LC88F85D0A Datasheet, PDF (26/31 Pages) Sanyo Semicon Device – FROM 256K byte, RAM 8K byte on-chip 16-bit 1-chip Microcontroller

LC88F85D0A
Characteristics of a Sample Subsystem Clock Oscillation Circuit
Given below are the characteristics of a sample subsystem clock oscillation circuit that are measured using a Our
designated oscillation characteristics evaluation board and external components with circuit constant values with which
the oscillator vendor confirmed normal and stable oscillation.
Table 2 Characteristics of a Sample Subsystem Clock Oscillator Circuit that uses a Crystal Oscillator (*5)
Nominal
Frequency
Vendor Name
Resonator
Name
Circuit Constant
Operating
Voltage
Oscillation
Stabilization Time
C3
C4
Rf2
Rd2
Range
typ
max
[pF]
[pF]
[Ω]
[Ω]
[V]
[s]
[s]
Remarks
SSP-T7-F
18
22 OPEN 750K 2.0 to 5.5
1.4
32.768kHz
(*1)
VT-200-F
Seiko Instruments (*2)
SSP-T7-FL
2
3
OPEN
0
2.0 to 5.5
0.8
VT-200-FL
3
CL=12.5pF (*3)
Normal XT mode
3
CL=4.4pF(*4)
Low power XT mode
(*1) Normal XT mode (*3) or low power XT mode (*4) should be selected for the sub-system clock oscillator circuit.
(*2) Contact Seiko Instruments, Inc., (http://www.sii-crystal.com) for further information about the use of the
resonator.
(*3) When considering the use of normal XT mode, use an resonator that has a large load capacitance.
(*4) When considering the use of low power XT mode, use a resonator that has a small load capacitance. The
applicable CL value of 4.4pF makes it possible to achieve a high time accuracy for the subclock oscillator as well
as high-speed oscillation startup and low power dissipation. In addition to this value, 6.0pF and 7.0pF also fall
within the applicable CL value range.
(*5) A sample PCB trace pattern for a Seiko Instrument resonator is shown below.
(Note 1) The oscillation stabilization time refers to the time interval that is required for the oscillation to get stabilized
after an instruction for starting the subclock oscillator circuit is issued or the time interval that is required for
the oscillation to get stabilized after the HOLD mode is released (see Figure 4).
(Note 2) The circuit constants shown are the reference values that are provided by the resonator vendor for evaluation.
To make final verification of the oscillation characteristics on production boards, call the resonator vendor for
evaluation on printed circuit boards.
(Note 3) When using an oscillator circuit, observe the following wiring precautions to avoid the possible adverse
influence of wiring capacitance, especially in low power XT mode:
• Place the components that are involved in oscillation as close to the resonator as possible with the shortest
possible traces as the oscillation characteristics are subject to the variation of trace patterns.
• Do not take a signal directly from the oscillator circuit.
• Do not place the oscillator circuit in the vicinity of any lines that carry large current.
• Exercise extreme care in the wiring method when using low power XT mode.
No.A1954-26/31