Power management for the LPC900 family

AN10367
Power management for the LPC900 family
Rev. 01 — 29 March 2005
Application note
Document information
Info
Content
Keywords
Power management for the LPC900 family.
Abstract
This document will describe different ways to reduce power consumption
on the LPC900 parts.
AN10367
Philips Semiconductors
LPC900 power management
Revision history
Rev
Date
Description
01
20050329
Initial version
Contact information
For additional information, please visit: http://www.semiconductors.philips.com
For sales office addresses, please send an email to: [email protected]
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LPC900 power management
1. Introduction
The purpose of this document is to explain the different power management methods for
the LPC900 family.
Many applications will have strict power requirements, and there are several methods of
lowering the rate of power consumption without sacrificing performance. Calculating the
predicted power use is important to characterize the system's power supply requirements.
The LPC900 peripherals can be put into low power modes by setting some bits in the
registers. The utility of these low power modes depends on the specific application.
The basic explanation of this note is based on the LPC935 tested with a limited sample,
but it is applicable to all of the LPC900 general purpose devices.
2. Power management modes
CMOS digital logic device power consumption is affected by supply voltage and clock
frequency. The amount of current consumption is directly proportional to the voltage of the
power. The power consumption depends on the number of active peripherals, and also
depends on whether the oscillator is On or Off and whether the CPU is On or Off.
The P89LPC935 is designed to run at 12 MHz (CCLK) maximum. However, if CCLK is
8 MHz or slower, the CLKLP SFR bit (AUXR1.7) can be set to '1' to lower the power
consumption further. On any reset, CLKLP is '0' allowing highest performance access.
This bit can then be set in software if CCLK is running at 8 MHz or slower.
The P89LPC935 supports three different power reduction modes as determined by SFR
bits PCON.1-0 shown in the following section.
2.1 Idle mode
In Idle mode the core is turned off, peripherals can still run or can be powered down with
the PCONA SFR. Any enabled interrupt source or reset will terminate Idle mode.
2.2 Power-down mode
Power-down mode stops the oscillator in order to minimize power consumption. Only the
System Timer / RTC, the Comparators, the Brown-out Detect and the WDT can still run (if
enabled in PCONA). The LPC900 can exit Power-down mode via any reset, or certain
interrupts - external pins INT0/INT1, brownout Interrupt, keyboard interrupt, real time clock
(system timer), watchdog, and comparators.
Waking up by reset is only enabled if the corresponding reset function on pin P1.5 is
enabled, and waking up by interrupt is only enabled if the corresponding interrupt is
enabled and the EA SFR bit (IEN0.7) is set. When the processor wakes up from
Power-down mode, the LPC900 will start the oscillator immediately and begin execution
when the oscillator is stable. Oscillator stability is determined by counting 1024 CPU
clocks after start-up when one of the crystal oscillator configurations is used, or 256
clocks after start-up for the internal RC or external clock input configurations.
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2.3 Total power-down mode
In total Power-down mode the CPU and oscillator will be turned off. Only the System
Timer / RTC and the WDT can still run (if enabled). The following are the wake-up options
supported: Watchdog Timer (can generate Interrupt or Reset), External interrupts INT0 /
INT1, Keyboard Interrupt, and Real Time Clock/System Timer.
2.4 Power management modes summary
Table 1 shows the different power management modes.
Table 1:
LPC900 power management modes
LPC900 mode
Crystal Oscillator
CPU Peripherals
Normal
On
On
On (individual peripherals can be powered down
with PCONA)
Idle
On
Off
On (individual peripherals can be powered down
with PCONA)
Power-down
Off[1]
Off
System timer / RTC, Comparators, BOD, WDT
can run when enabled
Total Power-down
Off[1]
Off
System timer / RTC, WDT can run when enabled
[1]
The crystal oscillator is turned on in Power-down mode if the RTC is enabled and a crystal is selected as
the clock source.
3. Measuring lowest power consumption modes
Since power consumption is affected by supply voltage and clock frequency, lowering the
clock frequency and operating voltage will lower the power consumption.
The oscillator frequency OSCCLK of the LPC900 family can be divided down, by an
interger, up 510 times by configuring the dividing register DIVM The output of the
frequency CCLK of the divider is according the formula CCLK = OSCCLK/2N. Where N is
the value of DIVM. The CCLK frequency can be in the range of OSCCLK to OSCCLK/510.
For N = 0 CCLK = OSCCLK.
The source for OSCCLK depends on the selecting in the UCFG register and can be from
an internal oscillator with an external crystal, Internal RC oscillator or internal watchdog
oscillator.
The LPC900 family has 2.4 V to 3.6 V VDD operating range. I/O pins are 5 V tolerant (may
be pulled up or driven to 5.5 V). The following samples include lower frequency and supply
voltage to lower the power consumption.
3.1 Current consumption in Idle mode
In Idle mode the core is turned off, peripherals can still run or can be powered down with
the PCONA SFR. Any enabled interrupt source or reset will terminate Idle mode.
