20-668-0003 Rabbit Semiconductor, 20-668-0003 Datasheet - Page 216

• Manufacturer Part Number: 20-668-0003
• Description: IC CPU RABBIT2000 30MHZ 100PQFP
• Manufacturer: Rabbit Semiconductor

Specifications of 20-668-0003

• Processor Type: Rabbit 2000 8-Bit
• Speed: 30MHz
• Voltage: 2.7V, 3V, 3.3V, 5V
• Mounting Type: Surface Mount
• Package / Case: 100-MQFP, 100-PQFP
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 30 MHz
• Operating Supply Voltage: 0 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Number Of Programmable I/os: 40
• Number Of Timers: 8 & 10 bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 20-668-0003; 316-1062

the gate input and allow the oscillator to operate at a lower voltage. This oscillator will
start at about 1.2 V and operate down to about 0.75 V. The 47 kΩ resistor limits the short-
circuit current when the CMOS gate is switching, and thus limits the overall current con-
sumption. The 330 kΩ resistor is needed to limit crystal drive at higher operating voltages,
but if the 330 kΩ resistor is too large, it will adversely affect low-voltage operation.
Typical 32.768 kHz crystals are specified for a maximum drive level of 1 µW. A modest
overdrive, perhaps 100% over this limit, will most likely have not any adverse effects
except to cause the crystal to age more rapidly than specified. Aging is a gradual change of
frequency of about 3 parts per million, and is most significant in the first few months of
operation. The drive power can be computed from P = (I
current and R is the effective resistance of the crystal. Typical values for R are 20 kΩ for
32.768 kHz turning-fork crystals. Maximum values are often specified as 35 kΩ or 50 kΩ.
If the effective resistance is 20 kΩ, then 1 µW of power is reached when I = 7 µA (RMS).
It is logical to use the typical effective resistance rather than the maximum total resistance
in computing drive power. If a particular crystal has a higher resistance, this indicates that
it is losing more energy on each oscillation, perhaps because of surface contamination, and
thus requires more power to sustain the same amplitude of physical flexure of the quartz.
Thus the stress on the quartz will not be greater even though the drive power is greater for
a unit that happens to have an effective resistance of 35 kΩ rather than the typical value of
20 kΩ. The current can be measured directly with a sensitive current probe, but it is easier
to calculate the current by measuring the voltage swing at the gate input with a low-capac-
itance oscilloscope probe. The RMS voltage at this point is related to the RMS current by
the relationship
where
If C
drive power (in µW) are given by
or
For a 5 V p-p swing, the power is 1.5 µW. The power is 1.0 µW for 4 V p-p, and the power is
0.5 µW for 3 V p-p.
TN235, External 32.768 kHz Oscillator Circuits, provides further information on oscilla-
tor circuits and crystals.
210
total
I = V
C
w = 2π * 32768
V
I = 2.5 * V
P = 0.125 * (V
I = 1.75 * V
P = 0.061 * (V
rms
total
= 12 pF, and the effective resistance is 20 kΩ, then the current (in µA) and the
rms
= 0.707 * V
= C2 + C
* w * C
rms
p-p
rms
p-p
i
total
+ C
p-p
)
)
2
2
probe
Rabbit 2000 Microprocessor User’s Manual
2
) * R, where I is the RMS AC