AZ143 – Running Freescale 8-bit MCUs from Single Cell 1.5V ...Standard microcontrollers do not operate from 1.5V single cells • Memories and logic elements often require voltages

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Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009.

AZ143 – Running Freescale 8-bit MCUs from Single Cell 1.5V Batteries(v4)Jose PalazziSales Manager – South America

July, 2009

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009.

Objective and Agenda

►Objective• Modern products require better effectiveness, reduced dimensions, and

increased autonomy. This session will show you how to run Freescale 8-bit MCUs from AA 1.5V batteries.

►Agenda• Why 1.5V?

Single cell operation requirements• Single 1.5V cell applications

Single cell applications with Freescale 8-bit MCUs and step-up converters• Step-up converter requirements & proposals

Battery characteristicsCase study: Flashlight with white LED supplied by AA 1.5V cell

– Circuit proposals– Performance analysis

What makes Freescale 8-bit MCUs suitable for single cell operation?• Conclusion


…so, why 1.5V?


Why 1.5V?

►1.5V batteries are readily available at low cost in many standard footprints

►Space-constrained applications require low power consumption and easy battery replacement

►Examples:• White LED light pens

Requirements: Size, reduced # of contact elements, longevity• Medical equipment – Data acquisition, hearing aid

Requirements: Ease of replacement, weight, quality of contacts.

• Industrial data loggers and telemetryRequirements: Size, weight, longevity

• IR remote controllersRequirements: Reduced # of contact elements, short duty cycles

• ToysRequirements: Size, cost, simplicity


Single Cell Operation Requirements

►Most ICs do not operate directly from a 1.5V single cell• ~600mV drop voltage of silicon bipolar transistors and diodes• ~1V minimum gate voltage required for MOSFET devices to switch on

►Standard microcontrollers do not operate from 1.5V single cells• Memories and logic elements often require voltages starting from 1.8V

to start operating• Freescale Semiconductor offers MCUs such as the MC9S08QG4 which

can operate from 1.8V to 3.6V

►An associated step-up converter is required to boost voltage to 1.8V

• This presentation shows Freescale microcontrollers operating from single cell 1.5V batteries, and circuit topologies that show how to implement this kind of step-up conversion


Single 1.5V cell applications


First, Assume We Have a Step-up Boost Converter

►For now, think of this as a black box• Able to operate from 1.5V to 1.0V• Generating:

3.3V at 50mA (general purpose)4.0V at 100mA (white LED light)

►Topologies• We will see these later in the presentation• Now we will see how Freescale 8-bit MCUs fit these applications


Wireless Humidity Sensor

► MC9RS08KA2• Low power RS08 MCU

operating from 1.8V to 5.5V• 2K byte single block FLASH• 63 byte RAM• Analog comparator• Precise and stable internal

oscillator• 8 pin SOIC

► Benefits• Extreme low cost

Disposable• Smaller footprint

Able to operate with watch batteries


IF Remote Control

► MC9S08QG4• Lower power S08 MCU

operating from 1.8V to 3.6V• 4K Flash• 256 bytes RAM• Precise and stable internal

oscillator• 3 stop modes allowing very

reduced power consumption when no keys are depressed

• 16-pin TSSOP

► Benefits• Fewer contact elements

compared to 2-battery solutions• Smaller and lighter


Motion/Presence Detector

► MC9S08QA2• Low power HCS08 core

operating from 1.8V to 3.3V• 10-bit SAR ADC converter• 8-pin SOIC

► Benefits• Lighter and smaller than 9V

powered systems• Efficient power saving

MCU wakes up, monitor ambient, sends data to host and goes to sleep again

• Able to operate from small solar cells


MC9S08QA4/2

► HCS08 Core• S08 8-bit CPU @ 20 MHz• Voltage range 1.8v to 3.3v

► Memory• QA4: 4K Flash, 256 bytes RAM• QA2: 2K Flash, 160 bytes RAM

► Clock• Internal Clock Source (ICS)

10 Mhz BusFLLOn-chip oscillatorExternal crystal support 2% accuracy over full operating range

► Peripherals• 4-channel, 10-bit ADC• One ACMP• One 1-channel TPM• One 8-bit MTIM• 4-channel KBI

► Input/Output• 5 GPIOs and 1 output-only pin

► Power Saving Mode• Wait mode• Stop1, Stop2, Stop3 modes

S08 Core

256/160BRAM

MTIM 4-ch 10-bitADC

ICSCOPBDM

16-bit Timer1ch + mod

GPIO

Flash

4-ch KBI

RTC ACMP4KFlash

2KFlash


Pocket MP3 Player with USB Interface and SD Card

►MC9S08JM32• Low-power HCS08 core• USB 2.0 Full Speed end point• 32 MB Flash memory• 2 KB RAM• 10-bit SAR ADC converter• SCI, SPI, I2C• 44-pin LQFP

