3.5. Powering Raspberry Pi Pico W

The simplest way to power Pico W is to plug in the micro-USB, which will power VSYS (and therefore the system) from
the 5V USB VBUS voltage, via D1 (so VSYS becomes VBUS minus the Schottky diode drop).

If the USB port is the only power source, VSYS and VBUS can be safely shorted together to eliminate the Schottky diode
drop (which improves efficiency and reduces ripple on VSYS).

If the USB port is not going to be used, it is safe to power Pico W by connecting VSYS to your preferred power source (in
the range ~1.8V to 5.5V).

 IMPORTANT

If you are using Pico W in USB host mode (e.g. using one of the TinyUSB host examples) then you must power Pico
W by providing 5V to the VBUS pin.

The simplest way to safely add a second power source to Pico W is to feed it into VSYS via another Schottky diode (see
Figure 7). This will ‘OR’ the two voltages, allowing the higher of either the external voltage or VBUS to power VSYS, with
the diodes preventing either supply from back-powering the other.

For example a single Lithium-Ion cell* (cell voltage ~3.0V to 4.2V) will work well, as will three AA series cells (~3.0V to ~4.8V) and any other fixed supply in the range ~2.3V to 5.5V. The downside of this approach is that the second power supply will suffer a diode drop in the same way as VBUS does, and this may not be desirable from an efficiency perspective or if the source is already close to the lower range of input voltage allowed for the RT6154.

VBUS VSYS
WL_GPIO2
R2
100K
1%
M060 3
50 mW
C1
47u
6.3V
20 %
M2012
X5R
R10
10K
1%
M060 3
50 mW
D1
MBR120VLS FT1G
2 1
R1
10K
1%
M060 3
50 mW
3V3_E N
V
D
Feed VSYS pin f rom
external supply (V) via
Schotty diode (D)
Figure 7. Pico W
power ORing using
diodes.

An improved way to power from a second source is using a P-channel MOSFET (P-FET) to replace the Schottky diode as
shown in Figure 8. Here, the gate of the FET is controlled by VBUS, and will disconnect the secondary source when
VBUS is present. The P-FET should be chosen to have low on resistance, and therefore overcomes the efficiency and
Raspberry Pi Pico W Datasheet

3.5. Powering Raspberry Pi Pico W 13

voltage-drop issues with the diode-only solution.

Note that the Vt
(threshold voltage) of the P-FET must be chosen to be well below the minimum external input voltage,
to make sure the P-FET is turned on swiftly and with low resistance. When the input VBUS is removed, the P-FET will not
start to turn on until VBUS drops below the P-FET’s Vt
, meanwhile the body diode of the P-FET may start to conduct
(depending on whether Vt
is smaller than the diode drop). For inputs that have a low minimum input voltage, or if the PFET gate is expected to change slowly (e.g. if any capacitance is added to VBUS) a secondary Schottky diode across
the P-FET (in the same direction as the body diode) is recommended. This will reduce the voltage drop across the PFET’s body diode.
An example of a suitable P-MOSFET for most situations is Diodes DMG2305UX which has a maximum Vt
of 0.9V and
Ron of 100mΩ (at 2.5V Vgs).
VBUS VSYS
WL_GPIO2
R2
100K
1%
M060 3
50 mW
C1
47u
6.3V
20 %
M2012
X5R
R10
10K
1%
M060 3
50 mW
D1
MBR120VLS FT1G
2 1
R1
10K
1%
M060 3
50 mW
3V3_E N
V
Feed VSYS pin f rom
external supply (V)
via P-channel
MOSFET
Figure 8. Pico W
power ORing using P
channel MOSFET.
 CAUTION
If using Lithium-Ion cells they must have, or be provided with, adequate protection against over-discharge, overcharge, charging outside allowed temperature range, and overcurrent. Bare, unprotected cells are dangerous and can
catch fire or explode if over-discharged, over-charged or charged / discharged outside their allowed temperature
and/or current range.
3.6. Using a batt