SN74LV8153: Works only with pullup even with Output = H

Hi,

the behavior is even more stranger:

Connecting  a pull up of 1K to one of the Y outputs, most of them work as aspected, even if the pull up is removed and even after power up down.

One exception is Y3. Does not work in either case.

Data format:

Testing is done in Windows 10 with visual basic

To get the start Bits with windows uart  the configuration is :

  \\.\com1  baud=14400 parity=n data=8 stop=2

   The first data bit is used as the second start bit (the +1)

   str1 = chr(2 * (offset + Register + 8 * (Sendbyte Mod 8)) + 1)

    str2 = chr(2 * (offset + Register + 8 * Fix(Sendbyte / 16#)) + 1)

Hi Bernd and welcome to the forums!

Can you provide an oscilloscope shot of the input and output when the problem is occurring?

Also, a schematic would be very helpful for troubleshooting.

You mentioned testing is being done in Windows 10 via programming -- these are analog devices. We will have to look at the input and output voltages to determine what is going wrong.

Hi,

 sorry, was not able to reproduce the error  after temporarily attaching a pull up.

 Same problem with all four SN74LV8153. Replaced two of them.

 Sync signal was shown, but all Yx remainded 0V. May be a problem with OE connected to GND when powered up?

 Y3 is also working. Bit was not set:  Mod 16 in the formular needed.

 Testing: Send  Byte "0" and Byte "255" to have a square Wave at the scope on all Lines.

 Scope Channels:

1: Sync  

2. Data Y (sqare wave)

3: TTL OUT

4. RS232

 

LEDS: 5V 5mA devices

I'm very confused by the information you have provided. Is one of those schematics supposed to be the SN74LV8153? I can't really tell what is going on.

If we are trying to troubleshoot an issue with the SN74LV8153, can you provide which scope trace is which input and output to the SN74LV8153?

I would also like to clearly see what the load is on each pin of the LV8153 -- since all the pins run to busses, I can't tell what's going on there either.

Hi,

the scope channels are marked at the left side:

Yellow 1: Sync  Output  Pin 9 of SN74LV8153;   blue 2. Data Y0  (sqare wave) ;  Red 3: TTL OUT of UART 75155;  Green 4. RS232

Schematic 1: RS232 Transceiver SN75155

Schematic 2: SN74LV8153 :

Schematic 3: One of two MUX ADG 1606 Inputs A0 to A3 

Load is

Y0 to Y3  quad 5 V LED 5mA against ground and Adressline A0 to A4 of MUX ADG1606

Y4 to Y7  Adressline A0 to A4 of  a second MUX ADG1606

Today I had to replace again four of the SN74LV8153. The SN74LV8153 Inputs Ax, Outsel, Reset and OE are directly connected to ground and +5 VCC. Latch up and / or power up problems?

Regards

Bernd

Hi,

replaced each SN74LV7153 twice but would be a great effort to return them. If you suggest measurement at the defectiv devices I can do that.

There is a hint in the datasheet:  "Latch Up Performance Exceeds 250mA Per JESD 17". But now Information about technology and which Pins may be affected by Latch Up under which condition.

Seems that the failors happens when the system ist powerd up and down frequently. One defektiv SN74LV8153 with high power consumptions lets the DC/DC converter restart automaticly very often affecting also the other SN74LV8153.

Is there any information available regarding prevention of LatchUp for the SN74LV8153 ?

Are diodes to VCC a way to get this rid without affectiing the functions?

Data rate: The datasheed says 24Kbps als recommend operation condition. Testing even with 115kbps worked very good. Is there a reason for the 24kbps suggestion?

Regards

Bernd

Hi Bernd,
These devices are used in thousands of systems worldwide and this is the first report I have had of latch up.

We have done testing here at TI and have not been able to replicate a latch-up condition, thus why I have requested to get your units.

In my experience, issues like this are specific to a system... I would check for things like:
* ESD strikes (especially likely on exposed devices or devices that connect off the board)
* intermittent shorts
* ground/supply spikes
* excessive current during operation (especially under transient conditions)
* failing or incorrect passive components
* nearby electromagnetic fields

I fixed electronics for many years prior to my current job -- that list is just a start in the possible causes.