Datasheet

XTR300
www.ti.com SBOS336C –JUNE 2005– REVISED JUNE 2011
ERROR FLAGS
The XTR300 is designed for testability of its proper function and allows observation of the conditions at the load
connection without disrupting service.
If the output signal is not in accordance to the transfer function, an error flag is activated (limited by the dynamic
response capabilities). These error flags are in addition to the monitor outputs, I
MON
and IA
OUT
, which allow the
momentary output current (in voltage mode) or output voltage (in current mode) to be read back.
This combination of error flag and monitor signal allows easy observation of the XTR300 for function and working
condition, providing the basis for not only remote control, but also for remote diagnosis.
All error flags of the XTR300 have open collector outputs with a weak pull-up of approximately 1μA to an internal
5V. External pull-up resistors to the logic voltage are required when driving 3V or 5V logic.
The output sink current should not exceed 5mA. This is just enough to directly drive optical-couplers, but a
current-limiting resistor is required.
There are three error flags:
• IA Common-Mode Over-Range (EF
CM
)—goes low as soon as the inputs of the IA reach the limits of the
linear operation for the input voltage. This flag shows noise from the saturated current mirrors which can be
filtered with a capacitor to GND.
• Load Error (EF
LD
)—indicates fault conditions driving voltage or current into the load. In voltage output mode
it monitors the voltage limits of the output swing and the current limit condition caused from short or low load
resistance. In current output mode it indicates a saturation into the supply rails from a high load resistance or
open load.
• Over-Temperature Flag (EF
OT
)—is a digital output that goes low if the chip temperature reaches a
temperature of +140°C and resets as soon as it cools down to +125°C. It does not automatically shut down
the output; it allows the user system to take action on the situation. If desired, this output can be connected to
output disable (OD) which disables the output and therefore removes the source of power. This connection
acts like an automatic shut down, but requires a 2.2kΩ external pull-up resistor to safely override the internal
current sources. The IA channel is not affected, which allows continuous observation of the voltage at the
output.
DIGITAL I/O AND GROUND CONSIDERATIONS
The XTR300 offers voltage output mode, current output mode, external configuration, and instrumentation mode
(voltage input). In addition, the internal feedback mode can be disconnected and external loop connections can
be made. These modes are controlled by M1 and M2 (see the function table). The OD input pin controls enable
or disable of the output stage (OD is active low).
The digital I/O is referenced to DGND and signals on this pin should remain within 5V of the DGND potential.
This DGND pin carries the output low-current (sink current) of the logic outputs. DGND can be connected to a
potential within the supply voltage but needs to be 8V below the positive supply. Proper connection avoids
current from the digital outputs flowing into the analog ground.
CAUTION
It is important to note that DGND has normally reverse-biased diodes connected to the
supply. Therefore, high and destructive currents could flow if DGND is driven beyond
the supply rails by more than a diode forward voltage. Avoid this condition during
power-on and power-off!
Copyright © 2005–2011, Texas Instruments Incorporated 25