[introduction] brilliant brace up outside the RTC application circuit of buy is general by RTC chip, outside buy 32k brilliant brace up, laden capacitance composition, the commonnest circuit principle plan is as follows roughly, among them U1 is RTC chip, y1 is 32k brilliant brace up, c1, C2 is brilliant brace up laden capacitance.

Brilliant brace up outside the RTC application circuit of buy is general by RTC chip, outside buy 32k brilliant brace up, laden capacitance composition, the commonnest circuit principle plan is as follows roughly, among them U1 is RTC chip, y1 is 32k brilliant brace up, c1, C2 is brilliant brace up laden capacitance.

In production, cause RTC to stop brace up the reason is as follows roughly:

1, should solder brilliant brace up use iron handiwork to solder when means, the likelihood because iron temperature is exorbitant, touch touch brilliant brace up noumenon and bring about brilliant brace up in-house quartz chip melts.

2, brilliant brace up in-house quartz chip is very small, external to coming from acuteness and mechanical vibration is unusually sensitive, especially cannot ultrasonic is cleaned with solder. The frequency of general ultrasonic equipment on market and rate of 32k brilliant Zhen Pin are adjacent, cause brilliant easily brace up chip resonance and attaint brilliant brace up.

3, the manufacturing staff of some manufacturer is cleaning brilliant brace up when, use bristle brushs force to procrastinate drag brilliant brace up cite a base, make its are pulled easily, create any crystalline substance brace up the contact is undesirable with flat, when bringing about RTC not to go.

4, although some manufacturer were not washed board working procedure, also can have likewise stop brace up the phenomenon appears, the problem may appear in design PCB Shi Jingzhen to bring a foot to be close to too, when solder, bring colophony gathers all round the foot or foreign matter is overmuch, the likelihood causes brilliant brace up shunt resistance is too little and stop brace up.

5, some engineers are in composing brilliant brace up when, meeting brilliant brace up noumenon ground connection, right now solder of this locality ground connection dish should not be too big, the meeting when soldering otherwise because solder dish absorption of heat is overmuch, more quantity of heat conveys brilliant brace up in-house, bring about brilliant brace up attaint.

6, brilliant brace up when composing wiring, brilliant brace up with RTC chip the distance shoulds not be too long, should make brilliant brace up close be next to RTC chip.

7, brilliant brace up the oscillation that maintained RTC jointly with laden capacitance, should match when electric capacity is too large, same meeting occurrence brilliant brace up stop brace up, I manage commendatory laden capacitance does not exceed 20pF commonly.

RTC stops brace up theoretical analysis

Following plan institute show circuit of RTC in-house oscillator:

Besides quartz brilliant brace up outside, parts of an apparatus of Mp, Mn, Rf, C1, C2 is all and compositive at chip in, the equivalent resistor R1 that cites a base to the ground considering OSCIN and OSCOUT, R2, the equivalent circuit structure that pursues on pursues as follows:

The transmission function of its S region is:

The real department that takes T(s) function is NRes (call oscillation to lose block) , take the place of the parameter with C0, L0, R0, Rf, Gm1, C1, appropriate C2, assume R1=R2, it is variable with R1, R2, the significance that draws a R1, R2 and NRes pursues as follows:

To assure brilliant brace up reliable oscillation, negative block of general requirement oscillation is more than the brilliant of 5 times brace up inside R0 of series connection resistor. Xing Weifan’s RTC is mature the design is redundant, capacitance of outer buy resonance is worth suitable case to fall, can stabilize job of reliable ground oscillation.

Article origin: Xing Weifan

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