WO2011033588A1 - 試験装置および試験方法 - Google Patents
試験装置および試験方法 Download PDFInfo
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- WO2011033588A1 WO2011033588A1 PCT/JP2009/004762 JP2009004762W WO2011033588A1 WO 2011033588 A1 WO2011033588 A1 WO 2011033588A1 JP 2009004762 W JP2009004762 W JP 2009004762W WO 2011033588 A1 WO2011033588 A1 WO 2011033588A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/28—Testing of electronic circuits, e.g. by signal tracer
- G01R31/317—Testing of digital circuits
- G01R31/31725—Timing aspects, e.g. clock distribution, skew, propagation delay
- G01R31/31726—Synchronization, e.g. of test, clock or strobe signals; Signals in different clock domains; Generation of Vernier signals; Comparison and adjustment of the signals
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/28—Testing of electronic circuits, e.g. by signal tracer
- G01R31/317—Testing of digital circuits
- G01R31/31727—Clock circuits aspects, e.g. test clock circuit details, timing aspects for signal generation, circuits for testing clocks
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/28—Testing of electronic circuits, e.g. by signal tracer
- G01R31/317—Testing of digital circuits
- G01R31/3181—Functional testing
- G01R31/319—Tester hardware, i.e. output processing circuits
- G01R31/3193—Tester hardware, i.e. output processing circuits with comparison between actual response and known fault free response
Definitions
- the present invention relates to a test apparatus.
- the source synchronous method is known as a high-speed data transmission method between semiconductor devices.
- a clock signal synchronized with the data signal is transmitted via two transmission lines. For example, at a transmission rate of 1.6 GHz, 1.6 Gbps data assigned to the 800 MHz reference clock and the negative edge of the positive edge of the reference clock are transmitted. On the receiving side, data is latched at the timing of the positive edge and the negative edge of the reference clock.
- the relative phase difference between the reference clock and data is calculated at the same frequency as the actual operation or at a frequency that is intentionally different from the actual operation. It is determined whether or not the measured relative phase difference falls within the test specification.
- the relative phase difference can be obtained by measuring the change point (change timing) of the reference clock and the data change point using a TDC (Time Digital Converter) and calculating the difference data.
- TDC Time Digital Converter
- a multi-strobe circuit is used to measure the relative phase difference (see Patent Document 1). This test method confirms whether a setup margin and a hold margin are secured.
- the change point of the clock signal and the data conversion point correspond one-to-one, so that the relative phase difference can be measured by comparing and calculating the corresponding change points.
- the present invention has been made in view of these problems, and one of the exemplary purposes of one aspect thereof is to provide a technique for evaluating a device under test in a transmission system in which the frequency of data is an integer multiple of a reference clock. It is in.
- the device under test outputs a data sequence (data signal) that is synchronized with the clock signal and includes the data of n phases (n is an integer of 2 or more) in one cycle of the clock signal.
- the test apparatus includes a first time digital converter, a second time digital converter, a calculation unit, and a determination unit.
- the first time digital converter receives the clock signal and generates clock change point information indicating the change timing of the clock signal.
- the second time digital converter receives a data string having a clock signal cycle as a unit, and generates data change point information indicating a change timing for each phase of data.
- the calculation unit calculates, for each phase, difference data between the change timing indicated by the data change point information of the phase and the change point timing indicated by the clock change point information.
- the determination unit evaluates the device under test based on the difference data from the calculation unit. According to this aspect, it is assumed that there is a change point indicated by the clock change point information in a phase where the change point (edge) of the clock signal does not exist, and the change timing of the virtual clock signal is set to each data. By comparing with each change timing, the device under test can be evaluated.
- the device under test can be evaluated in a transmission method in which the data frequency is an integer multiple of the reference clock.
- FIG. 2 is a block diagram illustrating a device to be tested by the test apparatus of FIG. 1 and a second device connected to the device during actual use. It is a circuit diagram which shows the structural example of a multi-strobe circuit. It is a time chart which shows the basic operation
- FIGS. 8A and 8B are diagrams for explaining jitter superimposed on the multiplied clock signal in the PLL circuit of the second device.
- the member A is connected to the member B means that the member A and the member B are physically directly connected, or the member A and the member B are electrically connected.
- the case where it is indirectly connected through another member that does not affect the state is also included.
