SN74AVC4T245 Replacement Recommendations

James Evans

Other Parts Discussed in Thread: SN74AVC4T245, PCA9306, TXB0104-Q1, SN74LVC8T245, SN74AVC8T245

Hi!

Does anyone have recommendations for a 4-bit dual-supply voltage translator that can drive higher current than the SN74AVC4T245 while operating at 13 MHz (McBSP bus)?

I looked at the PCA9306 device, which has an Ipass up to 64 mA, but the maximum frequency is 400 kHz.

Thanks for your help in advance!

James

over 10 years ago

0 James Evans over 10 years ago

TI__Mastermind 49692 points

I found the TXB0104-Q1 device to be very similar.

It has a higher max drive current (50 mA vs. 15 mA) than the SN74AVC4T245 part, and it has a max Frequency of 100 MHz.

However, can the TXB device be used on the McBSP bus?

Thanks,

James

0 Jennifer Joseph over 10 years ago in reply to James Evans

TI__Intellectual 2530 points

Hi James

Data rate is not a problem. But the TXS and TXB devices have low input current drive. What is the drive strength requirement and what are the translating voltage levels?

Thanks

0 James Evans over 10 years ago in reply to Jennifer Joseph

TI__Mastermind 49692 points

Hi Clarisa,

Thanks for your quick reply.

I need a minimum of 50 mA drive current.

After looking closely at the TXB0104-Q1, I realized its propagation delay is too long compared to the SN74AVC part.

I will keep looking, but any input here is most appreciated.

James

0 C. Ryan Land over 10 years ago in reply to James Evans

TI__Genius 9860 points

Hi James, which voltages are you translating across? Depending on the requirements, you may be able to use a buffer with TTL inputs.

0 James Evans over 10 years ago in reply to C. Ryan Land

TI__Mastermind 49692 points

Hi!

I am translating from 1.8 VDC to 3.3 VDC bi-directional (two pins go in one direction, two pins go in the other).

The propagation delay needs to be less than 4 ns.

Thanks again for your input here.

James

0 C. Ryan Land over 10 years ago in reply to James Evans

TI__Genius 9860 points

Hi James, I don't know if we have anything that can reliably drive 50 mA at just 1.8 V or 3.3 V. Our highest drive CMOS family is the LVC family. You can increase the drive strength by tying 2 inputs to each other, and 2 outputs to each other, then treating that as one line. Of course you'd need to move up to a higher bit count to accomplish that. The SN74LVC8T245 is an example of one where you could tie the I/Os together like that.

0 James Evans over 10 years ago in reply to C. Ryan Land

TI__Mastermind 49692 points

Hi Ryan,

Thank you for your recommendation.

I took a look at the SN74LVC8T245 device, but unfortunately it is too slow due to propagation delays more than 7 ns.

Could I tie 2 inputs/outputs together on the SN74AVC8T245 device to get 30 mA current drive strength (closer to my 40 mA requirement)?

James

0 C. Ryan Land over 10 years ago in reply to James Evans

TI__Genius 9860 points

Hi James, you could draw 30 mA that way, but your VOH might drop and your VOL might rise significantly. Even when drawing 12 mA from the part with a 3-V suppy, plan for the output voltage to go as low as 2.3 V. Further current consumption will drop the voltage even further and might not even trigger a 3.3-V CMOS input.

0 James Evans over 10 years ago in reply to C. Ryan Land

TI__Mastermind 49692 points

Hi Ryan,

Thanks for the detailed answers.

I appreciate it.

Best Regards,

James

Logic

Logic forum

SN74AVC4T245 Replacement Recommendations