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Debugging DC Voltage Lines Using an Oscilloscope
Kenny Johnson
Keysight Technologies
Power Integrity Program Manager
February 26, 2015
Page Webinar Goals or Outcome
Show you some things you can do today to:
– Debug and test PDN’s (power distribution networks) with
more precision, accuracy and confidence.
– More easily isolate root cause of PDN noise.
– Avoid false negative (or positive) test results.
– Become aware of specialized tools that can make your job
easier.
Simple Advanced things you can do today (10 things)
Debugging DC
Voltage Lines Using
an Oscilloscope 2
Page
Power Integrity Measurements
Believe it or not, this is what a
typical1.8V DC supply looks like if you
zoom-in on the top of it. The Need for Power Integrity
Measurements
• Increased functionality, higher power density
and higher frequency operation drives need for
lower supply voltages
• Power rail tolerances are much tighter (from +/-
5% down to +/- 1%)
• Ripple, noise and transients riding on these
lower DC supplies can adversely affect clocks
and digital data—Power Supply Induced Jitter
(PSIJ)
Debugging DC
Voltage Lines Using
an Oscilloscope 3
Page
The Case For Power Integrity
Debugging DC
Voltage Lines Using
an Oscilloscope
Moore’s Law: transistors on an integrated circuit will double every two years.
Past Present Past Present
Power and Current Density
10% 1-5%
Tolerances
Past Present
1-3%
Power
Savings
4
Page
The Case For Power Integrity
Debugging DC
Voltage Lines Using
an Oscilloscope
Power supply noise causes clock/data jitter.
Power Supply Tolerances
Switching Threshold Variation
Input
Output
Jitter
Jitter Jitter
5
Page
The Case For Power Integrity
Debugging DC
Voltage Lines Using
an Oscilloscope
PSIJ Example
73ps
114ps
1.10V Supply with 115mVpp Noise
Data Line Supply
1.10V Supply with 3mVpp Noise
6
Page
Power Integrity Measurements
Debugging DC
Voltage Lines Using
an Oscilloscope
Switching loads can
cause high frequency
supply noise.
Clock/Data
Power Rail
Additional Challenge
7
Page
The Case For Power Integrity
Debugging DC
Voltage Lines Using
an Oscilloscope
Switching Loads Example
Quiescent Counting up Simultaneously Switching
6mVpp 17mVpp 40mVpp
8
Page
Power Integrity Measurements
• Supply drift
• PARD (Periodic and Random
Disturbances)—noise, ripple and
switching transients on power
rails.
• Static and dynamic load
response.
• Programmable power rail
response.
• High frequency transients and
noise.
• Product electrical validation at
extended temperatures.
Common Power Integrity Measurements
Debugging DC
Voltage Lines Using
an Oscilloscope 9
Page
Power Integrity Measurements Fundamental Challenge
Challenge: Measure small
ac signal on top of large dc
signal
Measurement System Noise
(Scope, Probe, Connection…) 1. Measurement system noise
2. Large signal offset
Issues to overcome:
Tolerance Band
DC
Probing “golden” rule:
3. Do no harm (probe loading)
Debugging DC
Voltage Lines Using
an Oscilloscope 10
Page
Power Integrity Measurements The Set-up
InfiniiVision 6000 X-Series Oscilloscope
Debugging DC
Voltage Lines Using
an Oscilloscope 11
Page
Power Integrity Measurements Measurement Compare—Ends of The Spectrum
Specialized General Purpose
N7020A Power Rail Probe 10:1 Passive Probe
Debugging DC
Voltage Lines Using
an Oscilloscope 12
Page
Power Integrity Measurements Both Ends of The Spectrum
N7020A Power Rail Probe
Termination: 50Ω
Attenuation: 1:1
Bandwidth: 2GHz
Gnd connect: Coax “pigtail”
Passive Probe
Termination: 1MΩ
Attenuation: 10:1
Bandwidth: 500MHz
Gnd connect: “Alligator” clip
Good for qualitative measurements Good for quantitative measurements
Specialized General Purpose
Debugging DC
Voltage Lines Using
an Oscilloscope 14
Page
Power Integrity Measurements Both Ends of The Spectrum
N7020A Power Rail Probe
Termination: 50Ω
Attenuation: 1:1
Bandwidth: 2GHz
Gnd connect: Coax “pigtail”
Passive Probe
Termination: 1MΩ
Attenuation: 10:1
Bandwidth: 500MHz
Gnd connect: “Alligator” clip
Good for qualitative measurements Good for quantitative measurements
Specialized General Purpose
Debugging DC
Voltage Lines Using
an Oscilloscope 15
Page
Power Integrity Measurements Scope Input Termination—Lowest Noise Path
50Ω: 0.8mVp-p Noise
1MΩ: 2.7mVp-p Noise
Debugging DC
Voltage Lines Using
an Oscilloscope 16
Page
Power Integrity Measurements Things You Can Do.
