kxenos Posted July 2, 2011 Report Share Posted July 2, 2011 Hello, I wanted to put this project into Projects area but couldn't find the link so here it is.This schematic is part of a bigger project that was never completed. That means it's not complete, meaning that even though I believe that it will work ok, it has not been constructed. The firmware is not done also.Think of it more as a base or a starting point, if you want to start a project like this.The main functional requirements were1. A regulated 3.3V @ 800mA power supply2. Embedded 2 cell Li-ion battery pack 8.2V or 8.4V3. Device should be usable even when battery is charging4. User should have detailed information about battery status5. Visual indication of status (On wall adapter/charging/charged/fault)7. SPI interface w/ firmware update capabilityDescriptionThis circuit uses the MAX17015 Li-ion multicell battery charger. It charges a battery pack while providing current to the load. When it detects an external power source it switches the load to this source bu means of Q1 and N1 FETs.The output goes to 2 regulators. The MAX8718 acts as an always-on source for the internal circuits. You can shut it down if you want but I chose not to, because the stand-by current of the circuit is minimum. But if you let it running, finally it will drain the battery because it will switch off when the battery voltage will be less than 4V which is too late. If you don't want this, you can place a switch circuit to the /SHDN pin.The MAX1791 is a 3.3V/5V regulator and is controlled by the uC.The uC controlls the charge current by using PWM on pin PB1 or lets the default setting if PB1 is set as input. The default setting is controlled by R9. IINP is an analog voltage depending on the current drawn by the circuit so that the uC can calculate the power consumption. I'm really bored right now, so if you want to see what the other pins do, please read the datasheet of the 17015.The uC also controls 4 LEDs that indicate the power status of the device. The ISP pins are connected to the system header that goes to the system. That's why it's called a system header.Finally, the MAX17041 is a really cool fuel gauge. It communicates with the uC using I2C and can give detailed data about the battery status, aging etc.If you finally decide that you want to build this device, download the evaluation kit manuals for the maxim ICs because they provide schematics and other information about routing etc that will be very helpful.Bill of MaterialsC1 1uF 25VC2 4,7uF 25VC3 0.1uFC4 0.68uFC5 4.7uF 25VC6 4.7uF 25VC7 1uFC8 0.01uFC9 10uF 25VC10 1uFC11 0.1uFC12 10uFC13 1000pFC14 10nFC15 1000pFC16 1uFC17 10uF C18 10uF C19 1uF C20 0,1uF C21 220uF 10V C22 100nF C23 10uF D1 BAT54WS D2 BAT54WS D3 AC_OK LED WHITED4 CH LED ORANGED5 FAULT LED REDD6 CH_OK LED REDD9 ON LED GREENJ2 Power adapter mini jack J3 Battery connector 2 pinJ4 System connector 10 pinL1 2uH L2 7uH N1 IRF9410PBF N2 2N7002K N3 FDS8884 N4 FDS6690AS N5 FDS8958A P1 FDS8958A Q1-A IRF7319PBF Q1-B IRF7319PBF R1 0.015 R2 100K R3 1K R4 100K R5 49.9K R6 22.5KR7 113KR8 2MR9 50KR10 10KR11 1KR12 4.7KR13 660RR14 150KR15 660RR16 0R02R17 30.1KR18 10KR19 130KR20 30KR21 100KR22 660R R23 4.7K R24 10K R25 1K R26 660R R28 1M SW1 ON/OFF Switch Momentary contact N.O.U1 MAX17015B U2 MAX8718 U3 ATtiny48 ATtiny48 TQFP-32U4 MAX17041 U5 MAX1791 Quote Link to comment Share on other sites More sharing options...
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