User Manual

ams Datasheet Page 11

[v1-06] 2019-Feb-07 Document Feedback

CCS811 − Detailed Description

Note that a hardware reset (via the nRESET) pin can be triggered

irrespective of the power state (assuming On), for a SW_RESET,

the CCS811 needs to be Wake.

So, tying nWAKE to ground is the simplest hardware

configuration – CCS811 will always be Wake and ready to

communicate but consumes more power. If power

consumption is a concern, the master should set nWAKE low

before I

C communication and high afterwards. If

measurements are enabled, the CCS811 will use a timer to wake

up itself periodically to execute a measurement.

Modes of Operation

The CCS811 has 5 modes of operation as follows

• Mode 0: Idle, low current mode

• Mode 1: Constant power mode, IAQ measurement every

second

• Mode 2: Pulse heating mode IAQ measurement every 10

seconds

• Mode 3: Low power pulse heating mode IAQ

measurement every 60 seconds

• Mode 4: Constant power mode, sensor measurement

every 250ms

In Modes 1, 2, 3, the equivalent CO

concentration (ppm) and

eTVOC concentration (ppb) are calculated for every sample.

• Mode 1 reacts fastest to gas presence, but has a higher

operating current

• Mode 3 reacts more slowly to gas presence but has the

lowest average operating current.

When a sensor operating mode is changed to a new mode with

a lower sample rate (e.g. from Mode 1 to Mode 3), it should be

placed in Mode 0 (Idle) for at least 10 minutes before enabling

the new mode. When a sensor operating mode is changed to a

new mode with a higher sample rate (e.g. from Mode 3 to Mode

1), there is no requirement to wait before enabling the new

mode.

Mode 4 is intended for systems where an external host system

wants to run an algorithm with raw data and this mode provides

new sample data every 250ms. Mode 4 is also recommended

for end-of-line production test to save test time. For additional

information please refer to application note ams AN000373:

CCS811 Factory test procedure.

Note(s): Mode timings are subject to typical 2% tolerance due

to accuracy of internal clock