MCXW23 Transmitter Maximum Output Power Override Application Note

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1       Introduction

As documented in the MCX W23 [ERRATA] for WLCSP packaged devices, Tx modulation quality can potentially be violated on 2 data channels, i.e. channels 15 (2432 MHz) and 31 (2464 MHz) in the Long Range (coded) PHY modes. All other channels are not affected. Also the non-coded PHY modes (1 Mbps and 2 Mbps) are not affected.

The occurrence is low, but highest for high transmit output powers. For this reason, the maximum output power has by default been limited to 2 dBm on these 2 channels.

Since the Tx modulation performance testing aims to ensure interoperability between different Bluetooth Low Energy devices and has no impact on regulatory requirements, users could override the default configured limit on maximum output power for these 2 concerned channels. Bluetooth Low Energy (BLE) compliance testing (RFPHY.TS, PFPHY/TRM/BV – 13-C) does not cover these 2 channels.

2     Overriding the transmitter output power limit

2.1      API command

An API command is available, which allows a user to override the Transmitter output power limit of 2 dBm and configure at a higher level.

API command:

Command	OCF	Command arguments	Return parameters
HCI_CMD_OCF_LIMIT_PHY _TX	0x0338	tx_power_limit channels_to_limit_low channels_to_limit_high phy_mask	None

Arguments:

• tx_power_limit: transmitter output power limit, expressed in dBm.
  This power limit must not be higher than the output power supported in the configured power mode.
  • Supported power modes and maximum output power levels:
    • Power mode 0: maximum 2 dBm
    • Power mode 1: maximum 6 dBm
  • channels_to_limit_low: channel selection low mask (channel 0 to channel 31); 32 bits binary mask for the channels on which the power limit is applied.

channels_to_limit_low
Bit position	31	30	29	28 .. 3	2	1	0
Channel #	31	30	29	28 .. 3	2	1	0

• ‘0’: channel not selected
• ‘1’: channel selected
• Fields:
  • LSB = channel 0
  • LSB + 1 = channel 1
  • …
  • MSB = channel 31
• channels_to_limit_high: channel selection high mask (channel 32 to channel 39); 32 bits binary mask for the channels on which the power limit is applied of which only the 8 LSBs are used
  
  

channels_to_limit_high
Bit position	31 ..8		7	6	5 .. 3	2	1	0
Channel #	--		39	38	37 .. 35	34	33	32

• ‘0’: channel not selected
• ‘1’: channel selected
• Fields:
  • LSB = channel 32
  • LSB + 1 = channel 33
  • …
  • LSB + 7 = channel 39
• phy_mask: selection of PHY modes in which the output power limitation is applied; 4 bits
  
  

Bit position	3	2	1	0
PHY mode	Long Range S = 2	Long Range S = 8	2 Mbps	1 Mbps

• ‘0’: PHY mode not selected
• ‘1’: PHY mode selected
• Fields:
  • LSB = 1 Mbps mode
  • LSB +1 = 2 Mbps mode
  • LSB +2 = Long Range S=8 mode
  • LSB +3 = Long Range S=2 mode

2.2      Examples

• To remove the transmitter output power limit on channels 15 and 31 in both Long Range PHY modes:
  • HCI_CMD_OCF_LIMIT_PHY_TX (6, 0x00000000, 0x00000000, 0xC)
    • tx_power_limit = 6 dBm
    • channels_to_limit_low = 0x0000000, no power limit applied to any channel in range 0 .. 31
    • channels_to_limit_high = 0x00000000, no power limit applied to any channel in range 32 .. 39
    • phy_mask = 0xC = 0b1100: selection of both Long Range PHY modes

• To configure a transmitter output power limit of 4 dBm on channels 15 and 31 for Long Range S=8 PHY mode:
  • HCI_CMD_OCF_LIMIT_PHY_TX (4, 0x80008000, 0x00000000, 0x4)
    • tx_power_limit = 4 dBm
    • channels_to_limit_low = 0x8008000, power limit applied to any channels 31 (MSB = 1) and 15 (MSB – 16 = 1)
    • channels_to_limit_high = 0x00000000, no power limit applied to any channel in range 32 .. 39
    • phy_mask = 0x4 = 0b0100: selection of Long Range PHY mode S=8

References: 

https://www.nxp.com/products/MCX-W23

https://www.nxp.com/docs/en/errata/ES_MCXW236XUIK.pdf