AN10218 Philips LPC900 microcontrollers single cell power

AN10218 Philips LPC900 microcontrollers single cell power
INTEGRATED CIRCUITS
ABSTRACT
This application note describes the power supply of a P89LPC900
microcontroller from a single cell for low power applications like hand
held devices.
AN10218
Philips LPC900 microcontrollers
single cell power supply
Torsten Eggers
2003 Apr 11
Philips Semiconductors
Application note
Philips LPC900 microcontrollers single cell power
supply
AN10218
INTRODUCTION
BAT
This application note describes the power supply of a P89LPC900
microcontroller from a single cell for low power applications like
hand held devices.
D1
U1A
BAT
1
The LPC900 are low power microcontrollers with a supply voltage
range from 2.4 V to 3.6 V. The supply current varies from below
1 µA in total power down mode, over some 10 µA with low speed
oscillator to several mA at high speed. The current that is sourced
from the I/O pins is additional and has to be taken into account. In
applications that are often in low power mode like hand held devices
the average current is very low and the battery life can reach several
month.
C2
VDD
3
2
D2
R1
C3
C1
GND
GND
This application note describes an easy, low cost solution of a
capacitive step up DC–DC converter to create the supply voltage
from a single cell with a voltage from 1.2 V to 1.5 V.
Figure 2. Voltage Doubler
A Philips quad 2–input NAND Schmitt–Trigger 74LV132 is used to
generate the supply voltage.
The square wave output is connected to a voltage doubler with D1,
D2, C2 and the output voltage at C3. The principle can be extended
to higher voltages.
The 74LV132 has a wide operation voltage range from 1.0 V to
5.5 V and is optimized for low voltage operations from 1.0 V to 3.6 V.
This range is ideally suited to operate from a single cell.
With an extra inverter it is also possible to build a Dickson charge
pump, e.g. as a voltage tripler (see figure 3).
One Schmitt–Trigger NAND gate is used to build a
multivibrator/oscillator with a resistor and a capacitor (see figure 2).
BAT
D1
U1A
BAT
1
C2
VDD
3
2
D2
R1
C3
C1
GND
GND
Figure 1. Single cell power supply
D1
DIODE
BAT
U2B
BAT
U2A
C2
V2
D2
DIODE
C3
DIODE
C4
V4
D4
Vcc
DIODE
C5
C6
GND
6
3
5
74LV132
74LV132
R1
C1
GND
Figure 3. Dickson Charge Pump
2003 Apr 11
D3
4
1
2
V3
2
Philips Semiconductors
Application note
Philips LPC900 microcontrollers single cell power
supply
drop at 10 mA is maximal 320 mV. The voltage tripler would
generate a VDD of about 3 V. It is also possible to use a voltage
quadrupler for a higher VDD, but then the microcontroller must be
protected against voltages above maximum rating.
The output voltage is approximately:
V DD + n
AN10218
(V Batt * V Diode)
For best efficiency it is recommended to use diodes with low voltage
drop like the Philips BAT54 schottky diodes. The specified voltage
Figure 4 shows a complete application with an LPC932 driving a
LED.
BAT
U1
8
9
3
26
25
24
23
22
20
19
P3.1/XTAL1
P3.0/XTAL2/CLKOUT
P0.0/CMP2/KBI0
P0.1/CIN2B/KBI1
P0.2/CIN2A/KBI2
P0.3/CIN1B/KBI3
P0.4/CIN1A/KBI4
P0.5/CMPREF/KBI5
P0.6/CMP1/KBI6
P0.7/T1/KBI7
21
7
VDD
GND
GND
U2D
12
11
D5
LED
13
74LV132
U2C
1
2
13
14
15
16
27
28
P2.0/ICB
P2.1/OCD
P2.2/MOSI
P2.3/MISO
P2.4/SS
P2.5/SPICLK
P2.6/OCA
P2.7/ICA
VDD
R2
1k
18
17
12
11
10
6
5
4
P1.0/TxD
P1.1/RxD
P1.2/T0/SCL
P1.3/INT0/SDA
P1.4/INT1
P1.5/RST
P1.6/OCB
P1.7/OCC
9
8
10
74LV132
GND
P89LPC932–28
BAT
BAT
On/Off
BAT
U2A
1
Clk
4
3
2
C1
D1
10mF
DIODE
C3
10mF
D3
D4
DIODE
DIODE
VDD
6
5
74LV132
C5
D2
DIODE
U2B
74LV132
C2
10mF
C4
10mF
D6
Protection
R1
C6
47pF
470pF
470k
GND
GND
GND
GND
Figure 4.
consumption and capability can be switched from below 20 µA to
several mA.
Example
This is an application example where the LPC900 switches to total
power down and can be woken up by an external interrupt. The
interrupt routine flashes an LED and puts the LPC900 back into total
power down.
For higher currents the capacity of C1 to C4 can be increased and
the oscillator frequency can be raised (even in the MHz range).
For better load regulation it is also possible to drive the voltage
multiplier with a frequency from the LPC932. A port pin connected to
pin 1 (On/Off) of the NAND gate can switch off the oscillator and a
PWM signal from the LPC932 (e.g. from a timer) connected to pin 4
(Clk) drives the multiplier.
