Note that using STLINK-V3E for debugging when powering the board with an external power supply, it is
important to power the board before connecting the host PC to CN15. This requires the following sequence to be
respected:
1.
Set the jumper JP7 “E5V” [7-8].
2.
Connect the external power source to the pin 8 of CN5.
3.
Check that the green LED LD5 is turned ON.
4.
Connect the host PC to USB connector CN15.
If this order is not respected, the board may be powered by V
BUS
first from STLINK-V3E, and the following risks
may be encountered:
1.
If more than 500 mA current is needed by the board, the PC may be damaged or current can be limited by
the PC. As a consequence, the board is not powered correctly.
2.
500 mA is requested at the enumeration step, so there is a risk that the request is rejected and enumeration
does not succeed if the PC cannot provide such current.
Table 5.
External power sources: VIN from 7 to 12V
Input power
name
Connector
pins
Voltage
range
Max current
Limitation
VIN
CN5 pin 8
From 7 V to
12 V
800 mA
From 7 to 12 V only and input current capability is linked to
input voltage:
•
800 mA input current when VIN = 7 V
•
450 mA input current when 7 V < VIN < 9 V
•
250 mA input current when 9 V < VIN < 12 V
6.2.3
Supplying the board with an external USB charger: 5 V
When the STM32H735G-DK board is powered by an external USB charger through CN15, refer to
, the
jumper must be placed on pin 9-10 of JP7 (“CHGR” on the silkscreen). Note that in this power supply mode, the
debug features are not available.
Table 6.
External power source: 5V_USB_CHGR
Input power name
Connector pins
Voltage range
Max current
5V_USB_CHGR
CN15
5 V
-
6.2.4
MCU power supply - SMPS or LDO configurations
There are three possible solutions to provide power to the MCU V
CORE
logic supply: SMPS, LDO, and SMPS with
LDO. Power consumption in Run mode is significantly improved by generating VCORE from the internal DC/DC
converter (SMPS). The default power supply for VCORE logic must be SMPS. Some hardware modifications are
required to switch to LDO or SMPS with LDO configurations. The hardware modifications are listed below:
•
SMPS mode (default):
–
SB2, SB13, SB20, SB21, and L3: ON
–
SB1, SB3, SB16, SB18, and SB19: OFF
•
LDO mode:
–
SB1, SB3, and SB19: ON
–
SB2, SB16, SB18, SB20, SB21, and L3: OFF
•
SMPS with LDO mode:
–
SB3, SB13, SB19, SB21, and L3: ON
–
SB1, SB2, SB16, SB1, and SB20: OFF
Caution:
If the board SMPS/LDO firmware PWR configuration does not match its hardware configuration, a deadlock
occurs. After the reset, the ST-LINK cannot connect to the target anymore.
UM2679
Power supply
UM2679
-
Rev 1
page 13/42