- the state in which the member C is provided between the member A and the member B refers to the case where the member A and the member C or the member B and the member C are directly connected, as well as an electrical condition. It includes the case of being indirectly connected through another member that does not affect the connection state.
- the period of the clock signal refers to the period from that edge to the next corresponding edge when only one edge (positive edge or negative edge) of the clock signal is used for signal processing.
- the interval between positive edges and negative edges that is, a half cycle is meant. The same applies to the frequency.
- FIG. 1 is a block diagram showing a configuration of a test apparatus 100 according to the embodiment.
- FIG. 2 is a block diagram showing a device to be tested by the test apparatus 100 of FIG. 1 (hereinafter referred to as a DUT) and a second device that is a communication destination connected during actual use.
- a DUT a device to be tested by the test apparatus 100 of FIG. 1
- a second device that is a communication destination connected during actual use.
- the DUT 102 outputs a clock signal DQS and a data signal DQ.
- the data signal DQ is a data string that is synchronized with the clock signal DQS and includes n-phase (n is an integer of 2 or more) data in one cycle of the clock signal DQS.
- the frequency of the data signal DQ is n times the frequency of the clock signal DQS.
- the frequency of the data signal DQ is eight times the frequency of the clock signal DQS.
- the second device 104 which is a communication partner of the DUT 102 includes a PLL circuit 106 and a latch circuit 108 as interface circuits.
- the PLL circuit 106 receives the clock signal DQS and multiplies the frequency by n.
- the multiplied clock is referred to as a multiplied clock CK.
- the frequency of the multiplied clock CK matches the frequency of the data signal DQ output from the DUT 102.
- the latch circuit 108 latches the value of the corresponding data at the edge timing of the multiplied clock CK.
- the latched data Q is provided to the subsequent circuit.
- each edge of the multiplied clock CK needs to satisfy the setup time and hold time requirements with the corresponding data signal DQ.
- Test apparatus 100 receives clock signal DQS and data signal DQ output from DUT 102.
- the data signal DQ is a data string that is synchronized with the clock signal DQS and includes n-phase data D 1 to D n in one cycle of the clock signal DQS.
- the test apparatus 100 includes a first time digital converter 10, a second time digital converter 12, a calculation unit 14, and a determination unit 20 as main components.
- the first time digital converter 10 receives the clock signal DQS and generates clock change point information TC indicating the change timing of the clock signal DQS.
- the first time digital converter 10 may generate clock change point information TC 1 to TC n indicating the change timing of the clock signal DQS for each phase.
- the second time digital converter 12 receives a data string having the period of the clock signal DQS as a unit, and data change point information TD 1 to TD indicating the change (transition) timing for each phase of the data D 1 to D n. n is generated.
- FIG. 3 is a circuit diagram illustrating a configuration example of the multi-strobe circuit 300.
- the multi-strobe circuit 300 receives the signal to be evaluated (signal under test) S1, and calculates the value of the signal under test S1 at the timing of each edge of the multi-strobe signal MSTRB (STRB 1 to STRB N ) having a plurality of edges. A signal indicating the change timing is generated.
- the integer N here is determined regardless of the integer n in FIG.
- the multi-strobe circuit 300 of FIG. 3 employs a vernier method.
- N first delay elements D1 1 to D1 N (collectively referred to as first delay elements D1) are cascade-connected in multiple stages.
- the first delay element D1 1 of the first stage is input under test signal S1, is under test signal S1 each time through the first delay element D1 1 stage, given the predetermined delay Tpd. That is, the i-th first delay element D1 i outputs the signal under test S1 i delayed by i ⁇ Tpd with respect to the signal under test S1 output from the DUT.
- N second delay elements D2 1 to D2 N are provided for each of the N first delay elements D1 1 to D1 N and cascaded in multiple stages. .
- the first stage second delay element D2 1 of the strobe signal STRB to be a reference are input.
- the strobe signal STRB is given a predetermined delay (Tpd + ⁇ t) every time one stage passes through the second delay element D2.
- the i-th strobe signal STRB i delayed by i ⁇ (Tpd + ⁇ t) with respect to the reference strobe signal STRB is output from the i- th second delay element D2.
- a plurality of STRB 1 to STRB N are collectively referred to as a multi-strobe signal MSTRB.
- N latch circuits L 1 to L N are also provided for each of the N first delay elements D1 1 to D1 N.
- the i (i is a natural number satisfying 1 ⁇ i ⁇ N) -th latch circuit L i latches the output signal of the i-th first delay element D1 i at the timing of the edge of the i-phase strobe signal STRBi. That is, the value of the signal under test S1 is determined at the timing of N strobe signals (multi-strobe signals) STRB 1 to STRB N whose phases are shifted from each other by ⁇ t.
- the latch circuit L1 indicated by the D flip-flop in FIG. 1 can be replaced by various elements such as other flip-flops and latch circuits.
- Output signals SL 1 to SL N of the N latch circuits L 1 to L N are input to the logic operation unit 310.
- the logical operation unit 310 performs predetermined signal processing according to the evaluation items of the DUT, and outputs the change point information (TC or TD).
- the levels of the signal under test S1 input to the first delay element D1 and the strobe signal STRB input to the second delay element D2 The phase difference (timing) is adjusted.
- the operation of the multi-strobe circuit 300 will be described.
- the relative time difference between the signal under test S1 and the strobe signal STRB changes by ⁇ t.
- the timing of the edges of the two signals is reversed after passing through ( ⁇ / ⁇ t) stages.
- the values of the output signals SL 1 to SL N of the latch circuit change.
- the positions where the values of the output signals SL 1 to SL N change indicate the timing of changing the level of the signal under test S1.
- the output signals SL 1 to SL N are thermometer codes in which 0 and 1 change at the bit corresponding to the change point. Therefore, the logical operation unit 310 may include a priority encoder that converts the thermometer code into a binary code.
- the above is the outline of the configuration of the multi-strobe circuit 300 and its operation. If the multi-strobe circuit 300 is used as the time digital converters 10 and 12 in FIG. 1, the change timing can be detected suitably.
- the calculation unit 14 indicates difference data indicating a difference between the change timing indicated by the data change point information TD i of the phase and the change point timing indicated by the clock change point information TC k.
- ⁇ T i is generated.
- the integer k represents the phase where a valid change point of the clock signal DQS occurs.
- the calculation unit 14 includes n calculation elements CAL 1 to CAL n .
- the calculation elements CAL 1 to CAL n are provided for each phase.
- the arithmetic element CAL i of the i-th phase (1 ⁇ i ⁇ n) receives the clock change point information TC k and the corresponding i-th phase data change point information TD i .
- the calculation element CAL i calculates difference data ⁇ T i between the change timing of the clock signal DQS indicated by the clock change point information TC k and the change timing indicated by the i-th phase data change point information TD i .
- the determination unit 20 evaluates the DUT 102 based on the n pieces of difference data ⁇ T 1 to ⁇ T n . For example, the determination unit 20 calculates the minimum value, maximum value, or average value of ⁇ T 1 to ⁇ T n from the difference data, determines whether each is included in a predetermined specification range, and determines whether the DUT 102 is good or bad. Judge performance.
- FIG. 4 is a time chart showing the basic operation of the test apparatus 100 of FIG.
- test apparatus 100 of FIG. 1 it is possible to evaluate the test apparatus 100 by virtually reproducing the phase of the clock signal even for a phase in which no edge (change point) exists.
- the test apparatus 100 in FIG. 1 includes n first memories M1 1 to M1 n , n second memories M2 1 to M2 n, and a plurality of selectors SEL 2 to SEL n .
- the n calculation elements CAL 1 to CAL n need to have the clock change point information TC 1 of the phase having an effective change point as a calculation target.
- Each of the first memories M1 1 to M1 n holds clock change point information TC 1 to TC n for each phase.
- the first time digital converter 10 distributes the clock change point information TC 1 to TC n acquired for each phase to a plurality of first memories by interleaving.
- each of the second memories M2 1 to M2 n holds data change point information TD 1 to TD n for each phase.
- the second time digital converter 12 distributes the data change point information TD 1 to TD n acquired for each phase to a plurality of second memories by interleaving.
- the selectors SEL 2 to SEL n are provided for each phase.
- the i-th phase selector SEL i receives the clock change point information TC k from the first memory M1 k of the k-th phase at the first input terminal (1), and receives the i-th phase at the second input terminal (2).
- the clock change point information TC i is received from the first memory M1 i of the phase.
- the selector SEL i selects one corresponding to the control signal.
- the k-th phase selector SEL k can be omitted because it receives two k-th phase clock change point information TC k and is redundant.
- the i-th phase calculation element CAL i receives the clock change point information from the i- th phase selector SEL i and the data change point information TD i held in the j-th phase second memory M2 i , and receives them. The difference between is calculated.
- the calculation element CAL i corresponding to the i-th phase (1 ⁇ i ⁇ n) can be used for the k-th phase clock change point information TC k and the i-th phase clock change point information.
- One of TC i can be selectively received.
- the DUT 102 connected to the test apparatus 100 does not always perform the data transmission described with reference to FIG. That is, in order to increase the versatility of the test apparatus 100, it is necessary to assume a case where the frequency of the clock signal DQS and the data signal DQ are equal.
- each of the selectors SEL 2 to SEL n selects the second input terminal (2).
- the change points of the data D 1 to D n of each phase can be compared with the change points of the corresponding clock signals.
- each phase receives clock change point information TC 1 to TC n and selects one of them, and receives data change point information TD 1 to TD n and one of them.
- a selector to select may be provided.
- FIG. 5 is a block diagram showing a modification of the test apparatus of FIG.
- the test apparatus 100 in FIG. 1 employs an interleave method, but the test apparatus 100a in FIG. 5 employs a non-interleave method.
- the test apparatus 100a in FIG. 5 includes a shift register 30 and a selector (multiplexer) 32.
- the shift register 30 includes at least n stages. Each stage of the shift register 30 can be understood as corresponding to the first memories M1 1 to M1 n of FIG.
- the selector 32 selects one of the clock change point information TC stored in each stage of the shift register 30.
- the calculation unit 14 includes difference data ⁇ T 1 between the clock change point information TC selected by the selector 32 and the data change point information TD 1 , TD 2 ,... Sequentially output from the second time digital converter 12 for each phase. ⁇ T 2 ,... Are calculated.
- the test apparatus 100 may further include the following functions.
- FIG. 6 is a circuit diagram showing a configuration for measuring phase fluctuation. Although only a circuit for the data signal DQ is shown in FIG. 6, a similar configuration may be provided for the clock signal DQS. Or only either one may be sufficient.
- the shift register 30c includes at least n stages. Each stage of the shift register 30 can be understood as corresponding to the second memories M2 1 to M2 n in FIG.
- the calculation unit 14c of FIG. 6 includes calculation elements CAL 1 to CAL n provided for each stage of the shift register 30c.
- Data change point information TD j to TD n from the j-th stage to the n-th stage of the shift register 30 is input to the arithmetic element CAL j corresponding to the j-th stage.
- the calculation element CAL j calculates the difference between two data change point information TD that are adjacent or not adjacent.
- the difference between the two data change point information TD represents the phase fluctuation amount (jitter amount) of the data signal DQ.
- the determination unit 20 c includes a maximum value circuit 22 and a comparison circuit 24.
- the maximum value circuit 22 detects the maximum value of the difference data from the calculation elements CAL 1 to CAL n , that is, the maximum value of the phase fluctuation amount.
- the comparison circuit 24 determines the quality of the DUT 102 by comparing the maximum value of the phase fluctuation amount with predetermined specification data SPEC.
- FIG. 7 is a time chart for explaining the phase variation of the data signal DQ in the test apparatus 100c of FIG.
- the difference data ⁇ T indicates a phase change between adjacent phases. For example, when the spec is set to 30 ps, since the fluctuation amount exceeds 40 ps in the first phase and the second phase, and the third phase and the fourth phase, it is determined to be defective.
- the data signal DQ is multiplied by n by the PLL circuit of the second device 104, and the data of the corresponding phase is latched by each edge of the multiplied clock signal CK.
- Each edge of the multiplied clock signal CK is nothing but a virtual change point in the test apparatus 100. It is known that the frequency of the multiplied clock signal CK generated by the PLL circuit 106 drifts, that is, each edge of the multiplied clock signal CK has a jitter TJ corresponding to the performance of the PLL circuit 106.
- FIGS. 8A and 8B are diagrams for explaining jitter superimposed on the multiplied clock signal CK in the PLL circuit of the second device.
- the change point from the second phase to the n-th phase is the first phase. may vary within a range of ⁇ TJ relative change point indicated by the clock change point information TC 1 (Fig. 8 (a)).
- the test apparatus 100 compares the data change point information TD 1 to TD n of the corresponding phase on the assumption that the change point of the virtual clock signal is in the range of TC 1 ⁇ TJ (FIG. 8 (b)).
- FIG. 9 is a diagram illustrating a part of a configuration example of a test apparatus 100 d having an emulation function of the second device 104.
- the calculation unit 14d holds data indicating the jitter amount TJ acquired in advance.
- the jitter amount TJ may be different for each phase, or the same value may be used for all phases. Also, the same value may be used for the phase advance direction and the delay direction, or different values may be used.
- the jitter amount TJ is input to the calculation elements CAL 2 to CAL n .
- the j-th phase calculation element CAL j calculates the difference between TD j and TC 1 and further adds or subtracts TJ. Note that the jitter amount TJ may also be considered in the calculation element CAL 1 .
- the determination unit 20d determines whether or not the difference data ⁇ T 1 to ⁇ T n from the calculation unit 14d satisfies the specification. Note that the same processing can be performed by reflecting the jitter amount TJ in the determination condition in the determination unit 20d instead of calculating the jitter amount TJ in the calculation unit 14d.
- test apparatus 100d in FIG. 9 may take the interleave format in FIG. 1 instead of the shift register format.
- FIG. 10 is a diagram illustrating a configuration example of a test apparatus 100e having a frequency analysis function.
- the test apparatus 100e includes a first frequency analysis unit 40, a second frequency analysis unit 42, and frequency determination units 26 and 28.
- the first frequency analysis unit 40 and the second frequency analysis unit 42 are so-called logic circuits and have functions such as FFT (Fast Fourier Transform), IFFT (Inverse Fast Fourier Transform), and filters necessary for signal processing in the frequency domain. Implemented in hardware or software.
- FFT Fast Fourier Transform
- IFFT Inverse Fast Fourier Transform
- the first frequency analysis unit 40 includes a first conversion unit 50, a filter 52, and a second conversion unit 54.
- the first converter 50 receives the clock change point information TC from the first time digital converter 10.
- the first conversion unit 50 converts the clock change point information TC into a frequency domain signal (first clock change point frequency information FC1) using FFT.
- the filter 52 and the second conversion unit 54 will be described later.
- the second frequency analysis unit 42 is configured in the same manner as the first frequency analysis unit 40.
- the first conversion unit 50 of the second frequency analysis unit 42 converts the data change point information TD from the second time digital converter 12 into a frequency domain signal (first data change point frequency information FD1).
- the frequency determination units 26 and 28 compare the clock change point frequency information FC and the data change point frequency information FD with the specifications SPEC respectively defined to determine whether the DUT 102 is good or bad.
- the PLL circuit 106 on the second device 104 side multiplies the clock signal DQS.
- the bandwidth of the clock signal DQS that the PLL circuit 106 can follow is limited. 106 cannot be locked and a transmission error occurs.
- the frequency determination unit 26 can determine the quality of the DUT 102 by comparing the frequency component of the clock signal DQS indicated by the clock change point frequency information FC with the specification SPEC of a predetermined frequency band. For example, when the spectrum component indicated by the clock change point frequency information FC deviates from the range FPLL determined according to the bandwidth of the PLL circuit 106, the DUT 102 may be determined to be defective.
- the frequency band specification SPEC may be determined by factors other than the PLL circuit 106.
- FIG. 11 is a diagram illustrating processing of the test apparatus 100e of FIG.
- the first conversion unit 50 of the first frequency analysis unit 40 converts the clock change point information TC into the first clock change point frequency information FC1 in the frequency domain by FFT.
- the filter 52 of the first frequency analysis unit 40 filters the first clock change point frequency information FC1 to generate second clock change point frequency information FC2.
- the frequency characteristic of the filter 52 is desirably programmable.
- the second conversion unit 54 of the first frequency analysis unit 40 inversely converts the filtered second clock change point frequency information FC2 into a time-domain signal (second clock change point information TC2) by IFFT.
- the second clock change point information TC2 is output to the calculation unit 14 at the subsequent stage. 4).
- the calculation unit 14 calculates difference data ⁇ T 1 to ⁇ T n between the second clock change point information TC2 and the data change point information TD of each phase. 5.
- the determination unit 20 determines the quality of the DUT 102 based on the difference data ⁇ T 1 to ⁇ T n .
- the second time digital converter 12 and the second frequency analysis unit 42 may perform the same processing on the data signal DQ.
- the second data change point information TD2 is output from the second frequency analysis unit 42.
