KW45 SYS_LDO Output voltage spec and RF Drop Issue

[tomaru]

Dear Team,

I am working on custom board using KW45, Input Voltage - 1.6-3.3v coin cell battery.
We are facing RF Drop issue, so we started using EVAL board to identify issue.

We are using EVAL Board and 0dBm config extended BLE TX with ~248 bytes payload.

What we did - Provided power supply to its J8 pins. And did necessary pin config to provide supply using same. Board is configured in Both DCDC Buck as well as Bypass Mode, behaviour is same. Decreased voltage by 1V in step. LDO_CORE generating 1V.

What I observed - When we provide supply from J8 and drop voltage, everything works fine but once we reach 2.1v the RF drops.

I also checked till 2.2V the SYS_LDO generate an output of 1.8V but as soon as we reach 2.1V the LDO generate 1.7V.

Additional Detail - I checked the HW recommendation guide and it shows that SYS_LDO supply power to System Domain. In both cases DCDC and Bypass.

The LDO_SYS output states it can output 1.71 to 1.98V at Normal Drive.

Additionally, it can Automatically passthrough once voltage reach to 1.98

System Domain Spec - The System Domain spec says in Normal mode it needs VDD_SYS of 1.8V to 1.98V.

Question - When I give input voltage of 2.1V, the SYS_LDO output is ~1.7V which is lower than requirement of System Domain, and as my passthrough will work only in case when voltage reach ~1.98V the System Domain will not get enough voltage to work? Is this the case? 

I want to know why my RF Drops when you go from 2.2 ->2.1 V always.

Are we messing with some SW settings? Initially we thought must be custom board issue, but we faced same issue with EVK Board when supplied power through J8 and decreased voltage on step of 100mV/ 1V both.

RD-KW45-LOCALIZATION KW45B41Z-EVK KW45 

[tomaru]

Hi @luis_maravilla ,

I would like to add few more testing behavior, I am using BLE WUART Example Code. Bypass mode - 

1. I provided SYSTEM Domain by my own other power supply, but the results are same. The RF Disconnect (I cannot see anything on BLE) once my supply from J8 pin drop below 2.1 (Exact 2V).
2. I provided my VDD_RF with external supply 1.8V . Same behavior, the RF cannot be seen once my supply from J8 pin drop below 2.1 (Exact 2V).
3. I provided my LDO_CORE with external supply of 1.1V, The RF once my supply from J8 pin drop below 2.1 (Exact 2V) disconnect.

[luis_maravilla]

Hello Tomar,

I will be checking on your question

Could you help us share details about what does your RF Drop mean? It’s a loss of transmission, packet loss?

If you could bring details about how is the voltage been regulated it would be appreciated

Are there any additional components connected to the board that might draw current or affect the power rail?

Could you help us share your jumper configuration and set up description for your test in the KW45B41Z-EVK board?

Best Regards

Luis

[tomaru]

Hi @luis_maravilla ,

Please find my answer in Blue - 

Could you help us share details about what does your RF Drop mean? It’s a loss of transmission, packet loss?

There are multiple problems which i mean by RF drop - At 2.2 ->2.1V
1. RF Completely stops (No Adv or BLE even on Spectrum Analyzer) - Mostly Occurred
2. RF Adv only ON, unable to connect
3. RF ON, Adv ON, Connect OK, but No Data is received


If you could bring details about how is the voltage been regulated it would be appreciated

Voltage is provided using External Bench Power Supply - CV mode - Voltage dropped form 3.2V all the way to 1.8V. Current set to 500mA.
Voltage is dropped using the Knob on the Bench Power Supply

Link to Bench Power Supply Unit - https://www.metravi.com/product/rps-3005-dc-regulated-power-supply/

Are there any additional components connected to the board that might draw current or affect the power rail?

No

Could you help us share your jumper configuration and set up description for your test in the KW45B41Z-EVK board?

All Jumper config at default condition except -> JP5 set to 1,2 and JP32 set to 3,4 or 5,6 any will work.

Power Supply input provided using J8 Pin.
Test Code use to Provide dummy data. Receiver Used -> Mobile Phone NRF Connect Application.

I also tried an additional test where we provided 1.8V,1.9V from other supply (Ground Common) constant at VDD_SYS on JP40 Pin 1 and results are same no change.

Let me know if you need any more information.

BR,
Ankit

RD-KW45-LOCALIZATION KW45B41Z-EVK KW45 

[luis_maravilla]

Hello Tomar Ankit,

Could you help us confirm if using the NXP IoT Toolbox are you having the same disconnection issue?

Could you help us sharing your configuration in the EVK [Jumpers-Hardware Configurations modifications for using Bypass and Buck mode]? If you could share a photo, it would be highly appreciated. 

For Bypass mode and buck mode, you can check the Power modes configurations, this are described in the KW45B41Z-EVKUM chapter 2.1.2

Could you please help me pointing which is the JP32 that you are referring to?

Could you help me validate that you have the Jumper JP42 OPEN as it is mentioned in the KW45B41Z-EVKUM Table 8, in this same file you could find more recommendations about using the VBAT and coin cell usage.

All standard BLE profiles are based on Generic Attribute Profile [GATT] and must comply with it to operate correctly, the GATT establish how to exchange all profile and user data over BLE connection; Using Mobile Phone NRF Connect Application or third party applications could impact on the custom profile NXP is using on SDK examples, affecting with disconnections, as that applications have not the appropriate GATT client and server properties to communicate.

Best Regards

Luis

[tomaru]

Hello @luis_maravilla ,

I am using IOT ToolBox app, I think WUART works only on the same. For other applications used on Mobile Phone - We use our custom Code which TX the Data.

I will answer other questions for reference in sometime. 

We discovered the issue on Custom Board, it seems the Decoupling Capacitors on VDD_SYS and VDD_CORE are the root cause as we have not installed those considering the power is provided internally by LDO.

About NXP Dev Board - EVAL Board, I am not still sure why it disconnect.

For now I wiil close this Ticket, your timely response is really appreciated.

BR,
Ankit

[tomaru]

Hello @luis_maravilla ,

Apart from the tests I mentioned as additional

I run few More Tests,

1. Test involving separate supply to all Power Sources like VDD_IO, VDD_RF etc.  as per hardware design recommendation, but in all cases, RF drops at 2.1-2.2V.

2. I found that once I run my KW45 in PMIC Mode - Separate Bench Power Supply in all 4 Sources as Mentioned in Hardware Recommendation Guide, I see no RF drop till 1.8V which is exactly what is expected as per KW45 Spec.

Again, I will inform the code I am running - 
1. Custom Code to TX202 Bytes of Data using DLE.
2. KW45 SDK Provided WUART Code

Behavior is same in either case.

Waiting for resolution for the query.

RD-KW45-LOCALIZATION KW45B41Z-EVK KW45 BLE-NFC