1. Technical Field
The present invention relates to a timing generator and a test apparatus.
2. Related Art
A timing generator is known that adjusts pulse timings to generate a timing signal having pulses at prescribed phases, as shown in Patent Document 1, for example. The phase of each pulse in the timing signal can be adjusted over a wide range with a high degree of accuracy by using a combination of a wide-range delay section that delays each pulse of the input signal by an integer multiple of the period of a reference clock and a high-accuracy delay section that delays each pulse by an amount no greater than the period of the reference clock.    Patent Document 1: Japanese Patent Application Publication H08-320360
In order to generate a timing signal with a higher frequency, two timing signals with different pulse timings can be combined. For example, by combining a first timing signal in which the pulse timings are T, 3T, 5T, etc. and a second timing signal in which the pulse timings are 2T, 4T, 6T, etc., a high-frequency timing signal in which the pulse timings are T, 2T, 3T, 4T, etc. can be generated.
However, each timing signal is generated by a different timing generator. The wide-range delay section in each timing generator can cause the same delay by using the same reference clock in each timing generator. However, each high-accuracy delay section independently generates the delay amount according to a setting value supplied thereto, and therefore a delay error occurs between the timing generators due to element variation, for example.
For example, when there is an error of ΔT in the delay of the second timing signal, the pulse timings of the resulting combined timing signal become T, 2T+ΔT, 3T, 4T+ΔT, etc. In this case, the jitter is applied to this timing signal.