Jameco Electronics 3000, 2000 manual Maximum Clock Speeds

16.4 Maximum Clock Speeds

The Rabbit 3000 is rated for a minimum clock period of 17 ns (commercial specifications) and 18 ns (industrial specifications). The commercial rating calls for a ±5% voltage varia- tion from 3.3 V and a temperature range from -40 to + 70°C. The industrial ratings stretch the voltage variation to ±10% and a temperature range from -40 to + 85°C. This corre- sponds to maximum clock frequencies of 58.8 MHz (commercial) and 55.5 MHz (indus- trial). If the clock doubler or spectrum spreader is used, these maximum ratings must be reduced as shown in the following table. When the doubler is used, the duty cycle of the clock becomes a critical parameter. The duty cycle should be measured at the separate clock output pin (pin 2). The minimum period must be increased by any amount that the clock high time is greater or less than specified in the duty-cycle requirement.

Table 16-7. Maximum Clock Speeds at 3.3 V [Preliminary]

Conditions

Commercial Ratings		Industrial Ratings
Minimum	Maximum	Minimum	Maximum
Period	Frequency	Period	Frequency
(ns)	(MHz)	(ns)	(MHz)

Duty Cycle

Requirements

(ns)

No doubler or	17	58.8	18	55.5
spreader
Spreader only	20	50.0	21	47.6
normal
Spreader only	21	47.6	22	45.4
strong
Doubler only	19	52.6	20	50.0	1 > (clock low -
(8 ns delay)					clock high) > 0
Doubler only					1 > (clock low -
(internal 50%	20	50	21	47.6
					clock high) > -1
clock)
Spreader
normal with	21	47.6	22	45.4	4 > (clock low -
doubler					clock high) > 2
(8 ns delay)
Spreader
normal with					1 > (clock low -
doubler (8 ns	24	41.6	25	40.0
					clock high) > -1
delay), internal
50% clock
Spreader only	21.5	46.5	22.5	45.0
strong
Spreader strong					8 > (clock low -
with doubler	23	43.5	24	41.6
					clock high) > 6
(8 ns delay)

User’s Manual 227