10F202 datasheet(33/88 Pages) MICROCHIP

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DS40001239F-page 33

PIC10F200/202/204/206

8.2

Comparator Operation

A single comparator is shown in Figure 8-2 along with

the relationship between the analog input levels and

the digital output. When the analog input at VIN+ is less

than the analog input VIN-, the output of the comparator

is a digital low level. When the analog input at VIN+ is

greater than the analog input VIN-, the output of the

comparator is a digital high level. The shaded areas of

the output of the comparator in Figure 8-2 represent

the uncertainty due to input offsets and response time.

See Table 12-1 for Common Mode Voltage.

FIGURE 8-2:

SINGLE COMPARATOR

8.3

Comparator Reference

An internal reference signal may be used depending on

the Comparator Operating mode. The analog signal

that is present at VIN- is compared to the signal at VIN+

and the digital output of the comparator is adjusted

accordingly (Figure 8-2). Please see Table 12-1 for

internal reference specifications.

8.4

Comparator Response Time

Response time is the minimum time, after selecting a

new reference voltage or input source, before the

comparator output is to have a valid level. If the

comparator inputs are changed, a delay must be used

to allow the comparator to settle to its new state. Please

see

Table 12-1

for

comparator

response

time

specifications.

8.5

Comparator Output

The comparator output is read through CMCON0

may also be used internally, see Figure 8-1.

8.6

Comparator Wake-up Flag

The comparator wake-up flag is set whenever all of the

following conditions are met:

•CWU = 0 (CMCON0<0>)

• CMCON0 has been read to latch the last known

state of the CMPOUT bit (MOVF CMCON0, W)

• Device is in Sleep

• The output of the comparator has changed state

The wake-up flag may be cleared in software or by

another device Reset.

8.7

Comparator Operation During

Sleep

When the comparator is active and the device is placed

in Sleep mode, the comparator remains active. While

the comparator is powered-up, higher Sleep currents

than shown in the power-down current specification will

occur. To minimize power consumption while in Sleep

mode, turn off the comparator before entering Sleep.

8.8

Effects of a Reset

A Power-on Reset (POR) forces the CMCON0 register

to its Reset state. This forces the comparator module to

be in the comparator Reset mode. This ensures that all

potential inputs are analog inputs. Device current is

minimized when analog inputs are present at Reset

time. The comparator will be powered-down during the

Reset interval.

8.9

Analog Input Connection

Considerations

A simplified circuit for an analog input is shown in

Figure 8-3. Since the analog pins are connected to a

digital output, they have reverse biased diodes to VDD

and VSS. The analog input therefore, must be between

VSS and VDD. 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

10 k



recommended for the analog sources. Any external

component connected to an analog input pin, such as

a capacitor or a Zener diode, should have very little

leakage current.

–

Vin+

Vin-

Result

VIN-

VIN+

Note:

Analog levels on any pin that is defined as

a digital input may cause the input buffer

consume

current

than

specified.

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