AIDA ASIC Davide Braga Steve Thomas ASIC Design
AIDA ASIC Davide Braga Steve Thomas ASIC Design Group 14 October 2010
Input comparator: Now that the original diodes have been replaced by diode-connected pass transistors (not as fast or low impedance) the active-link circuit must take most of the input current. To avoid the build up of a large input voltage now that the passive link is slower, the active link must respond faster Necessary to optimize the input comparator 14 October 2010 2
Input comparator speed ~ -50% -80% Vin (d=100 ns) -with input diode-connected transistors -without 6. 7 ns 5. 5 ns 13 ns New comparator: appreciably faster across all corners Vin (d=200 ns) no significant difference between the two, the diodeconnected transistors don’t conduce 3. 3 ns old comparator Vin (d=300 ns) NB: speed function of input voltage. In this simulation Vin=Vthreshold ± 100 m. V, trise=tfall=10 ns 14 October 2010 3
High ref, Qin=900 p. C (~18 Ge. V) (1): inp ut link charge (d=100 ns-200 ns-300 ns) Q_ ut p _in Q_ HE C Q HE Q_ C Q ut inp Q_ EC _H LEC charge 14 October 2010 4
High ref, Qin=900 p. C (~18 Ge. V) (2): Q_input Q_HEC link charge (detail) (d=100 ns-200 ns-300 ns) Q_HEC 14 October 2010 5
p High ref, Qin=900 p. C (~18 Ge. V) (3): ol d co m p ne w co m p om c ew n om c old p new omp old p com c The new comparator is generally faster and loses less charge for very fast inputs 14 October 2010 6
High ref, Qin=900 p. C (~18 Ge. V) (4): d=100 ns d=200 ns old comp new comp Significant improvement for slower signals too. (NB: old and new configurations in these presentation have the same link, the only difference is the input comparator) d=300 ns 14 October 2010 7
Low ref, Qin=900 p. C (~18 Ge. V) (1): Q_HEC_old Q_HEC_new Q_input 14 October 2010 8
Low ref, Qin=900 p. C (~18 Ge. V) (2): new Vin old new old 14 October 2010 9
Low ref, Qin=900 p. C (~18 Ge. V) (3): new Vin old new old 14 October 2010 10
Low ref, Qin=900 p. C (~18 Ge. V) (3): new old new Current: fast (~ns) feature, total current comparable (NB: absolute value in this graph due to ancillary circuits in the schematic) old 14 October 2010 11
Link leakage current: Sample of the current through the HEC/LEC link for high-low input references, different process corners. The concern was that a possible offset between the amplifiers’ references could cause significant current. The current is <30 p. A in the worst case so it will be easily handled by the feedback compensation circuit [f. A] [p. A] low_ref (0. 4 V), comparator thresh=0. 35 V T= -10°C ÷ +50°C Vdd= 3. 0 V ÷ 3. 6 V Voffset_pre. Amps=± 1. 2 m. V high_ref (1. 6 V), comparator thresh=1. 65 V 14 October 2010 12
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