Product Info

DRAFT 8-1-2019 Technical Brief
A c l a r a R a d i o M o d u l e I m p l e m e n t a t i o n R e q u i r e m e n t s 4
Design Guidelines
Power Supply
The host board power supply shall provide a regulated 3.6 VDC output voltage
with less than 20 mVAC of ripple. The power supply shall be capable of
supplying up to 1.0 A and regulating the 3.6 V output voltage to ± 5% tolerance.
The transceiver voltage rail, VCC_TXRX, is all that is required to communicate
with the RF transceiver and operate the RF circuitry in receive mode. The
additional power supply rail, VCC_TX, is required for RF transmissions.
VCC_TX supplies the voltage to the RF power amplifier where most of the
current is required. An external power FET is typically used to switch the
VCC_TX power rail on and off when required.
SPI Interface
A host microcontroller running at 3.6 VDC shall provide the necessary 3.6 V
level SPI signaling required by the ARM. The clock frequency of the SPI interf
ace can operate up to a maximum of 10 MHz. The SPI clock is provided by the
host microcontroller operating as the master SPI device. The ARM operates as
the SPI slave device.
The host device controls all power level settings and valid operating frequencies
of the Si4467 transceiver. The firmware controlling the transceiver only supports
Aclara’s Standard, Extended, and Maximum power level settings. The firmware
can only program the Si4467 to use valid operating frequencies within Aclara’s
licensed 450MHz to 470MHz band of operation.
Antenna
The ARM antenna output shall connect to a host board strip-line that provides a
50 ohm controlled impedance path to an antenna. The strip-line can connect to a
RF connector in order to support an external (off-board) antenna or it can connect
to an etched (on-board) antenna with a matching network to provide the proper 50
ohm termination for the strip-line. The ARM’s maximum RF output level is 30
dBm (1 W) of RF power.
Host Board Stack-Up
The Host PCB stack-up shall be at least a 2-layer stack-up with an overall
thickness of 0.062” +/- 0.005” and use a minimum copper weight of 1/4 oz. There
shall be a ground flood underneath the ARM module to provide further isolation
from any digital interference. High temperature board materials such as Isola 410
or FR-408 with Tg ratings of 170 ºC minimum shall be used to maintain
coplanarity. The ARM uses castellated vias for connection pins and can be
reflowed along with other SMD devices.