U2407B TEMIC Semiconductors Simple Controller for Fast-Charge Systems Description The bipolar IC U2407B is a fast-charge battery controller for drained NiCd/ NiMH batteries. The IC enables the designer to create an efficient and economic charge system. The U2407B incorporates an intelligent multiple-gradient battery-voltage monitoring combined with temperature and failure mode detection. With automatic top-off charging, the integrated circuit ensures that the charge device stops regular charging before the critical stage of overcharging is achieved. It incorporates an additional algorithm for reactivating fully drained batteries especially after long time storage. It has four LED driver outputs for different indications of the charge status. Features Applications @ Multiple gradient monitoring Primary switch mode @ Temperature window (Tiin/Tmax) AC/DC all plug adapter e@ Exact currentless measurement ; ; @ Four LED status outputs @ Ultra-fast charge systems (10 minutes) @ Linear power control @ Preferred for externally regulated current sources @ Preformation algorithm for drained batteries @ Programmable top-off charge function Block Diagram 13 12 is 2 3 10 ! ahh Vret Oscillator 6.5 V/ALO mA 1 Status control] ~ Scan path pate OW 16 Q} Switch ouput bag Control unit Battery Gradi a detection < sradient Veep V ePV/dt? and -dV Ret 9 Power - on control ae Veatt moniter A ~ O.1w4 4 , 2 me Power supply -L 160 mV 4} m 1 Vs =8 to 26V Temp. control Charge break t es Tinax Sensor output 4 5 6 7 8 Figure 1. Block diagram Ordering Information | _Extended Type Number | Package Remarks jo U2407B __DIPI6 Tube WL U2407B-XFL so ., SOIL Tube Bs U2407B-xFL SOI16L __Taped and reeled . 170 Rev. A5, 08-Nov-99TEMIC Semiconductors U2407B Pin Description GND |. LED2 | 2. LED3 3 OPo [4 - OP; 15 | Tmax | 6_ Sensor 7 mH 8 Input Voltage 8Vto24V q Mounted on. heatsink D BYW52 U2407B SS 16 Output | LED4 12| Ose AL) St 190. LEDI O Veatt _ Pin Symbol / Function 1 | GND {Ground | ___ 2 LED2 | Display output top-off/ trickle charge 3 LED3 Display output Fast charge 4 OPo. Operational amplifier output | 5. | OP: Operational amplifier input _ 6 Tmax Maximum temperature _! _7_| Sensor Temperature sensor 8 _|__tp Charge break output _| 9 | Vpau Battery voltage i 10 LED1 Display output failure mode | - Ll Stu. | Test mode switch (status control) | 12 | Ose Oscitlator dd 13 Vref _ Reference output wolage i. 14 Vs Supply voltage i i 15 LED4 Display output top-off charge | 16 | Output Triggeroutput | roy ' ' ' ' L Battery \ 7 \ Sensor] 1-41 ' ' Lao-d Re Seemann Raf 10 kQ L c, OF 0.2 2 1] uF LL I Figure 3. Scheme for DC linear regulation 3 15 C2 a 4 0.22 uF} U2407B 13 Vref o oO 9 Tmax Rip 6 100 k2 7 Output Rr 16 L 1.5kQ 5 = 3 i 10nF | th Sim Rev. A5, 08-Nov-99 171U2407B TEMIC Semiconductors General Description The integrated circuit, U2407B, is designed for charging Nickel-Cadmium (NiCd) and Nickel-Metal-Hydride (NiMH) batteries, Fast charging results in voltage lobes when fully charged (see figure 4). It supplies two identifications (i.e., + d2V/dt2, and AV) to end the charge operation at the proper time. As compared to the existing charge concepts where the charge is terminated after voltage lobes according to - AV and temperature gradient identification, the U2407B takes into consideration the additional changes in positive charge curves, according to the second derivative of the voltage with respect to time (d2V/dt?). The charge identification is the sure method of switching off the fast charge before overcharging the battery. This helps to give the battery a long life by hindering any marked increase in cell pressure and temperature. Even in critical charge applications, such as a reduced charge current or with NiMH batteries where weaker Battery Battery insertion voltage { tT | charge characteristics are present multiple gradient control results in very efficient switch-off. An additional temperature control input increases not only the performances of the charge switching characteristics but also prevents the general charging of a battery whose temperature is outside the specified window. A specific preformation algorithm is implemented for reactivating fully drained batteries