BME280 datasheet(14/60 Pages) BOSCH

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Bosch Sensortec | BME280 Data sheet

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Modifications reserved | Data subject to change without notice

Document number: BST-BME280-DS001-23 Revision_1.23_012022

3. Functional description

3.1 Block diagram

Figure 2

shows a simplified block diagram of the BME280:

Logic

Pressure

front-end

OSC

NVM

Voltage

reference

Voltage

regulator

(analog &

digital)

VDDIO

GND

SDI

SDO

SCK

CSB

VDD

POR

Pressure

sensing

element

Humidity

sensing

element

Humidity

front-end

Temperature

front-end

Temperature

sensing

element

ADC

Figure 2: Block diagram of BME280

3.2 Power management

The BME280 has two distinct power supply pins

•

VDD is the main power supply for all internal analog and digital functional blocks

•

VDDIO is a separate power supply pin used for the supply of the digital interface

A power-on reset (POR) generator is built in; it resets the logic part and the register values after both

VDD and VDDIO reach their minimum levels. There are no limitations on slope and sequence of raising

the VDD and VDDIO levels. After powering up, the sensor settles in sleep mode (described in chapter

3.3.2).

It is prohibited to keep any interface pin (SDI, SDO, SCK or CSB) at a logical high level when VDDIO is

switched off. Such a configuration can permanently damage the device due an excessive current flow

through the ESD protection diodes.

If VDDIO is supplied, but VDD is not, the interface pins are kept at a high-Z level. The bus can therefore

already be used freely before the BME280 VDD supply is established.

Resetting the sensor is possible by cycling VDD level or by writing a soft reset command. Cycling the

VDDIO level will not cause a reset.

3.3 Sensor modes

The BME280 offers three sensor modes: sleep mode, forced mode and normal mode. These can be

selected using the mode[1:0] setting (see chapter 5.4.5). The available modes are:

•

Sleep mode: no operation, all registers accessible, lowest power, selected after startup

•

Forced mode: perform one measurement, store results and return to sleep mode

•

Normal mode: perpetual cycling of measurements and inactive periods.

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