3.1.1 Measurement configuration
• When using external crystal 32.768 kHz the capacitor C1=C2=33pF
• When using external crystal 11.0592 MHz the capacitor C1=C2=22pF
• All ports have been set as Quasi-bidirectional except P1.2,P1.3,P1.5 and at high level
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LPC900 power management
• After this, the MCU is put into idle mode
• Hardware configuration as in Figure 1.
Fig 1. Current measurement configuration
3.1.2 Software example
#include<reg935.h>
void delay(int x)
{
int j=0;
while(x>=0)
{
for (j=0; j<1100; j++)
{
}
x--;
}
}
void main(void)
{
P0M1 = 0x00; //set P0 as Quasi-bidirectional
P0M2 = 0x00;
P1M1 = 0x20;
P1M2 = 0x00;
P2M1 = 0x00;
P2M2 = 0x00;
P3M1 &= 0xfc;
P3M2 &= 0xfc;
P0 = 0xff;
P1 = 0xff;
P2 = 0xff;
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LPC900 power management
P3 = 0xff;
RTCCON&=0xfe; //stop RTC
WDCON=0x00; //stop WDT
//DIVM=0x64;
AUXR1|=0x80; // reduces power consumption in the clock circuits
// if CCLK is 8 MHz or slower,
P2=0xfe;
delay(100);
P2=0xff;
PCONA|= 0xff; // turn off all peripherals that can be turned off
PCON|=0x21;
// enter Idle mode
while(1);
}
3.1.3 Measurement results in Idle mode
The following tables and graphs show the measurement results of the LPC900 family in
Idle mode.
Table 2:
Current consumption IDD low frequency crystal
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD = 3.6 V
Idle DIVM = 00h
32.768 kHz
62.7 µA
72.5 µA
90.2 µA
Idle DIVM = 0Ah
1.6384 kHz
57.5 µA
64.8 µA
77.2 µA
Idle DIVM = 64h
0.16384 kHz 56.8 µA
64.1 µA
76.9 µA
Idle DIVM = FFh
0.06 kHz
55.8 µA
64.1 µA
76.2 µA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C) with a limited sample.
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LPC900 power management
Idle DIVM=00H
IDD Idle 32kHz crystal
Idle DIVM=0AH
Idle DIVM=64H
Idle DIVM=FFH
100.00
90.00
80.00
IDD [µA]
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
2
2.2
2.4
2.6
2.8
3
3.2
3.4
3.6
3.8
VDD [V]
Fig 2. IDD Idle with a 32 kHz crystal
Table 3:
Current consumption IDD high frequency crystal
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD = 3.6 V
Idle DIVM = 00h
11.059 MHz
2.50 mA
Idle DIVM = 0Ah
553 kHz
0.71 mA
1.09 mA
1.45 mA
Idle DIVM = 64h
55.3 kHz
0.63 mA
0.93 mA
1.28 mA
Idle DIVM = FFh
21.7 kHz
0.62 mA
0.92 mA
1.27 mA
3.61 mA
4.80 mA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C) with a limited sample.
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LPC900 power management
Idle DIVM=00H
IDD Idle 11.059MHz crystal
Idle DIVM=0AH
Idle DIVM=64H
Idle DIVM=FFH
6
5
IDD [mA]
4
3
2
1
0
2
2.2
2.4
2.6
2.8
3
VDD [V]
3.2
3.4
3.6
3.8
Fig 3. IDD Idle with a 11.059 MHz crystal
Table 4:
Current consumption IDD internal oscillator
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD = 3.6 V
Idle DIVM = 00h
7.3728 MHz
1.54 mA
Idle DIVM = 0Ah
369 kHz
0.35 mA
0.44 mA
0.54 mA
Idle DIVM = 64h
36.9 kHz
0.29 mA
0.36 mA
0.43 mA
Idle DIVM = FFh
14.5 kHz
0.29 mA
0.35 mA
0.43 mA
2.12 mA
2.80 mA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C) with a limited sample.
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Idle DIVM=00H
IDD Idle 7.373MHz Internal RC Oscilator
Idle DIVM=0AH
Idle DIVM=64H
Idle DIVM=FFH
3
2.5
IDD [mA]
2
1.5
1
0.5
0
2
2.2
2.4
2.6
2.8
3
VDD [V]
3.2
3.4
3.6
3.8
Fig 4. IDD Idle with a 7.37 MHz Internal oscillator
Table 5:
Current consumption IDD watchdog oscillator
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD = 3.6 V
Idle DIVM = 00h
400 kHz
159.8 µA
202.8 µA
256.8 µA
Idle DIVM = 0Ah
20 kHz
84.7 µA
99.6 µA
117.5 µA
Idle DIVM = 64h
2 kHz
81.1 µA
94.5 µA
110.9 µA
Idle DIVM = FFh
0.784 kHz
80.9 µA
94.2 µA
110.5 µA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C) with a limited sample.
