Abstract: DS2762 is the intelligent high accuracy lithium battery monitor chip which MAXIM Corporation promotes. This chip collection data acquisition, information storage and safekeeping of security in a body, and the function is formidable, the structure is simple. The article introduced the DS2762 characteristic, has given DS2762 and monolithic integrated circuit’s hardware junction circuit and the application software flow.
Key word: DS2762; Lithium battery monitor; Monolithic integrated circuit
1 main feature
In order to satisfy the current mobility and the portability request, designs when the portable product usually uses the battery power supply. But uses time the battery power supply, battery’s current condition often is one of user issues of concern, the current intelligent telephone, the digital camera and so on need the real time display battery’s current condition. Through MAXIM Corporation’s DS2762 then real-time monitor parameters and so on battery’s voltage, electric current, charging and discharging condition and dump energy, and may these information storage, provide to the monolithic integrated circuit do corresponding processing.
The DS2762 chip is the new generation intelligence lithium battery monitor chip which MAXIM Corporation promotes, this chip collection data acquisition, information storage, safekeeping of security in a body, moreover the function is formidable, the hardware wiring is simple. Its principal characteristic is as follows:
* only uses a bidirectional data line then to realize with monolithic integrated circuit’s communication.
* the content temperature sensor, may exempt in the battery block installs the thermistor.
* the internal modulus switch may carry on the battery voltage monitor, used in determining the battery charge and the electric discharge conclusion.
* total quantity which through the internal electric current accumulator may the real-time recording current inflow, flow out.
in * has two kind of electroresponse pattern 熞 emperor to look at 25mΩ the resistance induction way; second, may resistance induction way which the user chooses by the piece outside.
* has two kind of power source patterns: Namely working and sleep way. In the normal work pattern, DS2762 may real-time parameters and so on monitor electric current, voltage, temperature and dump energy, but in the sleep pattern, DS2762 will stop to these parameter monitor.
2 pin functions
DS2762 pin arrangement as shown in Figure 1, various pins’ function is as follows:
CC: Charge protection control foot;
PLS: User terminal voltage positive electrode;
DC: Electric discharge protection control foot;
SNS: Induction resistance coupling end;
DQ: Data feeds, output port;
IS1, IS2: Induces the input end;
PS: Power source pattern choice end;
VSS: Earth;
PIO: Programmable I/O end: May according to need to control the user definition the peripheral circuit;
VDD: Battery positive electrode input
Vin: Induced tension input.
3 DS2762 memory structures
DS2762 contains EEPROM, to be possible to lock saves EEPROM, SRAM and other function register, Table 1 is the DS2762 internal memory structure. And the EEPROM right and wrong volatility memory, has the power failure protection function, may use in storing up battery’s important information; Is when the lock saves the condition, also available may lock saves EEPROM to store up other fixed information; SRAM uses in storing up some unimportant temporary data generally. Gathers the data saves RAM first, then enters EEPROM; In fact, in the EEPROM information may also duplicate RAM, this both are the mirror image relations.
Table 1 DS2762 internal memory structure table
| Address | In Accommodation | Read-write condition |
| 00H | Protection register | But read-write |
| 01H | Condition register | Read-only |
| 02H-06H | Retention | |
| 07H | EEPROM register | But read-write |
| 08H | Special register | But read-write |
| 09H-0BH | Retention | |
| 0CH | Voltage register’s highest significant digit | Read-only |
| 0DH | Voltage register’s least significant bit | Read-only |
| 0EH | Electric current register’s highest significant digit | Read-only |
| 0FH | Electric current register’s least significant bit | Read-only |
| 10H | Electric current accumulator register’s highest significant digit | But read-write |
| 11H | Electric current accumulator register’s least significant bit | But read-write |
| 12-17H | Retention | |
| 18H | Temperature register’s highest significant digit | Read-only |
| 19H | Temperature register’s least significant bit | Read-only |
| 1AH-1FH | Retention | |
| 20H-2FH | EEPROM, block 0 | The lock saves when read-only, has not locked saves when may the read-write |
| 30H-3FH | EEPROM, block 1 | The lock saves when read-only, has not locked saves when may the read-write |
| 40H-4FH | Retention | |
| 80H-8FH | SRAM | But read-write |
| 90H-FFH | Retention |
The DS2762 operational order has two kinds: One kind is the address order, including reads the address, the address match, the jump, SWAP and so on. Another kind is the function order, including reads the data, to write the data, the duplication data, to cancel the data and the lock saves and so on.
