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| AN1464/1001 1/27 AN1464 application note low-cost double li-ion battery charger using st6255c/st6265c mcu by microcontroller division applications description in everyday life, more and more portable electronic appliances, such as mobile phones, are powered by rechargeable batteries with a requirement for high capacity, small size and low weight. li-ion batteries have been widely used to support these kind of devices due to their su- perior capacity for a given size and weight. this application note explains how to use the st6255c 8-bit microcontroller in a cost-effec- tive battery charger for li-ion batteries, as implemented in the li-ion battery charger demon- stration board. the design implemented on this board is easily scaleable to other types of li- ion batteries simply by changing the software parameters and primary input voltage/current. the charger has two slots. the front one can be used to plug in a simple battery or a mobile phone with an internal battery. the rear slot is for pluging in a stand-alone battery. a pair of leds (green/red) are assigned to each slot to indicate the charge status. the main target mcu is the st6255c. among other features, this microcontroller embeds an a/d converter, a pwm signal generator and 4k bytes of program memory, which is enough to embed the algorithm. the board also supports the st6265c mcu, which adds 128 bytes of internal eeprom to the features of the st6255c. the evaluation board is intended to be equipped with two mobile phone batteries and an st62t55c otp sample to execute the demonstration software. the software parameters are adapted to a fixed battery capacity of 600 mah. with minor modifications to the system, it is possible to make the charger read the battery capacity and change its parameters accordingly (feature not implemented on the evaluation board). the board must be powered by an external low-voltage dc supply (6 v, 800 ma). 1
2/27 table of contents 27 1 description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 theory of operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 battery charging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 slot priority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.3 man-machine interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 evaluation board implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1 charging circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.1 charging current control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 pwm signal switching generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.2.1 measurement circuitry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2.2 battery discharge protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.2.3 power supply restrictions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3 temperature sensing and battery detection . . . . . . . . . . . . . . . . 10 2.4 mcu software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4.1 architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4.2 on-chip peripherals usage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 2.4.3 state diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 2.4.4 slot monitor flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.4.5 source file organisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3 conclusion: a low-cost flexible solution . . . . . . . . . . . . . . . . . . . . . . . 24 4 appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 5 4.1 schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 4.2 bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3/27 low-cost double li-ion battery charger using st6255c/st6265c mcu 1 theory of operation 1.1 battery charging li-ion batteries have a very different charging procedure from nicd or nimh batteries. li-ion batteries should be charged using two different methods ( figure 1. ), constant voltage and constant current. figure 1. li-ion charging method during stage 1 (constant current charge), the charging current is kept at a constant value (i const ) until the battery voltage reaches the final cell voltage (v f ). note that the battery could suffer significant damage if this final voltage is exceeded. then, in stage 2 (constant voltage charge), the voltage is kept constant within this limit by slowly decreasing the current. charging is stopped when the current drops below the