Download Final Design Presentation

Current Monitor
Group (1606)
Maya Dubrow
Barath Parthasarathy
Andrew Pikul
Jason Stock
Advisor: Ali Gokirmak
Outline
Executive Summary
System Breakdown
Characterization and Data
Future
of this
Project
Executive
Summary:
We’ve designed a ranging HIGH-SIDE current monitor, which attaches directly to Phonon’s
DC supply. We use a low-resistance sense resistor and amplifier to measure the sense voltage
drop. We’ve characterized this circuit on a mix of breadboard and PCB. We’ve met the
requirements we were given and have designed improvements to be made in the future.
The company wants software too.
System Breakdown
Built and Tested
Sensing Circuit
Ranging Circuit
Designed
Signal Postprocess
Anti Aliasing Filter
Second Stage Gain
Microcontroller (Controls All ICs)
Power Circuits
Sensing Circuit
Amplifier: LTC6101
Amplifies signal to be used for output.
3 separate op amps are used to reduce error caused by FET
impedance. Trimmer’s will be used to correct gain variability.
Very low thermal coefficients
High power rating
Ranging Circuit
Optoisolators: P227G
Mosfet: BUK 72150
Mux: MAX 7368
Analog 2x 4:1 multiplexer
100 kHz bandwidth
Supply voltage 3.3V
Second Stage Gain
ADG704
Analog 1x 4:1 multiplexer
Large bandwidth (MHz)
Supply voltage 3.3V
OPA1612
Max supply voltage 36 V
Bandwidth of 40 MHz at G=1
Low input offset voltage and current
Anti-Aliasing Filter
Anti-Aliasing is a common practice using an anti-aliasing filter to limit, or restrict the bandwidth to that of
the Nyquist limit.
LTC1564
Digitally controlled antialiasing filter
Adjustable cutoff frequency from 10kHz to 150kHz in steps of 10kHz
The sampling frequency for our DAQ is 48kHz, so our cutoff frequency should be roughly 24kHz.
Using this filter would be problematic because we would have to use either 20kHz or 30kHz, so there would
be some insufficient sampling rates.
TI’s Webench
Ended up designing a 5th-order bessel filter from scratch using TI’s Webench
software.
LTC1065
After a bit of research, we ended up finding a 5th order Bessel filter IC.
This helps immensely, and cuts down on implementation time.
LTC1065
Antialiasing filter with linear phase response
Operates from +/- 2.375V to +/-8.0V
Maximum cutoff frequency of 50kHz (controlled by an internal or external clock)
An input RC circuit can be used to attenuate incoming signals close to the filter clock frequency
Choosing a certain resistance value, will keep the Bessel passband response constant.
100:1 clock-to-cutoff frequency ratio
LTC1065 Schematic
Power Circuits
Sense amplifier is self powered!
3.3 Volts for IC
24 Volts for 2nd Stage Gain (Post Processing)
Gate Driver
Voltage Regulation
LM2585 (24 V)
●
Necessary for 2nd Stage gain
LM26001 (3.3V)
MUX
Gate Driver for LM61001
Anti-aliasing filter
Microcontroller
Gate Driver
LTC1910
Responsible for detecting a current overload within the LTC6101.
The devices turns off in harsh environments.
This time can be adjusted by the capacitance on pin 2 (150,000*C=T(delay))
Example: .33uF resistor gives us 50ms termination
𝝻Controller
4 GPIO for 3 multiplexers (range and gain)
4 GPIO for serial to DAQ
3 for possible auto ranging (comparator detection)
3 for SPI to Filter
1 for Clock to Filter
Total: 15 I/O… we can use a ATmega328P!
(power up/power down behavior is very important)
DAQ (USB → Computer)
Company Device
8 analog in (or 4 differential) fs = (48 kHz / #channels)
16 GPIO (Software Polled)
Software
.NET Driver (VB Requested)
Can do a voltage sweep with the DC Supply
Collects Data and Displays
Exports to Excel
Collected Data for 15 ohm DUT
Blue- 0.1Ω Rsense
Red- 0.25Ω Rsense
Green- 0.5Ω Rsense
Data was collected for 6 other DUTs: 49Ω, 100Ω, 200Ω, 500Ω, 1.2kΩ, 2.5kΩ.
Analysis
Analysis
Analysis
Analysis
Conclusion: Areas of Success
Deliverables tasked to us by Phonon were achieved.
Relatively Low Budget
Sensing/ Ranging (<$150)
Power Supply, Anti-Aliasing, Second Stage Gain, Microcontroller (<$150)
Efficient code.
Conclusion: Areas of Improvement
Lack of precise parts to complete finishing touches:
Power Circuit (Singular Power Supply)
Anti-aliasing (Limiting Frequency)
Microcontroller (IC Control)
Second-stage gain (Automatic Range Switching)
Acknowledgements
Thank you to Phonon Corporation for access to parts.
Thank you Dr. Gokirmak for helpful discussions.