TLV9032: Ouput drive capability

Thanks for your post. We’re on break until January 3 and will provide a suitable response to your modeling question when we return. To best assist, would you be able to share more information about what you are driving at the output. Also, provide a better understanding of your need for 1.2v operation. 
thanks

chuck

Chuck,

This is a generic level shifting application - so it will be driving CMOS / TTL logic, likely in the 50-100pF capacitance load range with a parallel resistive element setting the DC load (ideally 20-25mA if the driver impedance is strong enough).

I would like to be able to level shift from 1.2V, but so far I have limited my application to 1.8V due to the lack of high speed comparators operating at 1.2V.

My initial thought is to use our open drain option to level shift to 1.2v rather than level shifting with resistor divider. But we can review further when we return.

chuck

Did you mean to say "from 1.2 V", and not "to 1.2 V"? What are the two voltages you want to shift between?

Would it be possible to use a higher supply voltage, and shift the result back down to 1.2 V with a logic buffer (e.g., SN74AUC34)?

Thanks Clemens for jumping in.  I understood the need as 1.2V logic system but fair to clarify.

Chuck

Hi,

I have simulated the output voltage of TLV9032 in TINA-TI for three different load resistors, 30R, 300R and 3k:

ka88_tlv9032.TSC

Looks like the output impedance of TLV9032 is modelled.

Kai

Thanks Kai for looking into this. 
chuck

Hello,

I was referring to the SPICE model (not the TINA-TI model) regarding the lack of output impedance.

In terms of the level shifting question, I do think that Chuck's suggestion to the use open-drain version (TLV902x) in order to get down to 1.2V would be appropriate.  However, I will need to buffer the output to get stronger drive strength.  Now looking for op amp buffers to follow the TLV902x with (a) >500V/us slew rate (b) >50mA output current capability (c) able to drive capacitive loads ~100pF, any suggestions here let me know.

The fully integrated level shifting options that Clemens suggested are not ideal here because (1) I don't need multiple channels (2) they still would require output buffering for higher drive current.

Thanks everyone. We can all review further when we’re back Jan 3. 
Chuck

Hi Ka88,

ka88 said:

The fully integrated level shifting options that Clemens suggested are not ideal here because (1) I don't need multiple channels (2) they still would require output buffering for higher drive current.

The hex buffers of the 74AUC34 are ideal to enhance the drive strength. Just put a few of them in parallel as if you would build a discrete MOSFET driver.

Kai

Thanks everyone for your support. 
Chuck

Kai,

When you say "put a few of them in parallel" do you mean to short multiple inputs/outputs of the hex buffer together (74AUC34 has 6x buffers) in order to combine the drive strength?

Yes; this is no problem with CMOS devices: [FAQ] Can I connect two outputs from a CMOS logic device together directly?

Hi Ka88,

I would do it this way:

ka88_74auc34.TSC

With the first, single inverter you guarantee that all paralleled inverters get the same input signal and are toggling at the same time.

The 48R resistor at the output represents the 25mA load.

The supply voltage of 74AUC34 has to be increased to 1.55V to allow an output signal of 1.2Vpp across the 48R output load.

Kai