manufacturer fixed threshold value (i sat ). this current indicates that the battery is saturated. battery voltage v f i const i sat t t battery current stage 1 stage 2 2 4/27 low-cost double li-ion battery charger using st6255c/st6265c mcu if the battery voltage drops below a certain threshold (v fast ), a fast charge is applied. during fast charging, the current is kept constant at i fast >i const . after a certain time (t fail ) of fast charging, and if battery voltage remains particularly low (under v fail ), the charger indicates a battery failure and stops charging. if the battery voltage is even lower (below v sc ), the charger indicates a battery failure without waiting (protection against short-circuit). if the charging time exceeds a certain expiration value (t exp ), charging is stopped even if the battery is not yet saturated. as the t exp value is greater than the t fail value, the charger indi- cates that the battery is in good condition and fully charged. the battery temperature is also monitored. if the battery overheats, charging is suspended until the battery cools down. once the battery is saturated, its voltage is still monitored to prevent the battery from dis- charging completely. if the battery voltage drops below v tri , charging restarts until v f is reached again. charge time is reset when trickle charging starts. table 1. charge parameters used by the evaluation board 1.2 slot priority battery presence in both slots is permanently monitored to implement the priority of the front slot over the rear slot. whenever a battery is plugged into the front slot while the rear slot bat- tery is being charged, rear charging is stopped and front charging begins. when front charging is terminated (battery saturated, expire time reached, battery failure or battery removed), rear charging restarts from the beginning. if the front battery requires trickle charging, rear battery full charging has the priority. if both batteries are saturated, the first battery to meet the trickle charge condition is charged, and then the second one. if both batteries meet trickle charge conditions at the same time, front slot has the priority. symbol meaning value unit v f final battery voltage 4.2 v v tri trickle charge voltage 4.12 v fast fast charge voltage 3.8 v fail battery failure voltage 2.5 v sc short-circuit voltage 1.5 i fast fast charge current 600 ma i const constant charge current 550 i sat battery saturation current 15 t fail battery failure time 30 s t exp charge expire time 2.5 h 5/27 low-cost double li-ion battery charger using st6255c/st6265c mcu priority rules are not changed even if charging is suspended because of overheating. 1.3 man-machine interface as the charger periodically checks battery presence, no button is needed to start or stop charging. a reset button is included on the evaluation board for development purposes. a pair of leds (green/red) are dedicated to each slot to indicate the charge status. table 2. led slot status color code color status off no battery in the slot or rear charge stopped by front charge red only battery under charge red and green overheat green only charge cycle completed flashing red battery failure 6/27 low-cost double li-ion battery charger using st6255c/st6265c mcu 2 evaluation board implementation 2.1 charging circuitry the evaluation board implements a solution with an external low-voltage dc supply, unlike the solutions described in other battery charger application notes. to obtain a constant voltage during one stage and a constant current during another, the st6 measures the battery voltage (v bat ) and current (i bat ). with this feedback, it regulates the charging voltage using a buck converter circuit ( figure 2. ): figure 2. schematic of pwm control of battery charging 2.1.1 charging current control the pwm signal generated by the st6255c switches the pnp transistor on and off. a schottky rectifier is needed to receive the current from the coil when the pnp transistor is off (free-wheeling mechanism). as a result, the pwm signal is transferred to the node a voltage: C when the transistor is on, v a =v supply - |v ce | sat and the rectifier is off; C when the transistor is off, the rectifier is on and v a =-v d . |v ce | sat is the collector-emitter voltage of the pnp transistor in saturation state. v d is the for- ward voltage drop of the schottky rectifier. let us first consider a small period of time, e.g. ~100 pwm cycles. battery