An open collector is a common type of output found on many integrated circuits (IC).Instead of outputting a signal of a specific voltage or current, the output signal is applied to the base of an internal NPN transistor whose collector is externalized (open) on a pin of the IC. The emitter of the ...

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Why does the I2C interface use the open-collector/open-drain?

The open-collector adds inconveniences like requiring an external pull-up resistor and slows down the throughput. Why did the I2C designers choose to use open-collector/open-drain?
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4answers
79 views

Open collector microcontroller output

I am building the following circuit, in order to control the P channel MOSFET as a high side switch for my load. The input of this circuit will be from a microcontroller (maybe an STM32F103), and I ...
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1answer
58 views

How does an open-collector gate work by using resistors?

I understand that that the purpose is to drive multiple signals to a wire bi-directionally. The two logic states are either 0 or flow (high-impedance). However, how do resistors come into play for the ...
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0answers
57 views

Converting a Low Side Driver to a High Side Driver

I've run into an issue with a product integration we are performing in which we are taking a device whose I/O is meant to accept high side digital inputs (+24VDC) but needs to be driven by another ...
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1answer
547 views

What's the difference between a 74LS05 hex inverter and a 74LS04 hex inverter?

It looks like the 74LS05 has "open collector outputs" (not sure what that is) and the 04 does not. Plus, it appears the ...
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43 views

Handling Open/Ground Input

I have an open collector output interfaced board using that how should I control an input of another equipment with below characteristics: 0 Ground 1 Open Thanks.
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192 views

Wired-or open drain with open collector outputs

I have a comparator with open collector output (LM311) and a gate with open drain output (SN74LVC1G06). I want join these two outputs to make a wired-or, with a pull-up resistor tied to +3.3V. In a ...
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2answers
559 views

Is the nRF24L01 IRQ line open-collector?

I need to know whether the nRF24L01(+) has an open-collector IRQ output, or a full push-pull driver. The datasheet doesn't mention this fact. The reason is that I'm working on a circuit involving two ...
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1answer
153 views

Controlling 2 relays with 1 Open-Collector output

I had a board with open/collector output pins, and i need to control 2 relays syncronioulsy (open and close at the same time) with 1 open collector output. So how can make the connectıon from pin to ...
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1answer
78 views

How to control bi-directional logic line bypassing the open-collector stage?

The uBlox Leon G100 GSM modem has a bi-directional RESET_N line (active-low) that controls the reset of the modem but also indicates whether the modem is up or down (modem out MCU in). Because the ...
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3answers
214 views

Is controlling a voltage regulator's EN/SHDN terminal directly by 3.3V microcontroller possible?

Let's take the LT1763. The datasheet says that "The SHDN pin can be driven either by 5V logic or open-collector logic with a pull-up resistor." On the other hand the chart "SHDN Pin Threshold ...
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1answer
241 views

How to replace bulb with LED in a PWM circuit (car)?

I want to replace a light bulb in a Peugeot 308 SW with a LED. The bulb works (lights) normally, but the LED blinks. I thought they are controlling the bulb in alternative current but my digital ...
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4answers
773 views

Why do they usually make comparators open collector?

I never see open collector opamps while I frequently see open collector comparators. What is reason for preferring open collector output in comparators? (Inside of LM193.)
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4answers
856 views

Purpose of pullup resistor in BJT LED driver circuit

One answer to this question suggests the following circuit to drive a LED from an open collector output of a 74LS47: simulate this circuit – Schematic created using CircuitLab What is ...
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2answers
119 views

Arduino + LS7407N to shift logic levels in serial communication

I'm trying to drive a device that uses 12-0V levels for serial communication. I decided to use LS7407N, a buffer with open-collector, so that I can use Arduino's TTL levels to send commands to the ...
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1answer
155 views

How to get the full Vcc output from comparator?

I am working on a circuit using a comparator for a school project, but in testing it is not acting as expected. Specifically, the output is not going all the way to the higher rail voltage attached ...
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2answers
2k views

SPI and pullups. Is it ever used in open collector configuration

Is SPI ever wired as open collector in devices calling for the use of pullup resistors? Everything seems to point to it usually being totem pole but I wonder if there are exceptions. The only pullup ...
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2answers
262 views

Using open collector as regular 5v output

I'm trying to use the following IC: SN74S289BJ so that the output is 5v when HIGH and ~0v when LOW, however I'm having problems due to the open collector nature of it, as I've written data to a ...
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1answer
588 views

Interfacing PS/2 Keyboard to 3.3V inputs

I have had wonderful success with my new Mojo FPGA, so I decided to try something more difficult, interfacing with a PS/2 keyboard, but I cannot get it to work. Of course, I took the proper ...
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2answers
152 views

Question regarding 7402 IC

I want to create a SR latch using 7402 IC. I would like to read the output (i.e. Q value) from the IC using an ADAM-6066 which has the following specs for digital input: Wet contacts: Logic level 0: ...
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2answers
1k views

Simulate tach signal of PWM fan

I have a power supply that uses a PWM fan with 4 wires. Wires: 12V (red), GND (black), PWM Control (brown), TACH Sig (white) The fan speed is controlled by the PWM control wire (brown). Fan speed is ...
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1answer
590 views

Open collectors & 74LVC245

I am trying to interface a PS/2 keyboard to a MSP430 for a toy. The PS/2 keyboard runs off 5V, but the MSP430 microcontroller runs off 3.3V. So I have a 74LVC245 level shifter to convert between the ...
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3answers
919 views

Fast opto-isolation with open collector output without VCC

I have a two wire communication channel, with a data line and a ground line, with the data line being pulled high via a resistor on the receiving end. I am supposed to send information on this line by ...
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1answer
489 views

Do you have to set the TRIS register when using open collector outputs on Microchip microcontrollers?

I'm using a dsPIC33FJ series microcontroller from Microchip. It has dedicated open-collector outputs/registers. I've read the documentation and it is extremely brief. Does setting the ODCx register ...
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2answers
640 views

PIC18F2550 I2C Open Drain?

As far as I have read, the I2C pins are Open Drain or Open collector, but in the PIC18F2550 the datasheet doesnt say anything about those pins, and even says they are a digital output if you select ...
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4answers
987 views

Using an open-collector output from one IC to trigger a level change on the input pin of another IC?

So my problem is simple: I have an IC that provides an output pin to alert you when some condition is met. The output pin is open-collector, high-impedance when active. I want to monitor this output ...
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2answers
3k views

difference between dry contact mode output and open collector output

We have a device which can work with dry contact input and a device which gives open collector output. Will it inter-operate? Is there any difference between dry contact mode output and open ...
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1answer
4k views

Open Drain vs Open Collector

Is there a practical difference between Open Drain and Open Collector outputs, or are the terms used interchangably? If they are indeed different, what are the contexts where each is advantageous? My ...