JP4828561B2 - Triangular / trapezoidal wave generator - Google Patents

Description

  The present invention relates to a triangular wave / trapezoidal wave generating circuit including a test circuit that generates a triangular wave or a trapezoidal wave synchronized with a reference clock signal and displays whether the triangular wave or the trapezoidal wave and the reference clock signal are in a phase synchronization state. .

  The triangular wave / trapezoidal wave generating circuit generates a triangular wave or a trapezoidal wave by a method of integrating a square wave or a method of switching charging / discharging of a capacitive load with a square wave.

  FIG. 8 shows a configuration example of a conventional triangular wave generation circuit (Patent Document 1). In this configuration, a triangular wave is generated by switching charging / discharging of a capacitive load with a square wave, and a waveform control circuit for synchronizing the period of the triangular wave with a reference clock signal using PLL (phase synchronization) technology is added. is there.

  In FIG. 8, the triangular wave generation circuit includes a charge / discharge circuit 50A, a load capacitor 60, a buffer 70, and a waveform control circuit 80A. The load capacitor 60 is charged / discharged by the output of the charge / discharge circuit 50A. Is output.

  The waveform control circuit 80A includes two comparison circuits 81 and 82, an SR latch 83, a phase comparator 84, and a loop filter 85. The two comparison circuits 81 and 82 compare the output signal (triangular wave) of the buffer 70 with the high potential Vref-H and the low potential Vref-L, respectively. When the triangular wave becomes Vref-H or Vref-L, the output of the comparison circuits 81 and 82 is latched by the SR latch 83, whereby the phase of the triangular wave is detected as shown in FIG. The output signal of the SR latch 83 is input to the charging / discharging circuit 50A as a charging / discharging switching signal that becomes the charging / discharging switching timing of the load capacitor 60. In addition, the phase comparator 84 compares the output signal (triangular wave phase) of the SR latch 83 with the phase of the reference clock signal, and outputs a pulse signal corresponding to the phase advance or delay to the loop filter 85. The loop filter 85 integrates the pulse signal output from the phase comparator 84, generates a charge / discharge current adjustment signal (analog voltage) for adjusting the bias voltage of the charge / discharge circuit 50A, and outputs it to the charge / discharge circuit 50A.

FIG. 10 shows a configuration example of the charge / discharge circuit 50A.
In FIG. 10, the charge / discharge current adjustment signal output from the waveform control circuit 80A is input to the reference current generation circuit 51 to change the generated reference current. When the reference current changes, the currents of the constant current circuits 52 and 53 change accordingly, and the charge / discharge current for the load capacitor 60 is increased or decreased via the switches 54 and 55 that are opened and closed by the charge / discharge switching signal. As a result, the slew rate (slope of the waveform) of the output triangular wave changes, and finally, the control is performed so that the cycle of the reference clock signal and the triangular wave become the same. Even when the phase is shifted due to noise such as power supply voltage fluctuation, the phase difference from the reference clock signal is adjusted to return to zero.
JP 2004-7324 A

  By the way, the conventional triangular wave generation circuit has a configuration in which the phase of the triangular wave is feedback controlled by the waveform control circuit 80A having a PLL configuration, and there is no means for confirming whether or not the reference clock signal and the triangular wave are in a phase synchronization state. In other words, it was impossible to monitor the synchronization lock / unlock state of the triangular wave generation circuit at the time of manufacturing or actual use, and to check non-defective products such as early and late phase synchronization with respect to the reference clock signal and operation margin. The same applies to the conventional trapezoidal wave generation circuit.

  An object of the present invention is to provide a triangular wave / trapezoidal wave generation circuit including a test circuit capable of displaying whether or not a triangular wave or a trapezoidal wave and a reference clock signal are in phase synchronization.

  The present invention generates a triangular wave or a trapezoidal wave having a slope between two different potentials by inputting a charge / discharge switching signal to the charging / discharging circuit to switch the charging / discharging of the capacitive load. In a triangular / trapezoidal wave generator circuit that includes a waveform control circuit that detects the phase difference, which is the difference between the period and the period of the reference clock signal, and controls the period of the triangular wave or trapezoidal wave to synchronize with the period of the reference clock signal A phase difference pulse signal corresponding to the phase difference between the triangular wave or trapezoidal wave and the reference clock signal is input from the control circuit, and a phase difference pulse signal having a predetermined pulse width or more in the cycle of the charge / discharge switching signal for generating the triangular wave or the trapezoidal wave. A test circuit that latches and outputs as a status signal indicating whether or not the phase is synchronized within a predetermined phase difference is provided.