voltage variations are far slower than pwm switching, so v bat can be considered as constant during this period. with this approximation, v c can be seen as the response of the lc network to the incoming pwm signal v a . the network acts as a low-pass filter. therefore, if the pwm frequency is far higher than cut-off frequency, v c is constant and equal to the mean value of v a . i bat l r a diode r b a v suppl y v c v b v a r s to st6 analog to st6 analog input v bat battery pwm signal schottky rectifier c 7/27 low-cost double li-ion battery charger using st6255c/st6265c mcu in this demo, l = 150 h and c = 220 f so the cut-off frequency is 876 hz. the pwm fre- quency is fixed at ~30 khz. this way, charging voltage ripple is minimized. if a is the pwm positive duty cycle in a, the mean value of v a is a *(v supply - |v ce | sat ) + (1 - a )*(-v d ). accordingly, the charging current is: where v d is the forward voltage of the diode. example with the evaluation board hardware: for the maximum current to apply (600 ma), typical values are: |v ce | sat = 0.5 v, v d = 0.4 v, v d = 0.9 v. in fast charge mode, i bat = 600 ma and the maximum battery voltage is 3.8 v. this requires a duty cycle of ~92%. in constant current charge mode, i bat = 550 ma and the maximum bat- tery voltage is 4.2 v. in this case, the required duty cycle is ~98%. these values show that the range of duty cycles is fully used, which improves pwm resolution. let us now consider the whole charging time. at this scale, a , i bat and v bat are not constant. the above equation helps to understand how a evolves during this time. during the 1 st charge stage, v bat increases, so the mcu increases a in order to keep i bat constant. during the 2 nd stage, a decreases gradually in order to reduce i bat , but this does not decrease v bat . 2.2 pwm signal switching generation the st6255c only provides one pwm signal. switching the signal from one slot to another is done through the e_front and e_rear signals, generated by standard output pins. it is less expensive to implement the and function using npn transistors than with and gates. () ()() s bat d d sat ce ply sup bat r v v v v v i - - - a - + - a = 1 8/27 low-cost double li-ion battery charger using st6255c/st6265c mcu figure 3. pwm signal generation circuit selecting the proper power pnp transistor is not enough to make sure the buck converter can actually output the maximum current. the driving resistors (r eb , r b , r en and r pwm ) should also be chosen accordingly. C when the pnp is on, |v ce | should be as small as possible to minimise losses. this requires to be in saturation state, with a high base current. this current is equal to: |v be | is the base-emitter voltage of the pnp. v son is the node s voltage when both npns are on. it equals the sum of saturation collector-emitter voltages for the 2 npns. r be and r b guarantee that i c /i b 10 even if i c is at its maximum. example with the evaluation board hardware: at maximum collector current (i c = 600 ma), |v be | = 0.9 v typically. at i s ~ 60 ma, v son = 0.2 v. r eb = 270 w and r b = 75 w meet the requirements (and then i s = 65 ma). C when on, the npn transistors must also be in saturation state. r en makes sure that i s /i en 10 even for the maximum value of i s . e_front and e_rear v pwm signal from st6 a rear v supply rear charge enable signal from st6 v dd a front supply front charge enable signal from st6 v dd r ebf r bf r br r ebr i cf i cr i bf i br s f s r i sf i sr r enf r enr r pw mf r pwmr i enf i enr i pwmf i pwmr eb be b son be ply sup b r v r v v v i - - - = 9/27 low-cost double li-ion battery charger using st6255c/st6265c mcu st6 pins are open-drain outputs, so here, unlike previous equations, (v be ) sat and (v ce ) sat refer to the npn transistor values. r pwm guarantees that (i s + i en )/i pwm 10 even if (i s + i en ) is maximum. v oh is the output high voltage of the st6 pin emitting the pwm signal. example with the evaluation board hardware: at maximum current (i s = 65 ma), typical values are (v be ) sat = 0.9 v and (v ce ) sat = 0.1 v. for i pwm = 7 ma, v oh = 4 v typically (cf. st6 datasheet). r en = 620 w and r pwm = 430 meet the requirements. 