HA7210IBZ Intersil, HA7210IBZ Datasheet - Page 6

• Manufacturer Part Number: HA7210IBZ
• Manufacturer: Intersil

Specifications of HA7210IBZ

• Output Level: CMOS
• Symmetry Max: 60%
• Operating Supply Voltage (typ): 5
• Pin Count: 8
• Mounting Style: Surface Mount
• Screening Level: Industrial
• Product Height (mm): 1.5mm
• Product Depth (mm): 4mm
• Product Length (mm): 5mm
• Rad Hardened: No
• Package / Case: SOIC N
• Lead Free Status / RoHS Status: Compliant

Crystal Pullability
Figure 4 shows the basic equivalent circuit for a crystal and
its loading circuit.
Where:
C
L
R
C
If loading capacitance is connected to a Series Mode
Crystal, the new Parallel Mode frequency of resonance may
be calculated with the following equation:
f
Where:
f
f
In a similar way, the Series Mode resonant frequency may
be calculated from a Parallel Mode crystal and then you may
calculate how much the frequency will “pull” with a new load.
C
P
P
S
M
M
M
0
CL
= Parallel Mode Resonant Frequency
= Series Mode Resonant Frequency
=
= Shunt Capacitance
= Motional Inductance
= Motional Capacitance
= Motional Resistance
f
=
S
-------------------------- -


1
------ -
C
1
+
1
C
--------------------------------- -
2 C
1
+
1
(
------ -
C
1
2
0
C
2
OSC IN


+
M
=
C
C
CL
M
Equivalent Crystal Load
)
L
FIGURE 4.
C
M
0
6
R
M
C
3
OSC OUT
2
V
DD
HA7210
Layout Considerations
Due to the extremely low current (and therefore high
impedance) the circuit board layout of the HA7210 must be
given special attention. Stray capacitance should be
minimized. Keep the oscillator traces on a single layer of the
PCB. Avoid putting a ground plane above or below this layer.
The traces between the crystal, the capacitors, and the OSC
pins should be as short as possible. Completely surround
the oscillator components with a thick trace of V
minimize coupling with any digital signals. The final
assembly must be free from contaminants such as solder
flux, moisture, or any other potential source of leakage. A
good solder mask will help keep the traces free of moisture
and contamination over time.
Further Reading
Al Little “HA7210 Low Power Oscillator: Micropower Clock
Oscillator and Op Amps Provide System Shutdown for Battery
Circuits”. Intersil Corporation Application Note AN9317.
Robert Rood “Improving Start-Up Time at 32kHz for the
HA7210 Low Power Crystal Oscillator”. Intersil Corporation
Application Note AN9334.
S. S. Eaton “Timekeeping Advances Through COS/MOS
Technology”. Intersil Corporation Application Note
ICAN-6086.
E. A. Vittoz, et. al. “High-Performance Crystal Oscillator
Circuits: Theory and Application”. IEEE Journal of Solid-
State Circuits, Vol. 23, No. 3, June 1988, pp774-783.
M. A. Unkrich, et. al. “Conditions for Start-Up in Crystal
Oscillators”. IEEE Journal of Solid-State Circuits, Vol. 17,
No. 1, Feb. 1982, pp87-90.
Marvin E. Frerking “Crystal Oscillator Design and
Temperature Compensation”. New York: Van Nostrand-
Reinhold, 1978. Pierce Oscillators Discussed pp56-75.
DD
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