A user can evaluate the current consumption of PN7642 in low power modes with the help of the PN7642 Evaluation Board (OM27642) and:
- MCUXpresso SKD example (LPCD)
- NFC Cockpit or MCUXpresso SKD example (ULPCD)
NXP defines the current consumption in ULPCD/LPCD as VBAT current + VDDIO current for the LPCD/ULPCD cycle time of 330 ms. Make sure that DC/DC is disabled (for ULPCD).
Where: VBAT current = VBAT_Current + VBATPWR_Current + VUP_Current
See the snapshot from the PN7642 Datasheet below:
See where to measure the currents on PN7642 EVK:
J63 and J64 are used for enabling/disabling the LEDs that are connected to PN7642 GPIOs. They must be disabled for a proper VDDIO current measurement.
A modification of R69 and R70 is necessary to perform the current measurement on VDDIO in LPCD mode.
1. ULPCD current consumption evaluation
For the ULPCD evaluation, the NFC Cockpit or SDK example can be used. In this article, we will focus on evaluation using the NFC Cockpit.
See the used ULPCD configuration:
Note: The current should be measured as an average over, e.g., 30 seconds.
1.1 Overall ULPCD current measurement
To measure all currents together on PN7642 EVK, a user can create a measurement fixture as shown below:
Then the overall results look as follows:
Note: The Antenna is tuned to approx. 35 Ohms
In this case, the ULPCD current is approximately 21 μA.
This current can be further optimized, for more details, see -> AN14518(Start-up optimization in ULPCD (PN5190/PN7642/PN76AC))
2. LPCD current consumption evaluation
The user has to import the example (pnev7642fama_nfc_low_power_mode_Pub) from the PN7642 SDK.
Before building it, the following change in the code has to be made:
-> Comment line 84
A user can adjust the LPCD cycle time as shown below:
1.1 VBAT Current measurement
In this case, the VBAT current is approximately 123 μA.
1.2 VBATPWR current measurement
In this case, the VBAT_PWR current is approximately 91,8 μA.
1.3 VUP Current measurement
In this case, the VBAT_PWR current is approximately 32,8 μA.
Note: This current depends on the LPCD VDPPA settings + Antenna Impedance tuning
1.4 VDDIO Current measurement
Note: Before VDDIO measurement, place jumpers J63 and J64 on PN7642 EVK. This will disable LEDs that are connected to PN7642 GPIOs.
The VDDIO current measurement requires the following steps:
- Run the "pnev7642fama_nfc_low_power_mode_Pub" example
- Once the example is running, disconnect the debugger (J-link, LPC-Link...) from J21 (NFC Debug connector)
- Remove R70
- Populate a 10K resistor on the R69 position (it disables the SWD interface)
- Once the measurement is done, change it back to the default state (R70=0R, R69=Open).
Note: It is recommended to prepare the board with the option to easily populate or remove R70 and R69 when the LPCD example is running. E.g., with the help of jumpers/pin headers as shown below.
Only then will the correct VDDIO be measured on PN7642 EVK.
See the VDDIO current measurement below:
In this case, the VDDIO current is approximately 5,48 μA.
Then the overall current comsumption in LPCD is I_VBAT + I_VDDIO= (123 + 91,8 + 32,8 + 5,48) = 253,08 μA
Note: For this measurement, the NFC Cockpit is not suitable because the IC does not go into standby mode between LPCD RF pings. Meaning LPCD works normally, but a user can measure higher current consumption.
Used Ampere meter -> Power Profiler Kit II
Measurement has been performed with FW 2.6
Board supply (jumpers J1, J2 and J4) -> 3.3V
Please note that this measurement is indication only!
