AN1740 Freescale Semiconductor / Motorola, AN1740 Datasheet - Page 7

• Manufacturer Part Number: AN1740
• Description: Applications Using the Analog Subsystem on MC68HC05JJ/JP Series Microcontrollers
• Manufacturer: Freescale Semiconductor / Motorola

Voltage Comparators
Comparator 1
AN1740
MOTOROLA
The voltage comparators are a basic design, but allow software
compensation for the offset voltage.
both voltage comparators. The common-mode voltage range is
sufficient for most low-level signal sources, but may be a limiting factor
for some applications where the input source must swing from V
V
Comparator 1 is a basic voltage comparator with its positive and
negative inputs tied permanently to the PB2 and PB3 pins respectively.
Its output can be monitored by both dynamic output and static flag bits
in the ASR (analog status register) located at address $001E. The
dynamic output bit, CMP1, becomes a logical 1 whenever the
comparator’s positive input is above its negative input and it follows the
output of the comparator regardless of its prior conditions. The static flag
bit, CPF1, becomes set whenever there is a rising output from the
comparator and remains set until cleared by writing a logical 1 to the
reset bit, CPFR1. Therefore, the CPF1 bit can be used to capture events
when the comparator’s positive input was above its negative input.
Comparator 1, therefore, permits software subroutines to either poll the
Common mode input range
Input offset
Input impedance (with input pulldowns OFF)
Response time
Supply current
DD
Freescale Semiconductor, Inc.
Direct, either comparator
With divider connected to comparator 2
Output Switching (10 mV overdrive)
Power up delay (analog bias ON)
Power up delay (analog bias OFF)
Comparator only
Bias source for both comparators
.
For More Information On This Product,
Table 1. Typical Voltage Comparator Features
Go to: www.freescale.com
Characteristic
Table 1
Symbol
t
t
t
CDELAY
CDELAY
V
CPROP
I
I
shows the main features of
V IO
Z
Z
DDC
DDC
CMR
IN
IN
V
Voltage Comparators
DD
1000
Typ
120
100
10
65
1
2
5
–1.5
Application Note
Units
SS
mV
k
k
V
s
s
s
to
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