LMH1228: Slew Rate Control

Marcelo Hebling

Part Number: LMH1228
Other Parts Discussed in Thread: LMH1297EVM

Hi everyone

I'm trying to lock each of the outputs, SDI_Out1 and SDI_Out2, with different slew rates following tables 3.14.5.2.1 and 3.14.5.2.2 in the programming manual.

I did a test trying to leave SDI_Out1 with slew rate in SD(270M) and SDI_Out2 with slew rate in HD(3G/1.5G).

At the entrance it was tested with 1080 and 2160, but in none of the cases did the commands work to lock in the desired slew rate settings.

I would like to know what can be done besides following what is described in the aforementioned tables.

Thanks, Marcelo

5 months ago

0 Nick Peabody 5 months ago

TI__Expert 3095 points

Hi Marcelo,

What is the exact procedure for the tests you have done? More specifically, what is the slew rate setting you are trying to achieve?

I would like to replicate your test in our lab. I will be able to do so if I have a detailed description of your test setup and test procedure.

Best regards,

Nick P.

0 Marcelo Hebling 5 months ago in reply to Nick Peabody

Prodigy 70 points

Hi Nick,

I will send you the part of the source code where I make this configuration.

void SMPTE_Data_Rate()
{
	//SDI_Out1

	HAL_GPIO_WritePin(GPIOA, CS_0_Pin, 0); //acesso a pg de driver
	operacao_rx = 0x00;
	endereco_rx = 0xFF;
	dado_rx     = 0x05;
	mascara_rx  = 0x07;
	comando_rx = operacao_rx+endereco_rx+dado_rx+mascara_rx;
	HAL_SPI_Transmit(&hspi1, &comando_rx, 1, 100);
	HAL_GPIO_WritePin(GPIOA, CS_0_Pin, 1);
	HAL_Delay(100);

	HAL_GPIO_WritePin(GPIOA, CS_0_Pin, 0); //inicio da configuração
	operacao_rx = 0x00;
	endereco_rx = 0x60;
	dado_rx     = 0x20;
	mascara_rx  = 0x20;
	comando_rx = operacao_rx+endereco_rx+dado_rx+mascara_rx;
	HAL_SPI_Transmit(&hspi1, &comando_rx, 1, 100);
	HAL_GPIO_WritePin(GPIOA, CS_0_Pin, 1);
	HAL_Delay(100);

	HAL_GPIO_WritePin(GPIOA, CS_0_Pin, 0); //SDI_Out1 travado em SD
	operacao_rx = 0x00;
	endereco_rx = 0x60;
	dado_rx     = 0x18;
	mascara_rx  = 0x18;
	comando_rx = operacao_rx+endereco_rx+dado_rx+mascara_rx;
	HAL_SPI_Transmit(&hspi1, &comando_rx, 1, 100);
	HAL_GPIO_WritePin(GPIOA, CS_0_Pin, 1);
	HAL_Delay(100);

	//SDI_OUT2

	HAL_GPIO_WritePin(GPIOA, CS_0_Pin, 0); //acesso a pg de driver
	operacao_rx = 0x00;
	endereco_rx = 0xFF;
	dado_rx     = 0x05;
	mascara_rx  = 0x07;
	comando_rx = operacao_rx+endereco_rx+dado_rx+mascara_rx;
	HAL_SPI_Transmit(&hspi1, &comando_rx, 1, 100);
	HAL_GPIO_WritePin(GPIOA, CS_0_Pin, 1);
	HAL_Delay(100);

	HAL_GPIO_WritePin(GPIOA, CS_0_Pin, 0); //inicio da configuração
	operacao_rx = 0x00;
	endereco_rx = 0x67;
	dado_rx     = 0x20;
	mascara_rx  = 0x20;
	comando_rx = operacao_rx+endereco_rx+dado_rx+mascara_rx;
	HAL_SPI_Transmit(&hspi1, &comando_rx, 1, 100);
	HAL_GPIO_WritePin(GPIOA, CS_0_Pin, 1);
	HAL_Delay(100);

	HAL_GPIO_WritePin(GPIOA, CS_0_Pin, 0); //SDI_Out2 travado em HD
	operacao_rx = 0x00;
	endereco_rx = 0x67;
	dado_rx     = 0x08;
	mascara_rx  = 0x18;
	comando_rx = operacao_rx+endereco_rx+dado_rx+mascara_rx;
	HAL_SPI_Transmit(&hspi1, &comando_rx, 1, 100);
	HAL_GPIO_WritePin(GPIOA, CS_0_Pin, 1);
	HAL_Delay(100);
}

I will send you the part of the source code where I make this configuration.

We are using an ARM microcontroller from ST, STM32F103C8T6, and the development is being done in the STM32CubeIDE environment.
As a reference for programming I am using the Texas SNAU 206 document, pg 23.

If you require any further information do not hesitate to contact me.

Best regards,

Marcelo

0 Nick Peabody 5 months ago in reply to Marcelo Hebling

TI__Expert 3095 points

Hi Marcelo,

I'm going to take a look at this today and hopefully can get back to you tomorrow.

Best Regards,

Nick

0 Nick Peabody 5 months ago in reply to Nick Peabody

TI__Expert 3095 points

Hi Marcelo,

Please allow me until the end of this week to get back to you.

Best Regards,

Nick

0 Nick Peabody 5 months ago in reply to Nick Peabody

TI__Expert 3095 points

Hi Marcelo,

The code makes sense and you are using the correct resource to program the LMH1228. I tried testing this in the lab and was able to get satisfactory results with similar programming.

Are you not able to get CDR lock with the SD and HD signals?

Best Regards,

Nick

0 Marcelo Hebling 5 months ago in reply to Nick Peabody

Prodigy 70 points

Hi Nick

Yes, I'm not able to get CDR lock with the SD and HD signals.

Do you have any thing to recommend me?

Best Regards,

Marcelo

0 Nick Peabody 5 months ago in reply to Marcelo Hebling

TI__Expert 3095 points

Hi Marcelo,

Yes, our final recommendation is to get a LMH1297EVM because that would allow you to prototype and compare with your current board. The LMH1297EVM is easier to get a CDR lock with and there wouldn't be any programming required. What could be useful is if you sent over the schematic for your board for us to review in the mean time. Can you do that through direct message?

Best Regards,

Nick

0 Marcelo Hebling 5 months ago in reply to Nick Peabody

Prodigy 70 points

Hi Nick,

I believe that I can to send you the schematic but I need to talk about it with my boss about it.

I have a question: is it possible to lock SMPTE data rate for individual outputs using the commands that I was send to you or no?

Best Regards,

Marcelo

0 Nick Peabody 5 months ago in reply to Marcelo Hebling

TI__Expert 3095 points

Hi Marcelo,

If the device is not able to lock to the rates before programming, it is unlikely that adjusting the slew rate specific to the rate will allow for a lock.

Please get back to me on the schematic.

Best Regards,

Nick

0 Marcelo Hebling 5 months ago in reply to Nick Peabody

Prodigy 70 points

Hi Nick

I believe I was not very clear in my questioning.
What I asked was the following: is it possible to lock the outputs with different frame rates? Of course, everything depends on programming...

Regarding sending the electrical diagram, I spoke with my boss and I am authorized to send you the electrical diagram, can I send it to you via the same communication channel that you sent me the Programming Guide?

Best Regards,

Marcelo

0 Nick Peabody 5 months ago in reply to Marcelo Hebling

TI__Expert 3095 points

Hi Marcelo,

Yes please send the electrical diagram via direct communication. I can get back to you next week.

Best,

Nick

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LMH1228: Slew Rate Control