Nowadays, charger of people hope batteries can support a variety of chemical composition easily and accept numerous voltage to input, include extensive solar battery board. Input voltage limits enclothes output batteries voltage above and the following circumstance are commonner and commonner, need its to hold a step-down and step up ability concurrently consequently (step-down – step up develop attacks) . LTC4020 step-down – source control of step up report implement with much more chemical composition batteries charges controller can accept 4.5V to be inputted to the wide range of 55V, produce the output tension that is as high as 55V. Its step-down – controller of step up DC/DC can offer prep above to batteries and system, under or the voltage that is equal to input of parts of an apparatus.

 

Charger can be aimed at a variety of batteries chemistry composition easily to undertake optimizing. For example: Its can abide by a kind constant electric current / constant voltage (CV/CC) charges algorithmic, use C/10 or time stop (in the light of the batteries system) that is based on nickel; One kind is used time those who stop is constant electric current (CC) is characteristic; Or acerbity batteries of lead of a kind of optimized 4 paces, 3 class charges mode.

 

Use at the 6.3A charger of voltage of 25.2V batteries float

 

Graph 1 show gave a 15V to come step-down of 55V input, 25.2V/6.3A – charger of step up batteries, its have efficient four switch (M2~M5) synchronism step-down – converter of step up DC/DC, need an inductor only (L1) . Framework of mode of average electric current uses proprietary two detect resistor (RCBRT1 and RCBRB1) will monitor inductor electric current. In this step-down – in step up solution, when VOUT of VIN prep above, converter works in step-down mode; When VIN under VOUT when, converter works in step up mode. When VIN is close to VOUT, converter job closes step-down at quarto – step up mode.

 

Image Removed. Graph 1: 15V comes step-down of 55V input, 25.2V/6.3A – charger of step up batteries

 

Graph 2: Be aimed at a graph the relation curve of the efficiency of 1 converter and load current IOUT (VOUT = 25.2V)

 

Converter with a programmable constant switch frequency is run, this frequency is in 50kHz inside the limits to 500kHz, use a resistor to come set (R13 = 100k, 250kHz) . Graph 1 show this solution that go out to be able to be offerred for systematic load be as high as 8A (VOUT= 25.2V) . If the graph is shown 2 times, full laden efficiency (IOUT = 8A, VIN = 24V) can amount to 98% above.

 

LTC4020 uses to bring the voltage divider of exterior feedback resistor with derivative foot to bring a foot in order to pass VFB to install batteries voltage from BAT. PowerPath™(Power source access) FET (M1) is in on-state during regular batteries charges, the meeting below probable condition is in batteries and step-down – a kind of low impedance is formed to join between output of step up converter. Batteries charging current detects through resistor (RCBAT1) will monitor. Charging current of the biggest average batteries can pass the block value that chooses RCBAT1 easily to install. Dynamic electric current is restricted to be worth adjust can bring crural implementation through RNG/SS.

 

Use PowerPath FET to come true to put through immediately with ideal diode function

 

Put electric batteries badly to, LTC4020 can pursue PowerPath FET (automatically 1 medium M1) configuration is a linear manostat, allow step-down thereby – output of step up converter rises to voltage of prep above batteries, still offer charging current to batteries at the same time. This function is called PowerPath puts through immediately, right now PowerPath FET acts as current source of a tall impedance, be in charge of offerring charging current for batteries.

 

Do not be in when batteries charger charge when cycle (it is step-down namely – step up converter runs) for systematic load only, LTC4020 is PowerPath FET configuration automatically an ideal diode. This allows batteries to maintain with converter output during normal operation receive. However, if systematic load current exceeded step-down – the power supply ability of step up converter, can pass this ideal diode effectively from the power with draw-out and additional batteries.

 

Other characteristic

LTC4020 supports those who be based on timer to charge algorithmic, a join brings the capacitor between foot and ground to be in charge of a setting charging in TIMER periodic be over.

 

LTC4020 has batteries to temperature monitors and control a function. Pass a negative temperature coefficient of a NTC () thermal resistor join cites a base to NTC, set cloth of this thermal resistor in batteries group (or the surveillant position of other need) around, if NTC brings crural voltage to exceed range (prep above 1.35V or under 0.3V) , criterion LTC4020 will spark breakdown of a NTC stops batteries to charge.

 

LTC4020 has two collector open a way to output (STAT1 and STAT2) , condition of charger of report of in order to and breakdown state, these two brought a foot to undertake the binary system codes.

 

Conclusion

LTC4020 is a current tall tension, efficient step-down – source control of step up report implement comprise batteries charger with much chemistry, prep above of supportive input voltage, under or be equal to output to batteries or systematic power supply. Its are compressed (only function of tall 0.75mm) heat-resisting increases model the 38 5mm X 7mm QFN that cite a base are enclosed agree with equipment of communication of power supply of portable industry and medical treatment equipment, solar energy system, for military use, and 12V comes 24V is embedded car system.

(origin: Yadenuo semiconductor)