By default, ensure the JP5 is not set on the USBC position. Nevertheless, some exceptions may apply, so refer to
the dedicated application note on this digital power buck
‑
boost function.
In this mode, the USBPD_VBUS nominal voltage must not exceed 15 V. A jumper must be set on JP1 to connect
VIN to USBPD. The double switch function, based on Q12 and Q13 transistors, connects or isolates
USBPD_VBUS and digital power buck
‑
boost VIN input. The double switch is controlled with the
BUCKBOOST_USBPD_EN signal (PC3) respecting the USB standard constraints.
Current protection is implemented to limit current drawn on VIN. This protection is managed thanks to a current
sensing function connected to BUCKBOOST_I_IN_AVG (PA2) for ADC conversion.
13.1.3
Power and data input to the audio Class-D amplifier feature
The USB Type-C
®
CN2 connector can also be used as a power and data input to demonstrate the Audio
Class-D amplifier feature of the B-G474E-DPOW1 product
Section 13.3 Audio Class-D amplifier
The audio Class-D amplifier uses the digital power buck-boost feature of the Discovery board. Audio data are sent
from the USB host through the USB 2.0 FS interface of the CN2 connector. Then, the STM32G474RET6
microcontroller is converting these audio data into HRTimer controls to output audio sound on a speaker
connected on JP2/JP3 footprints.
In this mode, the USBPD_VBUS nominal voltage must not exceed 12 V. A jumper must be set on JP1 to connect
VIN to USBPD.
The double switch function, based on Q12 and Q13 transistors, connects or isolates USBPD_VBUS to/from digital
power buck-boost VIN input. The double switch is controlled with the BUCKBOOST_USBPD_EN signal (PC3)
respecting the USB standard constraints.
Current protection is implemented to limit current drawn on VIN. This protection is managed thanks to a current
sensing function connected to BUCKBOOST_I_IN_AVG (PA2) for ADC conversion.
13.2
Digital power buck-boost converter
The B-G474E-DPOW1 includes a digital power buck-boost converter feature with two embedded resistor load
networks on VOUT.
Attention:
The digital power buck-boost converter feature may not support the JP5 setting on USBC. Refer to dedicated
application note for additional specific conditions.
Caution:
Check that the following default rules are applied, or permanent damage can occur:
•
The VIN input voltage source must not exceed 16 V.
•
When powered from CN2 USB Type-C
®
connector, the buck-boost converter must not consume a current
higher than 1.5 A.
•
The VOUT output voltage must not exceed 16 V.
•
For thermal and safety reason, each VOUT embedded resistor load network is protected against current
higher than 400 mA. Do not shunt the PTC fuse components.
The digital power buck-boost converter is composed of the following block functions:
•
The buck-boost converter function, which is based on HRTimers with advanced control, input/output voltage
regulation, and optionally input current regulation.
•
The double switch function, which isolates or connects the USB Type-C
®
V
BUS
to the buck-boost converter
input VIN.
•
The JP1 VIN header, which selects the input power source of the buck-boost converter (External VIN or VIN
from USB Type-C
®
V
BUS
).
•
The VOUT embedded resistor loads to demonstrate buck-boost behavior with static and dynamic loads.
•
The CN7 VOUT connector, which can be connected to a breadboard for direct access to an external
application.
UM2577
Digital power buck-boost converter
UM2577
-
Rev 2
page 27/54