- the calculation unit 14 may calculate a difference between the second clock change point information TC2 and the data change point information TD2.
- the frequency characteristic of the filter 52 may be determined according to the band of the PLL circuit 106 of the second device 104.
- the second clock change point information TC2 is a value that emulates the change point of the multiplied clock signal CK reproduced in the PLL circuit 106 in the actual second device 104.
- the second stage 104 accurately determines the data in the second device 104 at the time of actual operation by determining whether the DUT 102 is good or not based on the difference ⁇ T between the second clock change point information TC2 and the data change point information TD. Can be received or not.
- DESCRIPTION OF SYMBOLS 100 ... Test apparatus, 102 ... DUT, 104 ... 2nd device, 106 ... PLL circuit, 108 ... Latch circuit, 300 ... Multi-strobe circuit, DQ ... Data signal, DQS ... Clock signal, 10 ... First time digital converter, DESCRIPTION OF SYMBOLS 12 ... 2nd time digital converter, 14 ... Operation part, 20 ... Determination part, 22 ... Maximum value circuit, 24 ... Comparison circuit, 30 ... Shift register, 32 ... Selector, 40 ... 1st frequency analysis part, 42 ... 1st 2 frequency analysis unit, TC: clock change point information, TD: data change point information, SEL ... selector, CAL ... calculation element, M1 ... first memory, M2 ... second memory, FC ... clock frequency signal.
- the present invention can be used for a test apparatus.
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Abstract
Description
試験装置は、第1時間デジタル変換器、第2時間デジタル変換器、演算部、判定部を備える。第1時間デジタル変換器は、クロック信号を受け、クロック信号の変化タイミングを示すクロック変化点情報を生成する。第2時間デジタル変換器は、クロック信号の周期を単位とするデータ列を受け、各相のデータごとにその変化タイミングを示すデータ変化点情報を生成する。
演算部は、各相ごとに、その相のデータ変化点情報が示す変化タイミングと、クロック変化点情報が示す変化点タイミングの差分データを演算する。判定部は、演算部からの差分データにもとづき、被試験デバイスを評価する。
この態様によれば、クロック信号の変化点(エッジ)が存在しない相において、クロック変化点情報が示す変化点が存在するものと仮定し、その仮想的なクロック信号の変化タイミングを、各データの変化タイミングそれぞれと比較することにより、被試験デバイスを評価することができる。
第1遅延素子D1、第2遅延素子D2を1段通過するごとに、被試験信号S1とストローブ信号STRBの相対的な時間差は、Δtだけ変化する。被試験信号S1とストローブ信号STRBの初期の時間差がτである場合、(τ/Δt)個のステージを経由した段階で、2つの信号のエッジのタイミングは逆転する。2つのエッジのタイミングが逆転する位置において、ラッチ回路の出力信号SL1~SLNの値が変化する。