►Benefits• Small, cost-effective audio

player with SD card• Easier to build


MC9S08JM32Features / Benefits► 2.7 – 5.0V operation► 2x SCI, I2C, 2x SPI► 8 channel KBI► 16-bit timers: 1 x 2-ch, 1 x 6-ch► 12-bit 12-channel A-to-D converter► Analog comparator► Up to 51 general purpose I/O

Memory► 32 KB Flash► 2K RAM

Complete USB Solution► Integrated USB device ► Complimentary USB software Stack► CodeWarrior for Microcontrollers► Processor Expert

Packages► 64LQFP, 64QFP 48QFN, 44LQFP

13

Full Speed USB 2.0 Device32K Flash

256 Bytes USB RAM

2K RAM

S08 Core

ICE+BDM

Indep. Clocked COP

2 SCI

2 SPI

KBI

IIC

RTC

MCG

6-ch., 16-bit Timer

Comparator

2-ch., 16-bit Timer

12-ch., 12-bit ADC


Blood pressure meter

► MC9S08LL16• Low power S08 MCU operating

from 1.8V to 3.6V • 16 KB dual bank Flash • 2K RAM• 4 x 28 or 8 x 24 LCD controller

with integrated charge pump• Time-of-day module• 12-bit ADC with internal

temperature sensor• RUN, WAIT, two STOP modes

with fast wake-up Peripherals able to operate with core in stand-by

• 48-pin LQFP

► Benefits• High performance x power

consumption rate• Great system-level integration

with good battery autonomy• Easy battery replacement


LCD Driver 9S08LL16 Packages

MC9S08LL16LCD Driver Block diagram Packages

Based on 8 backplanes 8x24 = 192 segments


48 & 64 LQFP

48 QFN

►Features• 1.8V to 3.6V• 20 MHz CPU speed• 8-ch keyboard interrupt• Up to 38 GPIOs • Up to 18 LCD pins mux with GPIO• LVD (low voltage detect)• Time-of-day module

►Internal Clock Source (ICS)• FLL• On-chip oscillator• External crystal support • 2% accuracy over full operating range

2K RAM

LL16: 16KLL8: 8K

ICE + 08BDM

COP

KBI

LL16: 2x2-ch 16-bit Timer

LL8: 1x2-ch 16-bit Timer

LCD Driver

IICS08 CoreLVD

TOD

ICS

SCI

SPI

8-12 bits ADC

Comparator

LL16 LL8

48 QFN

48 LQFP

TMFreescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. All other product or service names are the property of their respective owners. © Freescale Semiconductor, Inc. 2009. 16

Extending Battery Life with MC9S08LL16 Clock Management

Time

Pow

erC

onsu

mpt

ion

Run Mode5 seconds elapsed, main application runs, increases bus frequency to complete task quickly

Run ModeSlower frequency bus to just take ADC reading

Stop3 with RTC EnabledExternal 32 kHz Osc.

Stop2 with RTC EnabledInternal 1 kHz Osc.

Run MCU in low-power run


Home Care Thermometer

► MC9RS08LE4• Low power RS08 MCU

operating from 1.8V to 3.6V• Integrated LCD controller• 4K byte single block FLASH• 128 byte RAM• 10-bit ADC• 28-pin SOIC

► Benefits• Very low cost• Excellent integration – just a

few discrete devices outside• Smaller and lighter


LCD Driver Packages

MC9RS08LE4LCD Driver 9RS08LE4 Packages

►Features• 2.7V to 5.5V• RS08 core• 1-20 MHz capability• 8-ch keyboard interrupt• Up to 26 GPIOs• LVD (low voltage detect)• RTI

►Internal Clock Source (ICS)• FLL• On-chip oscillator• External crystal support • 2% accuracy over full operating range

►Memory• 4K flash • 256 bytes RAM

256 RAM

4K Flash

RS08BDM 2x2-ch 16-bitTimer

LCD Driver8x14 or 4x18

ICSRS08 Core

SCI

RTI

COP

KBI

LVD

8-10 bits ADC 28 SOIC




Isolated Current Meter

► MC9S08LL64• Low-power S08 MCU operating from

1.8V to 3.6V• 64 KB dual bank FLASH• 4K RAM• Integrated RTC• 12-bit SAR ADC• Internal temperature sensor• 288 segment LCD controller• Very low power stop modes – best in

class• 64-pin LQFP

► Benefits• Isolated and independent operation• Small footprint• Low irradiated noise• Could be powered by solar cells


