Architectural Overview And Power Management Features; Power Supply Architecture; Subsystem Partitioning - Applied Data Systems Bitsy Plus User Manual

5.3

Architectural Overview and Power Management Features

This section provides an overview of the architecture of the Bitsy Plus power supply and a
description of the various features of the Bitsy Plus power management systems.
5.3.1

Power Supply Architecture

The Bitsy Plus power supply is laid out as shown in the following diagram. Incoming DC power
is regulated to 5 and 3.3 V. Other system voltages are derived from these power supplies.
DCIN_POS
VBATT_POS
DC_IN and VBATT voltages are mixed using a diode with a low forward voltage. This allows a
battery and DC power supply to be connected at the same time. If only one power supply is used
for your system, use the VBATT_POS input. See sections 5.3.7 and 5.5.3 for examples.
Several factory options are available and are indicated by dashed lines in the diagram above. The
supercapacitors (section ) are a standard factory option. The other options are available for
production customers, but are outside the scope of this manual. Contact your ADS sales
representative if you believe one or more of these options is required for your application.
Specifications for the Bitsy Plus power supply are listed in section 6.2.4.
5.3.2

Subsystem Partitioning

The Bitsy Plus can selectively turn off power to subsystems on the board. This load-shedding
feature can extend battery life and significantly increase the amount of time the supercapacitors
will hold up system power. Applications and the operating system determines how selective
power management is utilized.
Bitsy Plus systems that can be selectively disabled include the following:
•
•
•
•
•
ADS document # 110114-1001A
5 V
LCD display (panel power and signal buffers)
Vee (contrast control)
Audio output amplifier
Audio codec and microphone pre-amps
Serial 1 and 3 RS-232 buffers
Power and Power Management
Vcc
supercaps
Vddi
1.75 V
to CPU core
Vee
Vee
to display
Vddx
3.3 V
switcher
linear
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