We’re rewarding the question askers & reputations are being recalculated! Read more.

Questions tagged [logic-level]

Logic level refers to the output voltage levels of digital logic, which is often 3.3 V or 5 V.

Filter by
Sorted by
Tagged with
35
votes
1answer
121k views

Step up 3.3V to 5V for digital I/O

I normally use an Arduino for my projects because it has 5V inputs and outputs and has 5V Vin so that makes life very easy when interfacing with 5V components. For this project I want to use a ...
34
votes
5answers
7k views

How did people realize they could do logic with electronics? [closed]

How did people realize they could do logic with electronics? Are there anecdotes or records of the first realizations? I'm wondering about the first "eureka" moments.
27
votes
9answers
52k views

Is there any bidirectional 5v-3.3v level shifter?

Is there any IC that interfaces any 3.3V Input/Output to 5V Output/Input? I need it primarily for an Arduino Due but if there any bidirectional IC that works like that it would be great. Some people ...
20
votes
2answers
51k views

Single transistor level up shifter

I need a simple, single directionnal level shifter for 3.3V -> 5V conversion. There are many options on the internet, some using a logic ic and some using 2 NPN transistors (converter and inverter), ...
9
votes
1answer
683 views

What's the purpose of this diode in this level-shifter?

look at this circuit: I don't get that what's the usage/purpose of the BAS316 in this circuit?
8
votes
2answers
13k views

7400 series CMOS vs 4000 series logic IC

I understand the traditional difference between the 7400 series and the 4000 series logic ICs, but since there are CMOS versions of the 7400 series, is there an advantage to use the 7400 CMOS version ...
8
votes
2answers
575 views

Translating to “below ground” logic levels

I have an RF switch chip that is controlled by a logic signal with levels of 0 V and -3 V. I want to control this from a CPLD that's producing ordinary +3.3 V CMOS levels. Board area is at a premium ...
8
votes
4answers
3k views

Should I use CMOS vs. TTL?

Now, I know that this question has been asked so many times that it seems like I'm trolling, but I must point out that I couldn't find the right answer to this question anywhere. So yeah, CMOS and ...
7
votes
1answer
10k views

How to convert a digital signal from 24V to 5V

I have an industrial automaton that gives me a digital signal (24V or 0V) on its outputs and I want this signal to control an integrated circuit, but the integrated circuit only takes a TTL signal in ...
7
votes
2answers
2k views

Fast bidirectional 3.3 to 5V level shifter

For a hobby project of mine, I'm thinking about connecting some old 5V SRAM chips like this one to a 3.3V - capable FPGA. The target frequency is 50MHz. After some simulator experiments I found out ...
6
votes
4answers
2k views

Does a BJT controlled relay need protection diodes?

I am fairly new to electronics, so please pardon my mistakes. I am attempting to build a Wi-Fi controlled relay. The problem, however, is that the relay runs on 5 V, but my ESP-12E can only ...
5
votes
3answers
2k views

How do I invert a signal without deforming it, and without using a logic gate?

I have an IC which outputs pulses over an open collector pin. I need both these pulses and their inverses in my circuit. I want to do the inversion by using as few as possible transistors and without ...
5
votes
1answer
171 views

Need 1-4 pins controlling 16pins logic level

I have max four outputs coming from a PIC. I need these four outputs (or one serially) to simultaneously control 16 pins with a logic level. This is for a clock application. A BCD could accomplish ...
5
votes
2answers
4k views

Logic Levels between 5(V) and 3.3(V) devices

I am using a 5V microcontroller to communicate with a Bluetooth module operating at 3.3V. I have regulated the output from the 5V microcontroller rail to 3.3V rail for the Bluetooth module. Since I ...
5
votes
3answers
819 views

Ignore Pulses Less than a Given Width in a Pulse Train

Let's say I have a 5V pulse train that varies between 0 and 75000 pulses per second. Pulse width, let's say, is 5 microseconds. How could I calculate or determine the best way to filter out all pulses ...
5
votes
2answers
2k views

Methods to drive a multiplexed LCD with logic-level signals?

I've used such a technique in a couple of the products I've designed, but I've never seen anyone else do so. It's possible to drive a 3-way multiplexed LCD using a bunch of 74HC595's to generate an 8-...
4
votes
2answers
1k views

How can a Switching diode act as a level shifter?

