* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Introduction to Class
Mechanical filter wikipedia , lookup
Electric power system wikipedia , lookup
Electrification wikipedia , lookup
Solar micro-inverter wikipedia , lookup
Ringing artifacts wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Power inverter wikipedia , lookup
Immunity-aware programming wikipedia , lookup
Scattering parameters wikipedia , lookup
Audio power wikipedia , lookup
History of electric power transmission wikipedia , lookup
Power engineering wikipedia , lookup
Pulse-width modulation wikipedia , lookup
Voltage regulator wikipedia , lookup
Variable-frequency drive wikipedia , lookup
Amtrak's 25 Hz traction power system wikipedia , lookup
Distributed element filter wikipedia , lookup
Voltage optimisation wikipedia , lookup
Alternating current wikipedia , lookup
Mains electricity wikipedia , lookup
Buck converter wikipedia , lookup
Nominal impedance wikipedia , lookup
Distribution management system wikipedia , lookup
Power electronics wikipedia , lookup
Power supply wikipedia , lookup
Three-phase electric power wikipedia , lookup
Opto-isolator wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Ensuring Clean Power for RF and Digital Applications Tom Boehler and Steven Sandler AEi Systems Los Angeles, CA, 90045; 310-216-1144 [email protected] [email protected] Copyright © 2012 AEi Systems, LLC All Rights Reserved How Performance is Impacted By Poor Stability PSRR Reverse Reverse Transfer Transfer Accuracy Poor Stability Permeates System Performance Degrades PSRR Degrades reverse transfer Degrades output impedance Degrades output noise Degrades voltage accuracy Distributed Architecture Power System Bus Input Filter Converter LDO Filter 1.5V LDO Filter 1.8V LDO Filter 2.5V 3.3V Power Supply Measurements PSRR Voltage Regulation Crosstalk Ripple & Noise Filter Stability Dropout Step Load DUT Input Z Stability Output Z Tempco Reverse Transfer Bode Plots - Stability Measures: Bandwidth Phase Margin Gain Margin Pick your injection location carefully! Frequency response will vary with line voltage and load current The transformer is a crucial part of the measurement Injection signal size is very important as well Bode Plots - Stability Output Impedance Output Impedance Why is this important? Many PDNs have impedance requirements Identifies L-C resonances of filters or parasitics Provides and alternative way to measure the stability of a system 30 25 20 15 10 TR1/dB 5 0 -5 -10 -15 -20 102 103 104 105 f/Hz TR1: Mag(Impedance) 106 107 Output Impedance Tg Q d d Tg Freq Group Delay from Phase Quality Factor from Group Delay 4 1 1 4 Q 180 PM atan 4 2 Q Phase Margin Output Impedance Step Load Step Load Low resolution LM117 Step Load Transient High resolution Small signal vs. large signal measurements, slew rate limitations Ring Freq., Amp., & Phase are a function of the load step period! Sampling Issues – may miss L*di/dt spikes Step Load 30 25 20 15 TR1/dB 10 5 0 -5 -10 -15 -20 102 103 104 105 106 107 f/Hz TR1: Mag(Impedance) Corresponding Output Impedance How do we know the ringing is real? We measure it, we model it, and we can see it in the output impedance. And Resulting Transient Response Power Supply Rejection Ratio Power Supply Rejection Ratio Power Supply Rejection Ratio Performance is a strong function of stability IC manufacturers often spec PSRR at 60-120Hz which is not useful for space applications Poor PSRR performance can be a serious issue in distributed architectures Power Supply Rejection Ratio Going back to our PDN example… Bus Input Filter Converter LDO Filter LDO Filter 1.8V LDO Filter 2.5V 1.5V iac 3.3V Current perturbations on the output of a regulator can go right back through to the bus and due to real bus impedance will present itself as a voltage These voltage perturbations will then go through other regulators on the bus through their PSRR Power Supply Rejection Ratio Reverse Transfer Power Supply Rejection Ratio Reverse Transfer 1 10 TR1/dB 0 -10 -20 -30 f/Hz TR1/dB Cursor 1 20.134k 14.048 -40 102 103 104 105 106 107 f/Hz TR1: Mag(Gain) Unlike PSRR, at low frequency there is little to no signal attenuation Reverse transfer leads to crosstalk between regulators connected to the same power bus How RF and Digital Performance is Impacted By Poor Stability So how does poor stability affect a power supply? Many characteristics are severely degraded by poor phase margin • Crosstalk, Reverse Transfer, Phase noise, Jitter, ENOB, Noise in ADCs and other parameters Many of our classical measurement techniques are no longer valid Systems are more complex, requiring complete characterization & verification, moving towards more simulation becoming difficult • Many SPICE models offer poor fidelity How RF and Digital Performance is Impacted By Poor Stability PSRR Reverse Reverse Transfer Transfer Accuracy Poor Stability Permeates System Performance Degrades PSRR Degrades reverse transfer Degrades output impedance Degrades output noise Degrades voltage accuracy So why does it matter? So why does it matter? So why does it matter? 20MHz clock phase noise measurement Powered by regulator with 70º of phase margin Only 4.9ps of Jitter – very clean So why does it matter? 20MHz clock phase noise measurement Powered by regulator with 15º of phase margin Jitter now measures 481ps – NOT acceptable. Summary As load circuitry becomes more complex and the switching speeds and magnitudes grow, power systems design becomes more critical to the overall performance of the product We need better characterization data Measurement of all key aspects of a power system is ESSENTIAL We need to make measurements more accurately There are better test techniques and test equipment that can help us that don’t cost a fortune Think of better more stable power supplies as a free performance boost for digital and RF systems! Thank you for listening! Questions?