LMX8410L: LMX8410L Temperature issue

This was my configuration in TICS Pro to Extract the registers and programmed the PIC via SPI, didn't work. Lock detected does not appear.

Update: I solved some issues with registers. For some reason TICS Pro showed some registers first, and I re-changed the parameters and showed different registers, I applied those new ones, and now the PLL is able to Lock. The problem now is that when the PLL gets Locked, the temperature starts increasing. So now my problem is not about the registers, but the temperature. This temperature is on the chip, not on the board. 
If you know something about it, I will be more than glad to receive your advices. 

Hi Carlos,

This device consumes 3.3V x 650mA + 5V x 130mA = 2.795W of power. It is not surprising that the device is very hot. How many layer you have on your pcb? Do you have enough copper plane to dissipate the heat generated from the device? If you can measure the board temperature, we can estimate the die temperature. As long the die temperature is less than the junction temperature, it is fine.

Hi Noel,
Thank you so much for answering. We have 8 layers in our board. 

1. Top - Signal
2. Ground
3. Signal
4. Ground
5. Power
6. Power
7. Ground
8. Bottom - Signal

The problem is that, when the PLL gets Locked, the temperature starts increasing, and when it reaches around 40°C, the PLL loses the Lock, but the temperature is still increasing till 120°C that is the max we have ever read.

Hi Carlos,

What temperature? is it board temperature, device surface temperature or what? Is the current consumption normal?

Hi Noel,
As I told you, this is the chip temperature. By now, we have solved many problems with the temperature. The answer you provided about the current consumption and 2.79W led us to check the datasheet and with an adjustment in our hardware, the device is not reaching those high temperatures anymore. Is around 70°C, 80°C so now we assume is normal. The problem we are facing now, is as follows:

We programmed a whole set up for the device, writing to the correct registers to Initialize, Enable and change frequency on the device. Currently, we don't know what to do cause we are initializing the device, enabling it, and it gets locked. But when we re-do this process, the PLL keeps the lock even when it has not been re-enabled yet, so it basically stays in an infinite lock till we turn off the voltage. 

Since I commented that I solved the problem with the registers, I would like to add a new table with the new registers I obtained from TICs PRO, just to check if there is something else wrong. those who are not in this table, were settled to zero.

Hi Carlos,

Since you use TICS Pro, please send me the .tcs configuration file, thanks.

ForTexasForum.tcs

Hi Noel, 
Here is the .tcs file. Thank you very much.

(Update)
What we currently doing is: 

Supplying the device with 3.3V, activating the Enable process, starting the initialization in descending order (as the table I showed few messages back), then, the Calibration (with the 3rd bit of register R1), and when the device gets locked, we activate the Enables from the DCOC. Additionally, we are seeing the VCO Calibration bit, but despite that, when we deactivate the Enable, we're still seeing the MUX OUT on. We can only stop the lock by turning off the supply voltage completely. 

I hope this will make it clearer. Thanks.

Hi Carlos,

Unfortunately, I still don't understand your problem. 

Is the PLL unable to lock? Are you not able to change the frequency? Or something else?

Your configuration has an issue. There is restriction on the PLL_N value which is dependent on the MASH order.

The restriction is like this.

So for PLL_N=40, change the MASH order to 3rd order and change the PFD delay accordingly to 3.

Hi Noel,

We are working with a custom board that uses the LMX8410 as a demodulator, controlled via SPI by a PIC microcontroller. The configuration we attach from TICs Pro is the initialization we currently apply to the demodulator. After this initialization, we don’t change any other settings.

Our initialization sequence is as follows:

1. Enable the demodulator.
2. Write to registers 127 and 6 as recommended in the datasheet.
3. Trigger a reset through Register 0.
4. Write all registers in descending order.
5. Wait 10 ms, check the VCO lock status, and then enable DCOC calibration.

The temperature issue we had before is already solved, but now we are facing two main problems:

We check the VCO lock status through the MUXout pin. It indicates that there is lock after initialization, but if we disable the enable pin (set it to 0 V), the MUXout pin still shows a lock condition.

We are not observing the expected IF output corresponding to LO – RF. We suspect this could be related to incorrect configuration of mash order and delay (DLY) with respect to our VCO and PFD settings.

Our setup: PFD = 100 MHz, 50 MHz at OSCin with the doubler enabled.

• We target 6.5 GHz at the LO, so we aim for 13,000 MHz at the VCO with CHDIV2 enabled.
• Could you please help us with the following points?
• Why does the MUXout pin (VCO cal) remain HIGH even after the enable pin is de-asserted?
• Can you confirm whether our configuration is correct for achieving the LO output through CHDIV2, and if the rest of the setup looks valid?

The table information about N and MASH Order restrictions is clear, however, the file I sent you was using a 8000 Fvco Frequency, with N = 40, and MASH = 4th, DLY = 5. According to this table, this values should be correct. What would be the configuration for the values we are aiming? With N between 80 and 150.

I hope this clarifies our issue. If anything is not clear, I will be glad to provide further details.

Thanks a lot,
Best regards,

Hi Carlos,

After initialization and PLL lock, when you set CE pin = 0, did you see a significant current drop?

The min. N is 44 with 4th order MASH.

Let me check if I have a board in the lab I can try. 

Hi Noel,
We know that the voltage drops a little bit and the PLL heats between 70°C and 80°C, but we already assume that this temperature is normal. 

Hi Carlos,

I don't have the board in the lab, I rely on you to debug.

If the CE pin (pin 1) controls the whole chip, then making it =0 should reduce the current consumption significantly. Did you see this big change in current? If the CE pin controls only to the demodulator but not the synthesizer, you should still see maybe 300mA of current which is consumed by the synthesizer. If you program PLL_PD = 1 now, then MUXOUT should become 0V as the synthesizer is powered down. 

Hi Noel,

We implemented a method enabling and disabling the Power Down, establishing the R0 fourth bit = 1 for Activated, and = 0 for Deactivated. We tested this method and the Lock state is still On. The current is still in the same value, but we saw that turning off the Enable, generates a current drop, approximately of 500mA  but the Lock state is always there and the only way to remove it is turning off the voltage that feeds the entire PLL.

Hi Carlos,

PLL_PD is located in R0, bit 0. 

Hi Noel,
We so sorry, there was a confusion writing our previous answer. Effectively, we are writing to R0 bit 0. Our configuration is 0x0004 and when we activate it is 0x0005, and however, as we told you before, the problem with the Lock Status is still there. 

Could you please check if the configuration we are using with the rest of registers is ok or do you find something else wrong? Our tests include introducing a signal into the RF IN pin, and measuring the output pins (QP, QM, PQ, PM). Our LO configuration says we are at 6.5GHz, but the tests say we are around 8GHz and we cannot find why. Here's a table with some results we've obtained if it's useful: