SS6781AGNTB

SS6781A(G) Battery Charger Controller FEATURES Fast charge control of NiMH/NiCd batteries, even with a fluctuating charging current. Fast charge termination by: ∆T/∆t, -∆V, 0∆V, safety timer, maximum temperature or maximum voltage. Linearly adjustable ∆T/∆t detection slope and safety timer. Adjustable peak voltage timer for 0∆ V Battery voltage protection range selectable. Selectable battery temperature protection mode Protection against battery voltage and battery temperature faults Selectable LED display mode for battery status. Five pulsed trickle charge modes Discharge-before-charge function available for eliminating memory effect. Quick and easy testing for production Packaged in SO-16 or PDIP-16 DESCRIPTION The SS6781A fast charger controller IC is designed for intelligent charging of NiMH or NiCd batteries without the risk of overcharge. Using -∆V detection (-0.25%), 0∆V detection (peak voltage timer) and ∆T/∆t detection are the primary methods employed by the SS6781A to terminate fast charge. The fast charge can also be cut off by maximum battery voltage and maximum battery temperature detection, along with the safety timer to prevent charging under fault conditions of the charging system or the battery itself. Both ∆ T/∆ t and -∆ V detection methods have been proved powerful in terminating fast charging for NiMH and NiCd batteries. The SS6781A utilizes the combination of these two methods to reliably determine when to end fast charge and prevent mistakes caused by using -∆ V detection alone under certain conditions. Fig. 1 shows an example of a charging curve for a battery charged by a fluctuating current from a NiMH battery charger, which uses the SS6781A controller IC to achieve optimal charging. This technique, in conjunction ∆ with the 0∆ V detection (peak voltage timer), is particularly suitable for NiMH batteries, whose voltage drop is hardly significant yet temperature rises rapidly. The ∆T /∆ tt or -∆ V detection T/ circuitry may be disabled independently for different applications, such as system-integrated chargers, chargers with varying charge current, or battery packs which lack a temperature sensing thermistor. This device is available with Pb-free lead finish. APPLICATIONS Fast Battery Chargers for: Mobile Phones. Notebook and Laptop Personal Computers. Portable Power Tools and Toys. Portable Communication Equipment. Portable Video and Stereo Equipment. 1.55 100 Charge Current = 600 mA Cell Capacity = 550 mA NiMH Battery Cell Voltage 1.35 60 1.25 40 Temperature 1.15 20 0 10 20 30 40 50 60 Temperature (°C) Cell Voltage (V) 1.45 80 Charge Time (min.) The safety timer period, battery temperature protection mode, battery voltage protection range, pulsed trickle charge duty, and LED display mode are all adjustable or selectable. Fig. 1 Battery Charging Characteristics Resulting from a SS6781A-Controlled Charger with a Fluctuating Charging Current 1/11/2005 Rev.2.10 www.SiliconStandard.com 1 of 18 SS6781A(G) Discharge-before-charge function is included to eliminate memory effects of NiCd batteries without the risk of overdischarging. Test mode is provided for charger manufactures to dramatically reduce production test time. TYPICAL APPLICATION CIRCUIT D1 R1 1K IN4148 C2 1µF R5 120/0.5W U1 R4 390K 1 2 3 C1 470P SS6563 4 DC DE CF GND 8 BOOST 7 IS 6 VCC 5 FB + C3 D3 IN4148 RS 0.3/1W BAT1 **BATTERY RX THERMISTOR R3 R2 L1 220µH + C5 C4 220µF D2 IN5819 20/5W LED1 R8 300K + R9 91K C9 4.7µF C7 0.1µF R10 100K YELLOW 1 PEAK 2 C10 47nF Q1 MPS2222A SW1 LED2 PB SW R12 100K DSW ICON LED2 LED1 GND SEL1 SEL2 MODE 16 15 14 13 12 11 10 9 R16 680 R17 680 GREEN RED LED3 270 U2 0.1µF R15 680 VBT 3 DIS 4 VTS 5 VCC 6 ADJ SEL3 TMR D4 1N5819 R14 + 200K C11 C8 R6 50K R11 7 8 R7 220µF RY C6 0.1µF 100µF R13 470K 0.1µF SS6781A 100K VIN 11~15V + U3 78L05 VOUT + VIN C12 1µF Q2 MMBT2222A C13 10µF GND **3~5 NiMH/NiCd cells. Note: Charge Current=0.3/RS Ampere Safety Timer: 80min Battery Charge Circuit for Fluctuating Charging Current Application 1/11/2005 Rev.2.10 www.SiliconStandard.com 2 of 18 SS6781A(G) ORDERING INFORMATION SS6781AXXXX P acking TR: Tape and reel TB: Tubes Package type N : P DIP-16 ( o nl y avai lable i n t u bes ) S: SO-16 C: Commercial grade G: , C ommercial, with P b-free lead finish (Available for SO-16 only) E xample: SS6781ACSTR à i n SO-1 6 s hip ped o n t ape and r ee l SS 67 81 A G STR à i n SO-1 6 w ith P b - fr ee l eads s hipped o n tape an d ree l T OP VIEW P EAK V BT D IS V TS V CC A DJ S EL3 T MR 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 D SW I CON L ED2 L ED1 G ND S EL1 S EL2 M ODE PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS Supply Voltage ............................................… … … … ........................................ 5.5V DC Voltage Applied on any pin ......................… … … … … ...................................... 5.5V Sink current of ICON pin, LED1 and LED2 pin .......................… … … .................. 20mA Operating Temperature Range .....................................… … … … … .............. 0°C~ 70°C Storage Temperature Range .............................................… … … … ...... -65°C~ 150°C TEST CIRCUIT VCC VOLTAGE SOURCE + YELLOW R1 560 PEAK VBT DIS DSW R3 ICON LED2 560 R4 560 VTS LED1 R5 560 GND VCC ADJ SEL3 100K R2 TMR SEL1 SEL2 MODE VCC VCC VCC RED GREEN ORANGE - + VOLTAGE SOURCE VCC VCC (5V) VCC V1 (0.95V) V2 (3V) SS6781A 1/11/2005 Rev.2.10 www.SiliconStandard.com 3 of 18 SS6781A(G) ELECTRICAL CHARACTERISTICS (TA=25°C, VCC=5V, unless otherwise specified.) PARAMETER Supply Voltage Supply Current Battery Low During Initial Timer After Initial Timer (SEL3>3V) (SEL33V) (SEL33V) Fig. 9 Temperature (°C) VBT (High) Limit vs. Temperature (SEL33V, After Initial Timer) Fig.15 Temperature (°C) VBT (Low) Limit vs. Temperature (SEL3 (VCC/2) + 0.4V, the suggested divider resistance of RA and RB for the corresponding number of battery cells are as below: 1/11/2005 Rev.2.10 www.SiliconStandard.com 10 of 18 SS6781A(G) TABLE 2 BATTERY CELLS 2~4 3~6 4~8 5~10 6~12 8~16 RA/RB 2 3.3 4.9 6.4 7.8 10.8 RA (KΩ) 240 300 300 300 310 390 RB (KΩ) 120 91 62 47 39 36 VBAT VCC 5 VCC 4 Thermistor 0.1µF C7 VTS Battery Temperature Measurement The SS6781A employs a negative temperature coefficient (NTC) thermistor to measure the battery’ temperature. The thermistor is inherently s nonlinear with respect to temperature. To reduce the effect of nonlinearity, a resistor-divider network in parallel with the thermistor is recommended. A typical application circuit is shown in Fig. 18. For SEL3 < (VCC/2) -0.4V, the suggested divider resistance of RA and RB for the corresponding number of battery cells are as below: TABLE 3 BATTERY CELLS 2 3 4 5 6 8 10 12 16 RA/RB 1 2 3 4 5 7 9 11 15 RA(KΩ) 240 240 240 300 300 360 360 390 410 RB (KΩ) 240 120 80 75 60 51 40 36 27 Rx SS6781A Ry 12 GND Fig. 18 Battery Temperature Sense Circuit with a Negative Temperature Coefficient (NTC) Thermistor 1/11/2005 Rev.2.10 www.SiliconStandard.com 11 of 18 SS6781A(G) Power ON LED Flash 3 Times If VBT in Normal Range Yes No LED's Display Abnormal, ICON ON, Safety Timer Reset Yes If SEL3>VCC-0.3V or VCC/2-0.4V>SEL3 >1.4V If VNTC0.29VCC No If SEL3>VCC-0.3V or VCC/2-0.4V>SEL3 >1.4V Yes LED's Display, Abnormal, ICON ON, Safety Timer Reset Yes No If Discharge Finished Yes If Discharge Enabled Battery Replacement No LED's Display Fast Charge, ICON OFF Safety Timer Counts No Yes Yes If Initial Timer Finished ∆T/∆t Detector, -∆V Detector, Peak timer are all Disabled No Yes If Peak Timer Period has Finished No If 0.25% Decline of VBT is Detected No Yes Yes LED's Display Battery Fulll, Fast Charge Finished, Trickle charge Starts Battery Replacement Yes If ∆T/ ∆ t has Reached Yes No No If Safety Timer Period has Finished No Yes Fig. 16 Function Flow Chart of SS6781A 1/11/2005 Rev.2.10 www.SiliconStandard.com 12 of 18 SS6781A(G) 65 The calculation for Rx and Ry in the circuit is as following. 66 67 68 69 70 5.9 5.7 5.5 5.3 5.2 5.0 34.0 31.6 29.5 27.5 25.8 24.3 Ry//RTH 0.29 VCC = x VCC Rx + (Ry// RTH) RTH= The resistance of thermistor at upper limit of temperature protection. Ry//R TL 0.72 VCC = x VCC Rx + (Ry// R TL ) RTL= The resistance of thermistor at lower limit of temperature protection. Substitution and rearranging the equations yield Rx= 2.061 × Ry = TABLE 5 Values of Rx and Ry at TL = -10°C TH (°C) 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Rx (kΩ) 11.4 11.0 10.6 10.2 9.8 9.5 9.1 8.8 8.5 8.2 7.9 7.6 7.4 7.1 6.9 6.7 6.4 6.2 6.0 5.8 5.6 Ry (kΩ) 95.6 85.0 76.2 68.9 62.8 57.5 52.9 48.8 45.3 42.1 39.4 36.8 34.6 32.5 30.7 29.0 27.4 26.0 24.6 23.4 22.2 RTL × RTH RTL − RTH 5 . 3 × RTL × RTH RTL − 6 . 3 RTH If temperature characteristic of the thermistor is like that of SEMITEC 103AT-2, the resistance of Rx and Ry is tabulated for different TL and TH as below. (Note: TL is lower temperature limit and TH is upper temperature limit.) TABLE 4 Values of Rx and Ry at TL = 0°C TH (°C) 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 Rx(kΩ) 10.1 9.7 9.4 9.0 8.7 8.4 8.1 7.8 7.5 7.2 7.0 6.8 6.5 6.3 6.1 Ry (kΩ) 551.1 300.7 204.8 153.9 122.8 101.8 86.5 75.0 66.0 58.7 52.8 47.8 43.6 39.9 36.8 Setting the ADJ Pin Voltage The slope of ∆T/∆t detection is determined by the ADJ pin voltage of the SS6781A. The calculation of ADJ pin voltage is shown in the following procedure, followed by an example. 1/11/2005 Rev.2.10 www.SiliconStandard.com 13 of 18 SS6781A(G) Procedure (a) First, determine the temperature protection limits TH and TL. Then, substitute TH & TL into the following equation: ∆VTS 0.72V CC − 0.29V CC 0.43V CC = = ∆TBASE TH − TL TH − TL (b) Determine the safety timer to obtain the value of ∆tBASE . 56(sec.) ∆tBASE(sec.) = × Safety Timer (min .) 