X
V DDL
V DDH
V DDH
V DDH
Y
MP1
MN1
MP2
MP3
MP4
MN4
MN2
MN5 MN6
MN3
B
MP6
MP5
X
A
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Low-Power Techniques for Network-on-Chip
Figure 6.7
New low-to-high voltage level shifter.
are cross-connected to the drains of transistors MP3 and MP2, whereas the
sources of both transistors are connected to the higher supply voltage V DDH .
A node B is connected to an output buffer circuit, constituted by transistors
MP4 and MN4, which is connected to the higher supply voltage V DDH .
The operation of the new level converter circuit is explained here. When the
voltage level of the input signal swings high to low, the output voltage level of the
input inverter becomes the lower supply voltage V DDL . Therefore, MN2, MN5,
and MP6 are turned on. As a result, node A is then discharged to a reference voltage V SS . Thus, MP3 becomes on, and then the voltage level of node B becomes a
higher supply voltage V DDH . In this case, MP2, MN3, MN6, and MP5 are turned
off, and therefore, it is possible to prevent a short-circuit current from flowing
between the higher power supply voltage V DDH and the reference voltage V SS .
However, when the voltage level of the input signal is switched to logic high,
the output voltage level of the input inverter becomes a reference voltage V SS .
Therefore, MN3, MN6, and MP5 are turned on. As a result, node B is then discharged to a reference voltage V SS . In this case, MP2 is turned on, and therefore,
MP3 becomes off. Moreover, MN2, MN5, and MP6 are also turned off, and thus,
it is possible to prevent a short-circuit current from flowing between the higher
power supply voltage V DDH and the reference voltage V SS . It is clear that there are
three paths to speed up the output level transition in each input signal condition.
These results provide faster output transitions as well as an efficient voltage level
conversion. As such, it can reduce the contention problem on nodes A and B. As a
result, the propagation delay time of the circuit itself becomes short. Moreover, no
short-circuit current flows; therefore, it is possible to reduce power consumption.