About additional document of LM25037

Satoshi

Guru 19645 points

Other Parts Discussed in Thread: LM25037, LM5046, LM5045, UCC28251

Customer hope to described any document for two points below of LM25037.

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・Minimum frequency (kHz)

　ESP parametric is written 50kHz_min, but datasheet and other document is not described.

　(I found graph, but customer hope to see recommended operating range for minimum)

・Reference design of Full-Bridge application.

　Datasheet and User's Guide are Half-Bridge only.

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If there document or update schedule, please let me know.

Best regards,

Satoshi

over 8 years ago

0 Peter Meaney over 8 years ago

TI__Mastermind 31580 points

Hi Satoshi-san

Figure 6 in the datasheet shows the Frequency versus RT1 resistor value and the minimum frequency value is approximatley 20kHz. I would suggest that 20kHz is the minimum frequency value. What is the minimum frequency of the customers application.

I cannot see any full bridge designs with the LM25037, but TI has the LM5045 and LM5046 full bridge controllers which provide more functionality for full bridge applications.

www.ti.com/.../LM5045
www.ti.com/.../LM5046

There are EVMs available for both of these controllers.

Regards

Peter

0 Bernard Keogh over 8 years ago

TI__Genius 9130 points

Satoshi-san,

The minimum oscillator freq of the LM25037 is not explicitly stated in the datasheet. However, from Fig. 6 on page 7, it shows that with RT1 = 300 k-ohm, Fosc = ~22 kHz is possible. So I would assume that this is the minimum oscillator capability. I will confirm with the internal product line.

The LM25037 EVM and design example in the datasheet are for a push-pull power stage (not half-bridge). A push-pull or half-bridge controller could be used to drive a full-bridge, but external half-bridge drivers would be required for each leg of the full-bridge, with appropriate external gate drive signal dead-time management.

Alternatively, the LM5045 or similar could be considered for the full-bridge. This includes both half-bridge driver stages, SR drive (if required), and all gate signal dead-time management. LM5045 datasheet includes a full-bridge design example, and the LM5045 full-bridge EVM is available to order:

http://www.ti.com/tool/lm5045eval

I hope this helps answer your question, if so please click the "verify answer" button.

Thanks,

Bernard

0 Satoshi over 8 years ago in reply to Bernard Keogh

Guru 19645 points

Peter-san
Bernard-san

Thank you for quick reply,
I looking forward your update from internal.

About LM5045, customer want to use 60kHz frequency, but LM5045 is 100kHz_min from ESP parametric.
I confirming customer application, please wait a few days.

Best regards,
Satoshi

0 Bernard Keogh over 8 years ago in reply to Satoshi

TI__Genius 9130 points

Satoshi-san,

Can you confirm if the customer target is 60 kHz Fsw or 60 kHz Fosc?

From Fig. 6 in the LM5045 datasheet, you can see that with Rt = 50 k-ohm, Fosc ~200 kHz is achieved, which is Fsw ~100 kHz, which seems to be in agreement with ESP.

But the Rt value is still not so large, only 50 k-ohm, so it looks like a larger Rt could be used to get Fosc ~ 120 kHz, and Fsw ~ 60 kHz. From datasheet eqn. 1, Rt = ~83 k-ohm should achieve Fosc ~120 kHz.

I am checking with the internal product line to see if this is possible.

Thanks,
Bernard

0 Bernard Keogh over 8 years ago in reply to Bernard Keogh

TI__Genius 9130 points

Satoshi-san,

I am waiting for info about the Fmin capability of LM5045.

Meanwhile, maybe your customer can consider the UCC28251 - this has a capability to go down to Fsw min of 27 kHz (I.e. Fosc 54 kHz). Maybe this part is more suitable?

Thanks,
Bernard

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About additional document of LM25037