  The test circuit includes a pulse width expansion circuit that expands the pulse width of the phase difference pulse signal, a delay circuit that delays the charge / discharge switching signal, and a delay circuit that delays the phase difference pulse signal whose pulse width has been expanded by the pulse width expansion circuit. A latch circuit that latches with the charge / discharge switching signal and outputs the status signal.

  In addition, when the waveform control circuit is configured to output a phase difference pulse signal every half cycle of the reference clock signal, the test circuit includes a pulse width expansion circuit that expands the pulse width of the phase difference pulse signal, and charge / discharge switching. A delay circuit for delaying the signal, two latch circuits for latching the phase difference pulse signal whose pulse width has been expanded by the pulse width expansion circuit by the charge / discharge switching signal delayed by the delay circuit and its inverted signal, A selector that switches the output of the latch circuit according to the logic by a charge / discharge switching signal delayed by a delay circuit and outputs the status signal.

  The pulse width expansion circuit of the test circuit is replaced with a pulse width variable circuit that varies the pulse width of the phase difference pulse signal, and a phase difference that is used as a reference to determine whether the triangular wave or trapezoidal wave and the reference clock signal are in phase synchronization. It is the structure which adjusts the range. The pulse width variable circuit has a plurality of delay circuits with different delay amounts, and is configured to select the delay circuit and set the pulse width of the phase difference pulse signal.

  The triangular wave / trapezoidal wave generation circuit of the present invention can perform a test for confirming the phase synchronization state of a triangular wave or a trapezoidal wave with respect to a reference clock signal. As a result, it is possible to perform a non-defective test of the triangular wave / trapezoidal wave generation circuit and an evaluation of an operation margin in an on-chip state, and a great effect can be exhibited in a non-defective product inspection at the time of mass production.

(First Embodiment of Triangular Wave Generation Circuit of the Present Invention)
FIG. 1 shows a first embodiment of a triangular wave generating circuit of the present invention. FIG. 2 shows an operation example of the first embodiment of the triangular wave generation circuit of the present invention. Here, an example is shown in which a test circuit is added to the conventional triangular wave generating circuit shown in FIG.

  In FIG. 1, a charge / discharge circuit 50A, a load capacitor 60, a buffer 70 and a waveform control circuit 80A constituting a triangular wave generating circuit, and comparison circuits 81 and 82, an SR latch 83, a phase comparator 84, constituting a waveform control circuit 80A, The loop filter 85 is the same as the conventional configuration shown in FIG.

  The test circuit 10 </ b> A according to this embodiment includes an OR circuit 11, a pulse width expanding circuit 12, a delay circuit 13, and a D latch 14. As shown in FIGS. 2 (1) to (4), the OR circuit 11 inputs a pulse signal corresponding to the advance or delay of the phase of the triangular wave with respect to the reference clock signal output from the phase comparator 84, and calculates its logical sum. It is output as a phase difference pulse signal. As shown in FIG. 2 (5), the pulse width expanding circuit 12 expands the pulse width of the phase difference pulse signal and outputs it. As shown in FIGS. 2 (3) and 2 (6), the delay circuit 13 branches and inputs a charge / discharge switching signal output from the SR latch 83 to the charge / discharge circuit 50A and serving as a charge / discharge switching timing. Output with a predetermined delay. As shown in FIGS. 2 (5) to 2 (7), the D latch 14 delays the phase difference pulse signal output from the pulse width expanding circuit 12 and having the pulse width expanded from the delay circuit 13. The status signal is latched by the charge / discharge switching signal and used to determine whether or not the difference between the period of the reference clock signal and the period of the triangular wave is within a predetermined range.

  In the example of the status signal shown in FIG. 2 (7), if the phase of the reference clock signal and the phase of the triangular wave are out of phase and a phase difference pulse signal is generated, the status signal becomes high level and phase synchronization is in progress ( It can be seen that adjustment is in progress. In addition, when the phase difference between the reference clock signal and the triangular wave falls within a predetermined range and the phase difference pulse signal is not generated, the status signal becomes low level, indicating that phase synchronization is complete.

