ADR1

ADC

TEMPERATURE

RH

I

Registers

+

Logic

HDC1008

SDA

SCL

DRDYn

ADR0

OTP

Calibration Coefficients

VDD

GND

HDC1008

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SNAS649B – OCTOBER 2014 – REVISED DECEMBER 2015

8 Detailed Description

8.1 Overview

The HDC1008 is a digital humidity sensor with integrated temperature sensor that provides excellent

measurement accuracy at very low power and long term. The sensing element of the HDC1008 is placed on the

bottom part of the device, which makes the HDC1008 more robust against dirt, dust, and other environmental

the measurement time and can be 8, 11, or 14 bits for humidity; 11 or 14 bits for temperature.

8.2 Functional Block Diagram

8.3 Feature Description

8.3.1 Power Consumption

One of the key features of the HDC1008 is its low power consumption, which makes the device suitable in

battery or power harvesting applications. In these applications the HDC1008 spends most of the time in sleep

mode; with a typical 110nA of current consumption in sleep mode, the averaged current consumption is minimal.

Moreover its low consumption in measurement mode minimizes any self-heating.

8.3.2 Voltage Supply Monitoring

The HDC1008 monitors the supply voltage level and indicates when the voltage supply of the HDC1008 is less

than 2.8V. This information is useful in battery-powered systems in order to inform the user to replace the

battery. This is reported in the BTST field (register address 0x02:bit[11]) which is updated after POR and after

each measurement request.

8.3.3 Heater

The heater is an integrated resistive element that can be used to test the sensor or to drive condensation off the

sensor. The heater can be activated using HEAT, bit 13 in Configuration Register. The heater helps in reducing

the accumulated offset after long exposure at high humidity conditions.

Once enabled the heater is turned on only in the measurement mode. To have a reasonable increase of the

temperature it is suggested to increase the measurement data rate.

8.4 Device Functional Modes

The HDC1008 has two modes of operation: sleep mode and measurement mode. After power up, the HDC1008

times, read the status of the battery, trigger a measurement, and read measurements. Once it receives a

command to trigger a measurement, the HDC1008 moves from sleep mode to measurement mode. In

measurement mode, the HDC1008 acquires the configured measurements and sets the DRDYn line low when

the measurement is complete. After completing the measurement and setting DRDYn low, the HDC1008 returns

to sleep mode.

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