Echelon Series 6000 Chip databook - Manual (Page 73)

Clock Requirements
A Series 6000 chip requires a 10 MHz external crystal or oscillator to provide its input clock
signal. The chip then multiplies the input frequency by an amount specified in the device’s
hardware template (specified during device development using the IzoT NodeBuilder
Development Tool) to derive its internal system clock frequency. For multipliers greater
than one, the chip uses a phase-locked loop (PLL) to drive and manage the internal on-chip
system clock frequency.
This section describes the requirements for the external crystal and compares terminology
for Series 6000 chip clock frequencies with Series 3100 chip clock frequencies.
External Crystal
A Series 6000 chip requires a 10.0 MHz external clock signal for operation. An example part
that meets the requirements for a Series 6000 chip is the Abracon Corporation
ABMM2100000MHzD1 Ceramic Surface Mount Low Profile Quartz Crystal.
The crystal must have a load capacitance rating of 18 pF. Because a Series 6000 chip does
not have internal load capacitance on-chip, you must add 30 pF combined external series
capacitance, as shown in Figure 24.
Y 1
10.0000MHZ
200PPM
18pF
1 2
C2
30 pF
1
2
C1
30 pF
1
2
R1 1M
1 2
XIN XOUT
R2
200
1
2
Figure 24. Series 6000 Chip Clock Generator Circuit
Unlike the Series 3100 chip, the Series 6000 chip’s XOUT pin cannot be used to drive an
external CMOS load. However, if you maintain the required capacitance for the XOUT pin,
you can drive an external clock, for example, as shown for the LPT-11 Link-Power
Transceiver in Figure 23.
If your device requires a common clock signal, you can use an external 3.3 V oscillator
module (such as a Vishay ® Intertechnology XOSM-533 Surface Mount Oscillator), and leave
XOUT unconnected. You could also define an output frequency I/O model for one of the
Series 6000 chip’s I/O pins (IO0..IO11) and connect the load’s clock signal to the Series 6000
chip’s I/O pin.
A 60/40 duty cycle or better is required for the external oscillator, as shown in Figure 25.
An external oscillator must provide low-voltage transistor-transistor logic (LVTTL) voltage
levels (0 to 3.3 V) to the XIN pin.
Series 6000 Chip Data Book 61