図4に示すように、クロック信号DQSの変化点(ポジティブエッジ)は、第k相にのみ存在し、その他には存在しない。したがって、クロック変化点情報TC1~TCnは、k=1相目についてのみ有効な値として取得される。
セレクタSEL2~SELnは、第1入力端子(1)を選択する。その結果、図4のタイムチャートに示す動作が実現できる。
この場合、すべての相において有効な変化点が発生する。そこでセレクタSEL2~SELnそれぞれは、第2入力端子(2)を選択する。その結果、各相のデータD1~Dnの変化点を、それぞれ対応するクロック信号の変化点と比較することができる。
(a) クロック信号DQSの周波数がデータ信号DQの周波数のn倍である場合
クロック信号DQSの有効な変化点が第k相に発生するとき、そのクロック変化点情報TCkは、シフトレジスタ30上を順にシフトしていく。セレクタ32は、このクロック変化点情報TCkを追いかけるようにして、選択する段を1段ずつ後ろにシフトしていく。その結果、演算部14には常時、有効な変化点を有するクロック変化点情報TCkが供給され、図4のタイムチャートの動作が実現できる。
この場合、セレクタ32は常にシフトレジスタ30の1段目のクロック変化点情報を選択する。その結果、セレクタ32からは、各相のクロック変化点情報TC1、TC2、…が順に出力される。この動作によって、演算部14は、各相のデータ変化点情報TDiと、それに対応する相のクロック変化点情報TCiの差分データΔTiを順に生成できる。
マルチストローブ回路を用いる場合、帯域の制限を受けることなく、ナイキスト間隔までデータを取得することができる。したがって、シンボル間干渉ISI(Inter Symbol Interference)等に起因する位相変動を捉えることができる。
図1あるいは図3の試験装置では、クロック信号DQSの変化点が存在しない相において、仮想的な変化点が存在するものと仮定し、その変化点として、変化点が実在する第k相のクロック変化点情報TCkを一様に利用していた。
図9の試験装置100dにおいて、シフトレジスタ形式ではなく、図1のインタリーブ形式をとってもよい。
マルチストローブ信号MSTRBの周波数を高めることは、クロック信号DQSあるいはデータ信号DQのサンプリング周波数を高めることに他ならない。したがって、マルチストローブ信号MSTRBの周波数を高めることにより、クロック信号DQSあるいはデータ信号DQの周波数成分を解析することが可能となる。
図10は、周波数解析機能を備える試験装置100eの構成例を示す図である。試験装置100eには、第1周波数解析部40、第2周波数解析部42、周波数判定部26、28が設けられる。
2. 第1周波数解析部40のフィルタ52は、第1クロック変化点周波数情報FC1をフィルタリングし、第2クロック変化点周波数情報FC2を生成する。フィルタ52の周波数特性は、プログラマブルであることが望ましい。
3. 第1周波数解析部40の第2変換部54は、フィルタリングされた第2クロック変化点周波数情報FC2を、IFFTによって時間領域の信号(第2クロック変化点情報TC2)に逆変換する。第2クロック変化点情報TC2は、後段の演算部14に出力される。
4. 演算部14は、第2クロック変化点情報TC2と各相のデータ変化点情報TDの差分データΔT1~ΔTnを演算する。
5. 判定部20は差分データΔT1~ΔTnにもとづき、DUT102の良否を判定する。
Claims (14)
- 被試験デバイスから出力される、クロック信号および前記クロック信号と同期しかつ前記クロック信号の1周期にn相(nは2以上の整数)のデータを含むデータ列を受け、前記被試験デバイスを試験する試験装置であって、
前記クロック信号を受け、前記クロック信号の変化タイミングを示すクロック変化点情報を生成する第1時間デジタル変換器と、
前記クロック信号の周期を単位とする前記データ列を受け、各相のデータごとにその変化タイミングを示すデータ変化点情報を生成する第2時間デジタル変換器と、
各相ごとに、その相のデータ変化点情報が示す変化タイミングと、前記クロック変化点情報が示す変化点タイミングの差分データを演算する演算部と、
前記演算部からの差分データにもとづき、前記被試験デバイスを評価する判定部と、
を備えることを特徴とする試験装置。 - 前記第1時間デジタル変換器は、各相ごとに前記クロック信号の変化タイミングを示すクロック変化点情報を生成し、
前記演算部は、有効な変化点を有する相のクロック変化点情報を演算対象とすることを特徴とする請求項1に記載の試験装置。 - 前記演算部は、
各相ごとに設けられ、それぞれが、前記クロック変化点情報および対応する相のデータ変化点情報を受け、前記クロック変化点情報が示す前記クロック信号の変化タイミングと、その相の前記データ変化点情報が示す変化タイミングとの差分データを演算するn個の演算要素を含むことを特徴とする請求項1に記載の試験装置。 - 前記有効な変化点を有するクロック変化点情報が第i相(1≦i≦n)に生ずるとき、第j相(1≦j≦n)の演算要素は、第j相のクロック変化点情報と、第i相のクロック変化点情報の一方を選択的に受信可能に構成されることを特徴とする請求項2に記載の試験装置。
- それぞれが各相ごとの前記クロック変化点情報を保持するn個の第1メモリと、
