SN74LVC138A-EP

wanjeri kirubi

Other Parts Discussed in Thread: SN74HC138-Q1, SN74LVC138A-EP

We are considering switching from the SN74LVC138A-EP to the SN74HC138-Q1 due to some excessive overshoot associated with the 24mA output drivers on the LVC device. One major difference between the two parts is the propagation delay for different voltages. I see that for the HC device, the difference between the 6V VCC and the 4.5V Vcc isn’t nearly as much as the 4.5 to the 2V difference. We intend to operate the device at 3.3V. Is that an acceptable Vcc and if so how can we determine the min/nom/max tpd for the device? Are there any other 4-8mA decoders that have similar tpd times as the LVC138A product?

over 13 years ago

0 Chris Cockrill over 13 years ago

TI__Mastermind 46480 points

The correct part would be the SN74LV138 which would be specd at 3V, however it is not offered in the EP or Q1 option. Let me know what type device you need EP or Q1 and I can send this to th proper people HiRel or Automotive. Include your Email. We do not have the 3V data for the HC138.

0 wanjeri kirubi over 13 years ago in reply to Chris Cockrill

Prodigy 160 points

Thanks for the recommendation. I would still like an answer the question about the performance of the HC part with 3.3V Vcc.

0 Nate over 13 years ago in reply to wanjeri kirubi

TI__Genius 11680 points

Chris,

Can you explain? I see the SN74LVC138A-EP here - http://focus.ti.com/docs/prod/folders/print/sn74lvc138a-ep.html

- Nate Johnson, Centralized AFA

0 Chris Cockrill over 13 years ago in reply to Nate

TI__Mastermind 46480 points

The LV part is what you need,. not LVC. We dont offer this one in EP or Q1 right now so If you would like to see if the business is good enough then I will need to forward you to either the Hirel group or the automotive group. I only do standard temp and packaging parts

This part has slower edges and will help clean you system. http://focus.ti.com/lit/ds/symlink/sn74lv138a.pdf

The LVC is a high drive part with fast edges that can cause ringing into light loads. The HC will have slower edges but we have no 3V data. The LV part has slow edges and also has some other features making it a very quiet part.

0 Nate over 13 years ago in reply to Chris Cockrill

TI__Genius 11680 points

Understood. Thanks, Chris.

Logic

Logic forum

SN74LVC138A-EP