Renesas Electronics America Inc. © 2012 Renesas Electronics America Inc. All rights reserved. Class ID: Low Power Design Michael Thomas, Applications Engineer CL01B

© 2012 Renesas Electronics America Inc. All rights reserved.2 Michael Thomas (Applications Engineer) 5 years at Renesas Electronics RX200 Technical Support RTOS, USB, DDLCD Customer projects (RL78, RX) Embedded Engineer at D-link (1 year)

© 2012 Renesas Electronics America Inc. All rights reserved.3 Renesas Technology & Solution Portfolio

© 2012 Renesas Electronics America Inc. All rights reserved.4 Microcontroller and Microprocessor Line-up Wide Format LCDs  Industrial & Automotive, 130nm  350µA/MHz, 1µA standby 44 DMIPS, True Low Power Embedded Security, ASSP 165 DMIPS, FPU, DSC 1200 DMIPS, Performance 1200 DMIPS, Superscalar 500 DMIPS, Low Power 165 DMIPS, FPU, DSC 25 DMIPS, Low Power 10 DMIPS, Capacitive Touch  Industrial & Automotive, 150nm  190µA/MHz, 0.3µA standby  Industrial, 90nm  200µA/MHz, 1.6µA deep standby  Automotive & Industrial, 90nm  600µA/MHz, 1.5µA standby  Automotive & Industrial, 65nm  600µA/MHz, 1.5µA standby  Automotive, 40nm  500µA/MHz, 35µA deep standby  Industrial, 40nm  200µA/MHz, 0.3µA deep standby  Industrial, 90nm  1mA/MHz, 100µA standby  Industrial & Automotive, 130nm  144µA/MHz, 0.2µA standby bit 8/16-bit

© 2012 Renesas Electronics America Inc. All rights reserved.5 ‘Portable and eventually wearable electronics will be a hallmark of the Smart Society and powerful, energy efficient MCUs are a key component of this future’ Challenge: “The kind of electronics that would be pervasive in a Smart Society demand both powerful and highly energy efficient MCUs; unlike the low-current low-performance MCUs used in the past” Solution: “This class will show you how to determine the important MCU parameters and model the application to determine the best power vs performance tradeoff in choosing an MCU.” ‘Enabling The Smart Society’

© 2012 Renesas Electronics America Inc. All rights reserved.6 Introduction Choosing an MCU for a low power application Lab outline Run lab section 1-2 Discussion Run lab section 3 Summary Agenda

© 2012 Renesas Electronics America Inc. All rights reserved.7 Choosing an MCU for a Low Power Application RL78 Performance (CPU core) Power consumption 50MHz/78DMIPS 1.56DMIPS/MHz 0.2mA/MHz 4uA in Sleep Operating voltage 1.62 to 5.5V 32MHz/40.6DMIPS 1.27DMIPS/MHz 1.6 to 5.5V 0.07mA/MHz 0.7uA in Sleep

© 2012 Renesas Electronics America Inc. All rights reserved.8 Identify peripherals required in low power mode Determine low power numbers from data sheet Determine transition time and current draw Model the application for current draw Calculate battery lifetime for given battery capacity Choosing an MCU for a Low Power Application ParameterWake UpLow Power Mode Current (MCU X)3 mA0.6uA Time5uS (32 MHz) Current (RX200)18 mA4uA Time150uS (50 MHz)

© 2012 Renesas Electronics America Inc. All rights reserved.9 Codec sends out data over SPI at periodic intervals MCU performs 128 point FFT on data Results are displayed on an LCD with a fixed refresh rate Return to low power mode until next cycle Lab Outline SPI Codec FFT IIC SPI data LCD data MCU SPI FFT I2C Sleep LCD

© 2012 Renesas Electronics America Inc. All rights reserved.10 SPI Takes 6.4 ms to acquire 128 samples at 20KHz sample rate 128/20000 = 6.4ms Assume Codec has no buffer; thus MCU has to be reading each sample as generated FFT Performed on pre-generated data I2C LCD refresh takes 58 ms over I2C Sleep Mode with RTC running chosen Lab Outline SPI FFT I2C Sleep

© 2012 Renesas Electronics America Inc. All rights reserved.11 Start of low- power stage. SW3 Wake-Up Trigger Start of SPI stage Port toggle indicating first line of code executed after wake-up. End of SPI stage Start of FFT stage. End of FFT stage. Start of I2C stage. End of I2C stage. Current GPIO External Trigger Power Profile

© 2012 Renesas Electronics America Inc. All rights reserved.12 Low-ohm load resistor (1-2 Ohms) Voltage drop across resistor using scope probe Ammeter for steady state current Combine of these two methods for an accurate picture Measuring Transient Stage Current

© 2012 Renesas Electronics America Inc. All rights reserved.13 1 nA – 30 mA 200 mV – 5V Continuous ranging USB $900-$1500 pocketpico.com Measuring Transient Stage Current

© 2012 Renesas Electronics America Inc. All rights reserved.14 Measure current draw in each stage Calculate transition times Generate power profiles Plot current vs update rate graph Determine crossover point Lab Outline: Sections 1-2

© 2012 Renesas Electronics America Inc. All rights reserved.15 Start the Lab: Section 1-2 Please refer to the lab handout and let’s get started!

