Getting Started with Anabit's SymmBoost Converter

SymmBoost Converter Summary

Anabit's SymmBoost Converter Module is a compact, bipolar power source built using a boost and inverter DC to DC converter to give your projects ± rails from a single 5 V input. The SymmBoost comes in three voltage output versions: ±24 V, ±15 V, or ±9 V. The SymmBoost converter uses a blazing fast 2.4MHz clock to control its switching and conversion stages which enables great power efficiency. This high efficiency is the reason the SymmBoost converter delivers +/- high voltage rails in such a tiny form factor. Even though the SymmBoost converter is switch based, it is engineered to deliver low noise. See the specifications below for more information on the SymmBoost Converter's output noise levels.

Boost Converter Technical Notes

When working with Boost converters / inverters there is couple key points about output and input current to keep in mind. For more information on output and input current capabilities see the specifications at the end of this guide:

• A boost DC to DC converter architecture will have a certain power handling limit, which means as you go higher in output voltage the current output capabilities drop. The same is true for the SymmBoost design so each voltage version cannot support the same current output. 
• When you boost a voltage up during the conversion process there is also a current conversion aspect since power out has to equal power in, minus losses during the conversion process.
  • For instance to get 15V power source that can output 50mA from a 5V source means the input current has to be at least 150mA. Since the voltage is boosted by 3x, the current is divided by 3x to maintain the power balance.
  • If you have a dual rail (like the SymmBoost) that means you have to multiply the input current by 2x which is now 300mA.
  • That quick example calculation assumed 100% conversion efficiency, if we assume 80% efficiency then we need 300mA x (1 + (1 - .8) = 360mA of input current to get +/- 15V rails that can support 50mA of current on each rail.

Pin and connector diagrams and descriptions

Let's look at the pin and connectors on the SymmBoost Converter which you can see in the below diagram (diagram shows the board without the screw terminals installed). 

• To power the SymmBoost design requires a 5V input (5V +/- 200mV). There are two power inputs on the design to choose from. Both are labeled "Vin" on the design and "5V Pwr In" on the diagram.
  • The first is the two position screw terminal on the left side of the board (Vin and Ground)
  • The second is the through hole pins nearest to the input screw terminal
• Next to the power input through hole pin connections, are the positive and negative rail enable pins. By default these enable lines are pulled up, which means when input power is applied both power outputs are enabled. If you connect an active low digital logic to one of the enable pins it will disable the corresponding power supply output:
  •  "En Pos Out" or "ENP" is used to enable or disable the output positive rail of the design
  • "En Neg Out" or "ENN" is used to enable or disable the output negative rail of the design
• The output rails can also be accessed from two locations on the design, positive output rails is labeled "+Vout" and the negative is labeled "-Vout." 
  • The first is the three position screw terminal, which has the ground connection in the middle and the two power output connections on either side
  • The second is the through hole pins closet to the three position screw terminal. 

Electrical Specifications and limits (VIN = 5 V)

±24 V module:
--> Max output current (cont.): +24 V: 50 mA, −24 V: 25 mA
--> Max 5 V input current (both rails at max): ≈ 450 mA
--> -24 V rail noise (20 MHz BW): 30 mVpp at max load
--> +24 V rail noise (20 MHz BW): 50 mVpp at max load

±15 V module:
--> Max output current (cont.): +15 V: 0.1 A, −15 V: 50 mA
--> Max 5 V input current (both rails at max): ≈ 0.7 A
--> -15 V rail noise (20 MHz BW): 20 mVpp at max load
--> +15 V rail noise (20 MHz BW): 50 mVpp at max load

±9 V module:
--> Max output current (cont.): +9 V: 0.3 A, −9 V: 0.1 A
--> Max 5 V input current (both rails at max): ≈ 1.0 A 
--> -9 V rail noise (20 MHz BW): 20 mVpp at max load
--> +9 V rail noise (20 MHz BW): 70 mVpp at max load

Form factor:
--> 41.5 mm × 27 mm product dimensions
--> Pin spacing 2.54 mm
--> screw terminal spacing 2.54 mm
--> 4x Mounting holes 3 mm diameter