Logic forum - Recent Threads

RE: SN74AXC4T774EVM: B2 line not functioning as expected in RSV package whicle works fine with PW

Dylan Hubbard — Fri, 23 Apr 2021 16:54:56 GMT

Hi Adarsh,

That would be good, I want to make sure there isn't a fault in the connection between the EVM and breadboard. I looked over the PCB design and didnt identify any issues. I'll wait to hear from you Monday, and if the results remain the same, I'll grab an EVM myself and go run some tests.

SN74AXC4T774EVM: B2 line not functioning as expected in RSV package whicle works fine with PW

Adarsh Chengot Poonthottathil — Fri, 23 Apr 2021 10:51:46 GMT

Part Number: SN74AXC4T774EVM

Hallo,

1. Very recently I started using SN74AXC4T774EVM for SPI lines between a microcontroller (3V) and a sensor(1.8V). I am receiving proper signals as expected from PW package but not from RSV package. I was not able to find any difference in configuration of the two package in the user guide. DIR1, DIR2 and DIR3 are connected to VCCA using pull up (A->B), while DIR4 is grounded (B->A).

My connection is accordingly.

VCCA = 3V

VCCB = 1.8V

A1-> Chip select

A2-> MOSI

A3->CLOCK

A4->MISO

When I am using RSV package, I am only able to receive proper signal from B1,B3 and B4. While the B2 signal line is corrupted with some noise of ground issue, which I am not able to identify. When using PW package with the same configuration, all signal lines looks good.

Here are the screenshots from my scope.

This is the MOSI line from A2.

This is the MOSI line from B2. as you can see the signal is not restored.

What could be the reason for such a behavior? The PW package is working properly.

Thank you for your time.

with regards,

Adarsh

SN74AHC245: Vin(signal) operating voltage

Roy Chou1 — Thu, 22 Apr 2021 01:45:28 GMT

Part Number: SN74AHC245

Hi Team,

In datasheet, I only find the recommended operating voltage(OE/DIR) is 0-5.5?

May I know the recommended operating Vin(signal)? 0V-7V? or it's the same as 0-5.5 like OE/DIR?

Roy

RE: SN74AHC245: Vin(signal) operating voltage

Rami Mooti1 — Fri, 23 Apr 2021 16:34:33 GMT

Yes, this is ok

Thanks,
Rami

RE: TXS0108E: Level translator for MII interface

Rami Mooti1 — Fri, 23 Apr 2021 16:24:20 GMT

Abhi,

The TXS0108E could work, yes. I'd still recommend the two parts I listed above. They have the Vcc float Here's more information that may be useful and you can see on page 13 the low output channel-to-channel skew using the SN74AXC8T245 which would be favorable.
Low Voltage Translation For SPI, UART, RGMII, JTAG Interfaces

Thanks,
Rami

TXS0108E: Level translator for MII interface

Abhishek — Thu, 22 Apr 2021 11:21:02 GMT

Part Number: TXS0108E

Hello,

I am using DP83848J for Ethernet application. Microcontroller works at 1.8V and need to use level translator for the MII interface.

Is TXS0108E a good choice for MII interface or any other application specific level translators are available from TI.

Thank you,

Abhi

RE: SN74AHC245: Vin(signal) operating voltage

Roy Chou1 — Fri, 23 Apr 2021 16:12:44 GMT

Hi Rami,

So I think we may suggest our user the recommended operating Vin(signal) range following below spec. Is is ok?

Roy

RE: SN74AHC245: Vin(signal) operating voltage

Rami Mooti1 — Fri, 23 Apr 2021 15:27:12 GMT

Roy,

I agree with you in that the 0-Vcc contradicts the datasheet. The data sheets states : "The inputs can accept voltages to 5.5 V at any valid VCC making it ideal for down translation" and "Inputs are overvoltage tolerant allowing them to go as high as 5.5 V at any valid VCC" so I would say the recommendation looks to be 0 to 5.5V.
0-7V is the abs max though and would not be the recommendation.

