L9803 datasheet(32/126 Pages) STMICROELECTRONICS

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Voltage Regulator

L9803

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4.2

Digital Section Power Supply

The digital supply voltage VDD is available at pin number 42 and 9. The digital ground GND

is available at pin number 43 and 12.

Pin 42 and 43 are the actual voltage regulator output and external loads must be supply by

these pin. The 100nF compensation capacitor should be connected as close as possible to

pin 42 and 43.

Pin number 9 and 12 provide an external access to the internal oscillator supply.

Resonator’s capacitors should be grounded on pin 12.

The application board can improve noise reduction in the chip connecting directly pin 42 to

pin 9 and pin 43 to pin 12 using traces as short as possible. An additional capacitor mounted

close to pin 9 and 12 can lead additional improvement.

4.2.1

VDD Short Circuit Protection

The output current of the digital voltage regulator is controlled by a circuit that limits it to a

maximum value (IMAXVDD). When the output current exceeds this value the VDD voltage

starts falling down. External loads must be chosen taking in account this maximum current

capability of the regulator.

4.3

Analog Section Power Supply

The analog supply voltage is available on VCC pin. The external 100nF compensation

capacitor should be placed as close as possible to this pin and AGND pin.

VCC is the reference voltage for the AD conversion and must be used to supply ratiometric

sensors feeding AD inputs. Any voltage drop between VCC pin and the sensor supply pin on

the application board, will cause the ADC to be inaccurate when reading the sensor’s

output.

4.3.1

VCC Short Circuit Protection

The output current of the analog voltage regulator is controlled by a circuit that limits it to a

maximum value (IMAXVCC). When the output current exceeds this value the VCC voltage

starts falling down. External loads must be chosen taking in account this maximum current

capability of the regulator.

Warning:

The pin VB2 is not short circuit protected so a short circuit

on this pin will destroy the device.

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