topic Re: MKW36 VDD_1P8Out issue in Wireless MCU

MKW36 VDD_1P8Out issue

Sharma — Thu, 22 Jan 2026 10:35:34 GMT

Hello NXP Team,

We are using MKW36A512VFT4 as wireless BLE controller in my application. The application periodically acquires Tri-axis accelerometer data using SPI com in MKW36 and transfers periodic data to mobile App via BLE communication.

We are using MKW36 in Buck Mode power supply with the following connections:

Pins PSWITCH, DC_DC CFG, VDD_0, VDDA,VDD_1, VDCDC_IN, VREFH are connected to 3.3V with multiple 10uF/0.1uF Decoupling capacitors.

Pins VDD1P5OUT, VDD_RF1,VDD_RF2,VDD_RF3 are connected together and decoupling capacitor 10uF/0.1uF added to GND

Pins DC_DC_LP, DC_DC_Ln_1 are connected using a 10uH inductor

Pins VREFL, VSSA , GANT are connected GND

With the above power supply configuration, MKW36 can be programmed if the unused pin VDD_1POUT is left unconnected. If a Filter capacitor 10uF is used for the internal LDO, we are not able to program the MKW36 using MCU express . So can we keep the unused VDD_1POUT pin leave open in the ckt.?

Is MKW36 works only with inverted F antenna and doesn't work with PCB antenna like ANT3216A063R2400A ?. Please clarify

Regards

Sharma

Re: MKW36 VDD_1P8Out issue

Ricardo_Zamora — Thu, 22 Jan 2026 18:50:42 GMT

Hello,

Hope you are doing well. Can you please clarify what pin are you referring to? VDD_1P8OUT?

What DCDC mode are you using? You can refer to: AN5025.pdf

And related the antenna, you can refer to: Hardware Design Considerations for MKW35A/36A/35Z/36Z Bluetooth Low Energy Devices (section 5.3).

For example, our FRDM can be used with the printed f antenna, or switch to an external antenna connected to the SMA RF port.

Best Regards,

Ricardo

Re: MKW36 VDD_1P8Out issue

Sharma — Fri, 23 Jan 2026 05:57:19 GMT

Hello Ricardo,

I am doing good. Thanks for your quick reply on my query.

Here are the additional details on my question especially VDD_1P8 supply line.

We referred to the document AN5025 while designing power supply section for the application. We used Buck Mode of operation with AutoStart option as below with slight modification.

Sharma_0-1769146921284.png

In my last query, I was referring to the pin VDD_1P8. We had connected VDD_0 and VDD_1 to 3.3V source since we have an external accelerometer (3.3v ) connected on SPI communication to MKw36. Similarly we had connected VREFH,VDDA to 3.3V to power Analog section. Also we understood that it is recommended to connect a 10uF capacitor to GND for the VDD_1P8 pin.

With the above connection, If the VDD_1P8 pin is terminated using a 10uF capacitor to GND, we were not able to program the MKW36. If we keep the VDD_1P8 pin left open( No capacitor to GND), able to program the MKW36 IC using MCU Expresso. So in our design, do we need to keep the LDO o/p pin left open.

Let me know if you need any additional info on this query.

Regards

Sharma

Re: MKW36 VDD_1P8Out issue

Ricardo_Zamora — Tue, 27 Jan 2026 17:33:37 GMT

Hello,

I would recommend following the recommended design from the Application Note.

Using another configuration of DCDC, could cause unexpected behavior.

Best Regards,

Ricardo

Re: MKW36 VDD_1P8Out issue

Sharma — Wed, 28 Jan 2026 06:37:59 GMT

Hello Recardo,

In our design, especially VDD_0 and VDD_1 are connected to 3.3V since we have an I/O interface (Tri axis accelerometer ) device operating at 3.3V connected over SPI to MKW36 IC. Similarly to get better ADC resolution and noise immunity, we have connected VDDA and VREFH to 3.3 V. More over as per AN5025 application note, they are all 3.3V compatible , ( VDD_0 , VDD_1 , VDDA and VREFH ) .

So I am not sure the issue with our current design in keeping VDD_1P8 Out pin connected across capacitor to GND . Can I continue to use the same design by keeping VDD_1P8 Out pin open?

Regards,

Sharma

Re: MKW36 VDD_1P8Out issue

Sharma — Wed, 28 Jan 2026 10:09:57 GMT

Hello Ricardo,

Referring to Application note, can I use a single 3V coin cell battery to power up the MKW36 IC in bypass Mode as below. Please let me know.

Sharma_0-1769594863462.png

Re: MKW36 VDD_1P8Out issue

Ricardo_Zamora — Tue, 03 Feb 2026 21:47:00 GMT

Hello,

I would recommend checking this community post:

KW35_36 Bluetooth LE Power Profile Calculator Tool

Best Regards,

Ricardo