Rami

RE: SN74AXC4T774EVM: B2 line not functioning as expected in RSV package whicle works fine with PW

Adarsh Chengot Poonthottathil — Fri, 23 Apr 2021 15:26:41 GMT

Hallo Dylan,

I can test again directly on the EVM and let you know on Monday. I hope you can wait.

Best regards,

Adarsh

RE: SN74AXC4T774EVM: B2 line not functioning as expected in RSV package whicle works fine with PW

Dylan Hubbard — Fri, 23 Apr 2021 15:08:23 GMT

Hey Adarsh,

So you aren't able to test directly on the EVM? The breadboard can introduce a lot of noise.

RE: SN74AHCT244: SN74AHCT244DW vs SN74AHCT244MDWREP

Dylan Hubbard — Fri, 23 Apr 2021 14:59:55 GMT

Hi Aaron,

We will try and dig this documentation up, please allow for a few days since this device is fairly old.

SN74AHCT244: SN74AHCT244DW vs SN74AHCT244MDWREP

Aaron Spaete — Thu, 15 Apr 2021 19:26:55 GMT

Part Number: SN74AHCT244

Team,

Customer was looking for info regarding the mold compound and considering this is only available via MIC, can we at least make the following statement?

They are trying to move from the non-EP to the -EP variant. and are worried about the below.

If asking the requested info is hard to achieve then could you confirm this statement:

Would you please provide us a statement that the Material Contents, Mechanical Properties, Vibrational Properties/Environment and Thermal Properties are the same between SN74AHCT244DW and SN74AHCT244MDWREP?

Regards,

Aaron

RE: SN74AXC4T774EVM: B2 line not functioning as expected in RSV package whicle works fine with PW

Adarsh Chengot Poonthottathil — Fri, 23 Apr 2021 14:57:33 GMT

Hallo Dylan,

Yes. Indeed I have I do not have a direct connection. I use a breadboard so I can insert the probe in it.

Best regards

Adarsh

RE: SN74AXC4T774EVM: B2 line not functioning as expected in RSV package whicle works fine with PW

Dylan Hubbard — Fri, 23 Apr 2021 14:54:26 GMT

Hey Adarsh,

Are you measuring using the header pin or the included SMB connector?

RE: SN74AHC245: Vin(signal) operating voltage

Roy Chou1 — Fri, 23 Apr 2021 14:23:33 GMT

Hi Ladisch,

Okay. I think I may clarify my question. We just need to know the recommended operating voltage on every input signal pin.

I don't think that the range is 0-Vcc because as you said that the AHC input buffers indeed are overvoltage tolerant. So I think that the input pin range is the same as absolute max ratings 0-7V.

If you don't think so, maybe the suggested input signal range is 0-5V. I think it's ok to me, but I couldn't accept that the range is 0-Vcc.

In our application, our signal may over the Vcc so we select the AHC part. If this is not recommended, may you let me know your suggestion?

Thanks.

Regards,

Roy

RE: Student Software license

LeonardEllis — Fri, 23 Apr 2021 13:24:56 GMT

Hello Arley,

Please contact Calculator support: https://education.ti.com/en/customer-support .

Regards,

~Leonard

Student Software license

Arley Celis — Fri, 23 Apr 2021 12:45:55 GMT

I need help about this matter:

In 2015, I bought the product TI-Nspire CX II CAS but I forgot my license number. The problem is that I don't have the packing product and I lost the bill.

I need to have the TI-Nspire CX CAS Student Software for teaching maths to my students using the desktop sharing option on my computer.

Thank you for your attention
Kind regards.
Arley David Celis Vargas

SN74LVC138A: Electrical connection for center pad?

Ronnie Gaensli — Fri, 23 Apr 2021 13:05:29 GMT

Part Number: SN74LVC138A

For the RGY package, the datasheet doesn't clearly specify which electrical net the center / thermal pad shall be connector to. I'd assume GND but is this correct?

