Actel Fusion Mixed-Signal FPGAs
RC Oscillator
The RC oscillator is an on-chip free-running clock source generating a 100 MHz clock. It can be used
as a source clock for both on-chip and off-chip resources. When used in conjunction with the Fusion
PLL and CCC circuits, the RC oscillator clock source can be used to generate clocks of varying
frequency and phase.
The Fusion RC oscillator is very accurate at 1% over commercial and industrial temperature
ranges. It is an automated clock, requiring no setup or configuration by the user. It requires only
that the power and GNDOSC pins be connected; no external components are required. The RC
oscillator can be used to drive either a PLL or another internal signal.
RC Oscillator Characteristics
Table 2-9 • Electrical Characteristics of RC Oscillator
Parameter
Description
Conditions
Min.
Typ.
Max. Units
FRC
Operating
100
MHz
Frequency
Accuracy
Temperature: 0°C to 85°C
1
3
%
%
Voltage: 3.3 V 5%
Temperature: –40°C to 125°C
Voltage: 3.3 V 5%
Output Jitter
Period Jitter (at 5 k cycles)
100
100
150
ps
ps
ps
Cycle–Cycle Jitter (at 5 k cycles)
Period
Jitter
(at
5 k
cycles)
with
1 kHz / 300 mV peak-to-peak noise on power
supply
Cycle–Cycle Jitter (at 5 k cycles) with 1 kHz /
300 mV peak-to-peak noise on power supply
150
ps
Output Duty Cycle
Operating Current
50
1
%
IDYNRC
mA
Preliminary v1.7
2-21
ACTEL [ Actel Corporation ]