2.2.1 measurement circuitry a shunt (r s ) is connected to the battery in order to measure the charging current. the mcu reads the v s voltage with its on-chip a/d converter. the converter has a voltage range be- tween ground and v dd . when v s is too low, like in this case, an amplification circuit is needed, e.g. with an opamp. in our case, v supply = 6 v and the microcontroller is supplied with v dd = 5 v. therefore, it is safer not to read vbat directly, but to attenuate this voltage by using a resistor bridge (r a , r b ). however, this attenuation must not be too strong to take maximum profit of the whole adc input range (0 to v dd ). this must be taken into account when choosing a proper r a /r b ratio. note that the st6 does not measure v bat but v b , which is proportional to (v bat +r s *i bat ). some calculation must be performed on the conversion results to access the real battery voltage. 2.2.2 battery discharge protection if the charger is not powered on or if the battery is already fully charged, the pnp transistor is kept permanently off. the diode prevents the battery from discharging into the capacitor. therefore, the battery discharges into r a , r b and r s , which requires less current. 2.2.3 power supply restrictions the battery characteristics have a direct influence on the choice of the dc power supply: C the supply must be able to drive enough current to charge the battery, even in fast charge mode. () () en sat ce sat be dd en r v v v i - - = () pwm sat be oh pwm r v v i - = 10/27 low-cost double li-ion battery charger using st6255c/st6265c mcu C v supply must be larger than (|v ce | sat + v d + v fast + r s *i fast ) and larger than (|v ce | sat + v d + v f + r s *i const ), but does not need to be significantly larger. mcu, led and opamp consumption must be taken into account as well. the board is designed to work with a dc supply providing 6 v and 800 ma. v dd = 5 v is gen- erated from v supply by a voltage regulation circuit. if you intend to increase v supply , make sure you adapt this regulation circuit. 2.3 temperature sensing and battery detection the li-ion battery used in this demo contains a thermistor connected to the negative pole, as described in figure 4. figure 4. temperature sensing circuitry when the slot is empty (no battery plugged in), the st6 reads v dd on the analog input. thus, a low value of the voltage indicates that a battery is present. the thermistor resistance decreases with temperature, and so does the thermistor voltage. therefore, an anormally low value of this voltage indicates overheating. battery r s v dd to st6 analog input 11/27 low-cost double li-ion battery charger using st6255c/st6265c mcu figure 5. thermistor voltage indication table 3. thermistor voltage thresholds used by the evaluation board note: because the exact characteristics of the thermistor were unknown to us, the v heat value given in the table above is only an example. note that, generally, for this kind of batteries, the temperature limit is set to 45c. 2.4 mcu software 2.4.1 architecture the software provided with the evaluation board has a state machine architecture. as ex- plained further, 10 charging states can be defined for each slot. each slot is driven by its state machine, with some interactions to implement front slot priority. in order to measure the charge time, a timekeeper is implemented and counters are incre- mented periodically. most of the time, slot states are unchanged. this implies that the pwm duty cycle, charge en- able signals and led on/off states are constant. periodically, the st6 measures battery cur- rent, battery voltage and thermistor voltage for both slots. using the measurements and the timekeeper values, it updates slot states and the output configuration. if necessary, it resets the timekeeper. symbol meaning value unit v det battery detection voltage 4.7 v v heat overheat voltage 2.0 battery under normal temperature conditions v dd v det no battery v heat battery under overheat v ss 12/27 low-cost double li-ion battery charger using st6255c/st6265c mcu figure 6. st6255c software flowchart front slot monitor updates front slot state depending on: previous slot states measurements time-keeper reset initialise i/o ports and peripherals initialise slot states launch time-keeper wait for state update request from main time base perform the measurements correct battery voltage measurements with battery current measurements reset timekeeper update output configuration front rear voltage mean of 256 mean of 256 current mean of 256 mean of 256 thermistor 11 leds on/off front charge enable/disable leds on/off rear charge enable/disable output on/off common pwm duty