Application circuit

AN4387

6/22

DocID025465 Rev 1

3

Application circuit

Figure 2 shows the BlueNRG application board photo. The application is constituted from 2

boards: a daughterboard and a motherboard. The daughterboard (see Figure 1) holds the

BlueNRG with the circuits necessary for its works. The Bluetooth low energy protocol stack

(GAP, GATT, SM, L2CAP, LL, RF-PHY) is embedded on the device.

For the correctly functionality, the daughterboard have to be plugged on a motherboard (see

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

The motherboard is provided with a STM32L152VBT6 microcontroller to correctly program

the transceiver. The micro is programmed with a firmware developed for BlueNRG

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

BlueNRG.

The daughterboard is provided with a 16 MHz XTAL to provide the correct oscillator to the

BlueNRG. Also a low speed crystal oscillator is mounted on the board and used from

BlueNRG.

An internal SMPS is present on the BlueNRG to drastically reduce the power consumption.

The SMPS is fed from the battery (2.0 V to 3.6 V) and provide to device a programmable

voltage (1.4 V usually).

A SMA connector is present to connect the board at antenna or at instrumentation to verify

the correct functionality and verify the FCC standard requests.

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

amplifier (PA) and balun network for the receiver.

Figure 1. BlueNRG application daughterboard