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Idle DIVM=00H
IDD Idle 400 kHz Watchdog oscillator
Idle DIVM=0AH
Idle DIVM=64H
Idle DIVM=FFH
300
250
IDD [µA]
200
150
100
50
0
2
2.2
2.4
2.6
2.8
3
VDD [V]
3.2
3.4
3.6
3.8
Fig 5. IDD Idle with a 400 kHz internal Watchdog oscillator
3.2 Current consumption in Power-down mode
This example provides a static method of measuring the current consumption by the
microcontroller in Power-down mode and without any I/O activity, while the voltage
comparators are active.
3.2.1 Measurement configuration
•
•
•
•
•
•
When using external crystal 32.768 kHz the capacitor C1=C2=33pF
When using external crystal 11.0592 MHz the capacitor C1=C2=22pF
All ports have been set as Quasi-bidirectional except P1.2,P1.3,P1.5 and at high level
Enable analog voltage comparator
After this the MCU is put into Power-down mode
Hardware configuration as Figure 1.
3.2.2 Software example
#include<reg935.h>
void delay(int x)
{
int j=0;
while(x>=0)
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{
for (j=0; j<1100; j++)
{
}
x--;
}
}
void main(void)
{
P0M1 = 0x00; //set P0 as Quasi-bidirectional
P0M2 = 0x00;
P1M1 = 0x20;
P1M2 = 0x00;
P2M1 = 0x00;
P2M2 = 0x00;
P3M1 &= 0xfc;
P3M2 &= 0xfc;
P0 = 0xff;
P1 = 0xff;
P2 = 0xff;
P3 = 0xff;
RTCCON&=0xfe; //stop RTC
WDCON=0x00; //stop WDT
//DIVM=0x64;
AUXR1|=0x80; // reduces power consumption in the clock circuits
// if CCLK is 8 MHz or slower,
P2=0xfe;
delay(100);
P2=0xff;
PCONA|= 0xff; // turn off all peripherals that can be turned off
PCON|=0x22;
// enter Power-down mode
while(1);
}
3.2.3 Measurement results in Power-down mode
This example provides a static method of measuring the current consumption by the
microcontroller in Power-down mode and without any I/O activity, while the voltage
comparators are active.
Table 6:
Current consumption IDD in Power-down mode
Mode
IDD at VDD =
2.4 V
IDD at VDD =
3.0 V
IDD at VDD =
3.6 V
Power-down mode
51.9 µA
54.6 µA
58.1 µA
Power-down while Comparators are
active
66.5 µA
69.3 µA
73.2 µA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C) with a limited sample. Brownout is disabled, RTC and
watchdog timer are turned off.
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IDD powerdown
Pow er dow n
Pow er dow n
80
70
60
IDD [µA]
50
40
30
20
10
0
2
2.2
2.4
2.6
2.8
3
VDD [V]
3.2
3.4
3.6
3.8
Fig 6. IDD Power-down
3.3 Current consumption in total Power-down mode
This example provides a static method of measuring the current consumed by the
microcontroller in total Power-down mode, without any I/O ports and any peripherals
active.
3.3.1 Measurement configuration
•
•
•
•
•
When using an external crystal 32.768 kHz the capacitor C1=C2=33pF
When using an external crystal 11.0592 MHz the capacitor C1=C2=22pF
All ports have been set as Quasi-bidirectional except P1.2,P1.3,P1.5 and at high level
After this, the MCU is put into total Power-down mode
Hardware configuration as Figure 1.
3.3.2 Software example
#include<reg935.h>
void delay(int x)
{
int j=0;
while(x>=0)
{
for (j=0; j<1100; j++)
{
}
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x--;
}
}
void main(void)
{
P0M1 = 0x00; //set P0 as Quasi-bidirectional
P0M2 = 0x00;
P1M1 = 0x20;
P1M2 = 0x00;
P2M1 = 0x00;
P2M2 = 0x00;
P3M1 &= 0xfc;
P3M2 &= 0xfc;
P0 = 0xff;
P1 = 0xff;
P2 = 0xff;
P3 = 0xff;
RTCCON&=0xfe; //stop RTC
WDCON=0x00; //stop WDT
//DIVM=0x64;
AUXR1|=0x80; // reduces power consumption in the clock circuits
// if CCLK is 8 MHz or slower,
P2=0xfe;
delay(100);
P2=0xff;
PCONA|= 0xff; // turn off all peripherals that can be turned off
PCON|=0x23;
// enter total Power-down mode
while(1);
}
3.3.3 Measurement results in total Power-down mode
This example provides a static method of measuring the current consumed by the
microcontroller in total Power-down mode, without any I/O ports and peripherals is active.
Table 7:
Current consumption IDD in total Power-down mode
Mode
IDD at VDD =
2.4 V
IDD at VDD =
3.0 V
IDD at VDD =
3.6 V
Power-down mode
1 µA
1 µA
1 µA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C). Brownout is disabled, RTC and watchdog timer are
turned off.
3.4 Current consumption in active mode using DIVM
This example provides a static method of measuring the current consumed by the microcontroller in different power management modes.