especially in the case of batteries that have been stored for a long time. A constant charge current is necessary for continued charge-voltage characteristic. This constant current is generated from an external power supply and can be regu- lated with the help of an internal op-amp regulator (see figure 2), An external current source can also be con- trolled by the switch output Pin 16 (see figure 13). For further information please refer to the applications. Top-off charge stop Fast charge stop wv + de without charge control el -AV ao _ preformation 4 - | | | | I \ | | ! ( Fast charge rate Ip t T(Rean . | Top-off Trickle | { charge rate charge rate | | 1/4 J 1/256}, Alo 1256 lo t) =Smin t2 = 20 min t Figure 4. Charge function diagram, fos. = 800 Hz 172 Rev. A5, 08-Nov-99TEMIC Semiconductors U2407B Flow Chart Explanation, fose = 800 Hz (Figures 2, 4 and 5) Battery pack insertion disables the voltage lock at battery detection input Pin 9. All functions in the integrated circuit are reset. For further description, DIP-pinning is taken into consideration. Battery Insertion and -AV Monitoring After battery insertion fast charge [, begins when the input voltage Vpan is higher than 1.6 V. For the first 5 minutes the d?V/dt?-gradient recognition is suppressed, -AV monitoring is activated. In case the detected Vgat voltage is less then 1.6 V the special preformation procedure will be activated. The reference level with respect to the cell voltage can be adjusted by the resistor Rp3 (see figure 2). Preformation Procedure Before fast charge of fully drained or long-time stored batteries begins, a reactivation of it is necessary. The preformation current is dependent on pull-up resistor Rg. The fast charge starts only after the Vgatr is higher than 1.6 V. During the first 10 minutes the green LED2 is blinking. If after 10 minutes, Vga voltage has not reached the reference level, the indication changes to red blinking LED1. The charge will continue with preformation rate I (Rp ,). In case Var increases to 1.6 V reference level, the fast charge rate current, Ig, is switched-on and the green LED2 is blinking. -AV Cut-Off (Monitoring) When the signal at Pin 9 of the DA converter is 12 mV below the actual value, the comparator identifies it as a voltage drop of -AV. The validity of -AV cut-off is considered only if the actual value is below 12 mV for three consecutive cycles of measurement. d*V/at?-Gradient If there is no charge stop within the first 5 minutes after battery insertion, then d2V/dt? monitoring will be active. In this actual charge stage, all stop-charge criteria are active. When close to the batterys capacity limit, the battery voltage curve will typically rise. As soon as the +d2V/dt? stop-charging criteria are met, the device will stop the fast charge activities. Top-Off Charge Stage By charge disconnection through the +d2V/dt? mode, the device switches automatically to a defined protective top-off charge with a pulse rate of 1/4 Ip (pulse time, tp = 5.12 s, period, T = 20.48 s). The top-off charge time is specified for a time of 20 minutes @ 800 Hz. During top-off mode the LED4 is in ON mode. Trickle Charge Stage When top-off charge is terminated, the device switches automatically to trickle charge with 1/256 Ip (tp = 5.12 s, period = 1310.72 s). The trickle continues until the battery pack is removed. During trickle mode the LED2 output is in on mode, LED4 is in OFF-mode. Basic Description Power Supply (Figure 2) The charge controller allows the direct power supply of 8 to 26 V at Pin 14. Internal regulation limits higher input voltages. Series resistance, Rj, regulates the supply cur- rent, Is, to a maximum value of 25 mA. Series resistance is recommended to suppress the noise signal, even below 26 V limitation. It is calculated as follows. Vimax-26_V > Ri min = 25 mA V nin 8 Vv Rin SY Hot where Thor = Is + Trp +h Vmax, Vmin = Rectified voltage Is = Current consumption (IC) without load Trp = Current through resistance, Rp I, = Trigger current at Pin | Rev. A5, 08-Nov-99U2407B TEMIC Semiconductors | Start }+| Power on reset LED 1.2,3,4 off *) 70 mV > Vpatr > 5V Reset 1 a Preformation yes current ] LED} blinking Temp. range RBI ok 2 LED3 blinking