それぞれが各相ごとの前記データ変化点情報を保持するn個の第2メモリと、
それぞれが各相ごとに設けられた複数のセレクタであって、第j相のセレクタが、第j相および第i相の第1メモリから第j相のクロック変化点情報および第i相のクロック変化点情報を受け、制御信号に応じた一方を選択するように構成された、複数のセレクタと、
をさらに備え、
第j相の演算要素は、第j相のセレクタからのクロック変化点情報と、第j相の第2メモリに保持されたデータ変化点情報を受けることを特徴とする請求項4に記載の試験装置。 - 前記第1時間デジタル変換器から相ごとに出力されるクロック変化点情報が入力されるシフトレジスタと、
前記シフトレジスタの各段に格納されるクロック変化点情報のひとつを選択するセレクタと、
をさらに備え、
前記演算部は、前記セレクタにより選択された前記クロック変化点情報と、前記第2時間デジタル変換器から相ごとに出力される前記データ変化点情報の差分データを演算することを特徴とする請求項2に記載の試験装置。 - 前記被試験デバイスの実使用時において通信相手となる第2デバイスが、前記クロック信号を逓倍回路によってn逓倍し、逓倍されたクロック信号にもとづいて、各相のデータをラッチするよう構成されており、
前記試験装置の判定部は、前記第2デバイスの前記逓倍回路が前記クロック信号を逓倍する際に重畳されるジッタ量を、前記被試験デバイスの評価に反映させることを特徴とする請求項1から6のいずれかに記載の試験装置。 - 前記第1時間デジタル変換器からの前記クロック変化点情報を受け、周波数領域の信号に変換する第1変換部と、
前記第2時間デジタル変換器からの前記データ変化点情報を受け、周波数領域の信号に変換する第2変換部と、
をさらに備えることを特徴とする請求項1から7のいずれかに記載の試験装置。 - 前記第1、第2時間デジタル変換器はそれぞれ、
複数のエッジを有するマルチストローブ信号のそれぞれエッジのタイミングで、評価対象の信号の値を判定し、その信号の変化タイミングを示す変化点情報を生成するマルチストローブ回路であることを特徴とする請求項1から8のいずれかに記載の試験装置。 - 前記被試験デバイスの実使用時において通信相手となる第2デバイスが、前記クロック信号を逓倍回路によってn逓倍し、逓倍されたクロック信号にもとづいて、各相のデータをラッチするよう構成されており、
前記試験装置は、
前記第1時間デジタル変換器からの前記クロック変化点情報を受け、周波数領域の信号に変換し、第1クロック変化点周波数情報を生成する第1変換部と、
所定の周波数特性を有し、前記第1クロック変化点周波数情報をフィルタリングし、第2クロック変化点周波数情報を生成するフィルタと、
前記第2クロック変化点周波数情報を、時間領域の情報に逆変換し、第2クロック変化点情報を生成する第2変換部と、
をさらに備え、前記演算部は、前記第2クロック変化点情報と各相のデータ変化点情報の差分データを演算することを特徴とする請求項1に記載の試験装置。 - 被試験デバイスから出力される、クロック信号および前記クロック信号と同期しかつ前記クロック信号の1周期にn相(nは2以上の整数)のデータを含むデータ列を受け、前記被試験デバイスを試験する試験方法であって、
前記クロック信号の変化タイミングを示すクロック変化点情報を生成するステップと、
各相のデータごとに、その変化タイミングを示すデータ変化点情報を生成するステップと、
各相ごとに、前記クロック変化点情報が示す前記クロック信号の変化タイミングと、その相の前記データ変化点情報が示す変化タイミングとの差分データを演算するステップと、
n相の差分データにもとづき、前記被試験デバイスを評価するステップと、
を備えることを特徴とする試験方法。 - 前記被試験デバイスの実使用時において通信相手となる第2デバイスが、前記クロック信号を逓倍回路によってn逓倍し、逓倍されたクロック信号にもとづいて、各相のデータをラッチするよう構成されており、
前記第2デバイスの前記逓倍回路が前記クロック信号を逓倍する際に重畳されるジッタ量を、前記被試験デバイスの評価に反映させることを特徴とする請求項11に記載の試験方法。 - 前記クロック変化点情報を、周波数領域の信号に変換するステップと、
前記データ変化点情報を、周波数領域の信号に変換するステップと、
周波数領域の前記クロック変化点情報、前記データ変化点情報にもとづき、前記被試験デバイスを評価するステップをさらに備えることを特徴とする請求項11に記載の試験方法。 - 前記被試験デバイスの実使用時において通信相手となる第2デバイスが、前記クロック信号を逓倍回路によってn逓倍し、逓倍されたクロック信号にもとづいて、各相のデータをラッチするよう構成されており、
本試験方法は、
前記クロック変化点情報を周波数領域の信号に変換し、前記第2デバイスの前記逓倍回路の周波数特性に応じて周波数領域の信号をフィルタリングし、フィルタリングされた信号を時間領域の信号に逆変換するステップをさらに備えることを特徴とする請求項11に記載の試験方法。
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