3.4.1 Measurement configuration
• When using external crystal 32.768 kHz the capacitor C1=C2=33pF
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•
•
•
•
When using external crystal 11.0592 MHz the capacitor C1=C2=22pF
All ports have been set as Quasi-bidirectional except P1.2,P1.3,P1.5 and at high level
After this, the MCU is put into different power management mode
Hardware configuration as Figure 1.
3.4.2 Software example
#include<reg935.h>
void delay(int x)
{
int j=0;
while(x>=0)
{
for (j=0; j<1100; j++)
{
}
x--;
}
}
void main(void)
{
P0M1 = 0x00; //set P0 as Quasi-bidirectional
P0M2 = 0x00;
P1M1 = 0x20;
P1M2 = 0x00;
P2M1 = 0x00;
P2M2 = 0x00;
P3M1 &= 0xfc;
P3M2 &= 0xfc;
P0 = 0xff;
P1 = 0xff;
P2 = 0xff;
P3 = 0xff;
RTCCON&=0xfe; //stop RTC
WDCON=0x00; //stop WDT
//DIVM=0x64;
AUXR1|=0x80; // reduces power consumption in the clock circuits
// if CCLK is 8 MHz or slower,
P2=0xfe;
delay(100);
P2=0xff;
PCONA|= 0xff; // turn off all peripherals that can be turned off
while(1);
}
3.4.3 Measurement results in Active mode
In active mode, the CPU is still running and the peripherals are turned off in PCONA.
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Table 8:
Current consumption IDD low frequency crystal
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD =
3.6 V
Active DIVM = 00h
32.768 kHz
73.9 µA
88.1 µA
115.0 µA
Active DIVM = 0Ah
1.6384 kHz
61.7 µA
67.2 µA
84.8 µA
Active DIVM = 64h
0.16384 kHz 60.3 µA
66.6 µA
83.6 µA
Active DIVM = FFh
0.06 kHz
59.1 µA
66.3 µA
83.1 µA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C) with a limited sample.
Active DIVM=00H
IDD Active 32kHz crystal
Active DIVM=0AH
Active DIVM=64H
Active DIVM=FFH
140
120
IDD [µA]
100
80
60
40
20
0
2
2.2
2.4
2.6
2.8
3
VDD [V]
3.2
3.4
3.6
3.8
Fig 7. IDD Active with a 32 kHz crystal
Table 9:
Current consumption IDD high frequency crystal
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD = 3.6 V
Idle DIVM = 00h
11.059 MHz
4.56 mA
6.78 mA
8.83 mA
Idle DIVM = 0Ah
553 kHz
0.85 mA
1.41 mA
1.70 mA
Idle DIVM = 64h
55.3 kHz
0.67 mA
1.15 mA
1.35 mA
Idle DIVM = FFh
21.7 kHz
0.65 mA
1.14 mA
1.33 mA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C) with a limited sample.
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Active DIVM=00H
IDD Active 11.059 MHz crystal
Active DIVM=0AH
Active DIVM=64H
Active DIVM=FFH
10
9
8
IDD [mA]
7
6
5
4
3
2
1
0
2
2.2
2.4
2.6
2.8
3
VDD [V]
3.2
3.4
3.6
3.8
Fig 8. IDD Active with a 11.059 MHz oscillator
Table 10:
Current consumption IDD internal oscillator
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD = 3.6 V
Idle DIVM = 00h
7.3728 MHz
2.97 mA
Idle DIVM = 0Ah
369 kHz
0.43 mA
0.54 mA
0.68 mA
Idle DIVM = 64h
36.9 kHz
0.31 mA
0.38 mA
0.48 mA
Idle DIVM = FFh
14.5 kHz
0.29 mA
0.37 mA
0.44 mA
4.0 mA
5.3 mA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C) with a limited sample.
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Active DIVM=00H
IDD Active 7.373 MHz IRC oscilator
Active DIVM=0AH
Active DIVM=64H
Active DIVM=FFH
6
5
IDD [mA]
4
3
2
1
0
2
2.2
2.4
2.6
2.8
3
VDD [V]
3.2
3.4
3.6
3.8
Fig 9. IDD Active with a 7.373 MHz Internal RC oscillator
Table 11:
Current consumption IDD watchdog oscillator
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD = 3.6 V
Idle DIVM = 00h
400 kHz
249.5 µA
333.5 µA
420 µA
Idle DIVM = 0Ah
20 kHz
87.1 µA
110.5 µA
166.5 µA
Idle DIVM = 64h
2 kHz
85.7 µA
104.9 µA
128.0 µA
Idle DIVM = FFh
0.784 kHz
84.8 µA
103.6 µA
127.2 µA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C) with a limited sample.
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Active DIVM=00H
IDD Active 400 kHz WD oscilator
Active DIVM=0AH
Active DIVM=64H
Active DIVM=FFH
450
400
350
IDD [µA]
300
250
200
150
100
50
0
2
2.2
2.4
2.6
2.8
3
VDD [V]
3.2
3.4
3.6
3.8
Fig 10. IDD Idle with a internal Watchdog oscillator
3.5 Current consumption in Power-down with RTC
This example provides a static method of measuring the current consumed by the RTC.
