SN74AVC4T245-Q1: SN74AVC4T245-Q1

?? ?

Part Number: SN74AVC4T245-Q1
Other Parts Discussed in Thread: TXU0104-Q1

Tool/software:

Hi ALL,

when i am testing the current of VCCA,i found that VCCA has 2mA current, and when i conect 2A2 to gnd, zhe total current of VCCA decrease to 0.2mA.

The qustion is :2A2 is an output pin(in this apllication),why i confirm an output CMOS device will decrease VCC current?

If i confirm a vin state of CMOS device,the VCCA current decreased,that i can undestand.

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 318050 points

What was the voltage at the 2A2 pin with the 2 mA?

0 ?? ? over 1 year ago

Prodigy 40 points

2A2 pin is about 0.1V

0 Clemens Ladisch over 1 year ago in reply to ?? ?

Guru 318050 points

Without some other load, it should be exactly 0 V.

What are the voltages at the VCCB, 2DIR, and /2OE pins?

0 ?? ? over 1 year ago in reply to Clemens Ladisch

Prodigy 40 points

all of them are 0V

0 Clemens Ladisch over 1 year ago in reply to ?? ?

Guru 318050 points

When VCCB is powered off, then the outputs on both sides are disabled. But when VCCA is on, then the input buffers on the A side are active, and they must have a valid logic voltage to prevent them from floating.

If it is possible that one supply is powered off for more than a short time, then you should ensure that you have pull-up or -down resistors to the I/Os on the other side, or that those signals a driven by another source.

These problems happen because all I/O pins are both inputs and outputs. If the direction never changes, consider a unidirectional level shifter like the TXU0104-Q1 instead.

0 ?? ? over 1 year ago in reply to Clemens Ladisch

Prodigy 40 points

"then you should ensure that you have pull-up or -down resistors to the I/Os on the other side"

witch will decrese the currrent to the minimum?

0 Michael Ikwuyum over 1 year ago in reply to ?? ?

TI__Guru 54976 points

Hi,

Yes, avoiding floating inputs will decrease the current to the specification, thanks.

Best Regards,

Michael.

0 ?? ? over 1 year ago in reply to Michael Ikwuyum

Prodigy 40 points

i mean,pull-up or pull-down,which will decrease the current to the minimum?

0 Clemens Ladisch over 1 year ago in reply to ?? ?

Guru 318050 points

It does not matter. Use whatever makes sense for the idle or power-up state of that particular signal.

Logic

Logic forum

SN74AVC4T245-Q1: SN74AVC4T245-Q1