nRF 7002 current draw

[Samuel Carey]

The nRF7002 datasheet lists that the current draw for maximum power transmits is ~170 - 260mA depending on frequency and if you are using the CSP or QFN package. Please confirm that this current is drawn from the VBAT net and that it includes the complete power draw of the unit, not just the transmit sub-section.

Please also confirm the maximum current draw of IOVDD.

[Samuel Carey]

Similarly, this link says that the wifi transmission power has NO control? 

https://nrfconnectdocs.nordicsemi.com/addons/ncs-matter/latest/matter/getting_started/transmission_power.html?utm_source=kapa

Is it true that we will have no control over the transmit power of the device? Especially given that this website shows that in 'DTIM' mode the maximum power draw is much lower than in 'TWT' mode.

https://devzone.nordicsemi.com/power/w/opp/14/online-power-profiler-for-wi-fi

[matt.heins]

The current draw for tx is only the current for the amplifier to transmit and not the rest of the chip. It is the power drawn on VBAT for Tx only and doesn't include the rest of the circuitry.

IOVDD current is not specified because it is very low, in the noise relative to the Wi-Fi work. IOVDD only supplies the SPI port, the interrupt line and coexistence pins all of which should be generally high impedance so I would estimate current on average to be very low, below 1mA by a bunch. 

The page you reference is about Matter over Wi-Fi and appears to pertain to that context. You can specify maximum Tx power in the devicetree. You can use the nRF7002-EBII as a reference. 

&nordic_expansion_spi {
        status = "okay";

        nrf70: nrf7002-spi@0 {
                compatible = "nordic,nrf7002-spi";
                status = "okay";
                reg = <0>;
                spi-max-frequency = <DT_FREQ_M(8)>;     /* 8 MHz */

                /* Maximum TX power limits for 2.4 GHz (dBm) */
                wifi-max-tx-pwr-2g-dsss = <21>;
                wifi-max-tx-pwr-2g-mcs0 = <16>;
                wifi-max-tx-pwr-2g-mcs7 = <16>;

                /* Maximum TX power limits for 5 GHz (dBm) */
                wifi-max-tx-pwr-5g-low-mcs0 = <13>;
                wifi-max-tx-pwr-5g-low-mcs7 = <13>;
                wifi-max-tx-pwr-5g-mid-mcs0 = <13>;
                wifi-max-tx-pwr-5g-mid-mcs7 = <13>;
                wifi-max-tx-pwr-5g-high-mcs0 = <12>;
                wifi-max-tx-pwr-5g-high-mcs7 = <12>;

                iovdd-ctrl-gpios = <&nordic_expansion_header 5 GPIO_ACTIVE_HIGH>;
                bucken-gpios = <&nordic_expansion_header 4 GPIO_ACTIVE_HIGH>;
                host-irq-gpios = <&nordic_expansion_header 14 GPIO_ACTIVE_HIGH>;

                wlan0: wlan0 {
                        compatible = "nordic,wlan";
                };
        };
};

TWT is substantially lower power than DTIM. You can sleep for days at low uA. With DTIM, you need to ping the router constantly, at a minimum once per second. The difference can be many orders of magnitude lower with TWT. 

[Samuel Carey]

Thank you for the quick reply Matt. I appreciate you jumping in.

My concern with the current draw of the transmit section comes from our intention to use the npm1300 to supply 3.0V to the nRF7002. However, the bucks of the npm1300 are limited to 200mA maximum draw, so I presumed we could/would turn down the maximum power that the 7002 transmits at to limit our instantaneous current draw. Do you think this will be achievable with only limiting by one or two dB and keep the entire system below 200mA at 3.0V?

Finally, I have found one forum post talking about powering the 7002 via the 1300's VSYS rather than the 1300's bucks. If we do that there would be no current limitation. However, I have a couple concerns. The 7002 datasheet shows an absolute maximum input voltage of 4.5 but does not list a nominal. Can you please confirm that a continuous input of 4.2V from VSYS to VBAT will not damage the 7002? Similarly, VSYS from the npm1300 is unregulated. I can't have the RF output power from the 7002 varying as the input voltage changes. Can you please confirm that the 7002's RF output power is completely agnostic of the VBAT voltage as long as that voltage is within operational values?

reference forum post: https://devzone.nordicsemi.com/f/nordic-q-a/126318/power-management-of-nrf7000-using-npm1300 

[Kenneth]

Hello,

Lowering the output power will reduce the current consumption, you can see this for instance by adjusting the TX power steps in the online power profiler for a TX beacon (though the online power profiler only have 3 steps):
https://devzone.nordicsemi.com/power/w/opp/14/online-power-profiler-for-wi-fi 

The nominal voltage is 3.6V, using 4.2 is fine, since it's lower than the maximum 4.5:
https://docs.nordicsemi.com/r/bundle/ps_nrf7002/page/chapters/recommended_op_conditions/doc/recommended_op_conditions.html 

You can find expected variation in output power (in dB) as function of supply voltage and temperature here:
https://docs.nordicsemi.com/r/bundle/ps_nrf7002/page/chapters/elspec/doc/electrical_specification.html 

Hope that helps,
Kenneth