John Brown Art Kay Tim Green TinaTI
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High Current VI Circuits. The Four Musketeers of HPL. Recognize. Analyze. Synthesize. Tinaize. John Brown Art Kay Tim Green TinaTI. Potential Applications, End Equipment, Markets Circuit Topologies Circuit Stability Issues  PowerPoint PPT PresentationTRANSCRIPT
John Brown Art Kay Tim Green TinaTISynthesizeTinaizeThe Four Musketeers of HPLAnalyzeRecognizeHigh Current VI Circuits
VI Circuit Recognize ObjectivesPotential Applications, End Equipment, MarketsCircuit TopologiesCircuit Stability IssuesPower Dissipation IssuesTransient Protection IssuesPCB IssuesSemiconductor Overstress Issues
VI Circuit Analyze, Synthesize, Tinaize ObjectivesProvide Synthesis Techniques for Common TopologiesProvide Tools to Simplify Stability AnalysisProvide Analysis Techniques for Power DissipationProvide Solutions for Common Transient ProblemsProvide Tips for PCB LayoutsProvide Tricks for TinaTI Analysis
Power Amplifiers Strategy for Markets1. High Volume GrowthCommunications Optical Networking ONET (TECs, Laser Diode Pumps, Avalanche Photodiode Bias HV)DLP Digital Light Projectors (high voltage OPA)Industrial Electromechanical (OPA, PWM)Automotive Electromechanical (OPA, PWM)2. Gen Std Catalog Products Steady Growth Industrial, Medical, Lab, ATE, Some Audio, ConsumerHigh Speed Buffers, High Voltage, High Current OPAs
Power Amplifiers Applications in Markets1. Test, Particularly Automated ATEAnalog Pin Driver, Power V & I Excitation2. Power Line CommunicationHigh Pulse Current Drive Through Transformeror Capacitor Coupled ac Power Line (Residential & Commercial)3. Displays High Current Driver for Dithering Projected Light Beam, High Voltage for Ink Jet Printers4. Industrial, Medical, Scientific, Analytical, and Laboratory TEC Drivers, Electromechanical Linear Valve/Positioner Drivers, Motors, Power Supplies5. Optical Networking / Gen Laser SystemsTEC Drivers (Thermoelectric Coolers), Laser Pumps 6. Some AudioHeadphone and Speaker Drivers7. Some AutomotivePower Steering Pumps, Window MotorsCOMPETITION1. Mostly Discrete2. National Semiconductor, ST, Maxim, Allegro, ONSEMI, International Rectifier, Infineon, Toshiba
Review  Essential Principles Poles, Zeros, Bode Plots Op Amp Loop Gain Model Loop Gain Test and 1/ RateofClosure Stability Criteria Loop Gain RulesofThumb for Stability RO and ROUT
Commercial Break(Shameless SelfPromotion)See 15 Part Series: Operational Amplifier Stabilityhttp://www.analogzone.com/acqt0704.htm
Poles and Bode PlotsPole Location = fPMagnitude = 20dB/Decade SlopeSlope begins at fP and continues down as frequency increasesActual Function = 3dB down @ fPPhase = 45/Decade Slope through fPDecade Above fP Phase = 90Decade Below fP Phase = 0A(dB) = 20Log10(VOUT/VIN)
AC
R
C
VIN
VOUT
A = VOUT/VIN
Single Pole Circuit Equivalent
X100,000
0
20
40
60
80
100
10M
1M
100k
10k
1k
100
10
1
Frequency (Hz)
A (dB)
+90
90
+45
+45
10
100
1k
10k
100k
1M
10M
Frequency (Hz)
0
q
(degrees)
20dB/Decade6dB/Octave
45o @ fP
45o/Decade
fP
90o
0o
G
0.707G = 3dB
StraightLine Approximation
Actual Function
Zeros and Bode PlotsZero Location = fZMagnitude = +20dB/Decade SlopeSlope begins at fZ and continues up as frequency increasesActual Function = +3dB up @ fZPhase = +45/Decade Slope through fZDecade Above fZ Phase = +90Decade Below fZ Phase = 0A(dB) = 20Log10(VOUT/VIN)
AC
R
C
VOUT
A = VOUT/VIN
Single Zero Circuit Equivalent
X100,000
0
20
40
60
80
100
10M
1M
100k
10k
1k
100
10
1
Frequency (Hz)
A (dB)
+90
90
+45
+45
10
100
1k
10k
100k
1M
10M
Frequency (Hz)
0
q
(degrees)
+90o
0o
+45o/Decade
+45o @ fZ
fZ
+20dB/Decade+6dB/Octave
StraightLine Approximation
G
1.414G = +3dB(1/0.707)G = +3dB
Actual Function
Op Amp: Intuitive Model
+

K(f)
VDIFF
IN+
IN
RIN
RO
VO
VOUT
x1
Op Amp Loop Gain ModelVOUT/VIN = Acl = Aol/(1+Aol)If Aol >> 1 then Acl 1/Aol: Open Loop Gain: Feedback FactorAcl: Closed Loop Gain1/b = Small Signal AC Gainb = feedback attenuation
+