Fast charge begins 1 no LED] blinking LED3 off ' ~dV and d2V/dt2 monitoring activated yes . no Batt. inseried oa *) Batt temp yes range? dV disconnect d2v/dt disconnect ? i T | LED2 on | | | Trickle charge Top off charge 1/256 Io 1/4 jo 1 no Figure 5. Flow chart 174 Rev. A5, 08-Nov-99TEMIC Semiconductors U2407B Battery Voltage Measurement The battery voltage measurement at Pin 9 (ADC- converter) has a range of 0 V to 4 V, which means a battery pack containing two cells can be connected without a voltage divider. If the AD converter is overloaded (Vpay 2 4 V) a safety switch-off occurs. The fast charge cycle is terminated by automatically changing to trickle charge. Precaution should be taken that under specified charge current conditions, the final voltage at the input of the converter, Pin 9, should not exceed the threshold voltage level of the reset comparator, which is 5 V. When the battery is removed, the input (Pin 9) is terminated across the pulled-up resistance, Rg;. to the value of 5 V-reset- threshold. In this way, the start of a new charge sequence is guaranteed when a battery is reinserted. If the battery voltage exceeds the converter range of 4 V, adjusting it by the external voltage divider resistance, Rp2 and Rp; is recommended. q Toh j ~ Battery | ,Y Ve Value of the resistance, Rg3 is calculated by assuming Rp, = 1 k82 Rg = 10 kQ, as follows: The minimum supply voltage, Vemin. is calculated for reset function after removing the inserted battery according to: _ 0.03mA X RyRy, + Rao! + SV (Rp, + Reo + Rp, smin ~~ Rp; where: Vomax = Max. voltage at Pin 9 Vsmin = Min. supply voltage at the IC (Pin 14) Vpmax = Max. battery voltage The voltage conditions mentioned above are measured during charge current break (switch-off condition). Vpac . - dV Recognition Vpac DAC control comparator + Reset comparator Figure 6. Input configuration for the battery voltage measurement Table 1. valid when Vigmax = 3.5 V CellNo. | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 10 | Wl 2 | | Vsmin() 8 8 | 8 9 ul 13 5) 17 19 21. 23 25 | pt sore ot t+ oo ~ crea feo wen te wo ce | Rea (kQ) jo sl 160 $0} 75) 56 4 8D BB Rev. AS, 08-Nov-99 175U2407B TEMIC Semiconductors Analog-Digital-Converter (ADC), Test Sequence A special analog-digital-converter consists of a five-bit coarse and a five-bit fine converter . It operates by a linear count method which can digitalize a battery voltage of 4 V at Pin 9 in 6.5 mV steps of sensitivity. In a duty cycle, T, of 20.48 s, the converter executes the measurement from a standard oscillator frequency of fos = 800 Hz. The voltage measurement is during the charge break time of 2.56 s (see figure 7), i.e., no-load voltage (or currentless phase). Therefore it has optimum mea- surement accuracy because all interferences are cut-off during this period (e.g., terminal resistances or dynamic load current fluctuations). After a delay of 1.28 s the actual measurement phase of 1.285 follows. During this idle interval of cut-off conditions, battery voltage is stabilized and hence measurement is possible. An output pulse of 10 ms appears at Pin 8 during charge break after a delay of 40 ms. The output signal can be used in a variety of way, e.g., synchronising the test control (reference measurement). Plausibility for Charge Break There are two criteria considered for charge break plausibility: AV Cut-Off When the signal at Pin 9 of the DA converter is 12 mV below the actual value, the comparator identifies it as a voltage drop of AV. The validity of AV cutt-off is considered only if the actual value is below 12 mV for three consective cycles of measurement. d?V/dt? Cut-Off A four bit forward/ backward counter is used to register the slope change (d?V/dt?, Vga slope). This counter is clocked by each tracking phase of the fine AD-counter. Beginning from its initial value, the counter counts the first eight cycles in forward direction and the next eight cycles in reverse direction. At the end of 16 cycles, the actual value is compared with the initial value. If there is a difference of more than two LSB-bit (13.5 mV) from the actual counter value, then there is an identification of slope change which leads to normal charge cut-off. A