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Embedded Monitors on Chip for VDD Variation Measurement

IP.com Disclosure Number: IPCOM000223301D
Publication Date: 2012-Nov-15
Document File: 2 page(s) / 37K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to improve product performance in the presence of voltage droop in large product chips. The method uses ring oscillators that can be measured in non-contact mode along with a ring that is enabled with a photodiode.

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Embedded Monitors on Chip for VDD Variation Measurement

Voltage droop in large product chips is limits product performance. Precision measurement of local supply voltage helps designers optimize designs to compensate for voltage reduction.

Existing methods for estimating and measuring the local supply voltage and their drawbacks include:


 Probe power bus during circuit operation. This is a destructive measurement; the probe itself will distort the measurement signal.


 Prediction based on resistor-capacitor model and estimated transistor-switching current. This method is not able to verify through a hardware (HW) decision.


 Monitor power bus (e.g., VDD, ground) PIN current. This can map out current density, but is not able to measure voltage.

The disclosed solution is a method for using ring oscillators that can be measured in non-contact mode along with a ring that is enabled with a photodiode. During normal operation, the ring is in standby state. The advantages of this solution include:


 Compact structures can be placed multiple times in chip


 Capable of monitoring local VDD during any chip operation

Referring to the figure below:


 Schematic view of VDD droop monitor


- Ring stages are powered by local VDD voltage
- Ring "Enable" is powered by photo diode


 Description

- Ring is not active under normal condition
 No laser, ring is off, negligible leakage to power supply.

- During measurement
 Laser illuminate Photodiode to turn on ring,
...