the following circuit : My microprocessor which receives the signal uses 3.3V logic and is not 5V tolerant ...
Tommy95's user avatar
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The TC4420 push-pull MOSFET driver seems to latch its output on if the low input signal isn’t pulled to ground. The signal I am using for the input is purely an on-off signal where the off part of the ...
ElectronicsNoob's user avatar
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Imagine I have the following circuit: A register (74LS377N) has the inputs connected to a bus. In the picture, BUS0 is pulled down with a 10k resistor, so if nobody outputs to it the register will ...
Cincinnatus's user avatar
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I read online that the LM35 has a temperature range of -55°C to 150°C, but when testing I found that it was unable to go below 0°C. This is the code I've written to read from the temperature sensor. I ...
Shane Holmes's user avatar
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Please help me something that I don't understand: Why is there a need for pull-down resistors in the circuit below with push button if the ground has already zero voltage? This is the only thing I ...
Voloo's user avatar
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I've been reading a tutorial on open drain and I'm thoroughly confused. First, the terminology makes little sense. How can a resistor pull up or pull down current when its job is to resist current? ...
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I am using a TPS2546 in a USB charging hub, and I'm basing it on a preexisting design I found online (link to writeup for design). In the schematic for the hub design the ILIM_SEL, EN, CTL1, CTL2, and ...
Cole Morrel's user avatar
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I want to understand this and also to make sure this will work. This is a TP4056 USB-C charging circuit. The circuit is almost the same as the regular one you'll find ordering from China. The only ...
Domenico's user avatar
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The lower totem-pole transistor of a LSTTL IC frequently has an active pull-down from base to emitter (ground). Here is an example from TI's SN74LS93 datasheet. I was curious how this active pull ...
Math Keeps Me Busy's user avatar
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I'm building a 24hr clock out of discrete logic, and I forgot to include pulldown resistors, so I'm going back and adding them. I know to put pulldown resistors on the switch inputs, but do I also ...
Nicholas Bos's user avatar
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Some devices have a smart pull-down resistor. It is active until the user drives the pin, and as soon as a threshold is reached, the pull-down is deactivated. How is this implemented, e.g. if I wanted ...
trevor's user avatar
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I am using the AO3415 to do high-side switching. My aim is to reduce power consumption as this low-power device should run for ages on a single battery. System quiescent current is less than 5 μA. (...
UnknownDagger's user avatar
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I have seen some examples why we need to use pull up/down resistors, but do I need to use it if I use switch with common terminal? If I have the schema like so, do I need to use the pull up/down ...
krystof18's user avatar
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I`m trying to obtain a PWM signal from RA4 a PWM signal when a button is pressed (button connected to RA2) using a PIC12F1572. I'm in trouble with code because run as follow: Start simulation via ...
SkePsis's user avatar
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I'm trying to understand how it is possible to control a PNP and a NPN transistor simultaneously from one controlling pin. My issue is that when the INPUT pin is left floating, the transistors drive ...
AKTanara's user avatar
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I asked a question some time ago in regards to preventing back charging my back-up battery question. I was just using a diode, but a circuit was suggested for more protection. It doesn't lend itself ...
Feynman137's user avatar
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I thought about this question when I read an interesting comment by @Simon Fitch in his answer. In the complementary amplifier stage, in total there are three "pulling" elements - Q2 is a &...
Circuit fantasist's user avatar
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I am using S32K for current measurement purpose. Using pin no 113 as ADC input. I can see in the datasheet that ,we can configure this pin as pull down or pullup. May I know is this possible to set ...
Confused's user avatar
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The battery charger L6924U has two status pins, ST1 and ST2, to tell what is happening inside the charger: charge in progress, charging done, stand-by mode, etc. In the datasheet STM always writes ...
Lyoner's user avatar
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As a continuation of my previous question about what type of part I'd need to control a circuit with a higher voltage, I put together schematics for what I hope would achieve what I am looking for ...
klaasbob's user avatar
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A pulldown resistor seems to always be used for configurations where when the switch is open the normal state is low. For example The reasons always given are to avoid a short between voltage and ...
Daniel's user avatar
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I'm designing a board with a USB-C upstream-facing port (UFP) for power only (no data). I've included a common-mode choke, as well as a ferrite bead filter in pi configuration. Since I'm presenting as ...
TypeIA's user avatar
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I have been reading the datasheet of RV-3028-C7. Everytime it talks about a pin that might be unused in a certain scenario (should be logic low), it instructs to connect the pin to ground through a ...
Mora's user avatar
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Background I have an Fridland AC doorbell that I am about to make "smart". My approach is to connect a device named a shelly uni inside the doorbell that ...
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