Overview

Automotive heating, ventilation and

air conditioning (HVAC) systems are

designed to provide a comfortable cabin

driving environment while minimizing

power consumption and overall load on

the vehicle. This is done by taking inputs

from a variety of sensors, processing

those inputs with an ADC/DAC and

using the data to control different types

of motors. For example, stepper and

DC motors are used to control the air

vent flaps while DC and BLDC motors

are used to control the blowers. The

Freescale automotive HVAC control

platform reference solution utilizes

the scalable S12G 16-bit MCU family

along with MC33905, MC33932 and

MC33937 analog devices to drive each

of these types of motors and leverages

a configurable automatic climate control

software algorithm providing a feature-

rich solution for automotive HVAC

applications.

The automotive HVAC control platform

reference solution consists of a central

control board with human-machine-

interface (HMI), a motor control board,

flap and blower motors. It enables

the basic functions of an automotive

HVAC system using temperature,

light, humidity and air quality sense

interfaces together with the configurable

automatic climate control software

algorithm to more efficiently control the

vehicle climate. The LCD controlled by

the S08LG MCU (optional) can display

rich content for the driver including

temperature, wind speed and calendar.

This reference solution will reduce

the overall R&D effort for customers,

shorten overall time to market and

can be tailored for both 12 and 24 V

automotive HVAC systems.

The S12G MCU is the core controller

of this reference solution, offering 16 to

240 KB of flash and 20, 32, 48, 64, to

100 pin count, with full pin compatibility

and maximums module reuse within the

family. EEPROM on board and multiple

peripheral interfaces such as CAN and

LIN/SCI communications to link the

main control system with the distributed

motor units, SPI for analog connections

and PWM signal control makes the

S12G MCU ideal for automotive HVAC

applications.

BLDC Motor

Motor Control Board

Central Control Board with HMI

Stepper Motor

DC Motor

HVAC Control Platform Reference Solution

S12G 16-bit MCUs

HVAC Control Platform Reference Solution

Freescale and the Freescale logo are trademarks of FreescaleSemiconductor,Inc., Reg. U.S. Pat. & Tm. Off. All other product or service names are the property of their respective owners. 2012FreescaleSemiconductor,Inc.

Document Number: S12GHVACCTLPLTFS REV 0

For more information, visit freescale.com/automotive

HVAC Control Platform Key Features Threetypesofmotorcontrol(sensor-less

BLDC, DC and stepper motor)

Automaticclimatecontrol

Supportsmultipletemperaturezones

Ultra-low-powermode,canbewokeupbyHMI or LIN/CAN bus

CANandLINcommunicationinterfaces

3x3matrixkeypadandtwoencoderknob inputs

4x37segmentLCDandadjustablebacklighting

Sensorinterfacesfortemperature,light,humidity and air quality available

Twologicrelayinterfacestocompressor/defrost module

Real-timeclockanddatedisplay,adjustmentforcalendar

Extensiblewithtouchkeyboardortouchscreen board

Suitableforboth12and24VHVACsystems

S12G MCU Key Features S12CPUcore,25MHzbus

Upto240KBon-chipflashwithECC

Upto4KBEEPROMwithECC

Upto11KBon-chipSRAM

Uptoonemulti-scalablecontrollerareanetwork (MSCAN) module

SupportingCANprotocol2.0A/B

Uptothreeserialcommunicationinterfacemodules, supporting LIN communications

Uptothreeserialperipheralinterfacemodules

Precisionfixedvoltagereferenceforanalog-to-digital conversion

1MHzinternaloscillator

On-chipvoltageregulatorforinputsupplyand internal voltages

ThisproductisincludedintheFreescaleProduct Longevity program, with assured supply for a minimum of 15 years after launch

HVAC Motor Control Board Block Diagram

LM5022LM2694

MOSFETBridges

Flap Motors(Step Motor

or DCMotor)

H-BridgeMC33932

SamplingCircuit

BlowerMotor(BLDCMotor)

GPIOs

5 V 12 V

12 V

Current

DCB

RelaysINT

ADCs (Flap MotorPosition Feedback)

Feedback

ADCs (Status Feedback)U, V, W

U, V, W

SPI

ControlMOS CTL

Connectorto MotorControlBoard

Pre-DriverMC33937

Freescale Technology

HVAC Motor Control Board Block Diagram

10-bit ADC12-bit ADC (GA)

Up to 16-ch.GPIO

10-bit ADC12-bit ADC (GA)

Up to 16-ch.

Timers16-bit

Up to 8-ch.

PWM8/16-bit

Up to 8/4-ch.

AnalogComparator

(GN16 thru G64 only)

RAM(102411264 B)

Note: Not all peripherals are available in all package types

EP ROM4 Byte blocks

(ECC)(5124096 B)

LIN/SCIUp to 3

SPIUp to 3

Debug Interrupt2-ch. 8-bit

DAC(GA only)

Flash(ECC)

(16240 K)

S12G Family Block Diagram

MSCAN(Not on GN)

S12G Family Block Diagram

HVAC Motor Control Board Block HVAC Central Control Board Block Diagram

MC9S12G240

MC9S08LG32 Knob Inputs

Dead TimeUnit and

ProtectionUnit

RelayDriver

Connectorto MotorControlBoard

SBCMC33905

Debug UART

RESET

12 V MUXOUT

INT

VDD

SPIO

CAN

SCI1

PWM Inputs

ENV Inputs

Keypad

CAN

LIN

SCI1

Captures

ADCs

LCD Encoder

ADCs (Motor Position Feedback)

GPIO Interrupts (Fault Signals)

GPIO (Motor Control Inputs)

ADCs (BLDC Status Feedback)

SPIO

GPIOs

PWMs

GPIOs

Fault

Relays

Control

Feedback

SPI1 INT

Key InputsGPIOsSegment LCD

Freescale Technology

HVAC Central Control Board Block Diagram