1 / 10

AMS Assertions … beyond analog waveform checking

AMS Assertions … beyond analog waveform checking. Mike Demler. Categories of AMS properties. Connectivity properties Static electrical properties Functional properties Signal properties I: Single-event temporal properties Signal properties II: Cumulative temporal properties

latika
Download Presentation

AMS Assertions … beyond analog waveform checking

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. AMS Assertions… beyond analog waveform checking Mike Demler

  2. Categories of AMS properties • Connectivity properties • Static electrical properties • Functional properties • Signal properties I: • Single-event temporal properties • Signal properties II: • Cumulative temporal properties • Signal properties III: • Frequency domain properties • Mixed-signal interface properties

  3. Categories covered in initial proposal • Connectivity properties • Static electrical properties • Functional properties • Signal properties I: • Single-event temporal properties • Signal properties II: • Cumulative temporal properties • Signal properties III: • Frequency domain properties • Mixed-signal interface properties

  4. A Few ExamplesAnalog properties… that waveform checks miss • One of the most critical applications for mixed-signal verification is in SoC power management. • Functional verification of digitally-controlled power modes • How to verify consumption meets budget? • Integration of AMS IP • Is the power supply a signal?

  5. n3 (0,2.5V) Max=4 n7 n1 n2 (0,2.5V) Max=4 2.5V 1.2V 2.5V 1.2V n4 n8 n6 n5 (0,2.5V) Max=4 Analog properties… that waveform checks miss. • PROBLEM: • Multiple power domains. Low voltage inverter mistakenly connected to higher voltage drivers, “digitally” switched. • Output voltage waveform appears to be functionally correct. • assert property (V(G)<=1.2); ? • Requires device-level terminal property monitor. Vgs(Minimum, Maximum) NMOS

  6. 3.0 PDWN 3.0 3.0 DRIFT _PDWN Analog properties… that waveform checks miss. • PROBLEM: • Power down results in unexpectedly high power consumption. • Output waveform appears to be correct. Long time domain. • Requires device-level “X” (or high-Z) property monitor. 3.0 3.0 PDWN PDWN 3.0 3.0 Power Down 3.0 Hi-Z(0.0) 3.0 3.0 0.0 3.0 Seconds/Minutes _PDWN _PDWN

  7. Analog properties… that waveform checks miss. • PROBLEM: • DC paths result in wasted power. • Output voltage signals looks OK. • How to monitor supplies, DC terminal currents?

  8. AMS Assertions • Automation of time-domain signal analysis is valuable, but only covers a subset of important analog properties. • The waveform is not the circuit. • …and it is the circuit that must be verified. • Just as V-AMS LRM added SPICE constructs… • AMS assertions must also understand devices and circuits to provide adequate verification coverage.

  9. AMS Assertions • Previous examples are the most frequent causes of AMS SoC failures. • Recent customer quote: • “The following issues have caused silicon failures on our mixed-signal chips: floating gates, high voltage on single oxide transistors, level-shifter insertion…” • Failures occur most often because of the signal that wasn’t simulated! • Rarely because a simulated waveform could not be checked.

  10. Other Complex Analog Properties • From earlier preliminary discussion: • While ’a’ is true, the frequency of ’b’ is 100.0 Hz with a 1.0% tolerance. • The mean slew rate of ’a’ from 0.0 V to 5.0 V is 250.0 V/s with a 1.0% tolerance. • The −3 dB low pass cut-off frequency from ’a’ to ’b’ is 25 Hz with a tolerance of 2.5%. • The gain-bandwidth product from ’a’ to ’b’ is 2.5 MHz with a tolerance of 1.0%. • Let T1 and T2 be two sets of crossing times of various signals. Check that (maxT1 −minT1)+(maxT2 −minT2) < 2 max jitter . • (eye jitter)

More Related