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Questions tagged [open-drain]

Questions about Open-Drain devices and protocols. Open-Drain connections have two states, Open/Floating, or Drain to ground. Typically require Pullup resistors.

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6
votes
3answers
858 views

How can I float a pin that otherwise should be low?

I want to enable/disable a TI TPS54302 buck regulator with a microcontroller. The enable (EN) pin should float to enable the device, or be tied low to disable it. I currently have the EN pin ...
0
votes
1answer
38 views

Driving 5V mosfet with 5V tolerant pins on 3.3V dsPIC33F

I need to drive a MOSFET (IRFZ44N) with a microcontroller (dsPIC33FJ64MC202). The problem is, the PIC runs at 3.3V and the FET's Vgs(th) lies between 2V and 4V, so there will be times my PIC won't ...
0
votes
1answer
66 views

How to invert an open drain output?

I am trying to use a output signal to reset a counter, but the signal I have is "low when counting" and I need "low during reset". I want to "invert" an open drain output to a new signal so that when ...
0
votes
0answers
105 views

UART in open drain causes mosfet switching voltage spikes [duplicate]

I'm using an ATMEGA3208 and I have configured the UART peripheral to open drain mode. I'm using an external pullup 1KΩ. I'm experiencing switching voltage spikes that goes negative. They are about 0....
3
votes
4answers
186 views

multiple Open Drain UART over long distance [duplicate]

I have 9 microcontrollers ATMEGA3208 and I have connected the RX and TX lines of 8 of them in parallel. My configuration is in master-slave. The master microcontroller send data to one of the 8 RX ...
0
votes
0answers
89 views

Can I connect two MCUs directly to one micro SD card without additional components?

I am new to this community so I am sorry if I'm asking in a wrong place or something out of topic. I think I have considered everything. :) So, now the basic info: I am working on a project which ...
0
votes
1answer
77 views

Converting Open-Drain to Active-High (low voltage, low power)

In my design, I need an RTC (PCF85263A) to enable a boost converter (TPS61021A) after the RTC alarm triggers an interrupt. The interrupt pin on the RTC (INTA) is open-drain, but the enable pin on the ...
2
votes
2answers
592 views

Open Drain pin not going to GND

I'm using an MCP73833 (link to the datasheet) as the charging chip in one of my projects. We use its STAT1 pin (which is an open drain that goes to GND when a battery is being charged and floats if ...
0
votes
0answers
31 views

digispark + pcf8563 RTC interrupt not working

I have PCF8563 WAVESHARE board connected to DIGISPARK via I2C. Here is the code: ...
1
vote
1answer
53 views

Pullup resistor operation between the ESP32 and a Bus MCU

I have an ESP32 as my main controller and a Bus. The bus operates where Pins 55 & 56 needs to be HIGH in order for the bus to be OFF. My ESP will drive the bus by enabling it by pulling those ...
0
votes
2answers
69 views

Microcontroller Wired-OR connection

I would like to connect several microcontrollers as shown in the circuit diagram below. The software makes sure that the PA1 pin always has the low or floating state. It's a kind of open drain ...
0
votes
2answers
87 views

Does direct GPIO communication between 2 microcontrollers requires pull up/down

If I want to use GPIO pins of two microcontrolles as a mean of simple communication (e.g. reporting an event by sending 1 or 0), Do I need to enable internal pull up or pull down resistors on any of ...
0
votes
1answer
59 views

Multiple Open Drain Outputs to one MCU-pin

i want to use two DRV8844 (http://www.ti.com/lit/ds/symlink/drv8844.pdf) Motor Drivers. It has an Open-Drain output, that indicates an error, when it is LOW (nFault). What happens, when i connect ...
0
votes
3answers
119 views

Are activated open-collector and open-drain circuits wasting energy?

Consider the following reference circuit for a 6N137 optocoupler. My understanding is that this circuit uses a pull-up resistor on the output node so when the optocoupler led is activated, the ...
1
vote
3answers
153 views

Microcontroller overheating when sensor is plugged in [closed]

I am building a board based around an STM32L051C6 microcontroller, which will measure a hall effect sensor (AH3362Q) and count the time in between the edges the sensor sees. The sensor is powered from ...
0
votes
1answer
133 views

