41594B datasheet(51/372 Pages) MICROCHIP

51 / 372 page

 2011-2012 Microchip Technology Inc.

Preliminary

DS41594B-page 51

PIC12LF1840T48A

5.2.1.5

TIMER1 Oscillator

The Timer1 oscillator is a separate crystal oscillator

that is associated with the Timer1 peripheral. It is opti-

mized for timekeeping operations with a 32.768 kHz

crystal connected between the T1OSO and T1OSI

device pins.

The Timer1 oscillator can be used as an alternate sys-

tem clock source and can be selected during run-time

using clock switching. Refer to Section 5.3 “Clock

Switching” for more information.

FIGURE 5-5:

QUARTZ CRYSTAL

OPERATION (TIMER1

OSCILLATOR)

5.2.1.6

External RC Mode

The external Resistor-Capacitor (RC) modes support

the use of an external RC circuit. This allows the

designer maximum flexibility in frequency choice while

keeping costs to a minimum when clock accuracy is not

required.

The RC circuit connects to OSC1. OSC2/CLKOUT is

available for general purpose I/O or CLKOUT. The

function of the OSC2/CLKOUT pin is determined by the

state of the CLKOUTEN bit in Configuration Word 1.

Figure 5-6 shows the external RC mode connections.

FIGURE 5-6:

EXTERNAL RC MODES

The RC oscillator frequency is a function of the supply

voltage, the resistor (REXT) and capacitor (CEXT) values

and the operating temperature. Other factors affecting

the oscillator frequency are:

• threshold voltage variation

• component tolerances

• packaging variations in capacitance

The user also needs to take into account variation due

to tolerance of external RC components used.

Note 1: Quartz crystal characteristics vary according

to type, package and manufacturer. The

user should consult the manufacturer data

sheets for specifications and recommended

application.

2: Always verify oscillator performance over

the VDD and temperature range that is

expected for the application.

3: For oscillator design assistance, reference

the following Microchip Applications Notes:

• AN826, “Crystal Oscillator Basics and

Crystal Selection for rfPIC® and PIC®

Devices” (DS00826)

• AN849, “Basic PIC® Oscillator Design”

(DS00849)

• AN943, “Practical PIC® Oscillator

Analysis and Design” (DS00943)

• AN949, “Making Your Oscillator Work”

(DS00949)

• TB097, “Interfacing a Micro Crystal

MS1V-T1K 32.768 kHz Tuning Fork

Crystal to a PIC16F690/SS” (DS91097)

• AN1288, “Design Practices for

Low-Power External Oscillators”

(DS01288)

32.768 kHz

T1OSI

To Internal

Logic

PIC® MCU

Crystal

T1OSO

Quartz

OSC2/CLKOUT

CEXT

REXT

PIC® MCU

OSC1/CLKIN

FOSC/4 or

Internal

Clock

VDD

VSS

Recommended values: 10 k

  REXT  100 k, <3V

3 k

  REXT  100 k, 3-5V

CEXT > 20 pF, 2-5V

Note 1:

Output depends upon CLKOUTEN bit of the

Configuration Word 1.

I/O(1)

41594B 数据表(PDF) 51 Page - Microchip Technology

41594B 数据表(HTML) 51 Page - Microchip Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

数据表下载