reduce system energy by smart cpu management
DESCRIPTION
Renesas employ smart MCU power management techniques which include autonomous peripheral operation with DMA. The solution is to place the MCU in the lowest possible power mode whilst the peripherals are allowed to perform functions. In this presentation and tools demonstration, Renesas will show how to enable lowest system power using there RL78 MCU smart peripheral techniques.To extend the idea, individual peripherals could be given more functions and even reduce DMA operations. For example A/D converter with compare functionality so that the result register need not wake up the CPU if the result is within or outside the threshold limits. Similarly a serial interface could be checked for a valid and desired data and if that is not received then the CPU could be sleep mode. Renesas extends this idea of implementing the technique to other peripherals within the MCU to make them smarter.TRANSCRIPT
Renesas Electronics EuropeOctober 9th 2013
Reduce system energy by
smart CPU management
Mark Cullum – Senior Marketing Engineer
Agenda
Next generation microcontroller requirements Sensor application Portable HMI application
RL78 microcontroller Smart power management
– Snooze Mode Smart peripherals
– Event Link Controller (ELC)– Data Transfer Controller (DTC)
Smart LCD drive– Split Capacitor drive
Power consumption breakdown Using RL78 power modes
RL78 summary
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Microcontroller (MCU) Application Requirements
Sensor
Very low average current consumption
Efficient and well integrated power modes
Fast processing time
Ultra low standby current
Energy efficient and smart peripherals
Very fast wake up time
Small packages
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Portable HMI
Flexible efficient clocking architecture
Very low active current consumption
Efficient and well integrated power modes for MCU
Low power/ low cost LCD drive
Fast processing time
Ultra low standby current
Energy efficient and smart peripherals
MCU current Breakdown
Operation Current Comment
Power during RUN 4.7mA 32MHz, 3.0V, typ.Power CPU Idle 0.62mA 32MHz, 3.0V, typ.Power CPU Stop 0.23μA -40ºC to +70ºC, no WDT, typ.
Intelligent power mode -CPU stop current + active
functionRTC 0.02μA 32MHz, 3.0V, typ.
RTC + 32KHz Oscillation Current
0.54μA 32MHz, 3.0V, typ.
WDT 0.22μA 15KHz, 3.0V, typ.ADC 0.5mA Low-voltage mode, 3V, typ.
Temperature sensor 75μA 3V, typ.
LVD 0.08μA 3V, typ.
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RL78/G14 @ 32MHz operation
To enable lowest power MCU RUN time must be
minimised Smart peripherals must be
implemented to reduce RUN mode operation time
RL78 Peripheral Rich, True-Low-Power Platform
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RL78’s Multiple Low Power Modes
Snooze Mode Allows background operation without CPU running
Autonomous decision making peripherals
CPU wake up on conditional peripheral match
– Serial I/F with valid data reception
– Scan Analog inputs for trigger inputs
ADC, CSI/UART active
Halt Mode DMA and all peripherals available
STOP Mode RAM retained
Smart peripherals maintain lowest power
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RL78 Smart Peripheral Management
Standard processingStandard processing Processing with Smart peripheral ManagementProcessing with Smart peripheral Management
CPUCPU
ComparatorComparator
TimerTimer
A/DA/D
InterruptControllerInterruptController
External analog input voltage
CPUCPU
ComparatorComparator
TimerTimer
A/DA/D
Interrupt ControllerInterrupt Controller
Event LinkerEvent Linker
External analog input voltage
Usin
g I
nte
rru
pt:
14
cyc
ELC
: 3
cyc
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RL78 Event Link Controller (ELC) Reduce CPU interrupt processing Improve real time function Reduce program size Includes direct control of I/O ports and built in event timers Operational in low power modes
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DTC unused DTC used - reduces CPU workload
Data bus
Address bus
CPUPeripheral functionmemory
DTC
Data bus
Address bus
CPUPeripheral functionmemory
DTC
RL78 Data Transfer Controller (DTC) Allows automatic transfer between memory and register without CPU operation Data management is activated by an interrupt or by software CPU not operating during data transfer Up to 24 channels of DTC supported with 31 (39) activation sources Three transfer modes Direct specification of 64 kbyte address space possible Transfer is set in byte units CPU interrupt can be requested for the interrupt that activated the DTC
RL78 Smart Peripheral Management (2)
RL78 Smart Peripheral Management (3)
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RL78 Data Transfer Controller (DTC) DTC can be used in SNOOZE & Halt mode
– Ideal for battery powered applications
InterruptTransition timeProgram execution
Interrupt example
DTC example
A/D conversion end interrupt
A/D conversion
Busoperation
PUSHinstruction
Interrupt processing
Transfer conversion result to RAM
POPinstruction
RTEinstruction
Program execution
DTCStart time
Program execution DTC used
Transfer conversion result to RAM
Program execution
Operation
Shorten transfer processing time!
BusoperationOperation
12 cycles
22 cycles
Shorten transfer processing time!
RL78 Smart LCD Drive
RL78 Split Capacitor Drive No continuous wasted current
– Flowing through the resistive split bias chain– Through capacitive charge pump
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Resistor DividerSplit Capacitor Internal Boost
Split Capacitor Internal Booster External resistance division
Current Consumption
0.1uA 1.0uA 0.2uA
External components
Only 2 capacitors Only 3 capacitors Only 3 resistors
RL78 LCD Drive Comparison
RL78/L13Competitor
ACompetitor
BCompetitor
CCompetitor
D
RTC operation 0.5uA 0.7uA 1.9uA 0.7uA 2uA
Power consumption with LCD in sub HALT modes
Split Cap.TYP. 0.6uA
No No No NoMAX. 2.1uA
Split Resistor
TYP. 1.5uA1.7uA
(@2.2V) No
2.0uA
(@1.8V)No
MAX. 2.2uA2.5uA
(@2.2V)-
Internal Boost
TYP. 1.5uA 4.5uA 2.9uA
No
3.7uA
MAX. 4.2uA - - -
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RL78/L1x achieves lowest power in all drive modes
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ADC operation during standby state Four comparison criteria: Within/Outside Window, Higher/Lower than Limit
Sensor Application – Using RL78 ‘Snooze Mode’
Over 30%* power saving
* white paper ‘Reduce System energy by smart CPU management’ 09.13
HMI Application - Using RL78 ‘Split Capacitor’ Drive
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Capacitor Split used to generate LCD bias voltages No continuous wasted current
– Flowing through the resistive split bias chain– Through capacitive charge pump
Just 0.1uA current internal consumption
Battery life is doubled! 0.62uA @3V LCD active & RTC running (1.5uA using traditional drive modes) Allows data transfer between memory and register without CPU operation Data management is activated by an interrupt or by software CPU not operating during data transfer
Reducing System Energy – RL78
True-low-power operation is required in all modes RL78 from 46uA/MHz in operation
RL78 intelligent low power modes Background operation without CPU - Snooze mode
Memory retention and access in lowest power modes
RL78 smart autonomous peripherals Event link controller
Data transfer controller
Split capacitor drive
Scalability and integration enables system cost reduction Packages down to 3x3mm
1KB to 512KB, 10 to 128 pins
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www.renesas.eu/RL78
© 2013 Renesas Electronics Europe. All rights reserved.