UM1759 datasheet(13/50 Pages) STMICROELECTRONICS

13 / 50 page

DocID026279 Rev 1

13/50

UM1759

Hardware description

The band is indicated by a dummy resistor on the board (area A in Figure 9). An SMA

connector on the RF module (area B in Figure 9) allows connection with RF instruments like

spectrum analyzers and signal generators to the SPIRIT1 by RF cable, or connection with

an antenna like the one included in the demo kit. The board is powered by the RF

motherboard through the RF daughterboard connector (area D in Figure 9) and

communicates with the microcontroller through this connector via SPI and some GPIOs.

The Vcc_RF pin of the RF daughterboard connector is linked to the Vbat of the SPIRIT1

through a jumper that can also be removed to measure current consumption (area C in

Figure 9).

The RF module includes a memory EEPROM with RF module data stored at the time of

manufacture. The information is stored in the first pages of the EEPROM and the memory

may not be changed by user.

Figure 9. STEVAL-IKR002Vx (RF module)

3.2.1

Boost mode

The SPIRIT1 can be configured to increase the output power in transmission mode.

In the default configuration, the transmitter power amplifier (PA) output is biased by the

1.4 V SMPS voltage output through the L0 external inductor (position D0 in the schematic,

Figure 10). This limits the maximum output power to about +11 dBm, measured at the

50 Ohm connector via the reference design.

Biasing the PA output through the inductor L0 directly connected to the battery instead of

the SMPS output increases the maximum output power delivered at the 50 Ohm connector

(or at the antenna). The maximum output power changes with the voltage level applied at

the PA output.

To switch to boost mode, the inductor L0 must be removed from position 1-2 D0 in the

schematic and soldered at position 1-3 D0, then the voltage supply Vcc_RF must be

provided.

UM1759 数据表(PDF) 13 Page - STMicroelectronics