“The measure of intelligence is the ability to change” -Albert Einstein
British Columbia, Canada
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Here's an edge at the SW node when it transitions from the low side turning off to high side turning on. Blue trace is the PWM HI input of the GaNFET. Green trace is the SW node at the inductor.
The STM32 HRTIM hardware is configured to about 5ns of deadtime on the complementary outputs, which has some propagation delay. The roughly 10 ns negative interval occurs while both GaNs are off. The inductor current must continue flowing, so it pulls the SW node negative through third quadrant conduction until the high-side FET turns on. GaNs do not have a body diode like a MOSFET, and reverse voltage is higher.. in this case nearly -5V.
On the spectrum analyzer with a near field probe sitting over top of the hot loop, you can see the energy of the ringing at around 180MHz.
Going to see if I can pull off a CNC machined digital SMPS using an STM32G474 and LMG5200 GaN half bridge as a power distribution board for my hobby robot.
The GaN stage will be driven by the G474's HRTIM, with ~184 ps (~5.44 GHz equivalent) timing resolution.
Inductor current is measured with a 4 terminal kelvin shunt (much more reliable on CNC boards, as kelvin is internal to the resistor) and high side INA sense amp, feeding both an ADC and an on chip comparator.
Planning to run peak current-mode control.. an internal DAC set by the outer voltage loop defines the cycle by cycle current threshold on the comparator, which asynchronously terminates the PWM pulse through HRTIM hardware.
The outer voltage loop will use the G474's FMAC accelerator for 3P3Z IIR compensation from a voltage divider buffered using an internal opamp follower routed to another ADC channel. Also connected to a comparator for HRTIM fault events for fast hardware based over voltage lockout.
Includes a INA254 bidirectional sense amp with integrated 400uOhm shunt for monitoring battery current.
Added CAN bus to broadcast voltage, current and status telemetry across the platform.
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Power conversion tuning needs all the toys turned on.
Spectrum analyzer with a near field probe to watch ringing
500MHz scope to actually see ringing (switch nodes look clean and crisp on a bandwidth limited scope.. they aren’t.. board parasitics ring in the 100s of MHz)
PCBite with SQ 500MHz probes to match the scope bandwidth. Spring grounds to reduce noise pickup.
Arbitrary waveform generator which can be controlled be the scope in its bode plot functions. You can use this to inject perturbations into a control loop to measure gain and phase margins.
6 1/2 digit DMM. 4 wire kelvin resistance measurements, and Ethernet. Especially useful for agents talking SCPI as a reference to check ADC scaling.
200W Electronic load to provide static or dynamic load transients to the supply. Can also run tests like short circuits to validate protection measures. Also controllable over the network.
3 channel DC bench supply. Constant current is a must during bringup so you don’t blow FETs.
And a higher output 360W supply that I’ll move to when I run out of headroom on the triple channel.
Going to see if I can pull off a CNC machined digital SMPS using an STM32G474 and LMG5200 GaN half bridge as a power distribution board for my hobby robot.
The GaN stage will be driven by the G474's HRTIM, with ~184 ps (~5.44 GHz equivalent) timing resolution.
Inductor current is measured with a 4 terminal kelvin shunt (much more reliable on CNC boards, as kelvin is internal to the resistor) and high side INA sense amp, feeding both an ADC and an on chip comparator.
Planning to run peak current-mode control.. an internal DAC set by the outer voltage loop defines the cycle by cycle current threshold on the comparator, which asynchronously terminates the PWM pulse through HRTIM hardware.
The outer voltage loop will use the G474's FMAC accelerator for 3P3Z IIR compensation from a voltage divider buffered using an internal opamp follower routed to another ADC channel. Also connected to a comparator for HRTIM fault events for fast hardware based over voltage lockout.
Includes a INA254 bidirectional sense amp with integrated 400uOhm shunt for monitoring battery current.
Added CAN bus to broadcast voltage, current and status telemetry across the platform.
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At 10W load the STLink SWD probe is running hotter than anything on the board
Going to see if I can pull off a CNC machined digital SMPS using an STM32G474 and LMG5200 GaN half bridge as a power distribution board for my hobby robot.
The GaN stage will be driven by the G474's HRTIM, with ~184 ps (~5.44 GHz equivalent) timing resolution.
Inductor current is measured with a 4 terminal kelvin shunt (much more reliable on CNC boards, as kelvin is internal to the resistor) and high side INA sense amp, feeding both an ADC and an on chip comparator.
Planning to run peak current-mode control.. an internal DAC set by the outer voltage loop defines the cycle by cycle current threshold on the comparator, which asynchronously terminates the PWM pulse through HRTIM hardware.
The outer voltage loop will use the G474's FMAC accelerator for 3P3Z IIR compensation from a voltage divider buffered using an internal opamp follower routed to another ADC channel. Also connected to a comparator for HRTIM fault events for fast hardware based over voltage lockout.
Includes a INA254 bidirectional sense amp with integrated 400uOhm shunt for monitoring battery current.
Added CAN bus to broadcast voltage, current and status telemetry across the platform.
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It’s alive.. working on firmware bringup
Going to see if I can pull off a CNC machined digital SMPS using an STM32G474 and LMG5200 GaN half bridge as a power distribution board for my hobby robot.
