DSPIC30F4012 datasheet(148/238 Pages) MICROCHIP

148 / 238 page

dsPIC30F4011/4012

DS70135G-page 148

20.13 Configuring Analog Port Pins

The use of the ADPCFG and TRIS registers control the

operation of the ADC port pins. The port pins that are

desired as analog inputs must have their corresponding

TRIS bit set (input). If the TRIS bit is cleared (output), the

digital output level (VOH or VOL) is converted.

The A/D operation is independent of the state of the

CH0SA<3:0>/CH0SB<3:0> bits and the TRIS bits.

When reading the PORT register, all pins configured as

analog input channels are read as cleared.

Pins configured as digital inputs will not convert an ana-

log input. Analog levels on any pin that is defined as a

digital input (including the ANx pins), may cause the

input buffer to consume current that exceeds the

device specifications.

20.14 Connection Considerations

The analog inputs have diodes to VDD and VSS as ESD

protection. This requires that the analog input be

between VDD and VSS. If the input voltage exceeds this

range by greater than 0.3V (either direction), one of the

diodes becomes forward biased and it may damage the

device if the input current specification is exceeded.

An external RC filter is sometimes added for anti-

aliasing of the input signal. The R component should be

selected to ensure that the sampling time requirements

are satisfied. Any external components connected (via

high-impedance) to an analog input pin (capacitor,

zener diode, etc.) should have very little leakage

current at the pin.

DSPIC30F4012 Datasheet(PDF) 148 Page - Microchip Technology