2 Pin Crystal Oscillator 20mhZ

7/27/2019 2 Pin Crystal Oscillator 20mhZ

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HOLTEK Crystal Application Note

OSC : Crystal Oscillator

1. Overview

2. Application Circuit Diagram

3. Electrical Specification

4. Design Consideration

Last Updated : March 08, 1999 02:40 PM


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1. Overview

The crystal oscillator cells and their corresponding specification are listed in TABLE1. The following describes the notation for configurin crystal oscillator circuit using

oscillator cells.

TABLE 1: OSCILLATOR CELL SPECIFICATIONS

Cell name Frequency

(MHz)

Stop

Control

Internal

Feedback Resistor

Logic Symbol

OSCOL3 0.032 1 yes no Type A

OSCOM3 1 50 yes no Type A

OSCOH3 20 125 yes no Type A

OSCOL1 0.032 1 no no Type B

OSCOM1 1 50 no no Type B

OSCOH1 20 125 no no Type B

OSCOM5 1 50 yes yes Type C

OSCOH5 20 125 yes yes Type C

OSCOM4 1 50 no yes Type D

OSCOH4 20 125 no yes Type D

Note:XSCOL3 is same as OSCOL3. The others are the same.


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Type A Type C

Type B Type D

Figure 1: 4 types of logic symbol of the OSC cells


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2. Application Circuit DiagramFIG 2. Show examples of application circuit of crystal oscillator cells with built-in

feedback resistor. Oscillator cells which are used, should correspond to the frequencyrequired. And it is nessary that at least two cells : OSCI and OSCOXX must

be used in a design. The circuit constraints and electrical characteristics greatly

depend on the crystal oscillator used. And packing conditions on the printed circuit

board. Consult the crystal oscillator supplier for detail.

FIGURE 2: Application Circuit for OSC with internal resistor.

(OSCOM4, OSCOH4, OSCOM5, OSCOH5,

XSCOM4, XSCOH4, XSXOM5 and XSCOH5)


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HOLTEK Crystal Application NoteFIG 3. Show examples of application circuit of crystal oscillator cells with external

feedback resistor. The external component valuse are recommended as listed in

Table 2. When designing a system the unstable period which is found on oscillation

starting time or oscillation stopping time should be taken into account.

FIGURE 3: Application Circuit for OSC without internal resistor.

(OSCOL1, OSCOM1, OSCOH1, OSCOL3, OSCOM3, OSCOH3,

XSCOL1, XSCOM1, XSCOH1, XSCOL3, XSCOM3, XSCOH3)


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TABLE 2: OSCILLATOR EXTERNAL COMPONENT VALUS

Cell Name CrystalOscillator

Frequency

Feedback

Resistor (Rfb)

External

Capacitor(C1,C2)

Oscillation

Starting time

OSCOL1,3(XSCOL1,3) 32KHz

100K ~ 1MHz

10M

1K < X < 1M

10 ~ 30 pf

10 ~ 30 pf

< 200ms

don t care

OSCOM1,3 1M ~ 20MHz

20M ~ 50MHz

1M

1K< X

10 ~ 20 pf

10 ~ 20 pf

< 5ms

don t care

OSCOH1,3 20M ~ 40MHz

40M ~ 70MHz

70M ~ 125MHz

1M< X

1K ~ 5K

1K< X

10 ~ 20 pf

10 ~ 20 pf

10 ~ 20 pf

< 3ms

don t care

don t care

OSCOM4,5

( internal resistor 100K)

1M ~ 20MHz

20M ~ 50MHz

None

1K< X (don t care)

10 ~ 20 pf

10 ~ 20 pf

< 5ms

don t care

OSCOH4,5

( internal resistor 100K)

1M ~ 40MHz

40M ~ 70MHz

70M ~ 125MHz

None

5K

1K

10 ~ 20 pf

10 ~ 20 pf

10 ~ 20 pf

< 5ms

< 3ms

don t care


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HOLTEKCrystal Application Note

3. Electrical Specification

The IO pin, as O pin, should be treated as CMOS level during logic simulation.TABLE 3 shows the electrical specification of the HOLTEK oscillator cells under

some typical frequency. Contact HOLTEK Application Engineering for additional

information on circuit values and performance.

TABLE 3: OSCILLATOR CELL ELECTRICAL SPECIFICATION

(VCC=5V, Room Temperature, Typical Process )

Parameter Symbol Condition Typical Unit

OSCOL1&3 oscillation starting voltage VSTA 32Khz 1.8 V

oscillation holding voltage VHOLD 32Khz 1.3 V

supply current IDD 32Khz 10 uA

oscillation starting time TSTA 200 ms

OSCOM1,3,4,5 oscillation starting voltage VSTA 10Mhz 1.7 V

20Mhz 1.8 V

oscillation holding voltage VHOLD 10Mhz 1.4 V

20Mhz 1.6 V

supply current IDD 10Mhz 4 mA

20Mhz 10 mA


OSCOH1,3,4,5 oscillation starting voltage VSTA 30Mhz 1.8 V

40Mhz 1.9 V

oscillation holding voltage VHOLD 30Mhz 1.5 V

40Mhz 1.6 V

supply current IDD 30Mhz 18 mA

40Mhz 25 mA


OSCOM4&5 .Internal Feedback resistance Rint 170 Kohm

OSCOH4&5 Internal Feedback resistance Rint 170 Kohm


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4. Design Consideration

HOLTEKrecommend the following oscillator design consideration and guidelines

both in IC level and board level :

1. Arrange the pins to position the oscillator pins next to the VCC or GND pins.

Preferred positions of the pins that next to the oscillator pins also include :

the pin that is normally wired to a high or low level, the pin that is rarely

toggled and has a low impedance driving source, like reset pin.

2. Assign oscillator input and output pins as close as possible to minimize

straycapacitance and inductance.

3. Place the crystal as close as possible to the IC s oscillator pins to minimize

stray capacitance and inductance.

4. Power supply decoupling capacitor will give a more clean VCC to the

oscillator cells

5. Dedicated VCC, GND pins for high frequency oscillator cells are recommended.

2 Pin Crystal Oscillator 20mhZ

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