The GaN stage will be driven by the G474's HRTIM, with ~184 ps (~5.44 GHz equivalent) timing resolution.
Inductor current is measured with a 4 terminal kelvin shunt (much more reliable on CNC boards, as kelvin is internal to the resistor) and high side INA sense amp, feeding both an ADC and an on chip comparator.
Planning to run peak current-mode control.. an internal DAC set by the outer voltage loop defines the cycle by cycle current threshold on the comparator, which asynchronously terminates the PWM pulse through HRTIM hardware.
The outer voltage loop will use the G474's FMAC accelerator for 3P3Z IIR compensation from a voltage divider buffered using an internal opamp follower routed to another ADC channel. Also connected to a comparator for HRTIM fault events for fast hardware based over voltage lockout.
Includes a INA254 bidirectional sense amp with integrated 400uOhm shunt for monitoring battery current.
Added CAN bus to broadcast voltage, current and status telemetry across the platform.
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Honestly cleaner than I expected @zackslab .. blue is high side gate, green is SW node at 350MHz BW. 1.1V overshoot and ringing is only lasts a few cycles
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SMT components are populated except output bulk caps to leave room to get the iron in to solder the top side of the via pins next to the inductor
Going to see if I can pull off a CNC machined digital SMPS using an STM32G474 and LMG5200 GaN half bridge as a power distribution board for my hobby robot.
The GaN stage will be driven by the G474's HRTIM, with ~184 ps (~5.44 GHz equivalent) timing resolution.
Inductor current is measured with a 4 terminal kelvin shunt (much more reliable on CNC boards, as kelvin is internal to the resistor) and high side INA sense amp, feeding both an ADC and an on chip comparator.
Planning to run peak current-mode control.. an internal DAC set by the outer voltage loop defines the cycle by cycle current threshold on the comparator, which asynchronously terminates the PWM pulse through HRTIM hardware.
The outer voltage loop will use the G474's FMAC accelerator for 3P3Z IIR compensation from a voltage divider buffered using an internal opamp follower routed to another ADC channel. Also connected to a comparator for HRTIM fault events for fast hardware based over voltage lockout.
Includes a INA254 bidirectional sense amp with integrated 400uOhm shunt for monitoring battery current.
Added CAN bus to broadcast voltage, current and status telemetry across the platform.
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Going to see if I can pull off a CNC machined digital SMPS using an STM32G474 and LMG5200 GaN half bridge as a power distribution board for my hobby robot.
The GaN stage will be driven by the G474's HRTIM, with ~184 ps (~5.44 GHz equivalent) timing resolution.
Inductor current is measured with a 4 terminal kelvin shunt (much more reliable on CNC boards, as kelvin is internal to the resistor) and high side INA sense amp, feeding both an ADC and an on chip comparator.
Planning to run peak current-mode control.. an internal DAC set by the outer voltage loop defines the cycle by cycle current threshold on the comparator, which asynchronously terminates the PWM pulse through HRTIM hardware.
The outer voltage loop will use the G474's FMAC accelerator for 3P3Z IIR compensation from a voltage divider buffered using an internal opamp follower routed to another ADC channel. Also connected to a comparator for HRTIM fault events for fast hardware based over voltage lockout.
Includes a INA254 bidirectional sense amp with integrated 400uOhm shunt for monitoring battery current.
Added CAN bus to broadcast voltage, current and status telemetry across the platform.
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Made a breakout for an SSM2518 audio amp in a 0.5mm pitch QFN package that can push 2W per channel into a 4 ohm load on a 5V supply.
Connected it up to the jetson, and configured the DTB for I2S output, and it works.. sounds surprisingly good too.
They expose a register set for config and gain/attenuation over an I2C interface, which connects up to the Stemma QT port
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How long before someone suggests AI could cross an air gap by modulating the weight of USB drives?
Magnetic is just flipping polarity. But NAND flash is actually adding electrons.
I always am like “nah, NAND actually gets lighter when you add data because erased NANDs is all 1’s!” But then I remember how writing 0’s is actually what adds electrons because NAND is crazy like that.
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5Mbit CAN link to the custom motor controller is working from the Jetson using an MCP2518FD SPI interface.
Working end to end with a Bluetooth gamepad sending velocity targets over CAN, and the motor controller firmware does cascaded cycle by cycle current PI loop, and a velocity loop from the optical encoder.
Need to CNC a second motor driver, and a power distribution/voltage monitor board…
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Making a motor controller this evening. Trying out these LMG5200 GaN half bridges.
They have integrated high side drivers and only need an external bootstrap cap and logic level inputs which make things easy.
Also trying out an INA254 current sense package with integrated 400uOhm shunt and bidirectional sense amp biased to midrail, connected inline with motor so it measures true armature current
MCU is an STM32G431KB, paired with a CAN FD transceiver for control
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Building a simple differential drive bot.
Milled and brought up a carrier for a nucleo G431 with load switching, SPI connection to nvidia jetson, stemma qt connectors, and a header for the 8x8 ToF.
The STM32 handles optical encoders for odometry, acceleration profiles/motion segment execution, battery monitoring, load switching and comms to a sabertooth motor controller
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More here: pm.gc.ca/en/news/news-releas…
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