80(min .) (c) Determine the expected slope of ∆T / ∆t at which temperature rises y°C in x seconds and fast charge is subsequently cut off. ∆T y = ∆t x (d) Calculate the value of VADJ ∆VTS ∆T VADJ = 30 × × × ∆tBASE ∆TBASE ∆t TABLE 6 S.T. 40 min. (2C) 80 min. (1C) 120 min. (0.67C) 160 min. (0.5C) 200 min. (0.4C) 240 min. (0.33C) ADJ pin Voltage (TL=0°C, TH=50°C) 0.75 1.0 1.25 (°C/min.) (°C/min.) (°C/min.) 0.45 0.60 0.75 0.90 1.35 1.80 2.25 2.70 1.20 1.80 2.40 3.01 3.61 1.50 2.25 3.01 3.76 4.51 ∆T / ∆t A similar table for temperature range from 0°C to 60°C is as below. TABLE 7 ADJ Pin Voltage (TL=0°C, TH=60°C) ∆T / ∆t S.T. 40 min. (2C) 80 min. (1C) 120 min. (0.67C) 160 min. (0.5C) 200 min. (0.4C) 240 min. (0.33C) 0.75 1.0 1.25 (°C/min.) (°C/min.) (°C/min.) 0.37 0.50 0.62 0.75 1.12 1.50 1.88 2.25 1.00 1.50 2.00 2.50 3.01 1.25 1.88 2.50 3.13 3.76 Example (a) Let TH=50°C, TL=0°C, VCC =5V. We have ∆VTS 0.43 × 5 = 0.043V/° C = ∆TBASE 50 − 0 which means that VTS decreases 43mV as temperature rises 1°C. (b) If safety timer is equal to 80 minutes, ∆tBASE is then 56 seconds. (c) If fast charge should be terminated when temperature rises 1°C in 60 seconds, then 1 ∆T/∆t = = 0.0166 60 (d) VADJ =30 x 0.043x 0.0166 x 56 = 1.2(V) If the temperature range is from 0°C to 50°C, the voltage of VADJ under different setting conditions should be set as tabulated below. VBT Range and Temperature Protection The acceptable voltage range of VBT pin and mode of temperature protection function is determined by the voltage of SEL3 pin, shown as the following: (a) SEL3 > VCC - 0.3V Acceptable VBT Range: Before initial timer: 0.16V~2.7V After initial timer: 0.69V~2.7V Temperature Protection Mode: Entering charge-suspending mode when temperature is either too low or too high, same as abnormal battery voltage. Latch for charge-suspending function is provided for high temperature protection, but not for low temperature protection. 1/11/2005 Rev.2.10 www.SiliconStandard.com 14 of 18 SS6781A(G) (b) VCC - 1.4V> SEL3 > V cc + 0.4V 2 of the commonly chosen safety timer periods. Also shown in the table are their corresponding oscillator frequencies. 800 Acceptable VBT Range: Before initial timer: 0.16V~2.7V After initial timer: 0.69V~2.7V 600 Temperature Protection Mode: If temperature is too high, battery charging is regarded as completed. If temperature is too low, function of ∆T/∆t detection is disabled, just as thermistor is not existing. RTMR (KΩ) 400 200 0 0 100 200 300 400 500 V cc (c) - 0.4V>SEL3 >1.4V 2 Acceptable VBT Range: Before initial timer: 0.16V~2V After initial timer: 1.2V~2V Temperature Protection Mode: Entering as charge-suspending battery protection, mode when for low temperature is either too low or too high, same abnormal voltage. but not Latch for charge-suspending function is provided for high temperature temperature protection. (d) 0.3V> SEL3 Acceptable VBT Range: Before initial timer: 0.16V~2V After initial timer: 1.2V~2V Temperature Protection Mode: If temperature is too high, battery charging is regarded as completed. If temperature is too low, function of ∆T/∆t detection is disabled, just as thermistor is not existing. Setting the Period of Safety Timer The SS6781A provides a method for linearly adjusting the period of safety timer with an external resistor connected from TMR pin to GND. The relation between safety timer length and the external resistor (RTMR) is shown in Fig. 19. The table following shows the resistor values for some Safety Timer (min.) Fig. 19 TABLE 8 RTMR (kΩ) 11 23 48 74 100 152 206 314 491 667 OSC. Freq.