Ensure to always use a close jumper type on JP1 to avoid any unwanted short-circuit damage to the USB Type-
C
®
Host V
BUS
.
Table 11.
JP1 VIN configuration
Reference
Function
Comment
JP1
[1-2]
VIN connected to USBPD
Connects buck-boost VIN to the V
BUS
from
USB Type-C
®
when the double switch is
activated
OFF
VIN free for use
Enables the use of an external power supply
as buck-boost VIN input voltage
[2-3]
VIN connected to GND
Deactivates buck-boost function, VIN not
accessible
1. The default setting is in bold.
VOUT embedded resistor loads function
is based on two independent and identical resistor networks, each of
them being controlled by the STM32G474RET6 microcontroller. Each network presents an equivalent resistor of
33 Ω and has a fuse, which activates current protection. The Minimum current that will transition the fuse from low
resistance to high resistance is 400 mA at 23 °C. The buck-boost converter output can be loaded with 50 % or
100 % of these resistor loads, with BUCKBOOST_LOAD_50% (PC14) and BUCKBOOST_100%_LOAD (PC15),
which can be activated in any order. The maximum current, which each resistor load network passes without
interruption at +23 °C still air, is 200 mA. For a higher output current capability on VOUT, the external load can be
used on the VOUT connector CN7.
VOUT CN7 connector
is placed on the bottom side of the Discovery board to allow the easy use of additional
external resistor loads on a breadboard.
Note:
If the user wants to exercise I/Os used by the digital power buck-boost converter for another application, it is
very important to disconnect those I/Os from the buck-boost converter, to avoid permanent damage. Serial
resistors are available for this purpose.
13.3
Audio Class-D amplifier
The Discovery board can be used to demonstrate the audio Class-D amplifier application, based on the digital
power buck-boost feature. The JP2/JP3 4-pole connector is used to connect external stereo speakers of 8 Ω total
equivalent impedance. This application requires specific Hardware and software configuration, refer to the
dedicated application note to achieve the best possible performances.
By default, the JP1 VIN header selects power source from USBPD_VBUS of USB Type-C
®
CN2 connector, with a
closing jumper on the JP1 header to connect USBPD and VIN [1-2]. The user may also want to use external VIN,
and in that case, he must connect an external power supply on VIN and GND pins of the JP1 header, and the JP1
jumper must be OFF (Refer to
13.4
RGB power LED
Attention:
According to the photobiological safety of lamps and lamp systems (IEC62471), the B-G474E-DPOW1 product
is rated Risk 1 in its default configuration (low risk). The most restrictive optical radiation is the retinal blue light
hazard 300 to 400 nm. Associated technical reports with exposure hazard values and exposure distance are
deliverable on demand.
Caution:
In case of any modifications of this function, it is the user's own responsibility to ensure safe conditions. Do not
remove the LPB1 diffuser/protection placed over the RGB power LED LD1, else users could expose to higher
hazard values. It is also recommended to keep unchanged the RGB LED current limit examples set in the
Software Demo mode.
Attention:
In case the user wants to use DRIVE or SENSE controls of any RGB LED for another application, it is very
important to disconnect those controls from the buck
‑
LED converters. Serial resistors can be removed for that
purpose (Refer to schematics,
). The user may also alternatively remove SB7, SB8, SB9
to disconnect onboard RGB LED, if sufficient in its application.
UM2577
Audio Class-D amplifier
UM2577
-
Rev 2
page 29/54