+

S
VOUT
b network
b
RF
RI
VIN
Aol
S
+

VOUT
VIN
VFB
VFB
RF
RI
b =VFB/VOUT
VOUT
b network
Stability Criteria
Traditional Loop Gain TestOp Amp Loop Gain ModelOp Amp is Closed LoopSPICE Loop Gain Test:Break the Closed Loop at VOUTGround VINInject AC Source, VX, into VOUTAol = VY/VX
+

+

b network
RF
RI
VIN
VFB
VOUT
+

+

RF
RI
VIN
b network
VFB
VOUT
VX
VY
1GF
1GH
Short for ACOpen for DC
Open for ACShort for DC
and 1/ is easy to calculate as feedback network around the Op Amp1/ is reciprocal of Easy RulesOfThumb and Tricks to Plot 1/ on Op Amp Aol Curve
+

+

VOUT
b network
RF
RI
VIN
VFB
VFB
RF
RI
b =VFB/VOUT
VOUT
b network
Loop Gain Using Aol & 1/Plot (in dB) 1/ on Op Amp Aol (in dB)Aol = Aol(dB) 1/(dB)Note how Aol changes with frequency
Proof (using log functions): 20Log10[Aol] = 20Log10(Aol)  20Log10(1/) = 20Log10[Aol/(1/)] = 20Log10[Aol]
0
20
40
60
80
100
10M
1M
100k
10k
1k
100
10
1
Frequency (Hz)
Aol (dB)
fcl
1/b
Acl
Aol
Aol b(Loop Gain)
Closed Loop Response
Open Loop Response
Stability Criteria using 1/ & AolAt fcl: Loop Gain (Aolb) = 1
RateofClosure @ fcl =(Aol slope 1/ slope)*20dB/decade RateofClosure @ fcl = STABLE**40dB/decade RateofClosure@ fcl = UNSTABLE
0
20
40
60
80
100
10M
1M
100k
10k
1k
100
10
1
Frequency (Hz)
Aol (dB)
Aol
1/b1
1/b2
1/b3
1/b4
fcl1
fcl4
fcl3
fcl2
*
*
**
**
 Loop Gain Bandwidth Rule: 45 degrees for f < fclAol (Loop Gain) Phase PlotLoop Stability Criteria:
Poles & Zeros Transfer: (1/, Aol) to Aol
Aol & 1/ PlotLoop Gain Plot(Aol)To Plot Aol from Aol & 1/ Plot:
Poles in Aol curve are poles in Aol (Loop Gain)PlotZeros in Aol curve are zeros in Aol (Loop Gain) Plot
Poles in 1/ curve are zeros in Aol (Loop Gain) PlotZeros in 1/ curve are poles in Aol (Loop Gain) Plot[Remember: is the reciprocal of 1/]
0
20
40
60
80
100
10M
1M
100k
10k
1k
100
10
1
Frequency (Hz)
A (dB)
Aol
fcl
1/b
fp1
fp2
fz1
Aol
b
0
20
40
60
80
100
10M
1M
100k
10k
1k
100
10
1
Frequency (Hz)
A (dB)
fp1
fz1
fp2
fcl
Frequency Decade Rules for Loop GainLoop Gain View: Poles: fp1, fp2, fz1; Zero: fp3
Rules of Thumb for Good Loop Stability:
Place fp3 within a decade of fz1 fp1 and fz1 = 135 phase shift at fz1 fp3 < decade will keep phase from dipping further
Place fp3 at least a decade below fcl Allows Aol curve to shift to the left by one decade
+

+

VIN
RI
RF
VOUT
CL
Cn
Rn
0
20
40
60
80
100
10M
1M
100k
10k
1k
100
10
1
Frequency (Hz)
A (dB)
fcl
fp1
fp2
fz1
fp3
Aol
1/Beta
VOUT/VIN
Op Amp Model for Derivation of ROUT From: Frederiksen, Thomas M. Intuitive Operational Amplifiers. McGrawHill Book Company. New York. Revised Edition. 1988.ROUT = RO / (1+Aol)
+

RDIFF
xAol
RO
IN
+IN

+
VE
Op Amp Model
1A
VOUT
VO
RF
RI
IOUT
VFB
ROUT = VOUT/IOUT
Op Amp Model for Loop Stability AnalysisRO is constant over the Op Amps bandwidth RO is defined as the Op Amps Open Loop Output Resistance RO is measured at IOUT = 0 Amps, f = 1MHz (use the unloaded RO for Loop Stability calculations since it will be the largest value worst case for Loop Stability analysis)RO is included when calculating b for Loop Stability analysis
RO & Op Amp Output Operation Bipolar Power Op Amps CMOS Power Op Amps Light Load vs Heavy Load
RO Measure w/DC Operating Point: IOUT = 0mA
RO Measure w/DC Operating Point: IOUT = 0mARO = VOA / AM1RO = 9.61mVrms / 698.17Arms RO = 13.765
RO Measure w/DC Operating Point IOUT = 4.45mA Sink
RO Measure w/DC Operating Point IOUT = 4.45mA SinkRO = VOA / AM1RO = 3.45Vrms / 706.25Arms RO = 4.885
RO Measure w/DC Operating Point IOUT = 5.61mA Source
RO Measure w/DC Operating Point IOUT = 5.61mA SourceRO = VOA / AM1RO = 3.29mVrms / 700.98Arms RO = 4.693
RO Measure w/DC Operating Point IOUT = 2.74A Source
RO Measure w/DC Oper
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