cycle ? rear slot monitor updates rear slot state depending on: previous slot states measurements timekeeper 13/27 low-cost double li-ion battery charger using st6255c/st6265c mcu 2.4.2 on-chip peripherals usage the time base is given by the standard timer in output mode. when the timer counter reaches zero, the interrupt routine generates a state update request. in addition, it reloads the timer counter to start a new cycle. in order to minimise supply current, the st6 core puts itself into wait mode between two state updates. in this example, this same interrupt routine (timer zero) also increments the timekeeper counters. this means the timekeeper is synchronised with the state updates. the slot state update frequency is an important parameter. it must be high to maximise charging efficiency. on the other hand, if the output configuration has changed, it is useless to perform the next measurements before the system has stabilised. therefore, an excessive update frequency could prove harmful. thirdly, a low update frequency reduces overall power consumption. the timekeeper divides the standard timer frequency. to do so, it contains three counters: tick , chrono_lo and chrono_hi . table 4. charge timekeeper counters the pwm is generated by the auto-reload timer because a high frequency is required. in ad- dition, this significantly reduces the cpu load, allowing the core to stay in wait mode most of the time. if no charge is under way on either slot, the pwm output is switched off in order to re- duce consumption and increase a/d converter accuracy. the analog to digital converter (adc) is used intensively before each slot state update. in most cases, the pwm output cannot be disabled, so adc accuracy is not optimal. to reduce errors, the adc measures battery voltage and battery current 256 times in a row. the slot state monitoring software works with the mean values. the 256 measurements are added into a 16-bit word. the mean value is equal to the most significant byte of the word (rounded if the least significant byte is greater than 128). as explained in section 2.2 , battery voltage measurements must be corrected with battery current measurements. these corrections require some arithmetical computing, performed on the 16-bit words. tick chrono_lo chrono_hi increment condition timer zero it tick =0 chrono_lo =0 period general t tmz 256*t tmz 65536*t tmz eval board 6.1 ms 1.6 s 6 min 43 s compared with general t fail t exp eval board 30 s 2.5 h 14/27 low-cost double li-ion battery charger using st6255c/st6265c mcu the core puts itself into wait mode during each conversion in order to gain accuracy. preci- sion is improved even more by using the adc sync option bit. 2.4.3 state diagrams a slot can be in one of the ten states described in the slot states definitions table, where text in italic is valid only for the rear slot . table 5. slot states definitions note that this choice of states is only one solution - among many - of implementing the re- quired behaviour of the charger. here, periodically means at every state update. therefore, the state update frequency is equal to the pwm duty cycle increase or decrease rate in the ci, cv_d, cv_u and fast states. in fail state, the red led flashing frequency is half of the state update frequency. the diagram of state transitions is too complex to be described by only one figure. hence the three figures in figure 7. 't' stands for the timekeeper value. the rectangles represent actions performed once during a state transition. name meaning output configuration front priority request slot outputs pwm duty cycle idle slot empty or charge suspended by front charge priority charge disabled, both leds off unchanged no ci constant current charge charge enabled, green led off, red led on updated periodically to have i bat =i const yes cv_d constant voltage charge, duty cycle down incremented periodically cv_u constant voltage charge, duty cycle up decremented periodically fast fast charge updated periodically to have i bat =i fast tri trickle charge unchanged no sat battery saturated charge disabled, green led on, red led off exp charge time expired fail battery failure charge disabled, green led off, red led flashing (toggled periodically) heat charge suspended by overheat charge disabled, both leds on same as original state 15/27 low-cost double li-ion battery charger using st6255c/st6265c mcu the rear slot state is updated after the front slot