US 7,449,913 B1 | ||
Pre-driver having slew-rate and crowbar-current controls for a CMOS output buffer | ||
Kenneth Wai Ming Hung, Pak Shek Kok (Hong Kong Special Administrative Region of the People's Republic of China, The) | ||
Assigned to Smartech Worldwide Limited, Hong Kong (China) | ||
Filed on Jun. 20, 2007, as Appl. No. 11/765,751. | ||
Int. Cl. H03K 17/16 (2006.01); H03B 1/00 (2006.01) |
U.S. Cl. 326—27 [326/26; 326/83; 327/108; 327/112; 327/170; 327/207] | 20 Claims |
1. An output buffer having slew-rate control and crossbar current control, comprising:
a pull-up PMOS transistor coupled to a high voltage supply terminal VDD and having a gate configured to receive a signal PUP;
a pull-down NMOS transistor arranged between and the pull-up PMOS transistor and a low-voltage supply terminal VSS, wherein
the gate of the pull-down NMOS transistor is configured to receive a signal NDN;
a pull-up network coupled to the gate of the pull-up PMOS transistor, wherein the pull-up network comprises:
a first logic gate circuit having a threshold voltage VTHP for an input signal PPUP and configured to produce at least a portion
of PUP;
a first Schmitt trigger circuit configured to receive PUP as an input and output a signal FPUP, wherein the first Schmitt
trigger circuit has a switching threshold voltage VSTP for PUP; and
a second logic gate circuit having a threshold voltage substantially at VTHP for the input signal PPUP and configured to produce
at least a portion of PUP, wherein the second logic circuit is enable controlled by the signal FPUP; and
a pull-down network coupled to the gate of the pull-down NMOS transistor, wherein the pull-down network comprises:
a third logic gate circuit having a threshold voltage VTHN for an input signal PNDN and configured to produce at least a portion
of NDN;
a second Schmitt trigger circuit configured to receive NDN as an input and output a signal FNDN, wherein the second Schmitt
trigger circuit has a switching threshold voltage VSTN for NDN; and
a fourth logic gate circuit having a threshold voltage substantially at VTHN and an output connected to the gate of the pull-down
NMOS transistor, wherein the fourth logic circuit is enable controlled by the signal FNDN.
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