Choose the low noise path.
Debugging DC
Voltage Lines Using
an Oscilloscope 17
Page
Power Integrity Measurements Both Ends of The Spectrum
N7020A Power Rail Probe
Termination: 50Ω
Attenuation: 1:1
Bandwidth: 2GHz
Gnd connect: Coax “pigtail”
Passive Probe
Termination: 1MΩ
Attenuation: 10:1
Bandwidth: 500MHz
Gnd connect: “Alligator” clip
Good for qualitative measurements Good for quantitative measurements
Specialized General Purpose
Debugging DC
Voltage Lines Using
an Oscilloscope 18
Page
Power Integrity Measurements Attenuation Ratio Effects Noise—Ex. 50mVpp Sine Wave
1:1 Passive Probe—51mVpp
10:1 Passive Probe—68mVpp Overstated ~36%
Debugging DC
Voltage Lines Using
an Oscilloscope 19
Page
Power Integrity Measurements Things You Can Do.
Reduce attenuation ratio.
Debugging DC
Voltage Lines Using
an Oscilloscope 20
Page
Power Integrity Measurements Both Ends of The Spectrum
N7020A Power Rail Probe
Termination: 50Ω
Attenuation: 1:1
Bandwidth: 2GHz
Gnd connect: Coax “pigtail”
Passive Probe
Termination: 1MΩ
Attenuation: 10:1
Bandwidth: 500MHz
Gnd connect: “Alligator” clip
Good for qualitative measurements Good for quantitative measurements
Specialized General Purpose
Debugging DC
Voltage Lines Using
an Oscilloscope 21
Page
Power Integrity Measurements
Debugging DC
Voltage Lines Using
an Oscilloscope
BW Effects Noise—Ex. N7020A Probe/6000 X-Series Scope
3 GHz BW Limit
22
Page
Power Integrity Measurements
Debugging DC
Voltage Lines Using
an Oscilloscope
BW Effects Noise—Ex. N7020A Probe/6000 X-Series Scope
1.67 mVp-p
3 GHz BW Limit
23
Page
Power Integrity Measurements
Debugging DC
Voltage Lines Using
an Oscilloscope
BW Effects Noise—Ex. N7020A Probe/6000 X-Series Scope
1.07 mVp-p
1.5 GHz BW Limit
24
Page
Power Integrity Measurements
Debugging DC
Voltage Lines Using
an Oscilloscope
BW Effects Noise—Ex. N7020A Probe/6000 X-Series Scope
800 µVp-p
200 MHz BW Limit
25
Page
Power Integrity Measurements
Debugging DC
Voltage Lines Using
an Oscilloscope
BW Effects Noise—Ex. N7020A Probe/6000 X-Series Scope
670 µVp-p
20 MHz BW Limit
26
Page
Power Integrity Measurements Things You Can Do.
BW—use what is needed.
Debugging DC
Voltage Lines Using
an Oscilloscope 27
Page
Power Integrity Measurements Tradeoff with BW limiting—Use What is Needed
BW: 2.5 GHz
Captures high-freq transients
BW: 20 MHz
Attenuates high-freq transients
Switching
currents cause
transients that
can easily exceed
1GHz.
Supply noise is a
leading cause of
clock/data jitter.
