SN74AVC4T245: current consumption

Marco Hsieh

Intellectual 1060 points

Part Number: SN74AVC4T245

Team,

My customer is using SN74AVC4T245 as a level shift.

To minimize the current consumption, they pull #OE to high level.

but, the current still has 9mA. To remove SN74AVC4T245, he can get 50uA.

Is this normal to you? How he can improve his current consumption performance??

Here is there circuit (SYS_VCC=3.0V,V180=1.8V).

Marco

over 8 years ago

0 Clemens Ladisch over 8 years ago

Guru 317000 points

Is this schematic correct? Especially the value of R135?

0 Marco Hsieh over 8 years ago in reply to Clemens Ladisch

TI__Intellectual 1060 points

Ladisch,

Thanks for your reply.
I will double check with customer, please ignore R135 here.

Marco

0 Michael J Schultis over 8 years ago in reply to Marco Hsieh

TI__Mastermind 24975 points

Hello Marco,

Are all the inputs to the device being driven by a defined voltage and the outputs are not being driven by any other source?

Are you saying that the current consumption is happening during operation? Is the device operating at high frequencies which may be causing high switching losses?

The GND and VCC connections look fine. The direction pins look fine with channels 1A1 and 1A2 driving A to B and 2A1 and 2A2 being driven from the B side.

OE looks good as long as the 3.5V is not getting shorted to ground through R135.

Best,
Michael

0 Marco Hsieh over 8 years ago in reply to Michael J Schultis

TI__Intellectual 1060 points

Michael,

thanks for your reply.
they use 1.8V interface on A side, and 3V interface on B side.
but, when they test SN74AVC4T245. they disconnect A side (FPGA) and B side connection.
At this time, there are not operating. but, they got 9mA. when they remove SN74AVC4T245, they got 50uA.
could you provide any idea about this?
Or TI have alternative solution to replace SN74AVC4T245??

Marco

0 Clemens Ladisch over 8 years ago in reply to Marco Hsieh

Guru 317000 points

When the other devices are disconnected, the inputs are floating. The logic FAQ says that

floating inputs on CMOS devices can cause excessive supply currents, oscillations, and damage to the device. For a full explanation, please read our application report entitled Implications of Slow or Floating CMOS Inputs.

0 Michael J Schultis over 8 years ago in reply to Clemens Ladisch

TI__Mastermind 24975 points

Hello Marco,

Yes, I agree with Clemens, if the inputs to the device are floating it can cause excessive current.

Best,
Michael

0 Marco Hsieh over 8 years ago in reply to Michael J Schultis

TI__Intellectual 1060 points

Team,

any recommend solution can replace SN74AVC4T245??
if CMOS slution will cause current consumption issue, can we try TTL process??

Marco

0 Clemens Ladisch over 8 years ago in reply to Marco Hsieh

Guru 317000 points

Was the disconnection done just for testing, or is it required for operation?

In the latter case, you can just add pull-up resistors to any inputs (1A1, 1A2, 2B1, 2B2) that might be open. For how to calculate their value, see Choosing an Appropriate Pull-up/Pull-down Resistor for Open Drain Outputs (SLVA485), or just use 10 kΩ.

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SN74AVC4T245: current consumption