Tait TM8000 Series Applications Manual page 65

Output Circuitry
TM8000 3DK Hardware Developer's Kit Application Manual
September 2003 © Tait Electronics Ltd
The digital outputs are designed to interface to application circuitry in a
straightforward manner.
output lines (ESD protection not shown). For full details of the interface,
refer to the PCB information chapter of the TM8100 Mobile Radio Service
Manual or the technical support website.
Figure 3.9 Digital output lines - simplified circuit diagrams
+13.8V
+3.3V
100k
4.7k
The internal logic circuitry of the radio operates at 3.3V. Unless application
circuitry is able to operate at this voltage level, some form of level conversion
will normally be required. With the AUX and CH output lines, conversion
to 5V or 13.8V can be selected by moving the pullup resistor as indicated
in Figure 3.9.
Note
These resistors only provide a weak pullup and hence the output
is only able to source a very small current. In the logic low state,
the outputs can sink a higher current. For more information refer
to "Description of the Radio Interfaces" on page
The IOP output lines always operate at 3.3V logic levels and any level
conversion is the responsibility of the application circuit designer.
Figure 3.9 shows a simplified diagram of the digital
+5V +3.3V
*
* *
33k
AUX_GPIO4...7
CH_GPIO1
4.7k
56
+3.3V
33k
IOP_GPIO1...7
1k
a
a. With AUX_GPIO4...7, the
33kΩ resistor can be
moved to change the logic
high output voltage to +5V
or +13.8V.
15.
Programmable I/O Lines 65