second counter in the same configuration is operating in parallel with eight clock cycles delay, to reduce the total cut-off delay, from 16 test cycles to eight test cycles. Status v7 Charge break Charge 2.56 8 t> - T= 20.48 s charge break | output Mh J ae 10 ms i > a 40 ms | jt ADC conversion time Cinternal) Ahm ws 1.288] 1.285 t Figure 7. Operating sequence of voltage measurements 176 Rev. A5, 08-Nov-99TEMIC Semiconductors U2407B Temperature Control (Figure 8) When the battery temperature is not inside the specified temperature windows, the overal temperature control wil! not allow the charge process. Sensor short circuit or interruption also leads to switch-off (faulty mode). A permanent switch-off follows after a measurement period of 20.48 s, if the temperature exceeds a specified level, which is denoted by a status of LED. A charge sequence will start only when the specified window temperature range is attained. The temperature window is specified between two voltage transitions. The upper voltage transition is specified by the internal reference voltage of 4 V, and the VRef Rr) NTC sensor lower voltage transition is represented by the external voltage divider resistances Ry2 and Rr3. NTC sensors are normaily used to control the temperature of the battery pack. If the resistance values of NTC are known for maximum and minimum conditions of allowable temperature, then other resistance values, Rt), Rr2 and R73 are calculated as follows: suppose Rr2 = 100 kQ, then Vueerp 4V Rr = Ryremax <V Rr Ros = Ryremin R,, + High _ temperature Vere =4V Low temperature Figure 8. Temperature window Current Regulation The charge concept requires a constant charge current supply outside of the circuit. This is achieved by an external switchable current source or by an internal error amplifier regulation of an externally situated power stage. Charge Current Regulation (Figure 3) According to figure 3 the operational amplifier (OpAmp) regulates the charge current, [4 (= 160 mV/ Rgp), aver- age value. The OpAmp detects the voltage drop across the shunt resistor (Rgp) at input Pin 5 as an actual value. The actual value will then be compared with an internal refer- ence value of 160 mV. Rev. A5, 08-Nov-99 {77U2407B TEMIC Status Control Different status control modes can be designed by four LED outputs. Status control regards the running charge cycle before it has been started and also after it has been terminated. LED1 LED2 LED3 LED4 | Status OFF! OFF) sCOFF _ OFF (No battery (Vpan > 5 V) OFF _OFF____Blinking_ |= OFF = Fastcharge | OFF ON OFF ON Top-off charge oo OFF ON OFF OFF Trickle charge _ Blinking =| OFF OFF OFF Failure mode Failure mode: Temperature out of window, also before battery insertion or power-on. Battery break, short circuit, Vgan < 0.1 V To achieve custom specific display modes, several combinations between LED outputs | to 4 are recommended. (see applications) The blink frequency of LED outputs can be calculated as follows: Oscillator frequency. fos fiiep, = 'o9g.~C~C~sS Example |: Display mode similar to U2402B: Table 2. Status indication | io re ayy Vs LED! (red) | LED2 (green) Status | LED! ()___}q--["~} ___ (LED) (LED2/LED3) | 1kQ OFF OFF No battery LED? green * Vs (Vpatt > 5 V) am C+_ OFF Blinking __| Fast charge LED3 OFF ON Top-off, trickle charge 3 __Blinking OFF _[All failure mode _ Figure 9. Status indication Example 2: Table 3. Status indication 2 LEDI (red) | LED2 (green) | Status (LED1/ LED3) (LED2) OFF OFF _j No battery pan SV ON OFF Fast charge OFF ON Top-off, trickle charge Blinking OFF All failure mode C Figure 10. Status indication 178 Rev. A5, 08-Nov-99TEMIC Semiconductors U2407B Top-off Charge Rate Reduction The current amplitude during top-off charge can be reduced as shown in figure 11. During top-off mode, both the LED4 output (Pin 15) and transistor T are on. The actual current amplitude is influenced with the help of resistor R,, which is detected by the operational amplifier input OP; (Pin 5). The decrease of the current flow depends on the reciprocal value of Rx. S ey VRef = Battery . Figure 11. Topp-off charge rate rduction T 15 LED4 -~+ OP; Oscillator Time sequences regarding measured values and evaluation are determined