SN74LVCC3245A: possibility of damage VCCA:3.3V and VCCB:0V

Shinichi Inoue

Guru 19931 points

Part Number: SN74LVCC3245A

Dear Specialists,

My customer is considering SN74LVCC3245A and have a question.

I would be grateful if you could advise.

---

We are considering whether we can supply only 3.3V to update the F/W of 3.3V microcontrollers.

Because it is not necessary to operate the SN74LVCC3245A when writing to F/W.

When VCCA: 3.3V, VCCB: 0V, is there a possibility of damage?

A1-8, DIR may be applied with 3.3V.
G # is fixed 3.3V (inactive).

Is it possible to use under these conditions?

---

I appreciate your great help in advance.

Best regards,

Shinichi

over 3 years ago

0 Emrys Maier over 3 years ago

TI__Guru* 96661 points

Hello Shinichi-san,

No, there isn't any concern for damage in this condition, so long as all the inputs are in a defined state (0V or 3.3V).

The datasheet specifies a condition for only the VCCA supply being powered (up to 3.6V), in which case the supply current does not exceed 50uA:

0 Shinichi Inoue over 3 years ago in reply to Emrys Maier

Guru 19931 points

Hi Emrys,

Thank you for your reply.

I understand there is no problem VCCA:3.3V and VCCB:0V.

I'll share this information with the customer.

I appreciate your great help and cooperation.

Best regards,

Shinichi

0 Shinichi Inoue over 3 years ago in reply to Shinichi Inoue

Guru 19931 points

Hi Emrys,

I sent your answer to the customer and they have an additional question.

I would be grateful if you could advise.

---

(1) When VccA = 3.3V, VccB = open, OE is fixed at 0V (active),

What will be B1 to 8 when A1 to 8 are 3.3V?

(2) The B side depends on the voltage VccB,

Since VccB is open, it will be Hi-Z, is it correct.

(3) When DIR = H (A to B), is the output on the B side affected by the A side (3.3V)?

---

I appreciate your great help and cooperation.

Best regards,

Shinichi

0 Clemens Ladisch over 3 years ago in reply to Shinichi Inoue

Guru 256450 points

When V_CCB is at 0 V, then the outputs are disabled.

But when V_CCB is open, there might still be a voltage (i.e., the V_CCB decoupling capacitors might still be charged), and the transceiver might still be powered.

0 Shinichi Inoue over 3 years ago in reply to Clemens Ladisch

Guru 19931 points

Hi Clemens,

Thank you for your reply.

I understand I/Os are disabled when VCCB is 0V.

Disable means Hi-Z, is it correct?

Also, it should be remind charge of decoupling capacitor.

I appreciate your great help and cooperation.

Best regards,

Shinichi

0 Clemens Ladisch over 3 years ago in reply to Shinichi Inoue

Guru 256450 points

Yes, disabled outputs are Hi-Z. (Inputs always are Hi-Z.)

0 Shinichi Inoue over 3 years ago in reply to Clemens Ladisch

Guru 19931 points

Hi Clemens,

Thank you for your reply.

I'll also share this information with the customer.

I appreciate your great help.

Best regards,

Shinichi

Logic

Logic forum

SN74LVCC3245A: possibility of damage VCCA:3.3V and VCCB:0V