NI roboRIO User Manual
|
© National Instruments
|
7
Input Voltage Brownout Behavior
The NI roboRIO input voltage range is 7 V to 16 V. The input voltage monitoring circuit
monitors the voltage on the input voltage pin. When the input voltage drops to between 4.5 V
and 6.8 V, the NI roboRIO enters brownout mode with a staged response, as Table 2 describes.
Table 2.
NI roboRIO Input Voltage Brownout Behavior
Stage
Input Voltage
Range
Behavior
1
6.3 V to 6.8 V
The +6 V voltage rail starts to drop.
2
4.5 V to 6.3 V
The NI roboRIO enters a brownout fault condition and the
following precautions are taken:
• User voltage rails become disabled.
• All PWM generation stops at the conclusion of the current
cycle.
• GPIOs configured as outputs go to High-Z.
• Relay control outputs are driven low.
• CAN-based motor controllers become disabled.
The following systems continue to function normally with
valid data and communication:
• FPGA, processor, RAM, disk, and user code
• USB power and communication
• Radio, if powered by USB
• Ethernet
• CAN
• AI and AO
• I
2
C
• SPI
• RS-232 serial
• LED and RSL status lights
Stage 2 continues until the input voltage rises to greater than
7.5 V or drops to less than 4.5 V.
3
Less than 4.5 V
All controller functions cease and the controller state is lost.
This condition continues until the input voltage rises to greater
than 4.65 V, at which point the controller starts the normal
booting sequence. At startup, the controller remains in Stage 2
until the input voltage rises to greater than 7.5 V.
