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Rev 0.12
January 16, 2017
24
Hardware Integration Guide
Routing Constraints and Recommendations
3.4.
Antenna Recommendations
Connecting the antenna ground reference to the vehicle chassis is not recommended since that has
been known to cause noise from the engine to couple into the audio of the device. It is ultimately up to
the integrator to evaluate this performance.
3.5.
Interface Circuit Recommendations
The recommended interface implementation is to use a dual-supply bus transceiver with configurable
voltage translation. This allows a host processor operating at a different voltage to communicate with
the AirPrime AR758x Series using the appropriate voltage levels.
The figure below is a reference circuit for a digital input / output signal to / from the AirPrime AR758x
Series.
V
CCA
V
CCB
DIR
A
B
GPIOx
VCC_1V8
ApplVcc (1.2V
– 3.6V)
ApplGPIOx
Direction
L = B to A
H = A to B
Figure 5.
AirPrime AR758x Series Interface Reference Circuit
The dual-supply bus transceiver with configurable voltage translation used in the reference circuit
above is the Texas Instruments SN74AVC1T45.
If a Digital IO signal is used bidirectional in the application then a bidirectional level translator, such as
Texas Instruments TCA9406 is needed.
