Application circuit

AN4147

6/14

Doc ID 023516 Rev 1

2

Application circuit

Figure 1 shows an image of the SPIRIT1 application board. The application is made up of 2

boards: a daughterboard and a motherboard. The daughterboard contains the SPIRIT1 with

the circuits necessary for it to work. For correct functionality, the daughterboard must be

plugged into the motherboard (see

Figure 2) by two header 5x2 connectors (J6 and J7).

The motherboard is provided with an STM32L152VBT6 microcontroller to correctly program

the transceiver. The microcontroller is programmed with firmware developed for the SPIRIT1

application. A graphical user interface (GUI) is developed to correctly program the SPIRIT1.

The daughterboard is provided with a 52 MHz XTAL to provide the correct oscillator to the

SPIRIT1.

The SPIRIT1 has an internal SMPS that drastically reduces power consumption, making it

the best-in-class for applications on this bandwidth. The SMPS is fed from the battery (1.8 V

to 3.6 V) and provides the device with a programmable voltage (1.4 V typical). An SMA

connector is present to connect the board to an antenna or to instrumentation to verify the

correct functionality and verify the ETSI standard request.

A few of passive devices (inductors and capacitors) are used for matching/filtering in the

power amplifier (PA) and balun network for the receiver.

To reduce application costs, the SPIRIT1 is designed to work without an external antenna

switch. The daughterboard is designed to show the SPIRIT1 functionality in this condition.

Clearly, an application with antenna switch can be realized, but this is not described in this

document.

Figure 1.

SPIRIT1 application daughterboard

AM13146v1