We will measure power consumption of RTC using 32.768 kHz crystal and slow
down the clock frequency of the CPU when using internal RC oscillator.
3.5.1 Measurement configuration
•
•
•
•
When using an external crystal 32.768 kHz the capacitor C1=C2=33pF
All ports have been set as Quasi-bidirectional except P1.2,P1.3,P1.5 and at high level
Internal RC oscillator is used for the core
Hardware configuration as Figure 1.
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3.5.2 Software example
#include<reg932.h>
#include<intrins.h>
int RTC_Timer_Counter;
void delay(int x)
{ int j=0;
while(x>=0)
{for (j=0; j<1100; j++);
x--; }
}
}
void RTC_ISR() interrupt 10
{ RTC_Timer_Counter++;
if (RTCCON&0x80==0x80 )
{
RTCCON&=0x63;
// reset RTC interrupt flag
if(RTC_Timer_Counter++>10)
{
P2=~P2;
RTC_Timer_Counter=0;
}
}
}
void main(void)
{
P0M1 = 0x00;
P0M2 = 0x00;
P1M1 = 0x20;
P1M2 = 0x00;
P2M1 = 0x00; // set P2 to Quasi-bidirectional mode
P2M2 = 0x00;
P0 = 0xff;
P1 = 0xff;
P2 = 0xff;
RTCCON&=0xfe;
WDCON=0x00;
// DIVM=0x64;
AUXR1|=0x80; // reduces power consumption in the clock circuits.
RTCCON&=0x7F;
RTCH=0x0f;
RTCL=0xff;
RTCCON|=0x43;
EWDRT=1;
PCONA|= 0x7f; // turn off all peripherals that can be turned off
P2=0xfe;
delay(100);
P2=0xff;
EA=1;
//enable all interrupt
PCONA|= 0x7f; //turn off all peripherals except RTC
PCON |= 0x23; // switch to total Power-down mode
_nop_();
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_nop_();
while(1) {
PCONA|= 0x7f;
PCON |= 0x23; // switch to total Power-down mode
_nop_();
_nop_();
}
}
3.5.3 Measurement results RTC running
Table 12 shows the results of the power consumption when the RTC is running.
Table 12:
Current consumption IDD Power-down RTC running on low speed crystal
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD = 3.6 V
Active DIVM = 00h
32.768 kHz
105.1 µA
118.2 µA
138.9 µA
Active DIVM = 01h
16.384 kHz
96.2 µA
105.2 µA
116.5 µA
Active DIVM = 02h
8.192 kHz
96.0 µA
104.6 µA
116.3 µA
Total Power-down
0.0
6.4 µA
10.2 µA
18.0 µA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C) with a limited sample. Brownout is disabled, RTC is
enabled and watchdog timer is turned off.
Active DIVM=00H
Idle DIVM=00H
Active DIVM=01H
Idle DIVM=0AH
Active DIVM=02H
Idle DIVM=64H
Total Pow er dow n
Idle DIVM=FFH
IDD RTC on 32kHz
IDD Idle 32kHz crystal
160
100.00
90.00
140
IDD
[µA]
IDD
[µA]
80.00
120
70.00
100
60.00
50.00
80
40.00
60
30.00
20.00
40
10.00
20
0.00
2
2.2
2.4
2.6
0
2
2.2
2.4
2.6
2.8
3
VDD [V]
2.8
3
VDD [V]
3.2
3.2
3.4
3.4
3.6
3.8
3.6
3.8
Fig 11. IDD RTC enabled using a 32 kHz crystal
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Table 13:
Current consumption IDD Power-down RTC running on low speed crystal
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD = 3.6 V
Active DIVM = 00h
7.3728 MHz 3.02 mA
4.13 mA
5.36 mA
Active DIVM = 0Ah
369 kHz
0.47 mA
0.58 mA
0.72 mA
Active DIVM = 64h
36.9 kHz
0.35 mA
0.41 mA
0.49 mA
Active DIVM = FFh
14.5 kHz
0.34 mA
0.40 mA
0.48 mA
Total Power-down
0.0
6.6 µA
10.8 µA
19.0 µA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C) with a limited sample. Brownout is disabled, RTC is
enabled and watchdog timer is turned off.
Active DIVM=00
IDD using IRC and RTC on 32kHz
Active DIVM=0A
Active DIVM=64
Active DIVM=FF
Total Pow er dow n
6
5
IDD [mA]
4
3
2
1
0
2
2.2
2.4
2.6
2.8
3
VDD [V]
3.2
3.4
3.6
3.8
Fig 12. IDD core using Internal RC oscillator RTC enabled using a 32 kHz crystal
4. Summary
In the summary all the power measurement numbers will be put together in tables for each
clock source. The power consumption for the different modes can be seen clearly for each
clocks source.
