All Questions
65
questions
0
votes
0
answers
46
views
Counting up/shifting right, counting down/shifting left 4164 DRAM addresses using TTL/CMOS
I'm working on a design that uses 4164 (64kb x 1 bit) DRAM with 8 addresses (0-7), and I would like to be able to utilize a TTL/CMOS counter or shift register to make the data output count down/go in ...
1
vote
2
answers
72
views
Designing a particular clock cycle series with glue logic/CMOS/TTL for serial data without a uP
I am looking to design an interface for serial data that runs for 31 cycles (not 32, I know), but with uneven cycles to transmit serial data. Each cycle is 8 clock pulses (at 7MHz). For the first 20 ...
3
votes
1
answer
363
views
Using a function generator as a clock source to drive several ICs (CD4000 CMOS series & 74 TTL)
I am building a circuit that uses a 4 MHz reference carrier. The used ICs are basically XOR 7486 and NOT 7404, CD4013 flip-flop, etc.
I have a function generator which is capable of providing up to 5 ...
1
vote
3
answers
151
views
Converting a 74LS74 and a 74LS193 to CMOS. What inputs need pullups and what needs pulldowns
I have a circuit I traced out off an old, dead PCB that came from the early 90s. It was using TTL chips back then. One thing I noticed is that it has a dual flip-flop. One flip-flop is being used as a ...
- 87
0
votes
2
answers
99
views
Need help identifying circuit diagram symbol
In the datasheet for Hamamatsu s13131-1536 CMOS line sensor(https://www.hamamatsu.com/content/dam/hamamatsu-photonics/sites/documents/99_SALES_LIBRARY/ssd/s13131-1536_kmpd1159e.pdf) there is this ...
2
votes
2
answers
410
views
3V oscillator to 5V µC with an 74HCT inverter (12.8 MHz) - bad idea?
I'd like to use an AVR (ATmega328P-AU to be precise) in combination with a fairly accurate oscillator for timing purposes. I stumbled upon the fact that oscillators which have greater accuracy mostly ...
- 33
0
votes
1
answer
69
views
Is AM29F040B CMOS EEPROM TTL Compatible
I can't really make any sense of the datasheet regarding whether the AM29F040B EEPROM can be used with TTL inputs, so wanted to ask on here.
It is a 5V CMOS IC, but there are mentions in the datasheet ...
- 1,555
2
votes
4
answers
339
views
What is the correct maximum value for resistor R₁?
How do I calculate the maximum value of resistor R1 if the following values are known:
VDD = 5 V
inverter CMOS CD4069UB
IIL = IIH = 0 mA
VOH = 4.95 V
VOL = 0.5 V
IOH = IOL = 0.6 mA
VD = 1 V
maximum ...
- 121
0
votes
0
answers
86
views
J-K flip-flops TTL to CMOS
The following uses 3 TTL 74SLS76N J-K flip-flops, which are active low:
However, I'm trying to figure out what the settings for the PR and CLR inputs would be using CMOS CD4027 J-K flip-flops. For ...
- 57
0
votes
0
answers
149
views
Could I have a whole batch of bad AT26C16 EEPROM chips?
I am in TTL chip heaven (India) where I can get these things for pennies on the dollar, so I bought batches of chips to tinker with. Among them a 16 AT28C16 EEPROMs, looking like new, and then 2 very ...
- 1,541
2
votes
4
answers
235
views
74xxx logic. Cheapest, most space saving way to invert 10 logic outputs
Please see this circuit.
I'm trying to design a circuit that allows you to use a single button to increment a counter from 0 to 9 (then it will loop). Diode logic will convert the 10 logic outputs to ...
- 309
1
vote
1
answer
2k
views
What are the output logic levels of this STM32?
I am struggling getting my head around the input and output logic levels, mostly the output levels of this STM32 (STM32F446xC/E).
This table shows the output logic levels as dependent on if it is a ...
- 161
0
votes
1
answer
164
views
74f269 counter getting very hot
Hi I'm a DIY enthusiast and I got stuck with the circuit that I designed.
The counter is getting very hot from the moment It's powered up.
In my setup the 330Ohm resistors at the outputs are ...
- 21
2
votes
1
answer
344
views
Combining CMOS and TTL with drivers and Leds with relay driver
I need some practical advice on how to combine different component types.
I designed a circuit with at the heart an up/down counter (74f269) The outputs of the counter are connect to via 330 ohm ...
- 21
0
votes
0
answers
98
views
DC>DC Isolated Converter (ADuM5401)
I'm in a bit of a quandary as to if I've approached something the right way or if there's an obvious solution I'm missing.
(Sorry for lack of schematic, still WIP).
Goal:
Self-powered isolated USB >...
- 1
0
votes
1
answer
718
views
CMOS vs TTL power and impedance
I need to compare and contrast a CMOS IC with a TTL IC. I've chosen a quad 2 input NAND gate IC, 7400 for the ttl version and 4011 for the CMOS. I'm having a bit of trouble with 2 of the requirements.
