According to the energy requirements of the final application, a battery may contain up to 4 lithium ion or lithium polymer battery core, its configuration will have a variety of change, at the same time with a mainstream power adapter: direct adapter, USB interface or car charger. Remove the core quantity, core configuration or power adapter type difference, the battery has the same charge characteristics. So they charge algorithm. Lithium ion and li-ion polymer battery best charging algorithm can divided into three phases: trickle charge, rapid charging and stable charge.
Remove some very low-end equipment, now on the market/li-ion polymer lithium ion battery solutions are integrated with the outer components or, in accordance with the characteristics of the charging to charge, this is not just to get better effect charge, but also for safety.
LTC4097 can be used to exchange adapter or USB power supply for single quarter/polymer lithium ion battery. Figure 1 for double input 1.2 A lithium battery charger LTC4097 schemes. It USES constant current/constant voltage algorithm charging, from exchange adapter power charge, programmable filling up to 1.2 electric current A, and with USB power can be as high as 1 A, at the same time, automatic detection in each input voltage whether there. This device also provide USB the current limit. Applications include PDA, MP3 players, digital camera, light portable medical and test equipment and big color cellular phone. The performance characteristics: no external micro controller charging termination; The input power automatic detection and choice; Through the resistance from the exchange of charging adapter input can be as high as 1.2 A programming charge current; The resistance of programmable USB charging current is up to 1 A; 100% or 20% USB charging current set; The input power output and existing bias NTC (VNTC) pin as a 120 mA drive ability; NTC thermistors input (NTC) pin for temperature qualified charged; Pre-settings battery voltage with floating plus or minus 0.6% accuracy; Thermal regulation maximize charge rate and free hot air LTC4097 can be used to exchange adapter or USB power supply for single quarter/polymer lithium ion battery. The use of constant current/constant voltage algorithm charging, from exchange adapter power charge, programmable filling up to 1.2 electric current A, and with USB power can be as high as 1 A, at the same time, automatic detection in each input voltage whether there. This device also provide USB the current limit. Applications include PDA, MP3 players, digital camera, light portable medical and test equipment and big color cellular phone.
Lithium ion/polymer battery charge scheme for different number of core, core configuration, and power types are different. At present mainly have three main charging scheme: linear, Buck (step-down) switch and SEPIC (booster and step-down) switch.
When the input voltage in big with the charger with sufficient clearance of core after opening voltage, it is linear scheme, especially 1.0 C fast charging current than 1 A big too much. For example, MP3 players usually only one core, capacity from 700 to 1500 mAh differ, full charge voltage is open 4.2 V. MP3 player power is usually the AC/DC adapter or USB interface, the output is the rule of 5 V; At this time, the linear scheme is the most simple, most charger of the efficiency of the scheme. Figure 2 shows for lithium ion/polymer battery solution linear scheme, basic structure and linear voltage neat device.
MAX8677A is double input USB/AC adapter linear charger, built-in Smart Power Selector, used for rechargeable single quarter by Li + batteries portable devices. The charger integration of the battery and the external power source and load switch charging all the power switch, so that no external MOSFET. MAX8677A ideal used in portable devices, such as smart phones, PDA, portable media players, GPS navigation equipment, digital camera, and digital cameras.
MAX8677A can work in independent USB and the power input AC adapter or two input either one of the input. When connecting external power supply, intelligent power source selector allows the system not connect battery or can and depth discharge battery connection. Intelligent power source selector will automatically switch to the battery system load, use the system did not use the input power supply parts for battery, make full use of limited USB and adapter power supply input. All the needed electric current detection circuit, including the integration of the power switch, all integration in the piece. DC input current highest limit can be adjusted to 2 A and DC and USB input all can support 100 mA, 500 mA, and USB hung mode. Charge current can be adjusted to as high as 1.5 A, thus support wide range of battery capacitive. Other features include MAX8677A thermal regulation, over-voltage protection, charging status and fault output, power supply good surveillance, battery thermistors surveillance, and charging timer. MAX8677A using save a space, hot enhanced, 4 mm x 4 mm, 24 of the pins TQFN encapsulation, regulations, work in exceptional temperature range (40 ~ + 85 ℃).
When A 1.0 C of the charging current more than 1 A, or the input voltage of the core than with high voltage open many, Buck or step-down plan is A better choice. For example, based on the hard drive in the PMP, often use single core lithium ion battery, the full of open is 4.2 V voltage, capacity from 1200 to 2400 mAh range. And now PMP is usually use the car kit to charge, its output voltage in a 9 V to 16 between V. In the input voltage and battery voltage is the voltage difference between high (minimum 4.8 V) will make linear scheme lowers efficiency. This kind of low efficiency, plus more than 1.2 A 1 C fast charging electric current, have serious heat dissipation problems. To avoid this kind of situation, will the Buck scheme. Figure 3 for lithium ion/polymer battery charger scheme Buck diagram, basic structure with Buck (step-down) switching voltage regulators completely the same.
