LMZ34002: Inhibit Function

Erin Yu

Part Number: LMZ34002
Other Parts Discussed in Thread: , SN74LVC1T45, SN74AXC1T45

Hi Mr./Mrs.,

We follow LMZ34002EVM-001 Evaluation Module design with a level shifter(DCX144EH-7) at the INH / UVLO pin. We try to control LMZ34002 Enable/Disable by this pin. When the input signal of INH / UVLO (EVB TP7)=5V, LMZ34002 output is Enable, while when the signal of INH / UVLO (EVB TP7)=3.3V, LMZ34002 output is Disable. Because the intput signal of INH / UVLO in our design comes from the FPGA and the signal is 3.3V max, can we just bypass the level shifter (DCX144EH-7), then using two resistors divde the INH / UVLO signal 3.3V to 1V for example, to control LMZ34002 Enable/Disable?

ps.The VIN of LMZ34002 is 5V and A_OUT=-3V. If the input signal of INH / UVLO is 1V, VINH should be 1V-(-3V)=4V under the Absolute Maximum Rating of INH/UVLO?

over 3 years ago

0 Samuel Jaffe over 3 years ago

TI__Mastermind 25590 points

Erin,

The INH/UVLO pin has a threshold referenced to VOUT which is below GND. If your FPGA's output is also referenced to VOUT, this should work. If the FPGA output is referenced to GND, you will need a level shifter.

You can also probe the INH/UVLO pin in these conditions with respect to VOUT to see what you're getting from the level shifter.

-Sam

0 Erin Yu over 3 years ago in reply to Samuel Jaffe

Prodigy 80 points

Hi Sam,

Which part number of level shifter you will suggest when INH/ULVO input =3.3V?

Thanks

0 Samuel Jaffe over 3 years ago in reply to Erin Yu

TI__Mastermind 25590 points

Erin,

The evaluation lets you disable the device by grounding TP7 (level shifter input) and lets you enable the device by floating TP7. Do you have the ability to set your FPGA pin output to high-impedance?

If not, I can forward you to the logic level translation team.

-Sam

0 Erin Yu over 3 years ago in reply to Samuel Jaffe

Prodigy 80 points

Hi Sam,

For the design right now, I tie the enable pin of LMZ34002 with other enable pins of LDOs together.

Could you please help to foward to the logic level translation team and provide some suggestion?

Thanks

0 Samuel Jaffe over 3 years ago in reply to Erin Yu

TI__Mastermind 25590 points

Erin,

I have reached out to the voltage translators team who should get in touch shortly.

-Sam

0 Dylan Hubbard over 3 years ago in reply to Samuel Jaffe

TI__Mastermind 44895 points

Hi Erin,

I would recommend taking a look at the SN74AXC1T45 for .65 V to 3.6 V translation or the SN74LVC1T45 for 1.65 V to 5.5 V translation.

Power management

Power management forum

LMZ34002: Inhibit Function