"Real World" Problems in the Analog and Mixed Signal Domains
"Real World" Problems in the Analog and Mixed Signal Domains
"Real World" Problems in the Analog and Mixed Signal Domains
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DCC 08<br />
An even stage r<strong>in</strong>g Oscillator<br />
Slide 17<br />
A2<br />
B2<br />
XCell1 XCell2<br />
“bridge”<br />
Figure 1: “XCha<strong>in</strong>OfCells2”<br />
“bridge”<br />
Figure 2: An alternative view<br />
The complete description<br />
• * sr<strong>in</strong>g - a r<strong>in</strong>g oscillator with bridges<br />
• *-----------------------------------------------------------<br />
• * Libraries, parameters <strong>and</strong> models<br />
• *-----------------------------------------------------------<br />
• .protect<br />
• *.lib<br />
'/user/cad/process/tsmc65/model/spice/g+/v1.0/local/fets.li<br />
b' TT<br />
• .lib ./cln90g_lk.l TT<br />
• .unprotect<br />
• .model pch pmos<br />
• .model nch nmos<br />
• *-----------------------------------------------------------<br />
• * Operat<strong>in</strong>g po<strong>in</strong>t<br />
• *-----------------------------------------------------------<br />
• .temp 30<br />
• .param supplyVoltage=1.5V<br />
• *-----------------------------------------------------------<br />
• * Initial conditions <strong>and</strong> stimuli<br />
• *-----------------------------------------------------------<br />
• .IC V(A2)='supplyVoltage*1.'<br />
• *.IC V(B2)='supplyVoltage/2.'<br />
• Vdd vdd gnd supplyVoltage DC<br />
• *-----------------------------------------------------------<br />
• * Simulation controls<br />
• *-----------------------------------------------------------<br />
• .tran 25ps 5000ps UIC<br />
• .option post<br />
• .plot v(A2))<br />
DCC 08<br />
Slide 18<br />
“bridge”<br />
• *-----------------------------------------------------------<br />
• * Simulation netlist<br />
• *-----------------------------------------------------------<br />
• .<br />
• .param lp=1.0u ln=1.0u<br />
• .param wnbridge= 2u wpbridge=4u<br />
• * Circuit ceases to oscillate above this ratio<br />
• *.param ratioCha<strong>in</strong>ToBridge = 1.972<br />
• *<br />
• *Circuit ceases to oscillate below this ratio<br />
• *.param ratioCha<strong>in</strong>ToBridge = 0.31<br />
• *<br />
• .param wncha<strong>in</strong> = 'wnbridge*ratioCha<strong>in</strong>ToBridge'<br />
• .param wpcha<strong>in</strong> = 'wpbridge*ratioCha<strong>in</strong>ToBridge'<br />
• .global vdd gnd<br />
• .subckt INV <strong>in</strong> out psource nsource<br />
• Mpullup out <strong>in</strong> psource vdd pch l=lp w=wp<br />
• Mpulldown out <strong>in</strong> nsource gnd nch l=ln w=wn<br />
• .ends INV<br />
• .subckt CELL <strong>in</strong>p <strong>in</strong>m outp outm<br />
• X<strong>in</strong>v1 <strong>in</strong>p outm vdd gnd INV wp='wpcha<strong>in</strong>'<br />
wn='wncha<strong>in</strong>'<br />
• X<strong>in</strong>v2 <strong>in</strong>m outp vdd gnd INV wp='wpcha<strong>in</strong>'<br />
wn='wncha<strong>in</strong>'<br />
• X<strong>in</strong>v3 outp outm vdd gnd INV wp='wpbridge'<br />
wn='wnbridge'<br />
• X<strong>in</strong>v4 outm outp vdd gnd INV wp='wpbridge'<br />
wn='wnbridge'<br />
• .ends CELL<br />
• .subckt CHAINOFCELLS2 <strong>in</strong>a <strong>in</strong>b outa outb<br />
• XCell1 <strong>in</strong>a <strong>in</strong>b oa1 ob1 CELL<br />
• XCell2 oa1 ob1 outa outb CELL<br />
• .ends CHAINOFCELLS2<br />
• XCha<strong>in</strong>OfCells2 A2 B2 B2 A2 CHAINOFCELLS2<br />
• .end sr<strong>in</strong>g
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