ST LPS25H, Application Note

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Contents AN4450
2/26 DocID025978 Rev 1
Contents
1 Pressure sensor evaluation boards . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Hardware (designing PCB schematics and layout) . . . . . . . . . . . . . . . . 6
2.1 LPS25H device package, interconnect and polarization . . . . . . . . . . . . . . 6
2.1.1 Package drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.2 Pin mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1.3 Typical application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Pressure sensor PCB layout and soldering recommendations . . . . . . . . . 9
2.2.1 PCB design rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.2 Stencil design and solder paste application . . . . . . . . . . . . . . . . . . . . . . 10
2.2.3 Process consideration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.2.4 Manual soldering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3 Power supply: consumption estimation and optimization . . . . . . . . . 12
3.1 Common rules for low power consumption . . . . . . . . . . . . . . . . . . . . . . . 14
4 Using the device step-by-step, from basic to advanced . . . . . . . . . . . 15
4.1 First time bring-up (I²C example) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.2 Quick troubleshooting guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.3 One-shot mode measurement sequence . . . . . . . . . . . . . . . . . . . . . . . . . 16
5 Using FIFO modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.1 Effective use of the FIFO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.1.1 Accessing the FIFO data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
5.1.2 Bypass mode (F_MODE[2..0]="000" in FIFO_CTRL (0x2E)) . . . . . . . . 18
5.1.3 FIFO mode (F_MODE[2..0]="001" in FIFO_CTRL (0x2E)) . . . . . . . . . . 18
5.1.4 Stream mode (F_MODE[2..0]="010" in FIFO_CTRL (0x2E)) . . . . . . . . 18
5.1.5 FIFO mean mode (F_MODE[2..0]="110" in FIFO_CTRL (0x2E)) . . . . . 18
5.1.6 Hardware digital filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5.2 Extra FIFO modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5.2.1 Stream to FIFO mode (F_MODE[2..0]="011" in FIFO_CTRL (0x2E)) . . 20
5.2.2 Bypass to Stream mode (F_MODE[2..0]="100" in FIFO_CTRL (0x2E)) 20
5.2.3 Bypass to FIFO mode (F_MODE[2..0]="111" in FIFO_CTRL (0x2E)) . . 21