state. as a result, a front priority request de- pends on the updated value of front state. once the slot is in a given state, conditions to move to another state are not always incompat- ible. therefore, priority rules must be defined: 1 (highest priority) transition related to battery presence 2 front slot priority 3 temperature 4time 5 battery current 6 battery voltage figure 7. state diagram (1) - charging note: a slot is considered to be using the pwm if it is in a charging state (ci, cv_d, cv_u, fast or tri) or if it is in heat state. idle ci cv_d cv_u sat tri fast fail exp heat t>t ex p t>t exp v bat >v f v bat >v f v bat 16/27 low-cost double li-ion battery charger using st6255c/st6265c mcu figure 8. state diagram (2) C returning to idle state ci cv_d cv_u tri fail heat idle exp no battery detected front slot priority t sat fast 17/27 low-cost double li-ion battery charger using st6255c/st6265c mcu figure 9. state diagram (3) C heat state transitions 2.4.4 slot monitor flowchart in the software, slot states are updated by a subroutine called slot monitor. using a subrou- tine is possible because the front and rear slot state diagrams are almost identical. slot state is stored in a one-byte variable, coded in a way that facilitates decoding the condi- tion tree: idle equ 00000001b heat equ 10100000b fail equ 11000001b exp equ 11010001b sat equ 11011001b tri equ 11100001b fast equ 11110000b cv_d equ 11111000b ci equ 11111100b cv_u equ 11111110b decoding starts from the most significant bit. the least significant bit indicates front slot priority request (1 = no request). when the slot enters heat state, this bit is modified to be the same as in the original state. bit b 5 indicates if the slot is using the pwm (b 5 = 1) or not (b 5 =0). ci cv_d cv_u tri fail heat idle no overheat original state exp original state saved overheat sat fast 18/27 low-cost double li-ion battery charger using st6255c/st6265c mcu the flowchart, represented in slot monitor flowchart (1) , slot monitor flowchart (2) and slot monitor flowchart (3) , takes full advantage between transitions. for example, if the monitor knows that slot state is either ci, cv_d or cv_u, it can check the expiration time before switching to one of the three possibilities. the order in which questions are asked (e.g. time before battery voltage) defines the priority of the state transition. on the flowcharts, b 7 , b 6 , etc. refer to the corresponding bit in the slot state variable. 19/27 low-cost double li-ion battery charger using st6255c/st6265c mcu figure 10. slot monitor flowchart (1) slot monitor b 7 ? 0 battery detected? previously idle rear slot? yes front priority request? yes still idle yes no ci now no no 1 reset timekeeper pwm duty cycle at 50% idle now no b 6 ? battery detected? yes 0 overheat? no no still heat yes back to original state no rear slot? yes yes 1 previously heat s11 idle now front priority request? previously not idle 20/27 low-cost double li-ion battery charger using st6255c/st6265c mcu figure 11. slot monitor flowchart (2) previously fail b 5 ? 0 b 4 ? 0 still fail b 3 ? 1 0 still exp previously exp 1 previously sat v bat 21/27 low-cost double li-ion battery charger using st6255c/st6265c mcu figure 12. slot monitor flowchart (3) s1111 overheat? store original state enable priority request heat now yes no b 3 ? v bat >v fast ? yes previously fast v bat 22/27 low-cost double li-ion battery charger using st6255c/st6265c mcu figure 13. slot monitor flowchart (4) v bat 24/27 low-cost double li-ion battery charger using st6255c/st6265c mcu 3 conclusion: a low-cost flexible solution everything on the evaluation board has been designed to make it easy to adapt in any way (other type of battery, new behaviour specifications, additional design constraints, etc.). n the number of components needed for each slot (charging and feedback) is minimal, so replacing them is inexpensive. besides, the circuit has a simple and predictable behaviour. this avoids costly and time-consuming trial-and-error procedures. n the system has an inner self-adaptation capability thanks to its many closed loop regulations (voltage, current, temperature). for example, no software change is needed if v suppy changes C provided v dd remains at 5 v. n as explained in section 2.4 , parameter modifications in the software are easy to perform. n the software only occupies a fourth of the total mcu program memory. port c is not used at all; neither is the spi (nor the eeprom on the st6265c). subsequently, many improvements and/or new features can still be added without changing the mcu. n analog inputs available on port c can read the identification resistor included in the batteries to determine their capacity and adapt the charging parameters accordingly. n the eeprom can be used for adc calibration. 