ProASIC
PLUS
Flash Family FPGAs
Timing Control and
Characteristics
ProASIC
PLUS
Clock Management System
ProASIC
PLUS
devices provide designers with very flexible
clock conditioning capabilities. Each member of the
ProASIC
PLUS
family contains two phase-locked loop (PLL)
blocks which perform the following functions:
•
•
•
•
•
•
•
•
•
Clock Phase Adjustment via Programmable Delay
(250 ps steps from –7 ns to +8 ns)
Clock Skew Minimization
Clock Frequency Synthesis
Input Frequency Range (f
IN
) = 1.5 to 180 MHz
Feedback Frequency Range (f
VCO
) = 24 to 180 MHz
Output Frequency Range (f
OUT
) = 8 to 180 MHz
Output Phase Shift = 0 ° and 180 °
Output Duty Cycle = 50%
Low Output Jitter (maximum at 25°C)
–
–
–
f
VCO
<10 MHz. Jitter ±1% or better
10 MHz < f
VCO
< 60 MHz. Jitter ±2% or better
f
VCO
> 60 MHz. Jitter ±1% or better
follows (Figure
and
Global A (secondary clock)
•
•
•
•
Output from Global MUX A
Conditioned version of PLL output (f
OUT
) – delayed
or advanced
Divided version of either of the above
Further delayed version of either of the above
(0.25 ns, 0.50 ns, or 4.00 ns delay)
1
Output from Global MUX B
Delayed or advanced version of f
OUT
Divided version of either of the above
Further delayed version of either of the above
(0.25 ns, 0.50 ns, or 4.00 ns delay)
2
Global B
•
•
•
•
Each PLL has the following key features:
Functional Description
Each PLL block contains four programmable dividers as
shown in
These allow
frequency scaling of the input clock signal as follows:
•
•
The n divider divides the input clock by integer
factors from 1 to 32.
The m divider in the feedback path allows
multiplication of the input clock by integer factors
ranging from 1 to 64.
The two dividers together can implement any
combination of multiplication and division
resulting in a clock frequency between 24 and 180
MHz exiting the PLL core. This clock has a fixed
50% duty cycle.
The output frequency of the PLL core is given by
the formula in
(f
REF
is the reference clock
frequency):
EQ 2-1
Note:
Jitter (ps) = Jitter (%) × period
For Example:
Jitter in picoseconds at 100 MHz = 0.01 × (1/100E6) = 100 ps
•
Maximum Acquisition = 80 µs for f
VCO
> 40 MHz
Time
= 30 µs for f
VCO
< 40 MHz
Low Power Consumption – 6.9 mW (max. – analog
supply) + 7.0 µW/MHz (max. – digital supply)
•
•
•
f
OUT
= f
REF
× m
÷
n
•
The third and fourth dividers (u and v) permit the
signals applied to the global network to each be
further divided by integer factors ranging from 1
to 4.
Physical Implementation
Each side of the chip contains a clock conditioning circuit
based on a 180 MHz PLL block (Figure
Two global multiplexed lines extend along each
side of the chip to provide bidirectional access to the PLL
on that side (neither MUX can be connected to the
opposite side's PLL). Each global line has optional LVPECL
input pads (described below). The global lines may be
driven by either the LVPECL global input pad or the
outputs from the PLL block, or both. Each global line can
be driven by a different output from the PLL. Unused
global pins can be configured as regular I/Os or left
unconnected. They default to an input with pull-up. The
two signals available to drive the global networks are as
The implementations shown in
and
enable
the user to define a wide range of frequency multiplier
and divisors.
m
f
GLB
=
-----------------
(
n
×
u
)
EQ 2-2
m
-
f
GLA
=
----------------
(
n
×
v
)
EQ 2-3
1. This mode is available through the delay feature of the global MUX driver.
2 -1 0
v5.9
ACTEL [ Actel Corporation ]