Debugging DC
Voltage Lines Using
an Oscilloscope 28
Page
N7020A 2 GHz, 1:1
N2870A 35 MHz, 1:1
Power Integrity Measurements Having Enough BW is Critical
Specialized
General Purpose
Debugging DC
Voltage Lines Using
an Oscilloscope 29
Page
Power Integrity Measurements Things You Can Do.
BW—have enough.
Debugging DC
Voltage Lines Using
an Oscilloscope 30
Page
Power Integrity Measurements Both Ends of The Spectrum
N7020A Power Rail Probe
Termination: 50Ω
Attenuation: 1:1
Bandwidth: 2GHz
Gnd connect: Coax “pigtail”
Passive Probe
Termination: 1MΩ
Attenuation: 10:1
Bandwidth: 500MHz
Gnd connect: “Alligator” clip
Good for qualitative measurements Good for quantitative measurements
Specialized General Purpose
Debugging DC
Voltage Lines Using
an Oscilloscope 31
Page
Power Integrity Measurements Gnd Connection Length Effects Noise: Ex. Passive Probe
32.8 mVp-p
57.6 mVp-p (76% Larger)
Debugging DC
Voltage Lines Using
an Oscilloscope 32
Page
Power Integrity Measurements Gnd Connection Length Effects Noise
23.1 mVp-p
30.1 mVp-p (30% Larger)
Debugging DC
Voltage Lines Using
an Oscilloscope 33
Page
Power Integrity Measurements Things You Can Do.
Minimize ground loop area.
Debugging DC
Voltage Lines Using
an Oscilloscope 34
Page
Power Integrity Measurements Large DC Signal Offset
Remove DC Signal Offset
• Probe Offset
• DC Block
At larger V/div
• Sensitivity is decreased
• Scope noise relative to small ac
signal is increased. 131mVp-p
With Full Offset: 83mVp-p
(58% Larger)
Debugging DC
Voltage Lines Using
an Oscilloscope 35
Page
Power Integrity Measurements Removing Large DC Signal—Probe Offset or DC Block
DC Block
Using a DC Block
Using Probe Offset
Debugging DC
Voltage Lines Using
an Oscilloscope 36
Page
Power Integrity Measurements Removing Large DC Signal—Probe Offset of DC Block
0V
1.5V
DC Block
Using a DC Block
Using Probe Offset
Debugging DC
Voltage Lines Using
an Oscilloscope 37
Page
Power Integrity Measurements Things You Can Do.
Use probe offset.
Debugging DC
Voltage Lines Using
an Oscilloscope 38
Page
Power Integrity Measurements A Word of Caution: Direct 50Ω Connection
The scope you are using may have enough frame offset for some signals.
Beware of 50Ω load at dc.
Specialized
General Purpose
N7020A—50kΩ @ DC
DC Vrms= 3.31V
50Ω cable to oscilloscope 50Ω input
(50Ω @ DC)
50Ω @ DC pulled this
supply down ~60mV
(changed the target this
much)
DC Vrms= 3.25V
Debugging DC
Voltage Lines Using
an Oscilloscope 39
Page
Power Integrity Measurements Things You Can Do.
Minimize loading.
Debugging DC
Voltage Lines Using
an Oscilloscope 40
Page
Power Integrity Measurements Gaining Insight—Using The Frequency Domain
Example:
In time domain view
switching currents of
high speed digital
signals may not be
obvious
Debugging DC
Voltage Lines Using
an Oscilloscope 41
Page
Power Integrity Measurements Gaining Insight—Using The Frequency Domain
Example:
Using FFT’s can
enable identification
of possible noise
sources.
In this case, digital
circuits operating off
5V are causing noise
on 3.3V supply 3.3V supply
2.8MHz switcher 125MHz clock
Debugging DC
Voltage Lines Using
an Oscilloscope 42
Page
Power Integrity Measurements Things You Can Do.
Use The Frequency Domain
Debugging DC
Voltage Lines Using
an Oscilloscope 43
Page
Power Integrity Measurements Track Down Noise Sources with Trigger and Averaging.
Example:
Using FFT’s we see
that the digital
circuits are causing
noise on the 3.3V
supply.
Is it worth making
changes (how much
are they effecting the
supply)?
