Download HSM550 Technical Reference

HSM/550 Technical Reference - July 13, 1999 - © Systronix®, Inc.
Figure 9. Header P6, PWM signals from MCU Port 6.
The PWM outputs and the PWM clock signals are presented on header P6. If you don’t need PWM
functions, you can use these Port 6 pins as generic 8051 I/O pins. Note that the ADC_START input
is also a Port 6 I/O, although it has nothing to do with the PWM signals.
HSM/550 12-bit DAC
HSM/550 includes a high-quality
Linear Technology LTC1451 12-bit
DAC. The output of the DAC is
buffered and presented on P8.
Header P8 also provides access to
the ‘spare’ opamp inputs and
outputs.
Designer opamp preferences are
about as personal as political
choices. There’s no real ‘best’. We
chose the TLC27M4 because it has
good single-supply operation, is
Figure 10. Header P8, DAC output and available analog
low power, has low input current
opamp
input & output.
and low temperature drift. It drives
very well to within a few millivolts
of ground and up to 4 volts or so.
Heavily loaded it will drive to 3.5 volts, so be aware of this limitation. All the “rail-to-rail” opamps
we’ve investigated have other shortcomings which we felt made them a less desirable choice in this
application. But if you disagree, feel free to install your favorite opamp in the sockets we provided.
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