...
- 21
1
vote
0
answers
2k
views
LTspice - how to simulate real TTL gates?
I am trying to make simpler more general questions that might have more generally useful answers.
If you build a mixed analog digital circuit then you need to have models of real TTL or CMOS gates ...
- 1,541
0
votes
1
answer
39
views
Safety considerations (for parts) for a beginner building with expensive parts
I'm building for the first time (for me) a circuit with an expensive part (a $80 DEC J11 CPU) and would like to know some "safety" tips so I don't inadvertently destroy the thing while playing with it....
- 101
5
votes
1
answer
1k
views
pull-ups between logic gates
I'm trying to understand why, on this circuit bit, they used pull-ups resistors between logic ICs of the 74LS and CD4000 families. Specifically I'm talking about resistor array RM1 and R1. All the ICs ...
- 511
0
votes
1
answer
88
views
Are there combo gates XOR followed by AND? (4-bit identity comparator)
Is there no 4 bit identity comparator in TTL or CMOS? It could fit into a DIP-12 package as all it would have is 4 XOR gates for selectable invesion and 1 4-way AND gate.
OUT := (A1 xor B1) and (A2 ...
- 1,541
0
votes
0
answers
2k
views
Deciding between ULN2804 or ULN2803 with 74HC595
I'm making a circuit with Arduino + 74HC595 + (ULN2804 / ULN2803) to drive a few 12 V Motors.
I'm trying to decide whether to use the ULN2804 or ULN2804. On testing, performance of both is fine, ...
- 11
11
votes
2
answers
1k
views
Does this circuit have marginal voltage level problem?
As a research for the problem I described here I found this circuit by Maxim:
This is clock doubler, and must be a really good fit in my case as input frequency is very well defined.
However looking ...
- 7,120
0
votes
1
answer
2k
views
STM32F407 CMOS or TTL or HC
I wonder which logic technology is STM32F407 MCU based on.. CMOS or TTL or HC or LVT etc? Although its mentioned in the datasheet that the GPIO's are CMOS and TTL compliant. I am concerned about this ...
- 907
0
votes
2
answers
4k
views
What is the point of 2 inverters in series? [duplicate]
In the datasheet for the Nexperia HEF4543B, in the logic diagram, there are 2 inverters in series:
What is the point of these inverters in series?
- 662
2
votes
3
answers
631
views
74AS TTL to CMOS pull up resistor and maximum speed (or lowest delay)
I have to pilot a CMOS input 5 V chip device with a 7474 flip-flop with the lowest possible delay to minimize clock jitter. The signal is about 11.3 Mhz.
I have two options:
74HC74 (CMOS compatible) ...
- 461
0
votes
1
answer
384
views
Replacing CMOS SRAM with equivalent TTL SRAM
I want to replace an IS62WV51216BLL-55 (http://www.issi.com/WW/pdf/62WV51216ALL.pdf) with an AS7C4098A-12 (https://au.mouser.com/datasheet/2/12/as7c4098a_v1.2-1288279.pdf), as the latter has much ...
- 137
10
votes
2
answers
2k
views
How to manufacture chip on board?
I am a developer of a cheap product and i have no experience in mass production. Device is fully functional and represents a single sided PCB, a microcontroller, a bunch of diodes and a few passive ...
- 340
0
votes
1
answer
261
views
5V to 3.3V Converter
I have a problem in connecting Raspberry PI to an MCP3202. I am using MCP3202 at 5V and knowing that raspberry pi works on 3.3v. I have found a solution to convert from 3.3V to 5V using 74HCT244.
And ...
1
vote
2
answers
410
views
what logic family does tri state logic fall into?
Here is a good Wikipedia on logic families.
This seemed like a particularly important line.
Of these families, only ECL, TTL, NMOS, CMOS, and BiCMOS are
currently still in widespread use.
I'...
- 335
0
votes
2
answers
124
views
Are D flipflop inputs and clock thresholds the same for a given logic family?
I'm using an SOIC20 74ACT574 octal flipflop in a design.
Vcc is 5 V, and GND is 0 V. The datasheets give V_IH (logic high input, guaranteed minimum) as 2.0 V and V_IL (logic low input, guaranteed ...
- 1,104
1
vote
4
answers
758
views
Shifting a 2.7V digital signal to Arduino logical levels?
I'm pretty much a beginner in electronics and I'm currently working on a personal project, where I have a device, that is putting out a digital signal (square wave) that goes from 0V - 2.7V and I need ...
- 109
2
votes
0
answers
624
views
L298 distorts signal
I connected STM32 F334R8 microcontroller to L298 H-bridge. I made some measurements. The problem is output signal on L298 has quite slow slopes and is not as sharp as input signal. I do not understand ...
