MC68LC302 Datasheet, PDF (124/169 Pages) Motorola, Inc – Low Power Integrated Multiprotocol Processor Reference Manual

Electrical Characteristics
6.7.1 AC Electrical Characteristics - IMP Phased Lock Loop (PLL)
Characteristics
Characteristics
Expression
Min
Max Unit
VCO frequency when PLL enabled
PLL external capacitor (XFC pin to VCCSYN)
MF * Ef
MF * C_XFC (Note 1.)
@ MF < 5
@ MF > 5
10
f (Note 1.) MHz
MF * 340 MF * 480
pF
MF * 380 MF * 970
1. f is the maximum operating frequency. Ef is EXTAL frequency. CXFC is the value of the PLL capacitor (connected between XFC pin
and VCCSYN) for MF=1. The recommended value for C_XFC is 400pF for MF < 5 and 540pF for MF> 5. The maximum VCO frequency
is limited to the internal operation frequency, as defined above.
Examples:
1. MODCK1,0 = 01; MF = 1 fi 340 ≤ c_XFC ≤ 480 pF
2. MODCK1,0 = 01; crystal is 32.768 KHz (or 4.192 MHz), initial MF = 401, initial frequency
= 13.14 MHz; later, MF is changed to 762 to support a frequency of 25 MHz.
Minimum c_XFC is: 762 x 380 = 289 nF, maximum c_XFC is: 401 x 970 = 390 nF. The recommended
c_XFC for 25 MHz is: 762 x 540 = 414 nF.
289 nF < c_XFC < 390 nF and closer to 414 nF. The proper available value for c_XFC is 390 nF.
3. MODCK1 pin = 1, crystal is 32.768 KHz (or 4.192 MHz), initial MF = 401, initial frequency
= 13.14 MHz; later, MF is changed to 1017 to support a frequency of 33.34 MHz.
Minimum c_XFC is: 1017 x 380 = 386 nF. Maximum c_XFC is: 401 x 970 = 390 nF ⇒ 386 nF < c_XFC <
390 nF.
The proper available value for c_XFC is 390 nF.
3A. In order to get higher range, higher crystal frequency can be used (i.e. 50 KHz), in this
case:
Minimum c_XFC is: 667 x 380 = 253 nF. Maximum c_XFC is: 401 x 970 = 390 nF ⇒ 253 nF < c_XFC < 390
nF.
MOTOROLA
MC68LC302 REFERENCE MANUAL
6-7