MG2 ATMEL [ATMEL Corporation], MG2 Datasheet - Page 4

• Manufacturer Part Number: MG2
• Description: 350K Used Gates 0.5 ?m CMOS Sea of Gates
• Manufacturer: ATMEL [ATMEL Corporation]

Power Supply
and Noise
Protection
I/O Buffers
Switching
Protection
Matrix Switching
Current Protection
4
MG2
The speed and density of the SCMOS3/2 technology causes large switching current spikes, for
example, when:
•
•
Sharp edges and high currents cause some parasitic elements in the packaging to become sig-
nificant. In this frequency range, the package inductance and series resistance should be taken
into account. It is known that an inductor slows down the settling time of the current and causes
voltage drops on the power supply lines. These drops can affect the behavior of the circuit itself
or disturb the external application (ground bounce).
In order to improve the noise immunity of the MG core matrix, several mechanisms have been
implemented inside the MG arrays. Two kinds of protection have been added: one to limit the I/O
buffer switching noise and the other to protect the I/O buffers against the switching noise coming
from the matrix.
Three features are implemented to limit the noise generated by the switching current:
•
•
•
This noise disturbance is caused by a large number of gates switching simultaneously. To allow
this without impacting the functionality of the circuit, three new features have been added:
•
•
•
16 high current output buffers switch simultaneously,
or 10% of the 480,000 gates are switching within a window of 1 ns.
The power supplies of the input and output buffers are separated.
The rise and fall times of the output buffers can be controlled by an internal regulator.
A design rule concerning the number of buffers connected on the same power supply line
has been imposed.
Decoupling capacitors are integrated directly on the silicon to reduce the power supply drop.
A power supply network has been implemented in the matrix. This solution reduces the
number of parasitic elements such as inductance and resistance and constitutes an artificial
VDD and Ground plane. One mesh of the network supplies approximately 150 cells.
A low pass filter has been added between the matrix and the input to the output buffer. This
limits the transmission of the noise coming from the ground or the VDD supply of the matrix
to the external world via the output buffers.
4137O–AERO–06/05