PIC16F684-ISL Microchip Technology Inc., PIC16F684-ISL Datasheet - Page 58

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PIC16F684-ISL

Manufacturer Part Number
PIC16F684-ISL
Description
Manufacturer
Microchip Technology Inc.
Datasheets

Specifications of PIC16F684-ISL

Case
N/A
Notes
NEW
Date_code
11+
PIC16F684
8.1
Comparator Operation
A single comparator is shown in Figure 8-1 along with
the relationship between the analog input levels and
the digital output. When the analog input at V
than the analog input V
-, the output of the comparator
IN
is a digital low level. When the analog input at V
greater than the analog input V
-, the output of the
IN
comparator is a digital high level. The shaded areas of
the output of the comparator in Figure 8-1 represent
the uncertainty due to input offsets and response time.
Note:
To use CIN+ and CIN- pins as analog
inputs, the appropriate bits must be
programmed in the CMCON0 (19h)
register.
The polarity of the comparator output can be inverted
by setting the CxINV bits (CMCON0<5:4>). Clearing
CxINV results in a non-inverted output. A complete
table showing the output state versus input conditions
and the polarity bit is shown in Table 8-1.
TABLE 8-1:
OUTPUT STATE VS. INPUT
CONDITIONS
Input Conditions
CINV
V
- > V
+
0
IN
IN
V
- < V
+
0
IN
IN
V
- > V
+
IN
IN
1
V
- < V
+
1
IN
IN
FIGURE 8-2:
ANALOG INPUT MODEL
Rs < 10K
A
IN
C
PIN
VA
5 pF
Legend: C
PIN
V
T
I
LEAKAGE
R
IC
R
S
VA
DS41202C-page 56
FIGURE 8-1:
V
+
IN
+ is less
IN
V
-
IN
+ is
IN
V
-
IN
V
IN–
V
+
IN
V
IN+
Output
Output
8.2
Analog Input Connection
Considerations
A simplified circuit for an analog input is shown in
Figure 8-2. Since the analog pins are connected to a
digital output, they have reverse biased diodes to V
and V
. The analog input, therefore, must be between
SS
V
and V
SS
DD
range by more than 0.6V in either direction, one of the
CxOUT
diodes is forward biased and a latch-up may occur. A
0
maximum source impedance of 10 k is recommended
for the analog sources. Any external component
1
connected to an analog input pin, such as a capacitor
1
or a Zener diode, should have very little leakage
0
current.
Note 1: When reading the PORT register, all pins
configured as analog inputs will read as a
‘0’. Pins configured as digital inputs will
convert as analog inputs 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
DD
V
= 0.6V
T
Leakage
V
= 0.6V
T
±500 nA
Vss
= Input Capacitance
= Threshold Voltage
= Leakage Current at the pin due to various junctions
= Interconnect Resistance
= Source Impedance
= Analog Voltage
Preliminary
SINGLE COMPARATOR
+
Output
. If the input voltage deviates from this
R
IC
 2004 Microchip Technology Inc.
DD

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