Image Processing Reference
In-Depth Information
(a) On-chip sampling oscilloscope
(b) Simple analog measurement
Probe
Point
Probe
point
A V DD
A V DD 1
Voltage noise filter
PAD
PAD
Block
Diagram
AMP2
AMP
S/H
Digital
output
AVSS1
AVSS
Vref
VCO
AVSS n
Small footprint
Capability of many probes
integration
Digitization in vicinity of
measurement point
Feature
Requires equality of local ground
such as
AVSS1 = … = AVSSn = AVSS
Susceptible to noise
Large footprint
Problem
Fig. 3. Examples of on-chip voltage measurement scheme. (a) is an on-chip sampling
oscilloscope (Takamiya et al., 2004) and (b) is a simple analog measurement (Okumoto et al.,
2004).
A small, simple analog measurement was reported in (Okumoto et al., 2004). This probe
consists of a small first amplifier, and the output signal of the probe is sent to a second
amplifier and then transmitted to the external part of the chip. Because the probe is very
small and has the same layout height as standard cells and needs only one second amplifier,
many probes can be implemented in a single LSI with minimal area overhead. This method,
however, requires dedicated power supplies for measuring voltages that are different from
local power supplies V DD and V SS .
These measurements are therefore basically done under test-element-group (TEG) conditions,
and they may find it difficult to capture supply noise at multiple points in product-level
LSIs when actually running applications. To resolve this difficulty, an in-situ measurement
scheme is proposed. This method requires only a CMOS digital process and can be
applied to standard-cell based design. Thus, it is easy to apply to product-level LSIs. The
effect was demonstrated on a 3G cellular phone processor (Hattori et al., 2006), and the
measurement of power supply noise maps induced by running actual application programs
was demonstrated.
1.2 Key points for an in-situ measurement
Three key points need to be considered in order to measure the power supply noise at multiple
points on a chip: area overhead, transmission method, and dynamic range.
1. The first point is the area overhead of the measurement probes.
Because the power-consumption sources are distributed over the chip and many
independent power domains are integrated in an LSI, analyzing the power supply network
for product-level LSIs is very complicated. To analyze these power-supply networks,
many probes must be embedded in the LSI. Thus, the probes must be as small as possible.
Minimal area overhead and high adaptability to process scaling and ready-made electrical
design automation (EDA) tools are therefore very important factors regarding the probes.
2. The second point is the method used to transmit the measured signal.
It is impossible to transmit the measured voltage by using a single-ended signal, because
Search WWH ::




Custom Search