GPIO connected as open-drain to opto-isolator's cathode

When connecting GPIO output pins (RPi, uC, ...) to an opto-isolator, the classical way I know is the following (at least I understand that it can roughly be depicted like that): simulate this circuit ...
0
votes
1answer
51 views

si7021 with 5V MCU [duplicate]

i need to connect Si7021 wich is an 3.3v I2C humidity sensor with Arduino, this sensor has open drain SCL and SDA drivers. is it possible to connect this sensor directly to Arduino 5V?.
4
votes
1answer
167 views

Identify this open collector serial protcol

I'm trying to analyze the serial link between two devices, respectively a motor controller board and a Li-Po battery manager, which battery powers both devices. The application is a battery-powered ...
1
vote
2answers
200 views

Driving a power-good LED with two open drain outputs

So I have two same DC/DC step down converters and I'd like to have a green LED driven with the converters' open drain PGOOD signals. The signal is active-high and the LED should be on, when the power ...
-1
votes
1answer
365 views

STM32F303 Microcontroller open drain GPIO, Can it reach / be pulled up to 5 Volts?

I hope you are all doing well... :). I'm working on a project with pulse width modulation however I need my logical high output to be 5V. However, as my Vdd is 3.3V, the output high level is ...
0
votes
2answers
449 views

connecting Open drain and Push pull outputs to drive the same pin

I am designing a circuit in which has a voltage supervisor (MCP121-33)with active low output nRST connected to RESET input of the microcontroller which is straightforward. Also, there is a another ...
0
votes
3answers
83 views

Problems understanding I2C pullup calculation

I have been trying to read about I2C pullups such that I can select an appropriate pullup resistor for an EEPROM (24LC02B-I/P) which I want to use as serial ROM to drive some 7-segment displays. ...
0
votes
1answer
92 views

MOSFET Vgs doesn't go to zero when controlling it with open drain output

I have this simple circuit to drive on and off a 12v rail from a microcontroller. R707 = 10KOhm, R708 = 10KOhm, and Q701 is a P channel mosfet (IRLML6402TRPBF) I'm driving this with a ...
0
votes
2answers
140 views

Open Drain while transmitting data with port direction output

I am new to this information portal! However, I have question regarding open drain. I read that, in open drain mode, neither of the devices (slave/master) are allowed to drive the data line HIGH, ...
0
votes
1answer
134 views

Low voltage controlled open drain circuit

I have a power regulator with an output enable that can be used to shut the regulator off without actually unhooking it. I am trying to figure out how to control that using a GPIO port of a Jetson ...
0
votes
3answers
100 views

Is my reasoning about an ATMega328p connected to equipment requiring an open-drain pin correct?

I am part of a research group that is developing a concept for a PCB for an external piece of equipment. This piece of equipment can be controlled with a microcontroller. It communicates to my ...
0
votes
2answers
152 views

Open Drain Output to Microcontroller?

I want to check my Li-ion Charger( Microchip MCP73833 ) status with nRF52832. So i will connect Stat 1,2 and PG to nRF But MCP73833 have an open-drain output If i connect pins to nRF without Pull-...
2
votes
1answer
482 views

TPS56221 Open Drain PGOOD

The datasheet says the PGOOD signal is open drain but I want to use a 3.3V microcontroller to read PGOOD with the internal pulldown resistor, when PGOOD is asserted - will the voltage at the pin be ...
1
vote
1answer
180 views

When an open-drain output asserts low, where does the line capacitance discharge?

I was looking at the auto-retry functionality of the TI part TPS2553 (datasheet http://www.ti.com/lit/ds/symlink/tps2553.pdf) and came across something I didn't understand and thought it a good ...
1
vote
3answers
1k views

Open Drain Serial TX output on Arduino

I have been trying to implement an open drain Serial output using a Arduino Nano. In the following example I have used 2 Arduino Nanos (both operating at 5V Vcc), using one Arduino as the transmitter ...
0
votes
1answer
66 views

Sanity check on an open drain buffer (pull-up to 3.3V but 14V on gate?)

I want to make a simple open-drain buffer using the 2N7000 MOSFET. The input signal on the gate (Vgs) will be 14V and the voltage it is switching is 3.3V (Vds). Usually MOSFETs are used to switch ...
0
votes
2answers
456 views

Open drain on Attiny85

I'm quite new at MCU programming (mechanical engineering background), but managed programming an Attiny85 to source an LED and switching modes (blinking/solid) by using a switch. I would now like to ...
0
votes
2answers
1k views

Understanding PIC32 digital output with open-drain

I'm trying to understand how to operate digital pins configured as open-drain outputs on a pic32. As I've read on other forums, setting TRISx to 0 and ODCx to 1 configures the pin as open-drain output,...
0
votes
2answers
517 views

Open drain in I2C

In I2C, why SCK and SDA should be open drain? What will happen if they are not open drain. I am trying to implement I2C communication using bit banging. Should I enable Open drain circuitry of GPIO ...
5
votes
6answers
2k views

Why do I2C lines use open drain driver instead of tri-state drivers?