- 136
-2
votes
2
answers
545
views
Bidirectional TTL to CMOS
Is there a way to have bidirectional ttl logic levels to cmos logic levels conversion in a unique IC. Because right know im trying to create a z80 computer but using a avr as a peripheral as serial ...
user147140
1
vote
2
answers
161
views
How do voltages at outputs drop as current increases?
As I looked at some 74xxTxx ICs, such as this simple NAND gate, I noticed that the minimum \$V_{OH}\$ decrease as current flowing from the outputs increase.
But, from my understanding of Ohm's law, \$...
0
votes
2
answers
576
views
Pull down resistor value in debouncer circuit
I am from computer background and have made debouncer circuit (SR) using NOR gate IC HD74LS02P as a part of digital electronics project. I have used pull down resistor at all inputs of the gates used. ...
5
votes
5
answers
2k
views
Why do TTL pulse generators generate an asymmetrical square wave (unlike CMOS)?
I've read that the asymmetrical (about 1/3 mark-to-space) output waveform is due to input gate characteristics of a TTL inverter, but I want to know more about which characteristics of the TTL input ...
- 51
-2
votes
1
answer
377
views
convert TTL/CMOS output signals to 0V and 5V [duplicate]
Is there an easy way to convert TTL/CMOS output signals to 0 and 5V?
For example, if an ic outputs 0.1V as "0", I'd like to convert it to 0V and if it outputs something like 3.9V as "1", I'd like to ...
- 3
4
votes
2
answers
3k
views
Which logic families interpret a floating input as a definite value?
From what I remember, from decades ago, 1980's 5v TTL chips would see a floating input as a zero (because they switched on current, rather than voltage). Update: it seems they were interpreted as ...
- 982
0
votes
1
answer
864
views
How can I raise a CMOS 1.8V output to 5V LVTTL input with a MOSFET?
simulate this circuit – Schematic created using CircuitLab
I'm trying to drive a 5V LVTTL UART input on a ATMega32u4 with a 1.8V CMOS ouput on a Telit UL865. I'm using the NTE2987 enhancement ...
- 181
3
votes
2
answers
11k
views
Should I connect unused STM32 pins to ground?
I'm designing some circuit using STM32L152RBT6 microcontroller. I'm using STM32L-DISCOVERY scheme as a reference of good STM32 practices. I've noticed that free pins of programmer's MCU aren't ...
- 133
3
votes
3
answers
1k
views
Introduction dates of different 74xx or 40xx chips?
The 74xx family debuted in 1964 with the 7400 chip, and the 4000 family debuted in 1968, but not all chips with 74xx or 40xx part numbers debuted anywhere near that time. If one wanted to invent a ...
- 47k
2
votes
3
answers
175
views
A threshold version of a CMOS 4050?
I want a buffer that outputs Vcc (of 5 V) when I give it voltage about a threshold, say 1.5 V. And it outputs Vss (ground) below that threshold.
I have a 4050 CMOS thing but I think it does not have ...
- 121
7
votes
1
answer
4k
views
What to do with unused TTL and CMOS outputs?
Just about everything I've read on the Web, including on this site, say that unused TTL and CMOS outputs should be left floating. However, this TI article, Designing with Logic, states:
Unused ...
- 389
0
votes
1
answer
142
views
M48Z02 (16Kbit ZEROPOWER SRAM) is TTL compatible?
I've some problem using together TLL and CMOS integrated. I'm developing a project and only now I discovered that the two standards can create troubles together.
So I decided to use only TTL chips. ...
- 210
0
votes
2
answers
72
views
Bredboard compatible FAST TTL [duplicate]
I have been looking for 16-bit ICs for a project i`m working on. The project is to build a 16-bit computer from scratch, therefor i decided i nedded cgips that could handle high clock-frequensies. ...
- 49
8
votes
3
answers
8k
views
Connecting unused logic gates
Logic gates like AND, OR, NOT etc. often come packed as arrays in ICs.
Sometimes not all gates are used in a project. I would like to know how the remaining unused gates should be connected to ...
- 575
2
votes
1
answer
2k
views
Combining CMOS and TTL logic
I have a bunch of 74LS383 (TTL octal transparent latch with three-state outputs) and MM74C83N (CMOS 4-bit binary full adder) that I would like to connect together. I need to connect the output of the ...
user17592
3
votes
1
answer
251
views
Is there relation between logic chip names and their internal structure
I know that for instance an ATMega328 is a 8 bit MCU with 32k of program space, the same can be said for most other MCUs and some other ICs with a direct relation between the name and internal specs. ...
- 492
2
votes
4
answers
1k
views
Do logic families use different type of transistors?
Do the logic families such as TTL and CMOS represent only different logical structure? Or do they also use different type of transistors? Latest microprocessor chips with millions of components use ...
- 12.2k
1
vote
2
answers
203
views
More advice desired on my Model Railroad Building light controller circuit
Building is built in O Scale (1/48) and has 40 rooms that are lighted independently (masked out from each other with walls) Rooms are lighted with White LEDs. The rooms will light one at a time (but ...
- 15