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I have an amplifier circuit with a large number of digital control bits-- some of them adjusts the bias current and gain of the amplifier and some others disable the operation or cut-off all the current paths for power-down. To extract the bottom-up model of this circuit, I am mapping it to an 'amp_linear' UDM. But with such a large number of digital bits mapped to the UDM's 'mode' inputs, the MODELZEN's circuit characterization step takes a while simulating the circuit for all possible combinations of the digital inputs. I know not all the digital inputs are used in operation. For example, I can assume that the enable input 'EN' is always 1. Is there a way I can tell MODELZEN that the value of the 'EN' input is fixed at 1, so it can characterize the circuit more quickly?
Yes, there is. Starting with the XMODEL 2021.12 Release, MODELZEN introduced mode specification expressions for UDMs that can constrain the characterization space of the digital mode bits. For example, in your case, you can simply add the '==1' expression to the port mapping's level parameter to fix the value of 'EN' input to 1. The screenshot below shows an example of fixing the 'EN' input to 1 and the 'PWRDN' input to 0.
With the mode specification expressions (called 'mode spec' in short). you can describe a wider variety of constraints as well. For instance, you can specify that one mode bit always has an equal or opposite polarity of another mode bit. You can also specify that a set of mode bits are thermometer-coded or one-hot coded. Furthermore, you can also specify that the full range of trim bits is to be characterized only when the enable bit is 1, and so on. To learn more, please read this application note on "MODELZEN UDM Mode Specification Expressions".
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디지털 제어 입력의 수가 많은 아날로그 증폭기 회로를 모델링하고 있습니다. 그 디지털 제어 입력들 중에는 바이어스 전류나 증폭이득을 조절하기 위한 것도 있고, 증폭기의 동작을 멈추거나 파워다운시에 모든 전류 흐름을 차단하기 위한 것들도 있습니다. 이 회로의 bottom-up 모델을 MODELZEN으로 추출하기 위해, 이 회로를 'amp_linear' UDM에 매핑하였습니다. 하지만, 이 UDM의 mode 입력으로 매핑된 디지털 비트의 수가 매우 많아서, MODELZEN이 그 회로의 디지털 입력들의 모든 가능한 조합에 대해 특성추출 시뮬레이션을 수행하는데 시간이 상당히 걸리네요. 하지만, 사실 이 모든 디지털 입력들이 다 실제로 쓰이는 것은 아닙니다. 예를 들면, 동작을 활성화시키는 EN 입력은 항상 1이라고 가정해도 무방합니다. 모델 생성 시간을 단축하기 위해, MODELZEN에게 EN 입력은 항상 1로 고정되어 있다고 알려줄 수 있는 방법이 있을까요?
Yes, there is. Starting with the XMODEL 2021.12 Release, MODELZEN introduced mode specification expressions for UDMs that can constrain the characterization space of the digital mode bits. For example, in your case, you can simply add the '==1' expression to the port mapping's level parameter to fix the value of 'EN' input to 1. The screenshot below shows an example of fixing the 'EN' input to 1 and the 'PWRDN' input to 0.
With the mode specification expressions (called 'mode spec' in short). you can describe a wider variety of constraints as well. For instance, you can specify that one mode bit always has an equal or opposite polarity of another mode bit. You can also specify that a set of mode bits are thermometer-coded or one-hot coded. Furthermore, you can also specify that the full range of trim bits is to be characterized only when the enable bit is 1, and so on. To learn more, please read this application note on "MODELZEN UDM Mode Specification Expressions".
Please login or Register to submit your answer