3.3V supply
10MHz clock
Debugging DC
Voltage Lines Using
an Oscilloscope 44
Page
Power Integrity Measurements Track Down Noise Sources with Trigger and Averaging.
Example:
Triggering on
possible noise
source and enabling
averaging shows the
noise on the supply
that is coherent to
the noise source.
3.3V supply
Trigger on the clock Turn on averaging
Signal content not related to trigger source is averaged out.
10MHz clock
Debugging DC
Voltage Lines Using
an Oscilloscope 45
Page
Power Integrity Measurements Things You Can Do.
Use triggering and averaging.
Debugging DC
Voltage Lines Using
an Oscilloscope 46
Page
Power Integrity Measurements Summary
Good for qualitative measurements Good for quantitative measurements
Specialized General Purpose
1. Choose the low noise path.
2. Reduce attenuation ratio.
3. BW—use what is needed.
4. BW—have enough.
5. Minimize ground loop area.
6. Use probe offset.
7. Minimize loading.
8. Use The Frequency Domain.
9. Use triggering and averaging.
Bonus Tip: Use a specialized tool
Keysight N7020A Power Rail Probe:
www.keysight.com/find/N7020A
Debugging DC
Voltage Lines Using
an Oscilloscope 47
Page
Power Integrity Measurements N7020A Power Rail Probe
InfiniiVision
3000 X-Series Oscilloscopes
InfiniiVision
4000 X-Series Oscilloscopes
Infiniium S-Series High-Definition Oscilloscopes
+ N8833A Crosstalk Application
Also Compatible With:
Keysight N7020A Power Rail Probe:
www.keysight.com/find/N7020A
InfiniiVision 6000
X-Series
Oscilloscope
Debugging DC
Voltage Lines Using
an Oscilloscope 48
Page
Resources
Debugging DC
Voltage Lines Using
an Oscilloscope
Learning Center: www.keysight.com/find/infiniivision-knowledge
Webcasts: http://pages.electronicdesign.com/Digital-Design-Test-2017
Videos: youtube.com/keysightoscilloscope
Keysight Probes & Accessories: keysight.com/find/scope_probes
Other Resources: keysight.com/find/scopes-power
49
Page
InfiniiVision X-Series
Debugging DC
Voltage Lines Using
an Oscilloscope
1000 X-Series 2000 X-Series 3000T X-Series 4000 X-Series 6000 X-Series
Bandwidth 50 – 100 MHz 70 – 200 MHz 100 MHz – 1 GHz 200 MHz – 1.5 GHz 1 – 6 GHz
Channels 2 2 or 4 2 or 4 2 or 4 2 or 4
Sample Rate 2 GSa/s 2 GSa/s 5 GSa/s 5 GSa/s 20 GSa/s
Memory (Max) 100 k 1 M 4 M 4 M 4 M
Segmented
memory
Standard on DSO
models
Option Standard Standard Standard
Update Rate 50 k/sec 50 k/sec 1 M/sec 1 M/sec 500 k/sec
MSO Option No 8-Ch 16-Ch 16-Ch
16-Ch
Active Probe
Power
No No 2-Ch 4-Ch 4-Ch
Integrated tools FRA (Bode plot),
DVM, frequency
counter
DVM, Frequency
counter
DSOX2APPBNDL
DVM, Frequency
counter
DSOXT3APPBNDL
DVM, Frequency
counter
DSOX4APPBNDL
DVM, Frequency
counter
DSOX6APPBNDL
Display 7-in WVGA
display
8.5-in WVGA
display
8.5-inch capacitive
touch screen
12.1-inch capacitive
touch screen
12.1-inch capacitive
touch screen
50
Page
June 7, 2017
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and
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Score 2 Scopes for the price of 1 Oscilloscope Promotion
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• Complete the request form
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oscilloscope
• Provide date of purchase
To Claim the Free DSOX1102G Oscilloscope
Debugging DC
Voltage Lines Using
an Oscilloscope 51
Page
Debugging DC Voltage Lines Using an Oscilloscope
Thank you for your time.
Debugging DC
Voltage Lines Using
an Oscilloscope 52