The power consumption of the LPC932 in ‘total power down’ can be
below 1 µA, depending on configuration and supply voltage.
Special care must be taken to switch off all unnecessary functions,
e.g., watchdog oscillator or analogue functions.
The following code is a simple demonstration of the average low
power consumption. The watchdog oscillator is used and all
unnecessary peripherals are switched off.
With the configuration in figure 4 we reached total power
consumption below 20 µA for the whole circuit. To reach a high
dynamic between low power state and high current source capability
in active mode the LPC932 can switch the oscillator frequency on
demand. This is done with P0.7 and C5. In low power mode P0.7 is
driven low and C5 adds to the time constant and reduces the
oscillator frequency and therefore the current consumption. In active
state P0.7 is switched to input mode and the oscillator speeds up
and can source more current into the application. The current
2003 Apr 11
The software configures the LPC, initializes the keyboard interrupt,
flashes the LED at port 2 and enters total power down mode.
If P0.5 is pulled low the keyboard interrupt wakes up the LPC,
accelerates the RC–oscillator and the LED is flashed before the
LPC900 re–enters total power down mode.
3
Philips Semiconductors
Application note
Philips LPC900 microcontrollers single cell power
supply
/*===========================================*/
/*
;
SOURCE_FILE:
main.c
;
APPLICATION:
P89LPC932
;
Single Cell Demo
;
ORIGINAL AUTHOR: Torsten Eggers
;
PS BLM–Hamburg
;
VERSION:
1.0
;
DATE:
2003/03/01
;
;
(C) 2003: Philips
/*===========================================*/
AN10218
void main(void)
{
// configure Ports
P0M1 = 0x20;
P0M2 = 0xDF;
P1M1 = 0x03;//P1.3 Input
P1M2 = 0xFC;
P2M1 = 0x00;
P2M2 = 0xFF;
P2M1 = 0x00;
P2M2 = 0xFF;
P3M1 = 0x00;
P3M2 = 0xFF;
#include <Reg932.h>
unsigned int
unsigned char
P0=0xFC;
P1=0xFC;
P2=0xFF;
P3=0xFF;
i,loop;
off;
void keypad_init(void)
{
// P0.5 must be pulled high
KBPATN = 0x20;
// P0 must match KBPATN to generate interrupt
KBCON = 0x02;
// mask out all pins except P0.5
KBMASK = 0x20;
// enable keypad interrupt
EKBI = 1;
// enable interrupts
EA = 1;
}
// flash P2
for(loop=0;loop<4;loop++)
{
P2 = 0xFF; // turn off P2 (LED)
for(i=0;i<10000;i++){}
P2 = 0x00; // turn on P2 (LED)
for(i=0;i<100;i++){}
}
// turn off P2 (LED
P2 = 0xFF
IEN1 = 0xE8;
EKBI = IEN1^1;
void keypad_isr(void) interrupt 7 using 1
{
P1M2 = 0xFC;//fast Oscillator
//turn on peripherals
PCONA = 0x00;
keypad_init();
AUXR1 = AUXR1|0x80; //Set CLKLP Low Power Clk
WDCON = WDCON&0xFE; //WDOsci off
// flash P2
for(loop=0;loop<5;loop++)
{
P2 = 0xFF; //turn off P2 (LED)
for(i=0;i<10000;i++){}
P2 = 0x00; //turn on P2 (LED)
for(i=0;i<1000;i++){}
}
//turn off peripherals that can be turned off
PCONA = 0xEF;
P1M2 = 0xFF;//slow Oscillator
//switch to idle mode
//PCON |= 0x03;// total power down
while(1)
{
if (off) //power down flag
{
off = 0;
//turn off peripherals that can be turned off
PCONA = 0xEF;
// switch to total power down
P1M2 = 0xFF;//slow Oscillator
PCON |= 0x03;// total power down
};
}
// turn off P2 (LED)
P2 = 0xFF;
//clear KBIF by writing 0 to it
KBCON &= 0xFE;
off = 1; //power down flag
}
}
2003 Apr 11
4
Philips Semiconductors
Application note
Philips LPC900 microcontrollers single cell power
supply
AN10218
Definitions
Short-form specification — The data in a short-form specification is extracted from a full data sheet with the same type number and title. For detailed information see
the relevant data sheet or data handbook.
Limiting values definition — Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 60134). Stress above one or more of the limiting
values may cause permanent damage to the device. These are stress ratings only and operation of the device at these or at any other conditions above those given
in the Characteristics sections of the specification is not implied. Exposure to limiting values for extended periods may affect device reliability.
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.
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 license 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.
 Koninklijke Philips Electronics N.V. 2003
All rights reserved. Printed in U.S.A.
Contact information
For additional information please visit
http://www.semiconductors.philips.com.
Fax: +31 40 27 24825
Date of release: 04-03
For sales offices addresses send e-mail to:
sales.addresses@www.semiconductors.philips.com.
Document order number:
2003 Apr 11
5
9397 750 11377
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