(KHz) 256 131 65.8 43.1 32.8 21.6 16.0 10.6 6.89 5.04 Safety timer (min.) 10 20 40 60 80 120 160 250 380 520 Safety Timer vs. RTMR Selecting Mode of Operation The SS6781A provides three modes of operation: normal, test, and AC mode determined by the setting of MODE pin according to TABLE 9. The SS6781A will operate normally when the MODE pin is left floating (a 0.1µF capacitor is recommended to be tied to MODE pin if the charge circuit works in a noisy environment). When the MODE pin is biased to GND, the function of -∆V detection is disabled. When the MODE pin is biased to VCC, the SS6781A enters the test mode. The test mode can be used to significantly reduce production test time. For relevant information, please contact SSC directly. 1/11/2005 Rev.2.10 www.SiliconStandard.com 15 of 18 SS6781A(G) TABLE 9 MODE pin VCC Floating GND The Operating Mode of SS6781A Mode Test Function Safety timer period scaled down to 1/32....etc. -∆V detection disabled TYPE 2 Power ON LED1 LED2 1Hz 1Hz Charge Fault Fast Charging Completed Conditions ON 4Hz Flashing OFF ON 4Hz Flashing OFF Normal Normal operation AC The Mode of LED Display and Trickle Charge The SS6781A provides two LED display modes and five-pulsed trickle charge modes. The tri-level inputs, SEL1 and SEL2 pins, as in the TABLE 6 determine the modes of LED display and trickle charge. TABLE 10 Mode of LED Display and Trickle Charge SEL1 SEL2 VCC VCC Floating GND VCC Floating Floating GND VCC GND Floating GND Trickle Charge LED Display Duty Mode N/A 1/32 1/64 1/128 1/256 N/A 1/32 1/64 1/128 Type 1 Type 1 Type 1 Type 1 Type 1 Type 2 Type 2 Type 2 Type 2 Charging Current Control As shown in the typical application circuit, the SS6781A offers an open-drained output pin, ICON pin, to control the charging current flow in fast charge state and switch on to inhibit the charging current flow in fault conditions. When fast charge is completed, the SS6781A enters the trickle charge mode. In trickle charge mode, the ICON pin output switches with predetermined duty cycle. Refer to the table of trickle charge mode (TABLE 6), the duty cycle is determined by the setting of SEL1 and SEL2 pins. The following table summarizes how ICON pin corresponds to various charging states. Fast Charge Fault Power ON Charging Completed Conditions ICON ON OFF See pin 10 & 11 ON Display the Battery Charging Status The SS6781A provides two open-drain Test Mode Fig. 20 shows the timing diagram for externally controlled PEAK, ADJ, VBT, VTS, SEL1 and SEL2 pin voltages of a recommended SS6781A test scheme, utilizing TEST mode function. Output waveforms of LED1, LED2 and ICON of a properly functioning SS6781A are also shown in the figure. outputs, LED1 and LED2, to indicate the battery charging status. Refer to the table of LED display mode (TABLE 10), depending on the setting of SEL1 and SEL2 pins, the outputs of LED1 and LED2 pins are shown in the following table: TYPE 1 Fast Charge Fault Power ON Charging Completed Conditions LED1 LED2 1Hz OFF ON OFF OFF ON OFF OFF 1/11/2005 Rev.2.10 www.SiliconStandard.com 16 of 18 SS6781A(G) TIMING DIAGRAM VCC, SEL3, MODE=5V, (DSW FREQ.=820kHz, 25 TIMES of 32.8k) Power Init. ON PEAK TIMER TEST -∆V TEST 0V ∆T/∆t INITIAL TIMER ∆T/∆t TEST SAFETY TIMER TEST PEAK 5V 5V ADJ 3V 1.12V