PM8903A datasheet(28/33 Pages) STMICROELECTRONICS

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PM8903A demonstration board

PM8903A

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Doc ID 024147 Rev 1

7.1.1

Power input (VIN)

Connect a power supply to connectors J4(VIN) and J5(GND) on the demonstration board to

provide voltage on the power input pins of both devices. Input voltage can range from 2.8 V

to 6 V bus.

If the voltage is between 2.9 V and 5.5 V, it can also supply the signal input pins of both

devices (through the VCC pin). In this case, make sure that resistors R2/R20 are NM (not

mounted) and mount 0

Ω resistors on R1/R19 locations.

7.1.2

Signal input (VCC)

The controller is usually supplied separately from the power stage through the VCC input

pins.

Connect a power supply to connector J2 (pin one is VC and pin two is GND) on the

demonstration board to provide voltage on the signal input pins of both devices. Supply

voltage can range from 2.9 V to 5.5 V.

7.1.3

Output (VOUT)

On the standard demonstration board, the output voltage is programmed to be 1.5 V, but it

can be easily changed mounting one of the values suggested in

Table 9.

Select the ROS (R16/R34) resistor value with the following formula in order to program a

custom value for the output voltage of each device.

where:

●

VOUT is the desiderated output voltage

●

VREF is the internal voltage reference (0.6 V)

●

RFB resistor, on the demonstration board, is the sum of two resistors (R14/R15 for

device U1 and R32/R33 for device U2) and has a total value of 3.3 k

Ω.

Table 9.

Typical ROS resistors (R16/R34)

Programmed output voltage

Resistor value

0.6 V

0.8 V

10 k

1.0 V

4.9 k

1.2 V

3.3 k

1.5 V

2.2 k

1.8 V

1.65 k

2.5 V

1 k

REF

OUT

REF

–

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

⋅

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