Heating, ventilation and air conditioning (HVAC) gateways serve as a bridge between different network protocols and must support multiple wired and wireless standards including cloud access.
Design requirements
HVAC gateway designs often require:
Protocols for wired long-distance networks, high data-rates, and noisy environments.
Ability to meet IEC ESD, EFT and surge standards.
Support for multiple wireless communication protocols.
Wired-to-wireless bridge designs to retrofit existing wired hardware.
As shown in the figure below, HVAC gateway mainly consists of 11 parts, namely Non-isolated DC/DC power supply、Energy storage、User interface signal input/output protection、Input user interface、Digital processing、Wired interface、Wired interface signal input/output protection、Output user interface、Self-diagnostics/monitoring、Memory、Wireless interface. Each part has corresponding types and product models. If you are interested, you can browse below.
Non-isolated DC/DC power supply
Gateways are generally powered from an AC power adaptor. High-efficiency buck converters provide the voltage rails needed by the system components and maximize battery life. A power management multi-channel IC (PMIC) can generate all the voltage rails needed by the microprocessor and other system components using a small footprint in space constrained designs. Low-noise, high-PSRR linear regulators may be used to ensure EMI specifications are met and to improve wireless communication. Non-isolated DC/DC power supply include Buck converters (integrated switch)、Linear & low-dropout (LDO) regulators、Multi-channel ICs (PMICs)、Buck-boost, inverting & split-rail converters (integrated switch)、Buck controllers (external switch)、Boost converters (integrated switch)、Shunt voltage references、Buck modules (integrated inductor)、N-channel MOSFETs、Analog switches & muxes, the corresponding products are TPS62A01、TPS7A24、TPS65220、TPS63806、LM25148、TPS61022、TLVH431、TPSM63603、CSD17483F4、SN74LVC1G3157
Energy storage
A backup power source such as a battery or super capacitor may be included in the design to provide some protection against an unexpected power loss. A battery gas gauge device monitors the battery voltage. An OR'ing controller is used to combine the battery output voltage and the power from the DC adaptor. Energy storage include eFuses & hot swap controllers、Load switches、Battery fuel gauges、Battery charger ICs, the corresponding products are TPS2662、TPS25947、TPS22965、BQ27427、BQ25895M
User interface signal input/output protection
A number of ESD protection devices can be used to protect user interfaces such as keypads. User interface signal input/output protection include ESD protection diodes, the corresponding products are TPD1E10B06、TPD1E01B04、TPD4E05U06
Input user interface
A keypad may be included to allow the user to control and program the gateway. An I/O expander can be used to interface to the mechanical keypad. A capacitive keypad design can be used to completely eliminate mechanical buttons. Haptics feedback may also be included for a more robust user experience. Input user interface include MSP430 microcontrollers、Supervisor & reset ICs、I2C general-purpose I/Os (GPIOs)、Haptic motor drivers, the corresponding products are MSP430FR2111、MSP430F5528、TPS3840、TCA6424A、DRV2605
Digital processing
A gateway uses a microprocessor to perform all bridging functions, monitor the input user interface and control the output user interface. Digital processing include Low-power 2.4-GHz products、Wi-Fi products、Sub-1 GHz transceivers、Sub-1 GHz wireless MCUs、Arm-based processors、Arm Cortex-M0+ MCUs、MSP430 microcontrollers、Arm Cortex-M4 MCUs, the corresponding products are CC2674P10、CC3301、CC1125、CC1352R、AM3352、MSPM0G1107、MSP430G2955、TM4C123GH6PM
Wired interface
A gateway may include several wired interfaces to support wired protocols such as RS-485, RS-232, Ethernet and BACnet. An RS-485 or RS-232 transceiver may be used in this design to interface the system microprocessor to the network bus. An Ethernet PHY can be used to connect to a local area network. Wired interface include USB hubs & controllers、RS-485 & RS-422 transceivers、Ethernet PHYs、RS-232 transceivers、Isolated CAN transceivers、Isolated RS-485 transceivers, the corresponding products are TUSB320LAI、THVD1520、SN65HVD82、DP83825I、DP83848M、MAX3221、ISO1042、ISO1500
Wired interface signal input/output protection
A number of ESD protection devices are used to protect wired interfaces. Wired interface signal input/output protection include ESD protection diodes, the corresponding products are TPD1E10B06、TPD1E01B04、TPD4E05U06
Memory
The gateway may include non-volatile memory such as flash memory to store system settings and volatile memory to support microprocessor program and data accesses. Voltage reference devices and DDR termination regulators are used in systems utilizing DDR synchronous DRAM. Level translation devices and ESD protection devices are an option when using flash memory. Memory include Auto-direction voltage translators、Direction-controlled voltage translators、Noninverting buffers & drivers、Inverting buffers & drivers、I2C & I3C level shifters, buffers & hubs, the corresponding products are LSF0204、SN74AXC2T245、SN74LVC1G125、SN74LVC1G04、PCA9306
Wireless interface
The wireless interface allows the gateway to create a network bridge between a wired protocol and a wireless protocol which may include Wi-Fi, Bluetooth®, ZigBee® and proprietary Sub-1 GHz protocols. Additionally a near-field communication (NFC) radio can be used for wireless setup and user authentication. Dedicated RF radios are used to run the wireless protocol stacks. A range extender is used if additional range is required or if the gateway will be used in an area that can expect a weak radio signal. Wireless interface include Low-power 2.4-GHz products、Wi-Fi products、Sub-1 GHz transceivers、Sub-1 GHz wireless MCUs、Other wireless products, the corresponding products are CC2674P10、CC3301、WL1831MOD、CC1312R、CC2500、TRF7970A
Hope our reference designs and integrated circuits can help you address complex challenges while reducing time to market.
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