BitsyXb - User Manual
50 110118-0001A
5.2.8 Power Supply Efficiency
The BitsyXb power supply achieves high efficiency through several means. First, it utilizes high-
efficiency switching regulators. These regulators use conventional step-down switchers under
operating load conditions, but are configured by the system for linear and "burst" mode
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operation during low-load conditions that occur during system sleep. Additionally, there is only
one level of cascaded regulation, reducing the losses that multiply through each stage.
5.3 Designing for Optimal Power Management
Designing a system for optimal power management requires careful attention to many details.
This section provides some guidelines and tips for best power management.
5.3.1 Create a Power Budget for Peripherals
Embedded system designers using the BitsyXb should have a clear understanding of how power
usage will be allocated in the system they design. Designers should create a power budget that
takes into account the types of devices that are expected to be used with the BitsyXb.
The following lists detail some of the typical external loads that can be placed the BitsyXb power
supplies. Baseline power consumption of the BitsyXb is listed in section 6.3.5.
3.3 V Loads
Typical external loads on the 3.3 V power supply include the following:
• Display
• Personality Board
• CF and some PCMCIA cards
5 V Loads
5 V loads come from both onboard and external devices:
External:
• Display
• Backlight
Only if powered by 5 V BitsyXb power supply
• Most PCMCIA cards
• USB devices
• PS/2 keyboard
• Speaker(s)
Assume 80% efficiency
Onboard:
• 3.3 V Supply
Multiply by 115% to account for 3.3 V power supply efficiency
• Supercaps
Use peak inrush current in your budget
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"Burst mode" in this context is a registered trademark of Linear Technology Corporation
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