UM2179 datasheet(23/48 Pages) STMICROELECTRONICS

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UM2179 Rev 9

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UM2179

Hardware layout and configuration

Using VIN or E5V as an external power supply

When powered by VIN or E5V, it is still possible to use the ST-LINK for only programming or

debugging, but it is mandatory to power the board first using VIN or E5V, then to connect the

USB cable to the PC. In this way the enumeration succeeds, thanks to the external power

source.

The following power-sequence procedure must be respected:

Connect jumper JP6 between pin 1 and pin 2 for E5V or between pin 7 and pin 8 for VIN

Check that JP1 is removed

Connect the external power source to VIN or E5V

Power on the external power supply 7 V< VIN < 12 V to VIN, or 5 V for E5V

Check that the green LED LD6 is turned ON

Connect the PC to the USB connector CN1

If this order is not respected, the board may be powered by USB (U5V) first, then by VIN or

E5V as the following risks may be encountered:

If the board needs more than 300 mA, the PC may be damaged or the current supplied

can be limited by the PC. As a consequence the board is not powered correctly.

300 mA is requested during the enumeration phase (since JP1 must be OFF) so there

is the risk that the request is rejected and the enumeration does not succeed if the PC

cannot provide such current. Consequently the board is not power supplied (LED LD6

remains OFF).

External power supply input: + 3.3 V

If 3.3 V is provided by a shield board, it is worth using the +3.3 V (CN8 pin 7 or CN11 pin 16)

directly as power input. In this case the ST-LINK is not powered thus the programming and

debugging features are not available.

When the board is powered with +3.3 V, two different configurations are possible:

•

ST-LINK is removed (PCB cut)

•

SB6 (3.3 V regulator) and JP3 (NRST) are OFF

5.5.3

External power supply output

When powered by USB, VIN or E5V, the +5 V (CN8 pin 9 or CN11 pin 18) can be used as

output power supply for an ST Zio shield or an extension board. In this case the maximum

current of the power source specified in Table 6: External power sources must be respected.

The +3.3 V (CN8 pin 7 or CN11 pin 16) can also be used as power supply output. The

current is limited by the maximum current capability of the regulator U6 (500 mA max).

5.5.4

SMPS power supply

Power figures in Run Mode are significantly improved, by generating Vcore logic supply from

the external DC/DC converter (this function is only available on '-P' suffixed boards).

Board is populated with two different SMPS mounted on U15 and U16:

•

SMPS U15 allows to dynamically supply the VDD_1V2 pins in Run mode at 1.1 V with a

maximum current of 30 mA. For the NUCLEO-L4R5ZI-P, the VDD_1V2 pins in Run

mode are supplied at 1.2 V with a maximum current of 40 mA.

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