4 applications
As core design intelligent lithium battery observation system’s hardware architecture as shown in Figure 2 take DS2762. This system selects the internal resistance induction method.
This battery observation system by the DS2762 lithium battery monitor chip, 51 monolithic integrated circuits and the liquid crystal display module is composed. DS2762 mainly completes to the battery current condition monitor, including current battery sufficient, parameter and so on discharge condition, voltage, electric current, temperature and dump energy monitors, simultaneously it can also gather these data automatically, and places it in the memory. The field effect managed FET1, FET2 and so on to constitute DS2762 sufficiently, the electric discharge protection return route, might use in realizing functions and so on pressure, undervoltage, charge overflow as well as short circuit protection.
May defer to the user need through 8051 monolithic integrated circuits to carry on the read and processing to battery’s corresponding parameter, then escorts to the liquid crystal display module to carry on the demonstration. Because deposits these parameters EEPROM to have the non-volatility, therefore this system simultaneously has the power failure protection function. Figure 2 in electric circuit’s monolithic integrated circuit is overall system’s control processing station, because the massive work may complete by the monolithic integrated circuit, thus reduced this system’s hardware order of complexity obviously.
The liquid crystal display module may use for to demonstrate the user need understanding the battery current status messages, so that the user can may act according to these information to make corresponding processing. In fact, this liquid crystal display module only accepts monolithic integrated circuit’s control and the visit.
Because DS2762 and the monolithic integrated circuit carry on time the data communication only uses a data line, therefore, must request the write program strictly according to the chip read-write succession, like this can guarantee the data the correct read-write. The following introduction comes using the DS2762 chip to parameters and so on battery’s working and voltage, electric current, temperature, dump energy carries on the monitor to realize the method specifically.
(1) battery working monitor
Must determine that the battery is in what working in the use, may use in DS2762 the electric current register’s value to carry on the judgment. Monolithic integrated circuit each 88ms monitors one time the voltage, and (Vis=Vis1-Vis2) transforms IS1 and the IS2 both sides’ differential pressure the electric current to store the electric current register. If Vis is just, explained that the battery is charging; If Vis is a negative value, explained that the battery is discharging, is also the instrument is supplying power by the lithium battery. Its software flow chart see Figure 3 to show.
(2) battery voltage and temperature survey
Because the DS2762 chip interior integration has a/D switch and the digit temperature sensor, therefore, must obtain parameters and so on battery’s voltage, temperature, only need send out the gathering voltage, the temperature control command through the monolithic integrated circuit to DS2762, after and treats its sampling finished, automatically the register which the voltage, the temperature observed value stored corresponds, finally read register’s content again by the monolithic integrated circuit then.
(3) dump energy monitor
Battery’s dump energy is one which of important information the user needs, it may use in the electric current accumulator register’s value to obtain. The electric current accumulator register’s value is after the DS2762 real-time automatic sizing battery circuit obtains, thus does not need to carry on the control. Usually when the battery charges, this value increases, when battery discharge, this value reduces. Thus, reads this value through the monolithic integrated circuit then to obtain the dump energy. The dump energy monitor’s flow chart see Figure 4 to show.
When the monolithic integrated circuit carries on to DS2762 saves the command operation willfully, before each order sends out, must defer to DS2762 the replacement succession request to send out the reset signal first, and waited for that DS2762 the reply (shows DS2762 to prepare to accept or transmission data), then issues a ROM order to use in DS2762 which again chooses on the main line to visit. In this article program flow diagram, this process in the procedure has contained in “the DS2762 initialization”.
In ordinary circumstances, when read electric current accumulator register’s value, is prevents the read mistake, must inspect DS2762 first whether to be revising register’s content. This point may through judge EEPROM register’s EEC position to realize.
5 concluding remark
This article introduces based on the DS2762 chip intelligent lithium battery observation system is a portable instrument’s part. This system function is formidable, the ease of operation, can with other system joint operation. Along with each kind of portable electronic products’ widespread application, the battery real-time monitor has become the system design one kind of essential function, therefore, this article introduced the system has the strong usability.
