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Bosch Sensortec | BME690 - Datasheet

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Document number: BST-BME690-DS001-04

as well as in the event of applications for industrial property rights

Gas control registers

The sensor can have 10 programmable gas sensor heater steps. Each heater step consists of a target heater resistance

corresponding to heater temperature, heater-on time and optionally an initial heater current.

5.3.4.1 Heater current - idac_heat_x

BME690 contains a heater control block that will inject enough current into the heater resistance to achieve the requested

heater temperature. There is a control loop which periodically measures heater resistance value and adapts the value of

current injected from a DAC.

The heater operation could be speeded up by setting an initial heater current for a target heater temperature by using

register idac_heat_x<7:0>. This step is optional since the control loop will find the current after a few iterations anyway. The

current injected to the heater in mA can be calculated by: (idac_heat_7_1 + 1) / 8, where idac_heat_7_1 is the decimal

value stored in idac_heat<7:1> (unsigned, value from 0 to 127).

Heater steps

Address

Content

Description

0...9

idac_heat_x

x is from 0 to 9

0x50…0x59

idac_heat_x<7:0>

x is from 0 to 9

idac_heat of particular heater

set point

5.3.4.2 Target heater resistance - res_heat_x

Target heater resistance is programmed by user through res_heat_x<7:0> registers. The definition of res_heat_x is given in

Section 3.6.5.

Heater step

Address

Content

Description

0...9

res_wait_x

x is from 0 to 9

0x5A…0x63

res_heat_x<7:0>

x is from 0 to 9

Decimal value that needs to be

stored for achieving target

heater resistance

5.3.4.3 Gas Sensor heater-on time in Forced mode - gas_wait_x

Referring to Figure 2, the time between the beginning of the heat phase and the start of gas sensor resistance measurement

depends on gas_wait_x setting as mentioned below.

Heater step

Address

Content

Description

0...9

gas_wait_x

x is from 0 to 9

0x64…0x6D

gas_wait_x<5:0>

x is from 0 to 9

64 timer values with

1 ms step sizes, all zeros

means no wait

0...9

gas_wait_x

x is from 0 to 9

0x64…0x6D

gas_wait_x<7:6>

x is from 0 to 9

Timer multiplication factor as

shown in below table

gas_wait_x<7:6>

Gas sensor wait time multiplication factor

BME690 Datasheet(PDF) 39 Page - Bosch Sensortec GmbH

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