Itron 0001 ユーザーズマニュアル
4-10
July 23, 2002
Hardware Integration
CreataLink2 XT Hardware Integrator’s Guide
Host Interface
This is well above the absolute minimum of 480 ohms determined above, thus you
will not encounter current sink problems. If better V
will not encounter current sink problems. If better V
Ohmin
performance is desired,
this value can be lowered, with a lower bound given by the equation above.
This value for R
PU
can be cross checked to see if the system specifications can be
met. From the graph in Figure 4-3, with a pull-up of 2000 ohms, the V
OHmin
will be
approximately 10V, thus the specification is met.
Now that you have determined the value of the pull-up resistor, you must determine
the required power rating of the pull-up resistor. This is governed by the pull-up
voltage and the current passing through this resistor when the output is in the low
state.
the required power rating of the pull-up resistor. This is governed by the pull-up
voltage and the current passing through this resistor when the output is in the low
state.
P = (V
PU
) * (V
PU
/ R
PU
) = 72 mW
From the above values, it would be recommended to use a maximum value resistor
of 2000 ohms with a 125 mW minimum power rating.
of 2000 ohms with a 125 mW minimum power rating.
High Voltage Input/Driven Output Circuit
You can configure two of the programmable I/O lines,
HVIO_6
and
HVIO_7
, as
high voltage inputs or high current source driven outputs.
Figure 4-9 diagrams the High Voltage Input/Driven Output circuit. All relevant
signals are depicted.
Current Source Limitations
The driven output signals are capable of sourcing and sinking significant current
to their corresponding loads. Each of these two signals are capable of sourcing/
sinking up to 350 mA. Currents higher than this could cause permanent damage
to the circuit. The output high voltage provided by these two pins is approximately
equal to the voltage provided to pin 1 of the data transceiver’s 22-pin connector.
Thus, any unwanted noise on this line must be filtered before it is connected to the
CreataLink2 XT device, or on each individual output pin. When you design the
power supply for the CreataLink2 XT device, take into account these two I/O pins’
output current.
to their corresponding loads. Each of these two signals are capable of sourcing/
sinking up to 350 mA. Currents higher than this could cause permanent damage
to the circuit. The output high voltage provided by these two pins is approximately
equal to the voltage provided to pin 1 of the data transceiver’s 22-pin connector.
Thus, any unwanted noise on this line must be filtered before it is connected to the
CreataLink2 XT device, or on each individual output pin. When you design the
power supply for the CreataLink2 XT device, take into account these two I/O pins’
output current.
990125
Figure 4-9. High Voltage Input/Driven Output Circuit
LOAD
I/O Control
Low Voltage
Input
HVIO_6 -HVIO_7
Switching
Level
Shifting
Low Voltage
Output
CreataLink2 XT Device
and