SN74GTL2014: SN74GTL2014

Howard Li

Part Number: SN74GTL2014

hi TI,

I am Quanta EE, about SN74GTL2014PWR we want to know why there is no jitter on A-port when VCC=high, VREF=0, DIR=Low (from B to A)? may I ask how to prevent this problem?

because we can see jitter on another vender's GTL2014 A-port.

thanks.

GTL2014 design

SN74GTL2014PWR
Another vender GTL2014

over 3 years ago

0 Clemens Ladisch over 3 years ago

Guru 285080 points

This device compares the B input voltage against VREF:

When an input and VREF have the same voltage, the output is undefined.

Apparently, the TI device uses hysteresis.

Why are you saying that the absence of jitter is a problem?

0 Howard Li over 3 years ago in reply to Clemens Ladisch

Prodigy 10 points

hi TI,

Just want to know why SN74GTL2014PWR can avoid the A-port oscillation when VCC=high, VREF=0, DIR=Low (from B to A),

you say that TI use hysteresis, may I ask the range of hysteresis? because from the spec it is +-50mV.

Due to we saw Ti’s SN74GTL2014PWR SPEC have a link to describe the Bus-Hold can help to solve floating-input problem.

http://www.ti.com/lit/pdf/SCBA004

Is this cause TI GTL no oscillation when input and VREF have the same voltage?

0 Albert Xu1 over 3 years ago in reply to Howard Li

TI__Mastermind 27055 points

Hi Howard,

Howard Li said:
you say that TI use hysteresis, may I ask the range of hysteresis? because from the spec it is +-50mV.

Our team looked into this a bit more and couldn't find any information regarding a hysteresis period. The spec listed doesn't necessarily give the hysteresis period as this can also mean an adjustment for the input offset voltage.

Howard Li said:
Due to we saw Ti’s SN74GTL2014PWR SPEC have a link to describe the Bus-Hold can help to solve floating-input problem.

The link you sent is a generic application note regarding floating in/outputs. This will cause logic devices to have an undefined state (floating) and leads to uncontrollable behavior on your output. These two FAQs can help you understand this issue more:

[FAQ] How does a slow or floating input affect a CMOS device?
[FAQ] Do I still need pull-up/pull-down resistors with bus-hold circuitry?

This device DOES NOT have an internal bus-hold circuit.