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4.1 32 kHz crystal
A 32 kHz crystal can be used to get very low power consumption with a very accurate
clock source. When an application does not need to execute code or at a slow speed, the
power consumption can be even further reduced with power savings modes.
4.1.1 Power consumption with a 32 kHz crystal
Table 14 shows the power consumption in different modes when using a 32 kHz crystal.
Table 14:
Current consumption IDD low frequency crystal
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD =
3.6 V
Active DIVM = 00h
32.768 kHz
73.9 µA
88.1 µA
115 µA
Active DIVM = 0Ah
1.6384 kHz
61.7 µA
67.2 µA
84.8 µA
Active DIVM = 64h
0.16384 kHz 60.3 µA
66.6 µA
83.6 µA
Active DIVM = FFh
0.06 kHz
59.1 µA
66.3 µA
83.1 µA
Idle DIVM = 00h
32.768 kHz
62.7 µA
72.5 µA
90.2 µA
Idle DIVM = 0Ah
1.6384 kHz
57.5 µA
64.8 µA
77.2 µA
Idle DIVM = 64h
0.16384 kHz 56.8 µA
64.1 µA
76.9 µA
Idle DIVM = FFh
0.06 kHz
55.8 µA
64.1 µA
76.2 µA
Power-down
0 Hz
51.9 µA
54.6 µA
58.1 µA
Power-down comp
0 Hz
66.5 µA
69.3 µA
73.2 µA
Total Power-down
0 Hz
1 µA
1 µA
1 µA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C).
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IDD InternalIDD
Watchdog
oscillator 400kHz
32 kHz crystal
450
140
Active
Active DIVM=00H
DIVM=00H
400
120
Active
Active DIVM=0AH
DIVM=0AH
350
Active
Active DIVM=FFH
DIVM=FFH
100
300
Idle
Idle DIVM=00H
DIVM=00H
Active
Active DIVM=64H
DIVM=64H
Idle
Idle DIVM=0AH
DIVM=0AH
Idle
Idle DIVM=64H
DIVM=64H
IDD [µA]
80
250
Idle
Idle DIVM=FFH
DIVM=FFH
Pow
Pow er
er dow
dow nn
200
60
Pow
Pow er
er dow
dow nn comp
comp
Total
Total Pow
Pow er
er dow
dow nn
150
40
100
20
50
00
22
2.5
3
VDD [V]
3.5
3.5
44
Fig 13. IDD with a 32 kHz crystal
4.1.2 Conclusion
The 32 kHz crystal uses very low power. When using DIVM it makes little difference if the
value is 0AH, 64H or FFH. In other words, a 25 times performance increase over
DIVM = FF with very similar power numbers.
In Power-down modes having the analog comparators active will have most current
consumption, while having the brownout active will be slightly less. For the most power
savings, go into total Power-down mode.
4.2 11.059 MHz crystal
A 11.059 MHz crystal can be used to get high performance with a very accurate clock
source. Table 15 shows the current consumption when using a 11.059 MHz crystal. When
the performance of the 11.059 MHz crystal is not needed different power savings modes
can be used.
4.2.1 Power consumption with a 11.059 MHz crystal
Table 15 shows the power consumption in different modes when using a 11.059 MHz
crystal.
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Table 15:
Current consumption IDD low frequency crystal
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD =
3.6 V
Active DIVM = 00h
11.059 MHz
4560 µA
6780 µA
8830 µA
Active DIVM = 0Ah
553 kHz
850 µA
1410 µA
1700 µA
Active DIVM = 64h
55.3 kHz
670 µA
1150 µA
1350 µA
Active DIVM = FFh
21.7 kHz
650 µA
1140 µA
1350 µA
Idle DIVM = 00h
11.059 MHz
2500 µA
3610 µA
4800 µA
Idle DIVM = 0Ah
553 kHz
710 µA
1090 µA
1450 µA
Idle DIVM = 64h
55.3 kHz
630 µA
930 µA
1280 µA
Idle DIVM = FFh
21.7 kHz
620 µA
920 µA
1270 µA
Power-down
0 Hz
51.9 µA
54.6 µA
58.1 µA
Power-down comp
0 Hz
66.5 µA
69.3 µA
73.2 µA
Total Power-down
0 Hz
1 µA
1 µA
1 µA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C).
IDD 11.059 MHz crystal
10000
Active
Active DIVM=00H
DIVM=00H
Active
Active DIVM=0AH
DIVM=0AH
9000
Active
Active DIVM=64H
DIVM=64H
8000
Active
Active DIVM=FFH
DIVM=FFH
Idle
Idle DIVM=00H
DIVM=00H
7000
Idle
Idle DIVM=0AH
DIVM=0AH
IDD [mA]
6000
Idle
Idle DIVM=64H
DIVM=64H
Idle
Idle DIVM=FFH
DIVM=FFH
5000
Pow
Power
er dow
downn
Pow
Power
er dow
downn comp
4000
Total
Total Pow
Power
er dow
downn
3000
2000
1000
0
2
2.5
3
VDD [V]
3.5
4
Fig 14. IDD with an 11.059 MHz crystal
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4.2.2 Conclusion
The 11.059 MHz crystal has the most performance. When using the DIVM the
performance and current consumption goes down. DIVM will be very useful in modes
where only low performance is needed. When you are in a routine where you need the
maximum performance put the DIVM back to 00h.
