Renesas Electronics Europe
October 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
function
RTC 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 processing Processing with Smart
peripheral Management
CPU
Comparator
Timer
A/D
Interrupt
Controller
External
analog
input
voltage
CPU
Comparator
Timer
A/D
Interrupt
Controller
Event
Linker
External
analog input
voltage
UsingInterrupt:14cyc
ELC:3cyc
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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
CPU
Peripheral
function
memory
DTC
Data bus
Address bus
CPU
Peripheral
function
memory
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
Interrupt
Transition time
Program execution
Interrupt example
DTC example
A/D conversion end
interrupt
A/D conversion
Bus
operation
PUSH
instruction
Interrupt processing
Transfer conversion result to RAM
POP
instruction
RTE
instruction
Program execution
DTC
Start time
Program execution DTC used
Transfer conversion
result to RAM
Program execution
Operation
Shorten transfer processing time!
Bus
operation
Operation
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/L13
Competitor
A
Competitor
B
Competitor
C
Competitor
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 No
MAX. 2.1uA
Split
Resistor
TYP. 1.5uA
1.7uA
(@2.2V)
No
2.0uA
(@1.8V)
No
MAX. 2.2uA
2.5uA
(@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.