I am following a schematic about a one-way logic 3.3->2.8 level shifting circuit. The hardware in question is a MCU output that drives 3.3V and the input of the UART interface of a SIM800 GSM Module....
4
votes
4answers
3k 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 ...
4
votes
1answer
9k views

Help understanding 3.3v logic vs 5v logic with Raspberry Pi GPIO

This will probably be an extremely easy question for the seasoned EE's of you in the community. My question is this, I have 5v and 3.3v devices I want to interface with my Raspberry Pi's. I'm paranoid ...
4
votes
2answers
1k views

What is the usage of this resistor?

I'm thinking about this part of this board : As you can see, there is a resistor in the red rectangle (R26). my question is what is the usage of this resistor? Well being a resistor for D14(CANRX) ...
4
votes
1answer
3k views

What is the difference between a voltage-level translator and a logic-level translator?

(This is a follow-up to an earlier question of mine.) I would like to use the GTL2000 bi-directional translator IC to facilitate level translation between a 3.3V circuit and a 5V circuit (including ...
4
votes
1answer
136 views

Do high and low side labels on bidirectional logic level converters matter?

Logic level converters like this one from Sparkfun have high side and low side labels on them. Now i have an application where I think I need to shift logic levels but the high side and the low side ...
4
votes
2answers
144 views

How can a dominant state be the one with bigger voltage difference?

I am studying about CAN buses, and there is one thing I just can't find an explanation for. I understand that the idea of a wired-and connection is, that if any node is driving the bus to the dominant ...
4
votes
1answer
369 views

Is the logic level of a MCU the same as the operating voltage?

The Atmega328 has an operating voltage of 1.8V to 5.5V. If I was operating it at 3V (by supplying 3V to VCC) and set a pin to high, would that pin be at 3V?
4
votes
2answers
904 views

Interfacing 3V TI MSP430 to PC serial port

I am scratching my head to figure out a possible soloution for this scenario: I am developing a simple application using TI MSP430 microcontroller. The microcontrol part is powered by 2xAA batteries. ...
4
votes
1answer
662 views

Power Path Controlling with GPIO and MOSFET

I'm not particularly well acquainted with MOSFET logic design and need some verification on a few things to make sure I've got them correct, and to see if there's any better ways of doing it. I need ...
4
votes
1answer
1k views

TTL logical low isn't ground

I'm working with an Arduino Due and four 5V TTL pressure sensors. I'm using this logic level converter to convert from the 3.3V Due to the 5V sensors. I've been having problems using all four at a ...
3
votes
3answers
497 views

What design decisions must I make to select a suitable P-Channel MOSFET

I need a PFET with a logic level gate to trigger a power connection to a hobby servo that pulls more current than my MCU pin can handle. The requirement is simple but I'm trying to understand how to ...
3
votes
3answers
3k views

Replace BSS138 with AO3400A in level shifter circuit

I have to use level shifter circuit to interface MAX31855 with Arduino running on 5V. I found easy to build level shifter circuit at SparkFun website. It is using BSS138 (datasheet) which I don't ...
3
votes
3answers
2k views

how to increase the voltage of a digital signal?

I'd like my Raspberry Pi GPIO port to communicate with a digital circuit that works at 2x the GPIO voltage. The communication will be at a relatively high frequency (up to 500kHz). The main question ...
3
votes
3answers
865 views

Interfacing open-collector optoisolator to 3.3V microcontroller

I have a bit of a puzzle on my hands trying to interface a Fairchild MID400 optoisolator (popular "logic level" optoisolator for mains detection) to a 3.3V GPIO pin. The MID400 is a 5V part [*] and ...
3
votes
4answers
5k views

High Frequency Logic Level Conversion

I am using Arduino DUE for my project which gives a 3.3 volt output signal. I have to convert it to 5 volts to use it with another device. The problem is that my signal frequency is 1 MHz. I have ...
3
votes
2answers
259 views

Logic family for 3.3 V microcontroller interface

I need to generate a bunch of chip selects for a SPI bus that I want to use on a project. I will use a 36 position (similar to PCIExpress = cheap) card edge connector and etc. The bus is simple : <...
3
votes
3answers
891 views

Switch (Relatively) High Voltage from Logic Level

The Situation: Basically, I would like to switch a load that requires 30v using a switch that cannot have more than 5v across it. More descriptively, I am trying to drive the anode of a VFD segment ...
3
votes
1answer
189 views

making sense of HCT ACT cmos “addional supply current”