(Second Embodiment of Triangular Wave Generation Circuit of the Present Invention)
FIG. 3 shows a second embodiment of the triangular wave generating circuit of the present invention. The phase comparator 84 of the waveform control circuit 80A of the first embodiment is configured to perform phase comparison with the SR latch output every cycle of the reference clock signal, but the phase comparison of the waveform control circuit 80B of the second embodiment. The unit 84 is configured to compare the phase with the SR latch output every half cycle of the reference clock signal. The configuration of the triangular wave generation circuit is the same as that of the first embodiment except for the phase comparator 84, and the configuration of the test circuit is different from that of the first embodiment. FIG. 4 shows an operation example of the second embodiment of the triangular wave generation circuit of the present invention.

  In FIG. 3, the test circuit 10 </ b> B of the present embodiment includes an OR circuit 11, a pulse width expanding circuit 12, a delay circuit 13, D latches 14-1 and 14-2, and a selector 15. As shown in FIGS. 4 (1) to (4), the OR circuit 11 inputs a pulse signal corresponding to the advance or delay of the phase of the triangular wave with respect to the reference clock signal output from the phase comparator 84, and calculates its logical sum. It is output as a phase difference pulse signal. As shown in FIG. 4 (5), the pulse width expanding circuit 12 expands the pulse width of the phase difference pulse signal and outputs it. As shown in FIGS. 4 (3) and 4 (6), the delay circuit 13 receives the charge / discharge switching signal output from the SR latch 83, and outputs it with a predetermined delay. As shown in FIGS. 4 (5) to (7), the D latch 14-1 latches the phase difference pulse signal whose pulse width is expanded at the rising edge of the delayed charge / discharge switching signal. The D latch 14-2 uses the delayed charge / discharge switching signal as an inverted clock input, and, as shown in FIGS. 4 (5), (6), and (8), the phase difference pulse signal with an expanded pulse width, Latch at the falling edge of the delayed charge / discharge switching signal. The selector 15 selects the output of the D latch 14-1 when the delayed charge / discharge switching signal output from the delay circuit 13 is “1”, and the D latch 14 when the charge / discharge switching signal is “0”. -2 is selected and output as a status signal used to determine whether the difference between the period of the reference clock signal and the period of the triangular wave is within a predetermined range.

  In the case of this embodiment, the phase comparison with the triangular wave is performed every half cycle of the reference clock signal. Therefore, as shown in FIG. 4 (9), the phase adjustment of the triangular wave is performed in half cycle units of the reference clock signal. It can be determined from the status signal status.

(Third Embodiment of Triangular Wave Generation Circuit of the Present Invention)
FIG. 5 shows a third embodiment of the triangular wave generating circuit of the present invention. Here, although shown as a modification of the test circuit 10A of the first embodiment, it can be similarly applied to the test circuit 10B of the second embodiment.

  A feature of the test circuit 10C of this embodiment is that a pulse width variable circuit 16 capable of adjusting an expansion range of the pulse width of the phase difference pulse signal is used instead of the pulse width expansion circuit 12. The pulse width variable circuit 16 prepares a plurality of delay circuits having different delay times, selects a delay circuit by an adjustment signal input from the outside, and makes the pulse width of the phase difference pulse signal variable. As a result, it is possible to set a detectable range for the phase difference between the reference clock signal and the triangular wave, and the test reference can be arbitrarily adjusted according to the situation at the time of manufacture and the conditions at the time of use.

(Embodiment of trapezoidal wave generation circuit of the present invention)
FIG. 6 shows an embodiment of the trapezoidal wave generation circuit of the present invention. FIG. 7 shows an operation example of the embodiment of the trapezoidal wave generation circuit of the present invention.

  In FIG. 6, a charge / discharge circuit 50B with a charge / discharge stop function constituting a trapezoidal wave generation circuit, a load capacitor 60, a buffer 70 and a waveform control circuit 80C, and comparison circuits 81 and 82 constituting a waveform control circuit 80C, an SR latch 83 The phase comparator 84 and the loop filter 85 have the same basic functions as those of the conventional triangular wave generating circuit shown in FIG.

  The two comparison circuits 81 and 82 of the waveform control circuit 80C compare the output signal (trapezoidal wave) of the buffer 70 with the high potential Vref-H and the low potential Vref-L, respectively. When the trapezoidal wave becomes Vref-H or Vref-L, the phase of the trapezoidal wave is detected as shown in FIG. 7 (3) by latching the outputs of the comparison circuits 81 and 82 with the SR latch 83. . The output signal of the SR latch 83 is input to the charging / discharging circuit 50B with a charging / discharging stop function as a charging / discharging switching signal which is a charging / discharging switching timing of the load capacitor 60. Further, the charge / discharge switching signal is input to the EX-NOR circuit 86, exclusive ORed with the reference clock signal, and input to the charge / discharge circuit 50B with charge / discharge stop function as a charge / discharge permission signal. The charge / discharge circuit 50B with a charge / discharge stop function stops charging and discharging the load capacitor 60 when the charge / discharge permission signal is turned off (the signal level is low in FIG. 7), and the waveform is as shown in FIG. 7 (2). A trapezoidal wave is generated in a held state.