by the system oscillator. All the technical data given in the description are with the standard frequency 800 Hz. It is possibe to alter the frequency range in a certain limitation, Figure 12 shows the frequency versus resistance curves with different capacitance values. Oscillation Frequency Adjustment Recommendations: 0.5C charge 0.5 x 500 Hz = 250 Hz 1C charge 500 Hz 2C charge 2 xX 500Hz= 1000 Hz 3C charge 3. x 500Hz= 1500 Hz 10000, 1000 Ro( kQ) Co=10nk Co=4.7nF- 0.1 I 10 fo (kHz) Figure 12, Frequency versus resistance for different capacitance values Rev. A5, 08-Nov-99 179U2407B TEMIC Semiconductors Absolute Maximum Ratings Reference point Pin 2 (GND), unless otherwise specified Parameters Symbol Value Unit Supply voltage Pin 14 Vs 26 Vv | Voltage limitation Is = 10 mA Vs 31 Vv Current limitation Pin 14 Is 25 mA ots 10OMs Is 100 mA Voltages at different pins Pins 16, 2, 3, 10 and 15 v 26 Vv - Pins 11 upto 13,4 upto9 _ Vv 7 Vv Currents at different pins Pin | I 25 mA | ___ Pins 3 up to 14 and 16 up to 18 I 10 mA Power dissipation Tamb = 60C Prot 650 mW Ambient temperature range Tamb 10 to +85 C Junction temperature - Tj 125 C Storage temperature range Tag 40to+125 | ec Thermal Resistance Parameters Symbol Value Unit Junction ambient DIP16 Rina 100 K/W _ SO16 _ Rina 120 _ K/W Electrical Characteristics Vs = 12 V, Tamb = 25C, reference point Pin 1 (GND), unless otherwise specified Parameters | Test Conditions / Pins | Symbol Min. Typ. Max. Unit Power supply ; Pin 14 Voltage range ee Vs" 8 26 Vv Power-on threshold ON Vs 3.0 3.8 Vv _ ___OFF Vs AT 5.7 Vv Current consumption ___ without load __ Is 39 | | ot mA | Reference __ _ Pin 13 7 _ Reference voltage IRep = 5 MA VRef | 65 6.71 | Vv Po rep = 10mA Vref 6.5 6.77 | Vv Reference current _ IRet. 10 mA | Temperature coeffi icient | _ Tc -0.7 _ mv/K : Operational amplifier OP / / Output voltage range ITs = 0 Pin 4 V4 [ 0.15 5.8 Vv | Output current range 1Vs=3.25V Pind +l, | 80 _ | pA Output pause current Pin 4 ~Ipause__| __ 100 pA Non-inverting input voltage Pins | V5 0 3 Vv. Non-inverting input current 7 Pins +15 0.5 WA i Comparator or temperature control Input current Pins 6 and 7 +]6.7 ; _ 0.5 pA Input voltage range Pins 6 and 7 Vo.7._ | 0 . v Threshold voltage Pin? V7 | 3.85 4.15 | Vv | Charge break output Pin 8 _ | Output voltage |High, Ig = 4 mA Ve 8.4 vo / / Low, Ig = 0 mA Ve 100 _mV | Output current [Vg=i Ig | 10 mA _ 180 Rev. A5, 08-Nov-99TEMIC Semiconductors U2407B Parameters | Test Conditions /Pins | Symbol | Min. Typ. Max. Unit Battery detection Pin 9 | Analog- digital converter Conversion range | VBatt 0 4.0 Vv ae Full scale level | Veatt 3.85 Vv | Input current O.1V S Ver <= 45 V Ipatt ml 0.5 vA | Input voltage for reset Veatt 4.8 5.0 5.3 Vv [Input current for reset Vaart 2 SV Ipate 8 35 nA Battery detection Maximum voltage A Vpan 80 | 120 mV | Hysteresis | Maximum voltage Vays 15 mV | Mode select _ Pin I Treshold voltage _| Testmode (| Vv | ti HT Uv | Input current ae 1 20 | uA | Input current ______| Normal mode Pin L1 open , ly 0 | - ! uA [ Syne. oscillator Pin 12 Frequency R= 150kQ,C=10nF tose 800 | Hz _ Threshold voltage High level Vru 4.343% | v Low level | Vr 2.243%. Input current 8 0 os | ww Applications Input voltage 8Vt026V == Cio T 10 wF _ Controlled current source Insan4 on off tb STM Figure 13. Minimum charge system with external current source Rev. A5, 08-Nov-99 181TEMIC U2407B xe anpad apeu / 40 doy B AOL Vy Bl Wy JP Pay BAO! tly BHO! cod f # -- StleNt /yo doy ant 8 Bc0 GW BOL T Bay Wa 5 5 Te a | B01 65 101g ! Tl * . A | 6 I ct + Pay aLovcen [2 <3 oy BAT el w GAO samt Fda Pay cocWwTe/l d Se ee RSELENI t 1ndin0 a o aNp \ 4 TT yuisivay, uo paiunow GWI a aa dWol Adl dh aus Josey "> aaeyoa induy Figure 14. Dual-slot charger Rev. A5, 08-Nov-99 182TEMIC U2407B Package Information Package DIP16 Dimensions in mm 7.82 20.0 max 7.42 ed wala Pome H | uo _| 6.4 max | | in 33 0.5 min i 0.39 max } 9.75 : 1.64 0.58 | 8 % | 1.44 0.48 i | 2.54 Lg wtle ee Alternative 17.78 yt 16 a aahaaaan 3 @ technical drawings to DIN \P Ve VW? We We VW WW specications Package SO16L 105 9.25 Dimensions in mm 10.1 i AAABRRA technical drawings. according to DIN specifications POrevene Rev. A5, 08-Nov-99 183