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X Definition for Mixed Signal Designs

IP.com Disclosure Number: IPCOM000238438D
Publication Date: 2014-Aug-26
Document File: 6 page(s) / 805K

Publishing Venue

The IP.com Prior Art Database

Abstract

X definition for Mixed Signal Designs (Analog to Digital interface or vice versa) has many failure conditions. Unfortunately, current methods and tools limit us to define the “X” when it comes to Analog design behaviors. Some of the key aspects of re-defining “X” from/to an analog world are Power Architecture of SoC : Power supply Tracking for signal translation from analog world during : Functional boot sequence, Power Sequence Independent designs, Test mode entry, Low power checks. Other key aspects are Supply Ramp - Generation of “X” on Analog Signal output based on supply characteristics of the analog design, Slew profile based “X” propagation and signal translation, “X” input to an analog world is no longer VDD/2 but a profile which should identify design weaknesses especially for boot scenarios, Glitch Sensitivity for signal translation

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X Definition for Mixed Signal Designs

Abstract –

X definition for Mixed Signal Designs (Analog to Digital interface or vice versa) has many failure conditions. Unfortunately, current methods and tools limit us to define the “X” when it comes to Analog design behaviors. Some of the key aspects of re-defining “X” from/to an analog world are Power Architecture of SoC : Power supply Tracking for signal translation from analog world during : Functional boot sequence, Power Sequence Independent designs, Test mode entry, Low power checks. Other key aspects are Supply Ramp - Generation of “X” on Analog Signal output based on supply characteristics of the analog design, Slew profile based “X” propagation and signal translation, “X” input to an analog world is no longer VDD/2 but a profile which should identify design weaknesses especially for boot scenarios, Glitch Sensitivity for signal translation

Innovation –

We have  re-defined connect modules ( Signal translators between Analog(spice) and  Digital(verilog/SV) to define “X” propagation in a large mixed signal subsystem from/to the Analog modules . These connect modules are automatically inserted by the AMS tool at signal boundaries between Analog-Digital world. Our innovation has following components

•                Power supply intent in Analog Output i.e. “X” propagation if interface supply < 0.5V(parameter)

•                      Critical for Power sequencing sims wherein a signal will be treated “X” before its interface supply reaches a min value

•                Supply slope check and if slope > parameterized value , All Analog output goes to “X” for #ns(parameterized) . Can mimic an ESD event if regulator contention is seen faster than ESD ramp limits

•                Signal slope . Inserts a parameterized capacitance on interface to identify drive strength issues

•      Say if POR and LVD driver outputs have disparity in driver strength , at fast ramps , we may see LVD release before POR and may impact initialization sequence

•      Bad drive characteristics causes signal slew to become large enough to be captured as “X” on clocked domains and identify sensitivity of the architecture

•                Intentional Glitch propagation from analog : For 1-X-1 or 0-X-0 conditions at the interface due to analog behavior , generate 1-0-1 or 0-1-0 condition to create failure due to glitches in analog world

•                “X” input treated as Supply sensitive Sine Wave of parameterized frequency

•                                                                                                             Identifies if Digital “X” is properly Masked by Analog PMC for Boot sequence (Critical check)

•                                                                                                             Identifies if some critical signal is missing in masked PMC domain and creates failure conditions

•                Parameterized Current load on interface supply when “X” propagates. Can collapse the supply  Source if too many “X” regions are seen at interface e.g. Low power modes

Figure 1: Salient features of the innovation on “X” definition in mixed Signal designs

Snippet of the connect modules –

This methodology solv...