ALM2402F-Q1: Open-Loop Bode Plot with Inductive Load

Shinichi Yokota

Part Number: ALM2402F-Q1
Other Parts Discussed in Thread: ALM2402-Q1

Hello,

I'd like to know how an open-loop Bode plot of ALM2402F-Q1 looks like with an inductive load. Could you provide me with the data with the following inductance value?

Inductance: 0.39 to 0.78 mH at 10 kHz

Best regards,
Shinichi Yokota

over 3 years ago

0 Raymond Zhang1 over 3 years ago

TI__Mastermind 48006 points

Hi Shinichi-san,

Enclosed is the link for ALM2402F-Q1 EVM user guide. This is for resolver application.

https://www.ti.com/lit/ug/sbou227/sbou227.pdf?ts=1594047675212&ref_url=https%253A%252F%252Fwww.ti.com%252Ftool%252FALM2402FQ1EVM

It seems that your application is likely resolver based with 0.39-0.78mH at 10Hz excitation frequency. What is the inductance winding resistance?

All you have to do is place the inductance and winding resistance in series, and connected to J31 (output1) and J3.4 (output2). What kind of data are you looking for (feed forward response from ALM2402FQ1 driver)? Are you looking for driving stability from ALM2402Q1 IC? Can you tell me the transformation ration V_rotor/V_excitation = 0.5?

Best,

Raymond

0 Shinichi Yokota over 3 years ago in reply to Raymond Zhang1

TI__Genius 9715 points

Raymond-san,

Yes, the load is a resolver. I'm concerned if the gain of the excitation amplifier circuit became lower than a design target due to an inductive load. It'd be helpful if you take data on open-loop gain and phase characteristics with the inductive load.

Resolver impedance is 0.39 to 0.78 mH at 10 kHz plus 24.5 Ω.
Transformation ratio is lower than 0.5 - actually 0.286.

Best regards,
Shinichi Yokota

0 Raymond Zhang1 over 3 years ago in reply to Shinichi Yokota

TI__Mastermind 48006 points

Hi Shinichi-san,

With the limited information you provided, I copied the resolver circuit from ALM2402FQ1 from the EVM above.

Here is the data entered into the model: Zp = 24.5 Ohm, Transformation Ratio = 0.286, Zs = 0.286^2*Zp = 2 Ohm. Ns/Np= 0.286 --> Ns=572 Turns assuming Np=2000T. Inductance of Ns/Np = sqrt (Ls/Lp). Although the 0.39mH-0.78mH information is not entered, since it is transformer, the transformer model in Tina should taken into account of the information from winding ratios and impedance of windings. (Tina's model does not use sqrt of inductance ratios to define the transformer characteristics).

Based on the loop-gain analysis, the BW of ALM2402FQ1 resolver circuit is 74.7kHz with phase margin approx. 74.8 degree.

Enclosed is the model that you can simulate yourself.

/cfs-file/__key/communityserver-discussions-components-files/14/ALM2402_2D00_Q1-Open_2D00_loop_2D00_stabilityB-with-transformer-_2B00_-Loop-Gain-07072020.TSC

If you have any questions, please let us know.

Best,

Raymond

0 Shinichi Yokota over 3 years ago in reply to Raymond Zhang1

TI__Genius 9715 points

Raymond-san,

Please let me confirm one thing. Which device did you use as the model for the simulation? Non-F version (ALM2402-Q1) or F version (ALM2402F-Q1)?

Sorry that I have to rely on you because I don't have time to perform simulation myself.

Best regards,
Shinichi Yokota

0 Raymond Zhang1 over 3 years ago in reply to Shinichi Yokota

TI__Mastermind 48006 points

Hi Shinichi-san,

I was using the ALM2402-Q1 Model for the above simulation.

Ok, we seem to have ALM2402F macro model as well (I did not realize it that there are two macromodels in the part). There is a compensation capacitor in parallel with Rf. Do you have the value or exact schematic? I did a quick stability analysis, and the stability needs to be verified tomorrow. (Also the power supply symbol/label appears to be reversed from the reference design). Can you send me the actual customer schematic to my internal mailbox? So the simulation will be consistent per your request.

/cfs-file/__key/communityserver-discussions-components-files/14/ALM2402F-Macro-Model-Open_2D00_loop_2D00_stabilityB-with-transformer-_2B00_-Loop-Gain-07072020.TSC

Best,

Raymond

0 Raymond Zhang1 over 3 years ago in reply to Raymond Zhang1

TI__Mastermind 48006 points

Hi Shinichi-san,

I checked the compensation circuit that I sent out last night (with ALM2402F macro model), it looks ok. There is some over damping when performing the square wave function at 1kHz. Since I do not have the actual circuit from your customer, I would consider the op amp compensation and phase margin are acceptable.

If you have further questions, please let me know.

Best,

Raymond

0 Shinichi Yokota over 3 years ago in reply to Raymond Zhang1

TI__Genius 9715 points

Raymond-san,

Could you remove resistors and capacitors at the outputs to GND (R1, R3, C4, C5) from the schematic and post the result of open-loop gain and phase plots of the ALM2402F-Q1 here on the e2e?

Best regards,
Shinichi Yokota

0 kai klaas69 over 3 years ago in reply to Shinichi Yokota

Guru 140200 points

Hi Shinichi,

you mean something like this?

shinichi_alm2402.TSC

shinichi_alm2402_1.TSC

Unfortunately, I could not make the ALM2402F model to run. So here only the performance of ALM2402. Maybe Raymond can help?

Kai

0 Raymond Zhang1 over 3 years ago in reply to kai klaas69

TI__Mastermind 48006 points

Hi Kai,

Thanks for the simulation.

Hi Shinichi-san,

Could you remove resistors and capacitors at the outputs to GND (R1, R3, C4, C5) from the schematic and post the result of open-loop gain and phase plots of the ALM2402F-Q1 here on the e2e?

I believe that this is what you are requesting, see the image and simulation.

/cfs-file/__key/communityserver-discussions-components-files/14/ALM2402F-Macro-Model-Open_2D00_loop_2D00_stabilityB-with-transformer-_2B00_-Loop-Gain-07172020.TSC

Best,

Raymond

0 kai klaas69 over 3 years ago in reply to Raymond Zhang1

Guru 140200 points

Hi Raymond,

I don't get your simulation to run:

shinichi_alm2402F_raymond.TSC

What am I doing wrong?

Kai

0 Raymond Zhang1 over 3 years ago in reply to kai klaas69

TI__Mastermind 48006 points

Hi Kai,

Here is the running simulation. This is a feed forward circuit. It has no feedback from excitation side (e.g. 10-40 kHz) to resolver's receiver sides (sine and cosine windings).