In some use of three or four lithium ion/polymer core series equipments, charger of the input voltage is not always greater than the battery voltage. For example, laptop computers use 3 core lithium ion battery, full charge voltage is open 12.6 V (4.2 V x3), capacity is 1800 mAh to 3600 mAh from. Power supply input or output voltage is 1 6 V AC/DC adapter, or is car kit, the output voltage in a 9 V to 16 between V. Apparently, the linear and Buck solutions are not for this group of batteries. This is about to use SEPIC scheme, it can in the output voltage is higher than when the battery voltage, can be in the output voltage less than when the battery.
Many portable products use voltage measurements to estimate the remaining battery power, but the battery voltage and surplus power relationship but will with the discharge rate, temperature and battery aging degree of change, make this kind of method can top 50% margin of error. The market for longer to use product demand unceasingly strengthens, so the system design personnel need more accurate solution. Use capacity check plan come to measure battery or consumption of electricity, will be in a wide range of application power to provide more accurate estimate of the battery power.
The battery circuit description. Figure 4 (a) can be used for identification of IC functions with typical application circuit batteries. According to the use of IC testing program is different, the battery needs to have at least three to four outside the terminal.
VCC and BAT pins will even to the battery voltage, so that for, C power and the battery voltage measurement. The battery is connected a grounding resistance smaller detection resistors, let capacity check meter high impedance SRP and SRN input can monitor sensor resistance on both ends of the voltage. Through testing the current flows through a resistor can be used to judge the battery or release the amount of electricity. Designers choose detection resistance value must be considered when resistance on both ends of the voltage can't more than 100 mV, low resistance may be more hours in current errors. Circuit board layout must ensure that SRP and SRN to testing from as close as possible to the connection of the resistor sensor resistance end; In other words, they should be the Kelvin attachment.
HDQ pin need external and resistors, this resistance should be located the host or the main application, such capacity check plan to the battery and portable devices when sleep function enable connection broken. Advice and resistance choose 10 k Ω.
Once the battery through the appraisal, bq26150 will issue commands to ensure that the host and quantity test plan of material lines between normal communication. When the battery connection interruption or to connect, the whole the identification process will be repeated again.
Host to be able to read capacity check plan of variable voltage measurement battery, to make sure the end of discharging threshold and charging terminate threshold. As for the remaining state power (RemainingStateofCapacity), do not need to read can use directly.
The above bq2650x and bq27x00 etc capacity check plan provides the battery manufacturer a simple to use options, this scheme L [just measuring battery voltage to be precise, so these capacity check plan can be applied to various battery framework, and can support the battery identification and double the battery application '
Today's many manufacturers can provide a variety of voltmeter IC,, the user can choose the suitable function device, to optimize the product price. Use voltmeter measurement of storage battery parameters, the separate architecture allows users in the host custom power measurement algorithm within. Eliminating embedded processor battery cost. On this to Dallase semicconductor company called cases of DS2762 chip for typical analysis. A new separate voltmeter IC, its structure see chart 5 (a) below.
DS2762 is a single quarter of lithium battery voltmeter and protection circuit, integrated into a tiny 2.46 mm x 2.74 mm inversion of packaging. Due to internal integration for power detection of high precise resistance, this device is very save a space. It is the small size and incomparable high level of integration, for mobile phone battery and other similar handheld products, such as PDA, etc, are all very ideal. Integrated protection circuit continuously monitoring the battery voltage, over voltage and flow fault (charging or discharge period). Different from the independent protection IC, DS2762 allow main processor surveillance/control protection FET conduction state, such, can DS2762 through the protection of the power system and the control circuit implementation. DS2762 can also charge a battery consumption has depth, when the battery voltage within three V, provide a limit of the charging current recovery path.
DS2762 accurate monitoring battery current, voltage and temperature, the dynamic range and resolution of common satisfy any mobile communication product testing standards. The measurement of current for internally generated when the integral, realize the power measurement. Through the real-time, continuous automatic disorders correct, the precision of power measurement can be increased. The built-in measuring resistance due to eliminate manufacturing process and temperature and cause resistance change, further improve the precision of the voltmeter. Important data stored in 32 bytes, can add the lock EEPROM; 16 bytes of SRAM are used to keep dynamic data. And DS2762 all communication all through the 1-Wire, more communication interface node, minimize the battery and the connection to the host. Its main features for; Single quarter of lithium battery protector; High precision current (power measurement), voltage and temperature measurement; Optional integrated 25 m Ω measuring resistance, each DS2762 after fine-tuning alone; 0 V battery restore charge; 32 bytes can lock EEPROM, 16 bytes SRAM, 64 a ROM;
1-Wire, node, digital communication interface; Support more battery power management, and through the protection system control FET power; Dormancy mode power supply current only 2 µ A (most); Work mode power supply current for 90 µ A (most); 2.46 mm x 2.74 mm inversion of packaging or 16 feet SSOP package led, and both are can choose with or without detection resistance; After has with e