UM2032 datasheet(14/48 Pages) STMICROELECTRONICS

14 / 48 page

Hardware layout and configuration

UM2032

14/48

DocID029078 Rev 2

Figure 8. R90 and R92 resistors

6.3.4

Supplying the 32F412GDISCOVERY through

the ST-LINK/V2-1 USB port

To power the 32F412GDISCOVERY through the ST-LINK/V2-1, the USB host (a PC) gets

connected with the 32F412GDISCOVERY Micro-B USB receptacle CN6, via a USB cable.

This event starts the USB enumeration procedure. In its initial phase, the current supply

capability of the USB port located on the host, is limited to 100 mA. It is enough because

only the ST-LINK/V2-1 part of the 32F412GDISCOVERY discovery kit draws power at that

time. If the solder bridge SB18 is open (default configuration), the U8 ST890 power switch is

set to OFF position, and only the ST-LINK/V2-1 is powered. In the next phase of the

enumeration procedure, the host PC informs the ST-LINK/V2-1 facility of its capability to

supply up to 500 mA of current. If the answer is positive, the ST-LINK/V2-1 sets the U8

ST890 switch to ON position to supply power to the remainder of the 32F412GDISCOVERY

discovery kit. If the PC USB port is not capable of supplying up to 500 mA of current,

another power source should be used like VIN pin of connector CN2.

Should a short-circuit occur on the discovery kit, the ST890 power switch protects the USB

port of the host against current demand exceeding 600 mA. In such an event, the red LED

FAULT LD10 lights on.

The 32F412GDISCOVERY discovery kit can also be supplied from a USB power source not

supporting enumeration, such as a USB charger. In this particular case, SB18 solder bridge

must be closed. ST-LINK/V2-1 turns the ST890 power switch ON regardless of the

enumeration procedure result and passes the power unconditionally to the discovery kit.

The green LED LD6 turns on whenever the discovery kit is powered.

UM2032 Datasheet(PDF) 14 Page - STMicroelectronics