► Features• 1.8V – 3.6V operation• 2 x SCIs, IIC, SPI, KBI, TOD, ACMP• 2 x 2 ch 16-bit TPM• 10 ch 12-bit ADC• Vref1.2 (1.2v – 40 PPM/°C)• Up to 39 GPIO• 80LQFP/64LQFP package

► Memory• Dual bank 64K Flash • 4K RAM

► LCD Driver• Up to 288 segment LCD drive (8x mode)• BP/FP reassignment• Blink operation in low-power modes• Drive 3V and 5V LCD glass

► Internal Clock Source (ICS)• FLL• On chip oscillator• External crystal support (32 KHz, 1-16 MHz) • 2% accuracy over full operating range

► Scheduled Availability• November 2009

4K RAM

Flash32x2K=64K

BDM

COP

KBI

2x2-ch 16bit TPM

LCD Driver8x36=288

S08 Core LVD

ICS

2xSCI

SPI10ch-12 bits

ADC

IIC

TOD

Vref

MC9S08LL64

ACMP


Step-up Converter Requirementsand Proposals


Step-up Converter Requirements

►Important requirements:• Battery chemistry• Design requirements

Output voltageSupply current at no loadSupply current at nominal loadRegulation at full loadDynamicsEfficiencyIrradiated noise

►Consumers in general expect longer battery life in newer products►On the other hand, the evolution of battery-powered devices is driven

by the addition of even more power-consuming features


Disposable Batteries

►Alkaline• Convenient, cheap and easy to find.• Long shelf life makes them excellent for

products such as emergency equipment• 1.6V to 0.9V practical operating range• Often available in AA and AAA footprints

►Lithium• Very low self-discharge rate.• Longer shelf life compared to alkaline• 1.8V to 0.9V practical operating range• Often available in CRxxxx footprints (aka button

battery)►Carbon Zinc

• Very low cost• High leakage resulting in reduced shelf life• 1.5V to 1.2V practical operating range• This full voltage is only available when little

current is drawn from the cell during its initial discharge. The voltage of the cell diminishes as the load to the cell increases


Circuit Design

Portable flashlight with white LED supplied through a AA 1.5V cell

►Requirements:• Input voltage: 1.5V AA cell• Output voltage: 3.4V

While LED V_ak• Output current: 50 mA

Freescale MC9RS08KA2 MCU– 1.8V to 5.5V supply– Approx. 500μA/MHz consumption at 5V– Will operate at approx. 3.4V (limited by the LED)

White 5mm LED– 15000 mCd @ 45mA and 3.4V_ak

• Battery autonomy: 12 hours (continuous)


Converter Requirements

►Supply requirements: • Vin_nominal: 1.5V• Vin_min: 1.1V

►Battery draining analysis:• Scenario 1: Converter efficiency from 80% to 93%

[ (3.4v * 50mA) / 0.80 ] / 1.1V = 193 mA max[ (3.4v * 50mA) / 0.93 ] / 1.5V = 122 mA min

• Scenario 2: Converter efficiency from 65% to 85%[ (3.4v * 50mA) / 0.65 ] / 1.1V = 238 mA max[ (3.4v * 50mA) / 0.85 ] / 1.5V = 133 mA min

►2500 mA/h AA battery lifetime in non-interruptible operation (*) • Scenario 1: (**)

0.94 * 2500mA/h / [ (193mA + 122mA) / 2 ] = 14.9 hours• Scenario 2: (**)

0.92 * 2500mA/h / [ (238mA + 133mA) / 2 ] = 12.4 hours

(*) Assuming linear behavior of I_dc drop over time for simple average(**) 0.94 and 0.92 as respective constant operation factors for 150 mA and 190 mAcontinuous operation

Scenario 1 = High efficient IC controller

Scenario 2 = Low cost discrete controller


Proposal #1: Using an Integrated Step-up Converter

► Desired features• Low power, wide input range, able to start from


Integrated Step-up Circuit Diagram

►Minor details such as button on MCU PTA5 and Step-up_pin6 omitted for clarity

►Current mode brightness control with Freescale MC9RS08KA2 ultra-low-cost MCU


Integrated Step-up Circuit

►Implemented with evaluation boards

• Fast prototyping►Very efficient and precise

• Great brightness control►Operation from

1.5V to 0.9V• Long battery life

►Low noise operation►But complex and

expensive for a flashlight


Integrated Step-up Facts

►Pros:• Great conversion efficiency• Excellent load regulation (even at zero load)• Low noise generation• Low part count

Usually integrates synchronous rectifierTwo resistors to set output voltageInductor and two storage capacitors

►Cons:• Expensive

Step-up controller was the most expensive device in the BOM• Require special capacitors and inductors

