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U. Glaeser

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FIGURE 3.10 Layout of inverter gate with ECL and LS-APD-ECL circuits.<br />

FIGURE 3.11 Power-delay characteristics for conventional ECL and LS-APD-ECL circuits.<br />

The circuit under FO = 1 plus C L = 0.55 pF (2.5 mm metal interconnection) loading condition, which<br />

is often seen in a typical chip design, offers 300 ps delay at a power consumption of 1 mW/gate. This is<br />

a 4.4 times speed improvement over the conventional ECL circuit. Furthermore, the circuit consumes<br />

only 0.25 mW for a gate speed of 700 ps/gate, which is a 1/7.8 power reduction compared with the<br />

conventional ECL circuit. A better speed improvement and power reduction can be achieved under<br />

heavier loading conditions. For example, under FO = 1 plus C L = 1.41 pF (6.4 mm metal interconnection)<br />

loading condition, the speed improvement over the conventional ECL circuit is about 5.5 times at<br />

1 mW/gate, and the power reduction is about 1/11 times at 1.2 ns/gate. Even with the lightest loading of<br />

FO = 1 plus C L = 0.01 pF (0.02 mm metal interconnection), the LS-APD-ECL circuit outperforms the<br />

conventional ECL circuit. The speed improvement is about 2.2 times at 1 mW/gate, and the power<br />

reduction is about 1/2.8 times at 120 ps/gate.<br />

In Fig. 3.12, measured and simulated delay versus capacitive loading for the conventional ECL, the<br />

AC-APD-ECL, and the LS-APD-ECL circuits are depicted. The AC-APD-ECL circuit is optimized for<br />

0.5 pF loading, and therefore, for loadings heavier than 1.5 pF, the pull-down transition time degrades<br />

© 2002 by CRC Press LLC

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