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11-6
MC68349 USER'S MANUAL
MOTOROLA
11.6 AC ELECTRICAL SPECIFICATIONS CONTROL TIMING (See notes (a), (b),
and (c) corresponding to part operation, GND = 0 Vdc, TA = 0 to 70
°C; see numbered notes)
3.3 V or 5.0 V
5.0 V
16.78 MHz
25.16 MHz
Num.
Characteristic
Symbol
Min
Max
Min
Max
Unit
System Frequency1
fsys
dc
16.78
dc
25.16
MHz
Crystal Frequency
fXTAL
25
50
25
50
kHz
On-Chip VCO System Frequency
fsys
0.13
16.78
0.13
25.16
MHz
On-Chip VCO Frequency Range
fVCO
0.1
33.5
0.1
50.3
MHz
External Clock Operation
fsys
0
16
0
25
MHz
PLL Start-up Time2
trc
—
20
—
20
ms
Limp Mode Clock Frequency 3
SYNCR X-bit = 0
SYNCR X-bit = 1
flimp
—
fsys/2
fsys
—
fsys/2
fsys
kHz
CLKOUT stability 4
CLK
–1
+1
–1
+1
%
15
CLKOUT Period in Crystal Mode
tcyc
59.6
—
40
—
ns
1B6
External Clock Input Period
tEXTcyc 62.5
—
40
—
ns
1C 7
External Clock Input Period with PLL
tEXTcyc 62.5
—
40
—
ns
2,3 8
CLKOUT Pulse Width in Crystal Mode
tCW
28
—
19
—
ns
2B, 3B9 CLKOUT Pulse Width in External Mode
tEXTCW
28
—
18
—
ns
2C,
3C 10
CLKOUT Pulse Width in External w/PLL Mode
tEXTCW
31
—
20
—
ns
4,5
CLKOUT Rise and Fall Times
tCrf
—
5
—
4
ns
NOTES:
(a) The 16.78-MHz @ 3.3 V
±0.3 V specifications are preliminary and apply to the MC68349V.
(b) The 16.78-MHz @ 5.0 V
±5% specifications are preliminary and apply to the MC68349.
(c) The 25.16 MHz @ 5.0 V
±5% specifications are preliminary and apply to the MC68349.
1.
All internal registers retain data at 0 Hz.
2.
Assumes that a stable VCCSYN is applied, that an external filter capacitor with a value of 0.1 F is attached to
the XFC pin, and that the crystal oscillator is stable. Lock time is measured from power-up to RESET release.
This specification also applies to the period required for PLL lock after changing the W and Y frequency control
bits in the synthesizer control register (SYNCR) while the PLL is running, and to the period required for the clock
to lock after exiting LPSTOP.
3.
Determined by the initial control voltage applied to the on-chip VCO. The X-bit in the SYNCR controls a divide -
by-two scalar on the system clock output.
4.
CLKOUT stability is the average deviation from programmed frequency measured at maximum f sys.
Measurement is made with a stable external clock input applied using the PLL.
5.
All crystal mode clock specifications are based on using a 32.768-kHz crystal for the input.
6.
When using the external clock input mode (MODCK reset value = 0 V), the minimum allowable t EXTcyc period
will be reduced when the duty cycle of the signal applied to EXTAL exceeds 5% tolerance. The relationship
between external clock input duty cycle and minimum t EXTcyc is expressed:
Minimum tEXTcyc period = minimum tEXTCW / (50% – external clock input duty cycle tolerance).
Minimum external clock low and high times are based on a 45% duty cycle.
7.
When using the external clock input mode with the PLL (MODCK reset value = 0 V), the external clock input duty
cycle can be at minimum 20% to produce a CLKOUT with a 50% duty cycle.
8.
For crystal mode operation, the minimum CLKOUT pulse width is based on a 47% duty cycle.