Datasheet
I
2
C
Peripheral
I
2
C
Registers
+
Logic
OTP
Calibration Coefficients
GND
MCU
ADC
Temperature
RH
HDC1080
SDA
SCL
VDD
GND
VDD
- +
GPIO
GPIO
GPIO
GPIO
Button
Button
Button
Keyboard
GPIO
To Airconditioning
System
Temp 29°C
RH 40%
TIME xx:xx
Date xx/xx/xxxx
Display
Lithium Ion
Battery
TPL5110
GPIO
VDD
GND
DELAY/
M_DRIVE
DRV
EN/
ONE_SHOT
DONE
HDC1080
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SNAS672A –NOVEMBER 2015–REVISED JANUARY 2016
9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
An HVAC system thermostat control is based on environmental sensors and a micro-controller. The
microcontroller acquires data from humidity sensors and temperature sensors and controls the heating/cooling
system. The collected data are then shown on a display that can be easily controlled by the micro controller.
Based on data from the humidity and temperature sensor, the heating/cooling system then maintains the
environment at customer-defined preferred conditions.
9.2 Typical Application
In a battery-powered HVAC system thermostat, one of the key parameters in the selection of components is the
power consumption. The HDC1080, with 1.3μA of current consumption (average consumption over 1s for RH
and Temperature measurements), in conjunction with an MSP430, represents an excellent choice for low power
consumption, which extends the battery life. A system block diagram of a battery powered thermostat is shown in
Figure 15.
Figure 15. Typical Application Schematic HVAC
9.2.1 Design Requirements
In order to correctly sense the ambient temperature and humidity, the HDC1080 should be positioned away from
heat sources on the PCB. Generally, it should not be close to the LCD and battery. Moreover, to minimize any
self-heating of the HDC1080 it is recommended to acquire at a maximum sample rate of 1sps (RH + Temp). In
home systems, humidity and the temperature monitoring rates of less than 1sps (even 0.5sps or 0.2sps) can be
still effective.
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