ESR in function of extreme high operating frequencies


Proposal #2: Using a Discrete Step-up ConverterAssisted by the MCU

►Desired features• Extreme low cost• Just a few components outside• Able to operate from V_bat >1.0V• 60% minimum efficiency

►Solution proposed: Fly back converter with bipolar transistor initiated by the user and then assisted by the MCU in the continuity of the operation

• Manual start, then MCU takes control of the conversion• Output voltage up to 3x input voltage• Average efficiency from 60% to 88%

• Even with less efficiency than integrated controllers, the overall cost makes the discrete solution suitable for low-end/low-cost requirements


Discrete Step-up Converter Assisted by MCU

►Pros:• Extremely low cost• Lowest part count

Just a few resistors, capacitors, one diode, one bipolar transistor and inductorPower_on button used to start conversion

• Smaller board area

►Cons:• Less efficient, reducing battery autonomy

White LED works almost as shunt regulator• Higher noise than obtained with the IC controller



Voltage mode regulation► Step-up conversion starts with “ON” button pressed a few times► Then the MCU takes control of the step-up process



Prototype►Effective low-cost►Adjustable brightness

• Fixed resistors at ACMP►Operates from 1.5V to 1.0V

with standard alkaline batteries

►Over 12 hour continuous operation


Performance Analysis and Results

► Full operation from 1.5V to 1.1V with both IC and discrete solutions

• 65% min efficiency with discrete circuitry• 80% min efficiency with controller IC

► IC controllers• Better dynamic regulation• Higher efficiency• Low noise• Higher cost

► Discrete converters• Poor dynamic regulation

Good for stable loads• Average efficiency

Better with assisted control• Noisier• Low cost


What makes Freescale 8-bit MCUs suitable for single cell operation?

►S08 and RS08 cores operating from voltages as low as 1.8V • Easy start-up• Predictable power consumption in function of supply voltage and clock speed

► Internal 32 KHz clock oscillator with integrated FLL • Fast speed to change clock frequency in function of battery state

►RUN, WAIT and several STOP modes with fast wake-up►Flash memory read/write/erase in the full supply range

• No need for additional boosting►20 μS byte write time on Flash

• Short bursts of additional power consumption when storing contents• Some devices with dual bank Flash

► Internal pull-ups and controlled rise and fall times on GPIO• Fewer external devices leaking energy

►Efficient 10- and 12-bit ADC• Simple and continuous mode with programmable conversion and sample time • Internal and external clock sourcing (selectable)• Digital magnitude comparator integrated• Operates in WAIT and STOP3 modes in most of the low power devices


Freescale Battery Life Calculator

►www.freescale.com/lowpower►Determines the average current

the MCU is consuming and estimate the resulting battery life

►Based on application system variables: V, Hz, °C, % of time in in MCU modes (run, wait, stop3, stop2 and stop1), periodic wakeup interval

►User can select from a variety of standard battery sizes and types or enter battery characteristics directly


Conclusion

►1.5V batteries are readily available at low cost in many standard footprints and offer high power density, making them ideal in space constrained applications demanding low power consumption and easy replacement

►Freescale supplies a large 8-bit MCU portfolio containing a wide variety of peripherals, sizes of memory, numbers of GPIO, and exclusive low power features allowing the execution of simpler 1.5V systems


Q&A

►Thank you for attending this presentation.

►In you have any questions, please contact me at: [email protected]

THANK YOU!

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TM

AZ143 – Running Freescale 8-bit MCUs from Single Cell 1.5V BatteriesObjective and AgendaWhy 1.5V? Single Cell Operation RequirementsFirst, Assume We Have a Step-up Boost ConverterWireless Humidity SensorIF Remote ControlMotion/Presence DetectorMC9S08QA4/2Pocket MP3 Player with USB Interface and SD CardMC9S08JM32Blood pressure meterMC9S08LL16�Extending Battery Life with MC9S08LL16 �Clock ManagementHome Care ThermometerMC9RS08LE4Isolated Current Meter MC9S08LL64 Step-up Converter RequirementsDisposable BatteriesCircuit DesignConverter RequirementsProposal #1: Using an Integrated Step-up ConverterIntegrated Step-up Circuit DiagramIntegrated Step-up CircuitIntegrated Step-up FactsProposal #2: Using a Discrete Step-up Converter�Assisted by the MCUDiscrete Step-up Converter Assisted by MCU Discrete Step-up Converter Assisted by MCUDiscrete Step-up Converter Assisted by MCUPerformance Analysis and ResultsWhat makes Freescale 8-bit MCUs suitable for �single cell operation?Freescale Battery Life CalculatorConclusionQ&A

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AZ143 – Running Freescale 8-bit MCUs from Single Cell 1.5V ...Standard microcontrollers do not operate from 1.5V single cells • Memories and logic elements often require voltages