My understanding is that I2C lines use pull-up resistors to passively pull up the bus to logic high because the drivers used on the bus are active drivers, namely open collector/open-drain. Since open ...
2
votes
3answers
1k views

Open Collector/Drain vs Push pull

Given the situation where an LED is being used for a status indicator or similar, not toggling quickly. Which is the best configuration for the IO pin, push pull or open drain? As I see it either ...
0
votes
1answer
597 views

Open-Drain Through Schmitt Trigger

I am attempting to use a board that performs level shifting from a 5V GPIO pin to a 3.3V RSTn pin on a Decawave DWM1000 Module via a SN74LVC2G17DBVR. The problem is, as discussed in Section 5.6.3 of ...
-1
votes
1answer
812 views

3.3V to 5V PWM level shifting - ARM microcontroller

I am working with an STM32F0 running at 3.3 V. I'm trying to drive a motor controller with PWM from the microcontroller. The motor controller requires an analog input of between 0 - 5 V to control the ...
0
votes
1answer
134 views

Open drain Port Configuration [duplicate]

I was just learning about the port configurations of the GPIO pins. I came across the open drain configuration, and I was bit confused. I could not understand this properly. When this should be ...
0
votes
0answers
289 views

Use IC output sink to switch a MOSFET

I am using the BQ24075 battery charger IC (datasheet here). If I am reading the datasheet correctly, on page 6 it says that the absolute maximum sink current for the CHG output pin is 15mA. I require ...
0
votes
3answers
210 views

LTC3106 solar harvester example - open drain on power good pin

The part of the circuit of interest is highlighted on the image. The block with the antenna is just some device being powered, not important for the question except for providing the generic ...
0
votes
2answers
706 views

Optoisolator With LED in series not working

I'm using an FODM8061 Optoisoltor with and open collector Logic Output. I'm referencOptoisolator Logic Output Question Here's my current circuit: LED 1(on the left) connects to an open-collector ...
0
votes
1answer
78 views

Can a 74LVC1G07 handle 12V?

The 74LVC1G07 is open-drain, but I don't find anything in the datasheet that tells whether or not it can handle 12v on the output ("Y") pin.
3
votes
1answer
2k views

Confused between push-pull and open-drain

I am planning to use i2c based port expander (earlier I was using atmega328P's GPIO) for inputs and outputs. On a digikey search, I found MCP23008, MCP23009 and MCP23017 as possible replacements. Out ...
0
votes
2answers
646 views

Designing a open drain LED driver

Will this open drain LED driver circuit work ? The open drain IO is governed by the following equation 0.5 <= V_LED_OUT <= 3.6 V (abs_max) V_LED_OUT is the voltage from open drain IO pin to ...
0
votes
4answers
1k views

Oops! N-channel Mosfet on sinking output

I have designed a simple circuit to drive LEDs using a MAX6964 I2C LED driver/GPO chip. Unfortunately, I somehow missed missed that the outputs are open-drain current-sinking outputs. This is not ...
0
votes
1answer
131 views

Texas Instruments TPS57160 Enable Pin via P-Channel Open Drain Output

So I have a module that supposedly has a P-Channel Open Drain Output (INH on Infineon TLE6251-2G) and I am trying to interface that with the EN (Enable) pin of the Texas Instruments TPS57160-Q1 Step ...
0
votes
1answer
286 views

8 bit addressable latch at 3.3V with open drain output

I need to drive 40 leds from a 5V power source. These leds are controlled from a raspberry and I was thinking to use 5 TPIC6B259 but I need a logic level shifting from 3.3 to 5 V for the input of ...
1
vote
4answers
1k views

Input pins hardware interface uC

I am trying to figure out how to interface a A2235-H GPS module. The datasheet says that one pin(nRST) must be connected to open collector or open drain output of uC while an other one(ON_OFF) must ...
2
votes
2answers
358 views

Open collector with Atmega48

After looking at this, I think I already know the answer, but I just wanted some clarification. Open collector microcontroller output I have a part that is going to drive my mosfet at 15V. I have ...