For the most power savings go into total Power-down mode. In Power-down mode having
the analog comparators active will have most current consumption, while having the
brownout active will be slightly less.
4.3 7.373 MHz internal RC oscillator
The internal RC oscillator can be used when both performance and system cost need to
be reduced be saving the cost of an external crystal. The ±1 % trimmed internal RC
oscillator is not as accurate as an external crystal, but can still be used for UART
communications. When the performance of the 7.373 MHz internal RC oscillator is not
used different power savings modes can be used.
4.3.1 Power consumption with the 7.373 MHz IRC
Table 16 shows the power consumption in different modes when using the 7.373 MHz
internal RC oscillator.
Table 16:
Current consumption IDD low frequency crystal
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD =
3.6 V
Active DIVM = 00h
7.3728 MHz
2970 µA
4000 µA
5300 µA
Active DIVM = 0Ah
369 kHz
430 µA
540 µA
680 µA
Active DIVM = 64h
36.9 kHz
310 µA
380 µA
480 µA
Active DIVM = FFh
14.5 kHz
290 µA
370 µA
440 µA
Idle DIVM = 00h
7.3728 MHz
1540 µA
2120 µA
2800 µA
Idle DIVM = 0Ah
369 kHz
350 µA
440 µA
540 µA
Idle DIVM = 64h
36.9 kHz
290 µA
360 µA
430 µA
Idle DIVM = FFh
14.5 kHz
290 µA
350 µA
430 µA
Power-down
0 Hz
51.9 µA
54.6 µA
58.1 µA
Power-down comp
0 Hz
66.5 µA
69.3 µA
73.2 µA
Total Power-down
0 Hz
1 µA
1 µA
1 µA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C).
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IDD Internal RC oscillator 7.373MHz
6000
Active
Active DIVM=00H
DIVM=00H
Active
Active DIVM=0AH
DIVM=0AH
Active
Active DIVM=64H
DIVM=64H
5000
Active
Active DIVM=FFH
DIVM=FFH
Idle
Idle DIVM=00H
DIVM=00H
4000
Idle
Idle DIVM=0AH
DIVM=0AH
IDD [mA]
Idle
Idle DIVM=64H
DIVM=64H
Idle
Idle DIVM=FFH
DIVM=FFH
3000
Pow
Power
er dow
downn
Pow
Power
er dow
downn comp
Total
Total Pow
Power
er dow
downn
2000
1000
0
2
2.5
3
VDD [V]
3.5
4
Fig 15. IDD with the 7.3.73 MHz internal RC oscillator
4.3.2 Conclusion
Running at full speed the Internal RC oscillator has high performance. To greatly reduce
the power consumption (when this performance is not needed) use DIVM.
In Power-down modes having the analog comparators active will have the most current
consumption, while having the brownout active will be slightly less. For the most power
savings go into total Power-down mode.
4.4 400 kHz internal watchdog oscillator
The 400 kHz internal watchdog oscillator is a very low power oscillator with a wide
tolerance of +20 % −30 %.
4.4.1 Power consumption with a 400 kHz WDT
Table 17 shows the power consumption in different modes when using the internal
400 kHz watchdog oscillator.
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Table 17:
Current consumption IDD low frequency crystal
Mode\DIVM
fCCLK
IDD at VDD = 2.4 V IDD at VDD = 3.0 V IDD at VDD =
3.6 V
Active DIVM = 00h
400 kHz
249.5 µA
333.5 µA
420 µA
Active DIVM = 0Ah
20 kHz
87.1 µA
110.5 µA
166.5 µA
Active DIVM = 64h
2 kHz
85.7 µA
104.9 µA
128 µA
Active DIVM = FFh
0.784 kHz
84.8 µA
103.6 µA
127.2 µA
Idle DIVM = 00h
400 kHz
159.8 µA
202.8 µA
256.8 µA
Idle DIVM = 0Ah
20 kHz
84.7 µA
99.6 µA
117.5 µA
Idle DIVM = 64h
2 kHz
81.1 µA
94.5 µA
110.9 µA
Idle DIVM = FFh
0.784 kHz
80.9 µA
94.2 µA
110.5 µA
Power-down
0 Hz
51.9 µA
54.6 µA
58.1 µA
Power-down comp
0 Hz
66.5 µA
69.3 µA
73.2 µA
Total Power-down
0 Hz
1 µA
1 µA
1 µA
Note: measurements were taken with all peripherals turned off (PCONA = FFh) and at
room temperature (Tamb = ~25 °C).
