BME680 datasheet(29/50 Pages) BOSCH

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Document number: BST-BME680-DS001-00 Revision_1.0_072017

5.3.3 Gas control registers

The sensor can have 10 programmable gas sensor heater set-points. A set-point consists of a target heater resistance,

heater-on time and optionally an initial heater current.

5.3.3.1 Heater current - idac_heat_x

BME680 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 set-

point

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

5.3.3.2 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 3.3.5.

Heater set-point

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

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