UM1688 datasheet(39/41 Pages) STMICROELECTRONICS

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UM1688

How to change the supply configuration of the board

The configuration of the supply voltages can be changed through the jumpers from J1 to J6

as listed in Table 21.

When VREG pin is supplied through an external voltage source, particular care must be

taken in order to avoid that VS voltage falls below the VREG one (e.g. VS is floating and

VREG is supplied). In this case the internal ESD diode is turned on and the device could be

damaged.

Adding a low drop diode between VREG and VS protects the internal ESD diode from this

event.

Table 21. Device supply configurations

Configuration

JP1

JP2

Logic levels

Notes

Logic supplied by the integrated voltage

regulator and VDD shorted to VREG.

Open

Closed

3.3 V logic

compliant.

Default.

Logic supplied by the integrated voltage

regulator and VDD floating.

Open

According to

VDD voltage.

The VDD must be supplied

through the respective test point.

Logic supplied by the integrated voltage

regulator and VDD supplied through the

SPI connector.

Closed

Open

According to

VDD voltage.

The VDD must be supplied

through the SPI connector.

Logic and VDD supplied through the SPI

connector.

Closed Closed

3.3 V logic

compliant.

The supply voltage from the SPI

connector must be 3.3 V.

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