IDD Internal Watchdog oscillator 400kHz
450
Active
Active DIVM=00H
DIVM=00H
Active
Active DIVM=0AH
DIVM=0AH
400
Active
Active DIVM=64H
DIVM=64H
350
Active
Active DIVM=FFH
DIVM=FFH
Idle
Idle DIVM=00H
DIVM=00H
300
Idle
Idle DIVM=0AH
DIVM=0AH
Idle
Idle DIVM=64H
DIVM=64H
IDD [µA]
250
Idle
Idle DIVM=FFH
DIVM=FFH
Pow
Power
er dow
downn
200
Pow
Power
er dow
downn comp
Total
Total Pow
Power
er dow
downn
150
100
50
0
2
2.5
3
VDD [V]
3.5
4
Fig 16. IDD with a 400 kHz internal Watchdog oscillator
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4.4.2 Conclusion
The watchdog oscillator consumes very low power. When the DIVM is used it makes little
difference with the value is 0AH, 64H or FFH. In other words, a 25 times performance
increase over DIVM = FF with very similar power numbers.
In Power-down modes having the analog comparators active will have most current
consumption, while having the brownout active will be slightly less. For the most power
savings go into total Power-down mode.
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5. Disclaimers
Life support — These products are not designed for use in life support
appliances, devices, or systems where malfunction of these products can
reasonably be expected to result in personal injury. Philips Semiconductors
customers using or selling these products for use in such applications do so
at their own risk and agree to fully indemnify Philips Semiconductors for any
damages resulting from such application.
Right to make changes — Philips Semiconductors reserves the right to
make changes in the products - including circuits, standard cells, and/or
software - described or contained herein in order to improve design and/or
performance. When the product is in full production (status ‘Production’),
relevant changes will be communicated via a Customer Product/Process
Change Notification (CPCN). Philips Semiconductors assumes no
responsibility or liability for the use of any of these products, conveys no
licence or title under any patent, copyright, or mask work right to these
products, and makes no representations or warranties that these products are
free from patent, copyright, or mask work right infringement, unless otherwise
specified.
Application information — Applications that are described herein for any
of these products are for illustrative purposes only. Philips Semiconductors
make no representation or warranty that such applications will be suitable for
the specified use without further testing or modification.
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6. Contents
1
2
2.1
2.2
2.3
2.4
3
3.1
3.1.1
3.1.2
3.1.3
3.2
3.2.1
3.2.2
3.2.3
3.3
3.3.1
3.3.2
3.3.3
3.4
3.4.1
3.4.2
3.4.3
3.5
3.5.1
3.5.2
3.5.3
4
4.1
4.1.1
4.1.2
4.2
4.2.1
4.2.2
4.3
4.3.1
4.3.2
4.4
4.4.1
4.4.2
5
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Power management modes. . . . . . . . . . . . . . . . 3
Idle mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Power-down mode . . . . . . . . . . . . . . . . . . . . . . 3
Total power-down mode . . . . . . . . . . . . . . . . . . 4
Power management modes summary . . . . . . . 4
Measuring lowest power consumption modes 4
Current consumption in Idle mode . . . . . . . . . . 4
Measurement configuration . . . . . . . . . . . . . . . 4
Software example . . . . . . . . . . . . . . . . . . . . . . . 5
Measurement results in Idle mode . . . . . . . . . . 6
Current consumption in Power-down mode . . 10
Measurement configuration . . . . . . . . . . . . . . 10
Software example . . . . . . . . . . . . . . . . . . . . . . 10
Measurement results in Power-down mode . . 11
Current consumption in total Power-down
mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Measurement configuration . . . . . . . . . . . . . . 12
Software example . . . . . . . . . . . . . . . . . . . . . . 12
Measurement results in total Power-down
mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Current consumption in active mode using
DIVM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Measurement configuration . . . . . . . . . . . . . . 13
Software example . . . . . . . . . . . . . . . . . . . . . . 14
Measurement results in Active mode . . . . . . . 14
Current consumption in Power-down with
RTC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Measurement configuration . . . . . . . . . . . . . . 18
Software example . . . . . . . . . . . . . . . . . . . . . . 19
Measurement results RTC running. . . . . . . . . 20
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
32 kHz crystal . . . . . . . . . . . . . . . . . . . . . . . . . 22
Power consumption with a 32 kHz crystal . . . 22
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
11.059 MHz crystal. . . . . . . . . . . . . . . . . . . . . 23
Power consumption with a 11.059 MHz crystal 23
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
7.373 MHz internal RC oscillator . . . . . . . . . . 25
Power consumption with the 7.373 MHz IRC . 25
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
400 kHz internal watchdog oscillator . . . . . . . 26
Power consumption with a 400 kHz WDT. . . . 26
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Disclaimers. . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
© Koninklijke Philips Electronics N.V. 2004
All rights are reserved. Reproduction in whole or in part is prohibited without the prior
written consent of the copyright owner. The information presented in this document does
not form part of any quotation or contract, is believed to be accurate and reliable and may
be changed without notice. No liability will be accepted by the publisher for any
consequence of its use. Publication thereof does not convey nor imply any license under
patent- or other industrial or intellectual property rights.
Date of release: 29 March 2005
Published in The Netherlands