© 2012 Renesas Electronics America Inc. All rights reserved.16 Discussion

© 2012 Renesas Electronics America Inc. All rights reserved.17 Discussion MCUMaximum Update/Sec RL786.4 RX Hz 0.2 mA

© 2012 Renesas Electronics America Inc. All rights reserved.18 Configured via the OPCCR register Module Stop, Software Standby, Deep Software Standby RX210 Operating Modes ModeICLK Max Freq. F/PCLK Max Freq. BCLK Max Freq. Flash VCC Range Limitation Read Op. P/E Op. Internal Voltage Regulator Mode High Speed Mode50MHz32MHz12.5MHz V High Power Middle Speed Mode A32MHz/ 20MHz 32MHz/ 20MHz 8MHz/ 5MHz V/ V Middle Power Middle Speed Mode B V Low Speed Mode 11MHz 250kHz VN.A.Low Power Low Speed Mode 232kHz 4kHz VUltra Low Power

© 2012 Renesas Electronics America Inc. All rights reserved.19 RX210 Wake-Up to from S/W Standby 180 uA in S/W Standby Wakeup:150 uSec Flash powered ON HOCO powered ON RTC+SUBClk ON 5uA in S/W Standby Wakeup: 580 uSec Flash powered OFF HOCO powered ON RTC+SUBClk ON Thus there is a time/power tradeoff choice involved that has to be made depending on the application

© 2012 Renesas Electronics America Inc. All rights reserved.20 Add an extra stage to the program Account for power-down transition stage Choose a different low power mode Update graph to determine new crossover point Use battery calculator to determine battery life Lab Outline: Section 3

© 2012 Renesas Electronics America Inc. All rights reserved.21 Start the Lab: Section 3 Please refer to the Lab Handout and let’s get started!

© 2012 Renesas Electronics America Inc. All rights reserved.22 Discussion (0.01 Hz Update Rate) 1000 mAh Battery Life (days) RL78RX

© 2012 Renesas Electronics America Inc. All rights reserved.23 Discussion (0.1 Hz Update Rate) 1000 mAh Battery Life (days) RL78RX

© 2012 Renesas Electronics America Inc. All rights reserved.24 Discussion (0.4 Hz Update Rate) 1000 mAh Battery Life (days) RL78RX

© 2012 Renesas Electronics America Inc. All rights reserved.25 Discussion (1 Hz Update Rate) 1000 mAh Battery Life (days) RL78RX

© 2012 Renesas Electronics America Inc. All rights reserved.26 Discussion (6 Hz Update Rate) 1000 mAh Battery Life (days) RL78RX

© 2012 Renesas Electronics America Inc. All rights reserved.27 Discussion (15 Hz Update Rate) 1000 mAh Battery Life (days) RL78RX

© 2012 Renesas Electronics America Inc. All rights reserved.28 Discussion

© 2012 Renesas Electronics America Inc. All rights reserved Hz Discussion MCU – RX200Maximum Cycles/Sec Power/Cycle 7 uA sleep and 550 usec wake-up mA 186 uA sleep and 150 usec wake-up mA 3 uA sleep and 3120 usec wake-up mA

© 2012 Renesas Electronics America Inc. All rights reserved.30 What other operational parameters are missing from this discussion? Response time Overlapping stages Interrupt driven stages Discussion

© 2012 Renesas Electronics America Inc. All rights reserved.31 How to decide which MCU is better suited to a low power application How to model an application to determine its power profile The best low power MCU is the one that best fits the application Low power comparison spreadsheet Identify relevant information in the datasheet This approach can be used to compare any number of MCUs Summary

© 2012 Renesas Electronics America Inc. All rights reserved.32 Questions? Questions?

© 2012 Renesas Electronics America Inc. All rights reserved.33 ‘Portable and eventually wearable electronics will be a hallmark of the Smart Society and powerful, energy efficient MCUs are a key component of this future’ Challenge: “The kind of electronics that would be pervasive in a Smart Society demand both powerful and highly energy efficient MCUs; unlike the low-current low-performance MCUs used in the past” Solution: “This class will show you how to determine the important MCU parameters and model the application to determine the best power vs performance tradeoff in choosing an MCU.” ‘Enabling The Smart Society’ in Review…

© 2012 Renesas Electronics America Inc. All rights reserved.34 Please utilize the ‘Guidebook’ application to leave feedback or Ask me for the paper feedback form for you to use… Please Provide Your Feedback…

Renesas Electronics America Inc. © 2012 Renesas Electronics America Inc. All rights reserved.