Getting Started with Anabit's SymmPower Converter
SymmPower Converter Summary
The SymmPower Converter is a compact, power module that converts a single positive DC input (3.3V to 5V) into ±5V ultra low noise outputs. In addition to its regulated ±5V outputs, the converter also provides intermediate rails at approximately +6.2V and -6.2V, which can the user can also access.
The SymmPower Converter is available in two versions:
- Screw Terminal Version: accepts input power via a 2-position 2.54 mm screw terminal
- USB-C Version: accepts input power via a standard USB-C connector
Pin and connection overview
Below is a pin and connection diagram that shows the SymmPower Screw Terminal Version. Both versions have the same pins and connections except for the input where the other version is a USB C connector where you do not have to worry about polarity. Let's take a closer look at each connector and 2.54mm through pin:
- The input screw terminal Vin (3.3V to 5V) is located on the right if you are facing the connector and ground (GND) is on the left.
- The through hole pin (VIN) and ground pin (GND) can also be used as a power input (3.3V to 5V). The VIN pin is directly tied to the screw terminal VIN or the USB power input power pins.
- The 2.54mm through hole pins on the right are all power output pins
- The 4x GND pins are tied to ground, the same ground plane as the input power
- VSS pin is the -6.2V supply from the DC to DC inverter circuit
- VCC pin is the +6.2V supply from the DC to DC converter circuit
- -5V is the ultra low noise -5V output power source
- +5V is the ultra low noise +5V output power source
- If you are facing the power output screw terminals, the connector on the right is the -5V connector with the position on the right being the -5V connection and the left being ground. The connector on the left is for the +5V connector with the position on the right being the +5V connection and the left being ground. These -5V and +5V connections are directly connected to the through hole -5V and +5V connections.
Technical notes and low noise capabilities
Technical notes on Anabit's SymmPower converter and how it achieves its low noise power output:
- To achieve such a low noise output, the SymmPower Converter uses a two-stage power conversion architecture with power noise filtering. Each stage includes an LC filter for noise attenuation, and the final stage uses high PSRR linear regulators to deliver consistent low-noise performance across a wide frequency range. Not sure what PSRR is, check out this tutorial
- The intermediate power outputs of ~ +/- 6.2V are also low noise relative to other switch mode based DC to DC converter power sources. The low noise is achieved by feeding the +/- rails through the LC power noise filters before the output connections on the board.
- Other noise and ripple reduction tactics used on the SymmPower converter include
- Using high quality low ESR capacitors through out the design and ensuring bypass caps are placed < 0.1" from the IC pin they are bypassing
- Areas of the DC to DC inverter / converter design that handle noisy switching signals on the PCB are kept small and compact to prevent radiated EMI
- The PCB layout is done in such a way were noisy signals are kept separated from the low noise +/-5V outputs
Below is a screen shot from an Oscilloscope showing the noise measurement of the +5V output (green) and the -5V (yellow) under 80% load conditions. The oscilloscope is set for 20mV per division on the y axis and 2usec per division on the x axis.
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SymmPower Converter Specifications:
- The stable low noise ±5V rails have less than 20 mV peak-to-peak noise maximum, measured over a 20 MHz bandwidth.
- The maximum output current of the -5V and +5V outputs is 200mA simultaneously
- The +/- 6.2V switch based outputs will have less than 80 mV peak-to-peak noise measured over a 20MHz bandwidth.
- The maximum output current of the intermediate -6.2V and +6.2V outputs is 200mA simultaneously. But when using these outputs you must subtract the current used here from the corresponding -/+5V outputs. For instance if you are pulling 100mA of current from the 6.2V output then the 5V outputs is now limited to 100mA (100mA + 100mA = 200mA).
- To support the maximum power outputs from the positive and negative power sources requires a 5V input power source with a maximum current of 550mA and a 3.3V input power source with a maximum current of 625mA. You can use lower input power sources, but you must then also scale back the maximum output current draws accordingly.
- Form factor for both versions: 47mm x 32mm with 4x mounting holes with 3mm diameters. Power input and output through holes are 2.54mm spaced. Screw terminal input and output connectors are also 2.54mm and are rated for wire gauges 30 to 18 AWG