2009 Microchip Technology Inc.
Preliminary
DS41338B-page 37
MCV14A
7.2
Oscillator Configurations
7.2.1
OSCILLATOR TYPES
The MCV14A device can be operated in up to six differ-
ent Oscillator modes. The user can program up to three
Configuration bits (FOSC<2:0>). To select one of these
modes:
LP:
Low-Power Crystal
XT:
Crystal/Resonator
HS:
High-Speed Crystal/Resonator
INTRC: Internal 4/8 MHz Oscillator
EXTRC: External Resistor/Capacitor
EC:
External High-Speed Clock Input
7.2.2
CRYSTAL OSCILLATOR/CERAMIC
RESONATORS
In HS, XT or LP modes, a crystal or ceramic resonator
is
connected
to
the
RB5/OSC1/CLKIN
and
RB4/OSC2/CLKOUT
pins
to
establish
oscillation
the use of a parallel cut crystal. Use of a series cut crys-
tal may give a frequency out of the crystal manufactur-
ers specifications. When in HS, XT or LP modes, the
device can have an external clock source drive the
left open and unloaded. Also when using this mode, the
external clock should observe the frequency limits for
the Clock mode chosen (HS, XT or LP).
FIGURE 7-1:
CRYSTAL OPERATION
(OR CERAMIC
RESONATOR)
(HS, XT OR LP OSC
CONFIGURATION)
FIGURE 7-2:
EXTERNAL CLOCK INPUT
OPERATION (HS, XT, LP
OR EC OSC
CONFIGURATION)
TABLE 7-1:
CAPACITOR SELECTION FOR
CERAMIC RESONATORS
Note 1: This device has been designed to per-
form to the parameters of its data sheet.
It has been tested to an electrical
specification designed to determine its
conformance with these parameters.
Due
to
process
differences
in
the
manufacture of this device, this device
may have different performance charac-
teristics than its earlier version. These
differences may cause this device to
perform differently in your application
than the earlier version of this device.
2: The user should verify that the device
oscillator
starts
and
performs
as
expected. Adjusting the loading capacitor
values and/or the Oscillator mode may
be required.
Osc
Type
Resonator
Freq.
Cap. Range
C1
Cap. Range
C2
XT
4.0 MHz
30 pF
HS
16 MHz
10-47 pF
Note 1:
These values are for design guidance
only. Since each resonator has its own
characteristics, the user should consult
the resonator manufacturer for
appropriate values of external
components.
Note
1:
See Capacitor Selection tables for
recommended values of C1 and C2.
2:
A series resistor (RS) may be required for AT
strip cut crystals.
3:
RF approx. value = 10 M
Ω.
C1(1)
C2(1)
XTAL
OSC2
OSC1
RF(3)
Sleep
To internal
logic
RS(2)
MCV14A
Clock From
ext. system
MCV14A
OSC2/CLKOUT/RB4
RB5/OSC1/CLKIN
OSC2/CLKOUT/RB4(1)
EC, HS, XT, LP
Note 1:
RB4 is available in EC mode only.