25/27 low-cost double li-ion battery charger using st6255c/st6265c mcu 4 appendix 4.1 schematic a a b b c c d d e e 4 4 3 3 2 2 1 1 reference desi gn dc supply 6 v / 600 ma rear sl ot st at us fr ont sl ot st at us battery 1 li-ion battery charger demo board a3 11 monday, september 10, 2001 title size document number rev date: sh ee t of pwm e_rear e_front r_temp f_temp pwm pwm e_front r_temp e_rear f_temp v dd v dd v dd vsupply v dd v dd v dd v dd v dd v dd v dd v dd v dd r17 0.5 1% r7 560 q3 2n3904 d6a led-red u1 st6255 1 2 3 4 5 10 11 12 13 14 15 16 17 18 19 24 25 26 27 28 6 7 8 9 20 21 22 23 pb0 pb1 vpp/test pb2 pb3 pa0/an vdd vss pa1/ain pa2/ain pa3/ain pa4/ain pa5/ain pa6/ain pa7/ain pc4/sck/ai n pc3/sout/ain pc2/sin/ain pc1/tim1/ain pc0/ain pb4 pb5 pb6/artimin pb7/artimout oscin oscout /reset nmi - + u2b lm358 5 6 7 8 4 d1 1n4002 s1 reset sw r9 10k rid r2 30k 1% r3 30k 1% + c2 100uf/10v r24 10k c3 0.1u r1 4r7 d6b led-green x1 8mhz c5 22p r14 10k c4 22p r8 560 r6 560 cn1 power jack socket 2.5 mm 3 2 1 q6 2n3904 cn2 front slot 1 2 3 4 r23 430 r15 10k 1% r16 43k 1% li-ion cell d7a led-red r12 620 d2 1n5819 r18 4.3k 1% l1 150uh/900ma r27 0.5 1% r19 39k 1% q2 2n3904 d5 1n4001 d3 1n4001 + c8 220uf/16v + c7 220uf/16v rn1 10k x 8 r25 10k 1% r26 43k 1% + c1 470uf/16v r21 75 1/2w r11 75 1/2w r22 620 cn3 rear slot 1 2 3 4 r13 430 slot connector 1 2 3 4 d7b led-green q1 2sa1011 q5 2n3904 q4 2sa1011 d4 1n5819 r10 270 l2 150uh/900ma - + u2a lm358 3 2 1 8 4 r28 4.3k 1% r20 270 r4 10k r29 39k 1% v1 tl431 c6 0.1u r5 560 t ntc 26/27 low-cost double li-ion battery charger using st6255c/st6265c mcu 4.2 bill of material item quantity reference part 1 1 bt1 li-ion cell 2 1 cn1 power jack socket 2.5 mm 31cn2 front slot 4 1 cn3 rear slot 5 1 c1 470uf/16v 6 1 c2 100uf/10v 72c3,c6 0.1u 8 2 c5,c4 22p 9 2 c7,c8 220uf/16v 10 1 d1 1n4002 11 2 d2,d4 1n5819 12 2 d3,d5 1n4001 13 2 d6a,d7a led-red 14 2 d6b,d7b led-green 15 1 j4 slot connector 16 2 l1,l2 150uh/900ma 17 2 q1,q4 2sa1011 18 4 q2,q3,q5,q6 2n3904 19 1 rn1 10k x 8 20 1 rt1 ntc 21 1 rid r 22 1 r1 4r7 23 2 r2,r3 30k 1% 24 4 r4,r9,r14,r24 10k 25 4 r5,r6,r7,r8 560 26 2 r10,r20 270 27 2 r11,r21 75 1/2w 28 2 r12,r22 620 29 2 r23,r13 430 30 2 r15,r25 10k 1% 31 2 r16,r26 43k 1% 32 2 r17,r27 0.5 1% 33 2 r18,r28 4.3k 1% 34 2 r19,r29 39k 1% 35 1 s1 reset sw 36 1 u1 st6255 37 1 u2 lm358 38 1 v1 tl431 39 1 x1 8mhz 27/27 low-cost double li-ion battery charger using st6255c/st6265c mcu the present note which is for guidance only aims at providing customers with information regarding their products in order for them to save time. as a result, stmicroelectronics shall not be held liable for any direct, indirect or consequential damages with respect to any claims arising from the content of such a note and/or the use made by customers of the information contained herein in connexion with their products. information furnished is believed to be accurate and reliable. however, stmicroelectronics assumes no responsibility for the co nsequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of stmicroelectronics. specifications mentioned in this publicati on are subject to change without notice. this publication supersedes and replaces all information previously supplied. stmicroelectronics prod ucts are not authorized for use as critical components in life support devices or systems without the express written approval of stmicroele ctronics. the st logo is a registered trademark of stmicroelectronics ? 2001 stmicroelectronics - all rights reserved. purchase of i 2 c components by stmicroelectronics conveys a license under the philips i 2 c patent. rights to use these components in an i 2 c system is granted provided that the system conforms to the i 2 c standard specification as defined by philips. stmicroelectronics group of companies australia - brazil - canada - china - finland - france - germany - hong kong - india - israel - italy - japan malaysia - malta - morocco - singapore - spain - sweden - switzerland - united kingdom - u.s.a. http://www.st.com |
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