JPS59107287A - Electronic apparatus with clock - Google Patents

Abstract

PURPOSE:To prevent the malfunction and the destruction of an IC, by connecting a capacitor, Zener diode, etc. between an external terminal and a grounding line. CONSTITUTION:The grounding line of an electronic apparatus provided with a clock circuit 16 including a battery 6 internally, and a slave circuit 1, not including the clock, which receives signals and power from external terminals 1, 2, and 3 is operated, is connected to a case 7. A capacitor 18 and Zener diodes 31 and 32 are connected between external terminals 2 and 3 and the grounding line. Since the static electricity applied to external terminals 2 and 3 is flowed to the ground through the capacitor 18 and Zener diodes 31 and 32, the malfunction and the destruction of the IC of the salve circuit 17.

Description

[Detailed Description of the Invention] The present invention relates to an electronic device with a clock having an external holder,
In particular, the present invention relates to a structure for preventing malfunction or destruction of electronic devices with external terminals due to static electricity.

In recent years, higher integration of semiconductors has been promoted more and more.
This generally means that the electrostatic resistance level of ICs has become weaker. In addition, products using semiconductors have become more diverse, and electronic devices equipped with external terminals for receiving signals and power from external circuits are now on the market.

However, having external terminals means that static voltage is applied directly to the terminals of the IC, which were conventionally shielded with a metal case or insulated with a plastic case, which can cause malfunction or destruction of the IC. turn into.

The present invention aims to eliminate such problems,
This will be explained below with reference to the drawings.

Figure 1 shows a clock circuit containing an internal battery and a subordinate circuit other than a clock that has an external terminal and operates by receiving power and signals from the outside. This shows an example of wiring when this is not done. 1 is the external terminal for ground G, 2 is the external terminal for Fi signal S, 3 is the external terminal for external power supply V, 4 is the circuit board, 5 is the battery holder, and 6 is the external terminal for external power supply V.
indicates the battery, and 7 indicates the case. fc8 to fc15 are contact resistances between each member, and 16 is a watchmaker C517 is an IC of a dependent circuit. The capacitor 18 is a power mining capacitor or bypass capacitor of the engineering 017, and the capacitor 19 is a boosted power supply that creates twice the voltage of the battery by switching and switching the capacitor 20. Most of the circuits of the engineering 016 are operated by this boosted power supply. are doing. 21 is a capacitance C farad, which represents an electrostatic voltage application model of voltage Vs volts and charge aV coulombs.

Now, when static voltage is applied between case 7 and external terminal 2,
Static electricity flows into the slave circuit 017 and destroys it. If static or pressure is applied between the case 7 and the external terminal 3, some of the static
It flows to the ground through 8, but depending on the capacitance of the capacitor, it may also flow into 017, causing damage to 0. In addition, since a large current flows through the capacitor, a voltage is generated between A and B due to the pattern resistance between A and B, which causes the Va81 level of the boost capacitor to fluctuate, causing IC malfunction. Similarly, between AC, BC
Because of the pattern resistance between the potential of Vasl and Vu.

Fluctuations in the level of the VDD potential occur, causing IC malfunction. When static voltage is applied to the case 7 and the terminal 1, a voltage is generated between OA and CB mainly due to the contact resistance 11 between the circuit board 4 and the battery holder 5. The potential fluctuates.

FIG. 2 shows an embodiment of the present invention in which Zener diodes 31 and 32 are connected between terminal 2 and terminal 3 and ground, respectively.
I encourage you. The Zener voltage is set to a voltage level at terminals 2 and 5, which does not normally flow. By connecting in this way, terminal 2
The static electricity added to the zener diode 3
1 and flows into the ground. Furthermore, the static electricity applied to the terminal 3 flows into the ground via the Zener diode 52 and the capacitor 1B, thereby preventing damage to the IC.

However, in the second case, Ir14 due to malfunction of l016
However, it is not perfect, but in order to minimize IC malfunction, 1.
It is necessary to reduce the pattern resistance between dBD and the contact resistance K between the circuit board 4 and the battery holder. That is, the pattern width between B'D is widened. Gold plate the battery holder. It is necessary to take measures such as welding the battery and battery holder together.

FIG. 3 shows another embodiment of the present invention, in which Zener diodes are connected with 31 and 32 gold wires between terminal 2 and terminal 3, respectively, to prevent damage to the wire 017 and to prevent static electricity from flowing through the loop. By wiring the clock IC power supply loop t'' so that it does not overlap, V'nD, V8
This eliminates potential level fluctuations between F31 and Vssz, and prevents malfunction of C16.

In the fourth part, the structure of this embodiment is explained using a television display wristwatch as an example.
The watch part is always displayed by the watch operator C42 and the watch battery 43. When watching television, power and signals are supplied from a separate tuner through an external terminal 44, and are supplied to an active matrix panel 46 for television display via a synchronization controller 45 and other circuit elements.

Using the a7Fi Zener diode, static electricity applied between the case 48 and the external terminal 44 is grounded through the battery holder 49t. 50i! A piezoelectric speaker attached to the back cover. In order to prevent malfunction of the watch IC, the ground of the watch power source is connected to the battery holder via the coil spring 52fc.

Although the present invention has been described in detail above, the second factor and the srA must be used depending on the product.

In this embodiment, a Zener diode is used as an element for electrostatic bypass, but the present invention also includes the use of other diodes, capacitors, etc. alone or in combination. Further, even if other conductive parts such as a switch spring are interposed between the battery holder and the circuit board, this is considered to be a battery holder in a broad sense including other conductive parts, and is included in the present invention. .

According to the present invention, by simply adding parts, it is possible to prevent damage caused by static electricity applied to external terminals.

Furthermore, IC malfunctions can be prevented by simple wiring techniques without having to worry too much about pattern resistance or contact resistance.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing damage caused by static electricity and malfunctions, FIGS. 2 and 3 are block diagrams showing embodiments of the present invention, and FIG. 4 is a diagram showing a structural example of the present invention. 1-3 Old...External terminal 4...Circuit board 5...Battery holder 6...Battery 7... ...Case 51.52 ...Zener diode and above Applicant Suiwa Seikosha Co., Ltd.

Claims (4)

[Claims] (1) In an electronic device with a clock that includes a clock circuit including a FjL battery, and a circuit other than a clock that has an external terminal and operates by receiving an external power supply, the ground line must be connected to the ground line. An electronic device with a clock, which is connected to a case and has devices such as a capacitor and Zener diode connected between an external terminal and a ground line to release static electricity. (2) The glass side of the clock circuit power supply is connected to ground,
2. The electronic device with a timepiece according to claim 1, wherein the wiring is such that the main loop through which static electricity flows separately from the external terminal and the current loop of the timepiece circuit power supply do not overlap. (3) The electronic device with a clock according to claim 1, wherein the positive line of the clock circuit power source and the positive line of the boosted power source using a capacitor are wired at the same location on the pattern. (4) The electronic device with a clock according to claim 1, wherein the positive line of the clock battery is connected to the battery holder without going through another signal loop.