  The charge / discharge switching signal output from the SR latch 83 is input to the phase comparator 84 and the delay circuit 13 of the test circuit via the delay circuit 87. The phase comparator 84 compares the charge / discharge switching signal (trapezoidal wave phase) delayed by the delay circuit 87 with the phase of the reference clock signal, and outputs a pulse signal corresponding to the phase advance or delay to the loop filter 85. . The loop filter 85 integrates the pulse signal output from the phase comparator 84, generates a charge / discharge current adjustment signal (analog voltage) for adjusting the bias voltage of the charge / discharge circuit 50B with charge / discharge stop function, and performs a charge / discharge stop function. Output to the charge / discharge circuit 50B.

FIG. 11 shows a configuration example of a charge / discharge circuit 50B with a charge / discharge stop function.
In FIG. 11, the charge / discharge current adjustment signal output from the waveform control circuit 80C is input to the reference current generation circuit 51, and the generated reference current is changed. When the reference current changes, the currents of the constant current circuits 52 and 53 change accordingly, and the charge / discharge current for the load capacitor 60 is increased or decreased via the switches 54 and 55 that are opened and closed by the charge / discharge switching signal. The output of the charge / discharge current is turned on / off by a switch 56 that is opened / closed by a charge / discharge permission signal. As a result, the slew rate (the slope of the waveform) and the waveform holding period of the trapezoidal wave to be output are changed, and finally the period of the trapezoidal wave and the reference clock signal are controlled to be the same.

  The OR circuit 11, the pulse width expanding circuit 12, the delay circuit 13, and the D latch 14 that constitute the test circuit 10D of the present embodiment have the same configuration as the test circuit 10A of the triangular wave generation circuit of the present invention shown in FIG. That is, like the test circuit 10A of the triangular wave generation circuit, the OR circuit 11 outputs a phase difference pulse signal, and the pulse width expansion circuit 12 expands the pulse width of the phase difference pulse signal as shown in FIG. And output. As shown in FIGS. 7 (5) and (8), the delay circuit 13 receives the charge / discharge switching signal delayed by the delay circuit 87, gives a predetermined delay, and outputs it. As shown in FIGS. 7 (7) to (9), the D latch 14 delays the phase difference pulse signal output from the pulse width expanding circuit 12 and having the pulse width expanded from the delay circuit 13. The status signal is latched by the charge / discharge switching signal, and a status signal used for determining whether or not the difference between the period of the reference clock signal and the period of the trapezoidal wave is within a predetermined range is output.

  In the example of the status signal shown in FIG. 7 (9), if the phase of the reference clock signal and the phase of the trapezoidal wave are shifted and a phase difference pulse signal is generated, the status signal becomes high level and phase synchronization is in progress. (Under adjustment) In addition, if the phase difference between the reference clock signal and the trapezoidal wave falls within a predetermined range and no phase difference pulse signal is generated, the status signal becomes low level, indicating that phase synchronization is complete.

  As described above, the test circuit 10D of the trapezoidal wave generation circuit according to the present embodiment can be operated in the same manner with the same configuration as the test circuit 10A of the triangular wave generation circuit. Further, the test circuit 10B corresponding to the half cycle comparison of the reference clock signal shown in FIG. 3 can also be supported, and the test circuit 10C for adjusting the pulse width of the phase difference pulse signal shown in FIG. A detectable range can be set for the phase difference between the signal and the trapezoidal wave.

  As described above, the test circuit according to the present invention latches the phase difference pulse signal corresponding to the phase difference between the reference clock signal and the triangular wave or trapezoidal wave with the charge / discharge switching signal corresponding to the period of the triangular wave or trapezoidal wave. By outputting as a status signal, it can be determined whether it is in a phase synchronization state or in a phase synchronization process. A triangular wave / trapezoidal wave generation circuit that generates a triangular wave or a trapezoidal wave that is phase-synchronized with the reference clock signal can obtain a phase difference pulse signal and a charge / discharge switching signal. Without being limited to the triangular wave / trapezoidal wave generating circuit as shown in FIG. 6, the test circuit of the present invention for determining the phase synchronization state of the triangular wave or trapezoidal wave can be applied.