I'm trying to make a low-current level shifter from low voltage (~2V) CMOS up to 5V CMOS. I had the idea to use TTL-compatible CMOS gates in the HCT or ACT families. But this line in the 74HCT04 ...
3
votes
3answers
4k views

Low power serial bluetooth module with Arduino

I plan to use the HC-06 serial bluetooth module with an Arduino Leonardo. To my knowledge, the Arduino's serial pins output at 5V with 40mA of current. The HC-06's datasheet says it will accept input ...
3
votes
1answer
365 views

MCU HIB pin only pulls Buck/Boost EN pin every-other Hibernation

MCU: TM4C1294NCPDT Buck/Boost Converter: TPS63051 Hib dedicated LDO: MIC5504-3.3YM5-TR I have a LiPo battery coming into the board, feeding both the TPS63051 and the MIC5504. Tiva's HIB pin is ...
2
votes
3answers
1k views

Why are so many pins of 8086 active-low?

Why are so many pins of 8086 active-low? Does it have to do something with the fact that more circuits are able to sink current than to source current, or is there another reason for it?
2
votes
2answers
419 views

Logic-level converter FET

I have been using the BSS138 level converter circuit for a while now and today it struck me I get how the voltage is stepped up by the FET or the BSS138 when you are applying say 3.3 V on the LV side. ...
2
votes
2answers
169 views

NPN: Not fully sinking to GND

I'm using an NPN to pull a 12v (5mA) signal low from an MCU (logic level). My problem is that when I pull the 12v line low, 7.4v are still present at the 12v side of the line using the circuit below: ...
2
votes
1answer
657 views

How to turn a DIP switch into an array of logical values

Is there a better way to turn a open/closed switch into a logical value (capable or sinking or sourcing current) other than: simulate this circuit – Schematic created using CircuitLab I'm ...
2
votes
1answer
2k views

Is PIC running at 3.3v, 5V logic tolerant?

Can a micro-controller that is capable of running at voltages ranging from 2.3 to 5.5 V, tolerate 5V logic levels while operating at 3.3V? I need to interface GPS (5V) and raspberry Pi (3.3V) with my ...
2
votes
2answers
462 views

Where is the ground/earth used in the Sparkfun Logic Level Converter

I am studying the Sparkfun Logic Level converter and the basic aim of this is to understand how these BSS138 transistors are used in logic level conversion. I have used transistors before in driving ...
2
votes
1answer
2k views

Detect logic signal in a long distance. What type of interface to use?

My daughter board uses a comparator(LM339) to output logic 1 or 0 under a 3v3 supply. The cable connecting daughter board and main board is at least 1.5m. Luckily, the frequency is not fast but the ...
2
votes
2answers
3k views

Control relay from sensor output when LOW is 0.2V

I used this circuit as a reference to drive a relay from the digital output of an arduino. This circuit worked as expected. simulate this circuit – Schematic created using CircuitLab ...
2
votes
3answers
515 views

Logic level converter for H-bridge and UART for Raspberry Pi

Here is my situation: I'm using a raspberry Pi to control a H-Bridge. The H-Bridge is not tolerant of both it's inputs being high logic value, which causes a short through the transistors, bypassing ...
2
votes
1answer
54 views

What is the purpose of Vih and Vil in the comparator's datasheet?

Looking into the MAX999 datasheet I can not figure out how to utilize information given for the Vih and Vil ...
2
votes
1answer
65 views

Can a Z84C00 CPU directly drive 74HCxxx series logic?

I'm getting confused by the datasheet for the Z84C00 CPU, while trying to work out if I can use it to drive 74HCxxx chips, or if I need TTL-compatible logic (i.e. either 74HCTxxx or 74LSxxx). It's ...
2
votes
1answer
184 views

Large range input single level shifter

I have an application where I will be taking serial signals will need to level shift the signal to 3.3V. The input signal will be from 15 to 5V for a high input and I need them all shifted down to 3....
2
votes
1answer
115 views

Enable connected to unpowered regulator on another board

I have an ARM board which uses a VIO of 1.8V and requires that no i/o line be driven before it is fully powered up. It signals this readiness by asserting its "SYSEN" line. My design has SYSEN from ...