ST AN676 Application note
AN676
APPLICATION NOTE
Battery charger using the ST6-REALIZER ®
INTRODUCTION
Because competition becomes greater and greater it is important to reduce time to market. The ST6 Realizer helps to fullfill this duty. The time needed to realize a design is dramatically reduced. Design of an application takes a few days instead of a few weeks.
Users who develop ST6 applications are systems electronics engineers; Often they do not know the assembler well and there are reluctant to use it. The ST6 Realizer allows users to design their applications using symbols known by hardware designers such as comparators, counters, multiplexers. Once the design is over, the ST6 Realizer generates assembly code or executable code for the different ST6 target hardware.
June 2008 |
Rev 2 |
1/14 |
BATTERY CHARGER USING THE ST6-REALIZER
APPLICATION NOTE GOAL
This note aims at introducing the different features of the ST6 Realizer graphic tool. It is also a tutorial to firstly help you get started with ST6 Realizer design, then for you to implement advanced features to optimize your design or to evaluate the target hardware requirements.
The application note describes a battery charger because it illustrates the different features of the ST6 Realizer throughout it. The charger implements a simple charging method. Nevertheless charging end points using the negative voltage slope detection method or voltage inflection points can be implemented with this battery charger ST6 board.
HARDWARE SCHEMATICS
The schematics describes the different hardware parts of the application:
The microcontroller connections
The power supply
The charging indicators
The start push button
The power command
2/14
BATTERY CHARGER USING THE ST6-REALIZER
Figure 1 : Simple Battery Charger Circuit Schematic
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CURRENT |
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VOLTAGE |
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470 |
R8 LOW |
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HIGH |
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SUPPLY POWER |
GND |
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JACK J1 |
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ohms 68 |
R2 |
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T1 |
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470 |
T3 R10 |
VCC |
GND |
22MF |
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C1 |
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5Ah.0 - 2V.1 / type AA cell: Battery |
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GND |
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U1 |
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ohms 10 |
R4 |
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BATTERY |
BT1 |
BATTERY NiCd |
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ohms 2 |
R6 |
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45V-PNP-BD236 |
GND |
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7805 |
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IMAX |
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VCC |
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GND |
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ADJUST |
CURRENT MAX |
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XT1 P-XT-8MHZ |
10pF |
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READY |
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LO LED |
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HI LED |
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RV50K- |
RV1 |
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C3 10pF |
GND |
GND |
C2 |
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CURRENT CHARGE |
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ST6210 1MF |
C4 |
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5MM-RED-LED |
R7 LD3 |
5MM-RED-LED |
R2 LD2 |
5MM-RED-LED |
R1 LD1 |
INDICATOR |
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GND |
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VCC |
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GND |
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MCU ST6210/20 |
IMAX |
VOLTAGE |
CURRENT |
GND |
100K |
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VCC |
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470 |
470 |
470 |
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10 |
5 6 7 8 9 |
1 2 3 4 |
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GND |
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PUSH START |
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SW1 |
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PB0 TEST PB1 RESET/ PB2 PB7 PB3 PB6 PB4 PB5 |
PA0 TIMER PA1 OSCIN PA2 OSCOUT PA3 NMI |
VSS VDD |
U2 |
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BUTTON- |
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START |
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LOW 11 |
HIGH 12 |
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DISCHRG 16 START 15 14 |
20 READY 19 HI LED 18 LO LED 17 |
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Note that in the circuit diagram the Microcontroller is shown as a simple box. The objective of the ST6 Realizer is to enable you to write the program code for the microcontroller with the same ease and in the same manner as you have drawn the hardware schematic.
3/14
BATTERY CHARGER USING THE ST6-REALIZER
Figure 2 : Functional Diagram
Start
READY
Imax
HIGH
Icharge
MCU
LOW
Vcharge
HIGH CHARGE
LOW CHARGE
The MCU manages all the functions of the application:
At reset the READY LED blinks to indicate that the charger is ready to charge. The user pushes the START button to begin the HIGH charge.
The READY LED switches off. The HIGH LED highlights.
The LOW charge takes place when the VOLTAGE threshold of 1.5 V is reached. The HIGH LED switches off. The LOW LED switches on.
The battery charge is over when the delay of LOW charge is reached. The LOW LED switches off. The READY LED blinks.
When the current in the battery is too high, HIGH charge or LOW charge are bypassed.
4/14
BATTERY CHARGER USING THE ST6-REALIZER
Figure 3 : Flow Chart
Start |
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HIGH charge |
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Voltage > 1,5V |
No |
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No |
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Current Too High |
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Yes |
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Yes |
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LOW charge |
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Charging time |
No |
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expired |
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No |
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Current Too High |
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Yes |
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5/14
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