UM0401 datasheet(6/17 Pages) STMICROELECTRONICS

6 / 17 page

Getting started

UM0401

6/17

1.4.1

Power supply

The demo board should be powered from an external supply of 5 V, 1 A. (Connector X1 is

for +5 V and Connector X2 is GND). This supply is regulated to get the required VCC, VIO

and Vpull-up voltages by adjusting the Resistor divider components.

Figure 3 below shows the Voltage regulation circuit used. For example, a VCC of 1.8 V can

be achieved by fixing the R6_1 resistor to 680 ohms and calculating R7_1 using the formula:

Equation 1

where, the VOUT we need is 1.8 V, VREF is 1.25 V and IADJ is 50 µA.

By default, the resistors are chosen to fix the voltages at VCC = 1.8 V, VIO = 3.3 V and

Vpull-up = 2.3 V in the demo board.

Figure 3.

Voltage regulation from +5 V supply (VIN)

1.4.2

Jumper settings

There are several jumpers on the board that should be properly set to ensure proper

functioning of the board.

●

JP10_1: as shown in Figure 4 below, the JP10_1 jumper should be set to power the

voltage Regulators with +5V from the X1 and X2 connectors. This is the main power

connection for all the components on the board.

Figure 4.

JP10_1 for Power supply

OUT

REF

-------------------

⎝⎠

⎛⎞ I

ADJR71

UM0401 Datasheet(PDF) 6 Page - STMicroelectronics