The figure which shows 1st Embodiment of the triangular wave generation circuit of this invention. The time chart which shows the operation example of 1st Embodiment of the triangular wave generation circuit of this invention. The figure which shows 2nd Embodiment of the triangular wave generation circuit of this invention. The time chart which shows the operation example of 2nd Embodiment of the triangular wave generation circuit of this invention. The figure which shows 3rd Embodiment of the triangular wave generation circuit of this invention. The figure which shows embodiment of the trapezoidal wave generation circuit of this invention. The time chart which shows the operation example of embodiment of the trapezoidal wave generation circuit of this invention. The figure which shows the structural example of the conventional triangular wave generation circuit. The time chart which shows the operation example of the conventional triangular wave generation circuit. The figure which shows the structural example of 50 A of charging / discharging circuits. The figure which shows the structural example of the charging / discharging circuit 50B with a charging / discharging stop function.

Explanation of symbols

10A, 10B, 10C, 10D Test circuit 11 OR circuit 12 Pulse width expansion circuit 13 Delay circuit 14 D latch 15 Selector 16 Pulse width variable circuit 50A Charge / discharge circuit 50B Charge / discharge circuit with charge / discharge stop function 51 Reference current generation circuit 52, 53 constant current circuit 54, 55, 56 switch 60 load capacity 70 buffer 80A, 80B, 80C waveform control circuit 81, 82 comparison circuit 83 SR latch 84 phase comparator 85 loop filter 86 EX-NOR circuit 87 delay circuit

Claims (5)

A charge / discharge switching signal is input to the charge / discharge circuit to switch charge / discharge of the capacitive load, thereby generating a triangular wave or trapezoidal wave having a slope between two different potentials, and the period of the triangular wave or trapezoidal wave and the reference clock In the triangular wave / trapezoidal wave generation circuit including the waveform control circuit that detects the phase difference that is the difference in the signal cycle and controls the period of the triangular wave or trapezoidal wave and the period of the reference clock signal to be synchronized,
A phase difference pulse signal corresponding to a phase difference between the triangular wave or the trapezoidal wave and the reference clock signal is input from the waveform control circuit, and a predetermined pulse is generated at a cycle of the charge / discharge switching signal for generating the triangular wave or the trapezoidal wave. A triangular wave / trapezoidal wave generation circuit comprising a test circuit that latches a phase difference pulse signal that is equal to or greater than a width and outputs a status signal indicating whether or not a phase synchronization state is within a predetermined phase difference. The triangular wave / trapezoidal wave generating circuit according to claim 1,
The test circuit is
A pulse width expansion circuit for expanding the pulse width of the phase difference pulse signal;
A delay circuit for delaying the charge / discharge switching signal;
A latch circuit that latches the phase difference pulse signal whose pulse width has been expanded by the pulse width expansion circuit with the charge / discharge switching signal delayed by the delay circuit, and outputs the latched signal as the status signal. Triangular / trapezoidal wave generator. The triangular wave / trapezoidal wave generating circuit according to claim 1,
The waveform control circuit is configured to output the phase difference pulse signal every half cycle of the reference clock signal,
The test circuit is
A pulse width expansion circuit for expanding the pulse width of the phase difference pulse signal;
A delay circuit for delaying the charge / discharge switching signal;
Two latch circuits for latching the phase difference pulse signal whose pulse width has been expanded by the pulse width expansion circuit with the charge / discharge switching signal delayed by the delay circuit and its inverted signal, respectively;
A triangular wave / trapezoidal wave generation circuit comprising: a selector that switches the outputs of the two latch circuits according to logic with the charge / discharge switching signal delayed by the delay circuit and outputs the status signal . In the triangular wave / trapezoidal wave generating circuit according to claim 2 or 3,
The pulse width expanding circuit of the test circuit is replaced with a pulse width variable circuit that varies the pulse width of the phase difference pulse signal, and whether the triangular wave or the trapezoidal wave and the reference clock signal are in a phase-synchronized state. A triangular wave / trapezoidal wave generating circuit characterized by adjusting a range of the phase difference serving as a reference. The triangular wave / trapezoidal wave generating circuit according to claim 4,
The pulse width variable circuit includes a plurality of delay circuits having different delay amounts, and is configured to select a delay circuit and set a pulse width of the phase difference pulse signal. .

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