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U. Glaeser

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FIGURE 21.10 E-R latches used with pass-transistor logic ([28] © 1997 IEEE).<br />

FIGURE 21.11 Various pulse-to-level converter designs.<br />

Static Logic<br />

As was previously discussed, clock-powered signals can be used directly with precharged and passtransistor<br />

logic. First, no pulse-to-level conversion is required; second, the latch-stage of the E-R latch<br />

consists of a 3-transistor dynamic latch. The limitation for these logic styles is that the clock voltage<br />

swing V ϕ should be equal to V dd + V th. This subsection investigates how clock-powered signals can operate<br />

with static logic. The main problem with static logic is that clock-powered signals may have long transition<br />

times. Therefore, they cannot drive static gates directly, because these gates would experience short-circuit<br />

current even if V ϕ were larger than V dd. To solve this problem, pulse-to-level converters (P2LC) must be<br />

introduced between the E-R latches and the static logic blocks. A similar static-dissipation problem arises<br />

for conventional static-logic systems with multiple supply voltages; the outputs of low-supply-voltage<br />

gates cannot drive high-supply-voltage gates directly, because short-circuit current would be drawn in<br />

the high-supply-voltage gates. To solve this problem, low-to-high voltage converter designs have been<br />

proposed [26]. These low-to-high voltage converters can be slightly modified to operate as pulse-to-level<br />

converters (Fig. 21.11).<br />

The first design (Fig. 21.11(a)) is a dual-rail-input, dynamic P2LC (DD P2LC). On every ϕ 1, exactly<br />

one of xp or xp is pulsed, setting the outputs xl or xl accordingly. Assume that xl is high and xl is low.<br />

If xp is pulsed, then xl and xl remain unchanged. If xp is pulsed, then transistor M3 turns on, discharging<br />

xl . This turns on M2, which charges xl to Vdd, cutting off M1. At the end of the operation, the outputs<br />

xl and have been flipped. The second design (Fig. 21.11(b)) is a dual-rail-input, static P2LC (DS P2LC).<br />

x l<br />

© 2002 by CRC Press LLC<br />

z i<br />

w i<br />

ϕ 1<br />

E-R Latch<br />

ϕ 1<br />

E-R Latch<br />

x p ∧ϕ 1<br />

x l<br />

V dd<br />

M 1<br />

M 3<br />

V iso<br />

V iso<br />

V dd<br />

M 2<br />

M 4<br />

ϕ 2<br />

z o ∧ϕ 2<br />

ϕ 2<br />

x p ∧ϕ 1<br />

w o ∧ϕ 2<br />

xl xp∧ϕ1 (a) Dual-rail-input Dynamic P2LC<br />

x l<br />

V dd<br />

M 1<br />

M 3<br />

Pass-<br />

Transistor<br />

Gate<br />

M 2<br />

M 4<br />

u i<br />

ϕ 2<br />

E-R Latch<br />

x p ∧ϕ 1<br />

V dd<br />

x l<br />

xl ϕ2 (c) Single-rail-input Dynamic P2LC<br />

V iso<br />

ϕ 1<br />

u o ∧ϕ 1<br />

xl xp∧ϕ1 (b) Dual-rail-input Static P2LC

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