Microchip Technology MCP1630DM-DDBS1 Ficha De Dados

DS41211D-page 52

©

 2007 Microchip Technology Inc.

A simplified circuit for an analog input is shown in
Figure 8-3. Since the analog input pins share their con-
nection with a digital input, they have reverse biased
ESD protection diodes to V

DD

 and V

SS

. The analog

input, therefore, must be between V

SS

 and V

DD

. If the

input voltage deviates from this range by more than
0.6V in either direction, one of the diodes is forward
biased and a latch-up may occur.

A maximum source impedance of 10 k

Ω

 is recommended

for the analog sources. Also, any external component
connected to an analog input pin, such as a capacitor or
a Zener diode, should have very little leakage current to
minimize inaccuracies introduced.

Note 1: When reading a PORT register, all pins

configured as analog inputs will read as a
‘

0

’. Pins configured as digital inputs will

convert as an analog input, according to
the input specification.

2: Analog levels on any pin defined as a

digital input, may cause the input buffer to
consume more current than is specified.

V

A

Rs < 10K

C

PIN

5 pF

V

DD

V

T

 

≈

 0.6V

V

T

 

≈

 0.6V

R

IC

I

LEAKAGE

±500 nA

Vss

A

IN

Legend: C

PIN

= Input Capacitance

I

LEAKAGE

= Leakage Current at the pin due to various junctions

R

IC

= Interconnect Resistance

R

S

= Source Impedance

V

A

= Analog Voltage

V

T

= Threshold Voltage

To ADC Input