RE: SN74LVC138A: Electrical connection for center pad?

Clemens Ladisch — Fri, 23 Apr 2021 13:23:29 GMT

Yes; see [FAQ] Where do I connect the thermal pad of the logic QFN devices?

RE: TXB0304EVM: SPI lines experiencing high noise

Adarsh Chengot Poonthottathil — Fri, 23 Apr 2021 09:50:15 GMT

Hallo,

I received the SN74AXC4T774 EVM board recently and now the signals looks good as expected.

Thank you.

best regards,

Adarsh

TXB0304EVM: SPI lines experiencing high noise

Adarsh Chengot Poonthottathil — Thu, 08 Apr 2021 12:20:09 GMT

Part Number: TXB0304EVM

Hallo,

First up all thank you for your time and consideration. I am using TXB0304EVM to communicate with a sensor (1.8V) and a controller (3V) using SPI. I am able to somehow read and write the registers of the sensor when the ground of TXB0304 kept floated. However, when connected when the ground pin of the TXB0304 is connected to the common ground, the signal lines experiences high noise and hence the read and write commands fail.

here are the scope screenshots when ground pin of TXB0304 is connected to common ground. As you can see below, the signal lines are corrupted with noise.

Here is a screenshot when ground pin is floating. I am able to read and write at low frequency, but as you can see this is not at all a proper way. The signals are not grounded properly.

There are no pullup resistors used in the signal lines. Below you can see the schematics. The SPI signal from TXB0304 (A1, A2, A3 and A4) is connected to spi pins of a microcontroller directly. nrfVDD and MAX(1.8) are the voltage 2.8V and 1.8V respectively. NOTE: We have not yet developed the custom board. So we are using EVM Boards of both microcontroller and logic level shifter. Therefore there are long jumper wires (~10cm or even large seperations) between each connections. And the two power supplies are provided from a separate power sources for the moment.

I have had tested the TBX0304 EVM board and it functions properly with direct DC signals applied. What could be the reason for such a big noise in the signal lines?

The frequency of SPI used is 4M. I tested with 125KHz, but even then the noise exists.

Please inform me if anymore details are required. Please also suggest a method to debug this issue.

Thank you for your time.

Kind regards,

Adarsh

RE: TXS0108E: Level translator for MII interface

Abhishek — Fri, 23 Apr 2021 08:33:48 GMT

Hello Rami Mooti1,

In my case Max data rate is 10Mbps. So TXS0108E would be fine.

Thank you,

Abhishek

RE: SN74AHC245: Vin(signal) operating voltage

Clemens Ladisch — Fri, 23 Apr 2021 08:28:59 GMT

AHC input buffers indeed are overvoltage tolerant.

However, in this device, every I/O pin is connected to both an input buffer and an output buffer, and the output buffer is not overvoltage tolerant.

If you need to be able to use higher input voltages, you must use a unidirectional buffer like the SN74AHC541.

RE: SN74LV14A: what is the input transition rate of SN74LV14A?

Clemens Ladisch — Fri, 23 Apr 2021 08:23:36 GMT

Devices with Schmitt-trigger inputs have no limit on the allowed input transition rate. Allowing slow edges is the only purpose of Schmitt-trigger inputs.

SN74LV14A: what is the input transition rate of SN74LV14A?

Hung Ching Hsu — Fri, 23 Apr 2021 07:55:30 GMT

Part Number: SN74LV14A

Hi Team

My customer wants to know the input transition rate of SN74LV14A. It is not shown in datasheet.

I found following material showing LV family have 100ns/V(max) input transition rate.

https://www.ti.com/lit/wp/slla364a/slla364a.pdf#page=2

Is this still true for SN74LV14A? I am asking because it has schmitt trigger, customer wonders if there's any difference for input transition rate with and without schmitt trigger.

For example, SN74LV540A, which have no schmitt trigger, shows 100ns/V input transition rate at Vcc=3V to 3.6V condition.

Thanks.

Regards,