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| SM6781BV NIPPON PRECISION CIRCUITS INC. Ni-MH/Ni-Cd Battery Charger IC OVERVIEW The SM6781BV is a quick charge control IC for Nickel Metal Hydride (NiMH) and Nickel-Cadmium (NiCd) rechargeable batteries. Quick charging ends in response to negative delta voltage detection (-V) and maximum charging time detection functions. Also, quick charge mode is placed on hold if the battery voltage becomes abnormal, until normal conditions are restored. The SM6781BV requires few external components to realize a high-stability quick charge battery charger. FEATURES I I PINOUT (Top view) pre lim ina I I I I I I Ni-MH/Ni-Cd battery quick charge control -V and maximum charge time cutoffs 15min (typ) -V detection invalid time - 4mV (typ) -V detection accuracy Inhibit function Charge condition LED indicator output (on, pulsed, off) Low power dissipation standby mode (< 1A) 8-pin VSOP package ORDERING INFORMATION Device Package SM6781BV 8-pin VSOP PACKAGE DIMENSIONS (Unit: mm) ry TIME CHGN INH NC VDD LEDN BATT VSS TBD NIPPON PRECISION CIRCUITS--1 SM6781BV BLOCK DIAGRAM VDD DC Input Current Source Reference Regulators BATT Max/Min Cell-voltage Check Battery Pack INH OSC Number 1 Name TIME lim I/O I O I - Ground - Supply - I No connection (must be open) O PIN DESCRIPTION Timer mode select input (3-level) HIGH and LOW levels applied using pull-up and pull-down, respectively. MID-level is applied using a voltage divider resistor network with voltage VDD/2. Charge status display LED driver output (open-drain output) LOW-level output in quick charge mode. 1Hz pulse output when abnormal battery voltage is detected during quick charge. High impedance when charging finishes. Battery voltage detector input. Connect a high-impedance resistor voltage divider between the poles of the battery for voltage detection. 2 LEDN 3 4 5 6 BATT VSS pre NC 7 INH 8 CHGN VDD Inhibit input Charging operation is stopped when HIGH. Charging recommences with the same charging parameters when INH goes LOW again. Charge control (open-drain output) High impedance output when charging current is flowing. LOW-level output when charging current stops. ina ry CHGN Timer Mode Selector CHG Driver A/D -V Function Block Timing Control Logic LEDN Charge Control Logic LED Driver NC VSS VDD TIME VDD Description NIPPON PRECISION CIRCUITS--2 SM6781BV SPECIFICATIONS Absolute Maximum Ratings VSS = 0V Parameter Supply voltage range Input voltage range Storage temperature range Operating temperature range Power dissipation Symbol VDD VIN Tstg Topr PD Condition Rating - 0.3 to 7.0 Unit V V DC Characteristics 1 VDD = 4.0 to 5.5V, VSS = 0V, Ta = 25C Parameter Minimum battery voltage Maximum battery voltage Symbol VMNV VMXV VBATT < VMNV charge cutoff or prohibition VBATT > VMXV charge cutoff or prohibition ina ry - 0.3 to 7.0 - 55 to 125 - 25 to 85 150 Condition Rating 0.6 2.0 Variation 0.2 0.1 Rating Condition min 4.0 0 0.7 - VDD - 0.5 (VDD/2) - 0.5 - 1 - VDD - 1.5 - - 10 - -5 typ 5.0 - - - - - - - 1 - - - - - - max 5.5 VDD - 0.1 - (VDD/2) + 0.5 0.5 2 - VDD - 0.5 0.5 1 - 1 - C C mW Unit V V DC Characteristics 2 VDD = 4.0 to 5.5V, VSS = 0V, Ta = 0 to 85C unless otherwise noted Parameter VDD supply voltage BATT input voltage lim Symbol VDD VBATT VIH1 VIL1 VIH2 VIM VIL2 VDET fLED VSTB IDD VDD = 5V, no load VDD = 5V, VBATT = VDD , no load VOL = VSS + 0.8V VINH = VTIME = VSS to VDD ISTB IOL IL IOZ Unit V V V V V V V V Hz V mA A mA A A INH HIGH-level input voltage INH LOW-level input voltage TIME HIGH-level input voltage TIME MID-level input voltage TIME LOW-level input voltage BATT -V detection voltage range pre LEDN output pulse frequency BATT standby voltage VDD current consumption VDD standby current LEDN, CHGN sink current INH, TIME input leakage current LEDN, CHGN output leakage current NIPPON PRECISION CIRCUITS--3 SM6781BV Maximum Quick Charging Time VDD = 5V, Ta = 25C TIME pin HIGH MIDDLE LOW min 192 96 64 typ 240 120 80 max 288 144 96 Unit min min min -V Detection Voltage VDD = 5V, Ta = 25C min -V detection voltage - -V detection prohibit time VDD = 5V, Ta = 25C min -V detection prohibit time 720 900 pre NIPPON PRECISION CIRCUITS--4 lim ina ry typ -4 max - Unit mV typ max Unit sec 1080 SM6781BV FUNCTIONAL DESCRIPTION Charging Flowchart Supply applied Standby mode released Initialization (approx. 200ms) Maximum quick charge time count start -V detection prohibit time count start Battery voltage check start (Abnormal battery voltage detection at VBATT 2V or 0.6V > VBATT) Continuously battery voltage check operation Quick charge mode (-V detection prohibit condition) LEDN = LOW (ON) CHGN = High impedance Abnormal battery voltage detection NO -V detection prohibit time passed YES Quick charge mode (-V detection active condition) LEDN = LOW (ON) CHGN = High impedance lim YES NO - V detection or Maximum quick charge time passed pre NIPPON PRECISION CIRCUITS--5 Quick charge finished Battery voltage check stop LEDN = High impedance (OFF) CHGN = LOW ina ry Abnormal battery voltage detection Maximum quick charge time count stopped -V detection prohibit time count stopped Quick charge hold LEDN = High impedance (pulsing) CHGN = LOW Abnormal battery voltage detection cleared (Return status in force before abnormal battery voltage detected) Battery voltage check (Battery voltage: VBATT 2V or 0.6V > VBATT) CHGN = LOW (Quick charge current stop condition) NO Peak voltage data clear Maximum quick charge time count restarted -V detection prohibit time count restarted Abnormal battery voltage detection cleared YES SM6781BV Initialization The SM6781BV charging operation commences when power is applied or when a battery is inserted (standby mode released). Approximately 200ms are required when operation starts to initialize all internal circuits. When initialization finishes, the charging mode is determined by the BATT input voltage and the timer mode. Battery Voltage Check -V Detection Prohibit Time -V detection is not performed for approximately 15 minutes from when quick charge commences (quick charge cumulative time). CHGN Output CHGN becomes high impedance during quick charge. CHGN goes LOW when quick charge mode finishes or when abnormal battery voltage is detected. Hi-Z CHGN Low LEDN Output LEDN is LOW during quick charge (LED is ON), and high impedance after quick charge finishes (LED is OFF). When an abnormal battery voltage is detected before quick charge finishes, a pulse of approximately 1Hz is output (LED flashes). Also, a 1Hz pulse is output when INH is HIGH. pre Quick Charge Termination Quick charge finishes when either -V voltage is detected or the maximum charging time has elapsed. lim Hi-Z LED OFF Low Approximately 200ms Power ON or Standby mode cancel Figure 2. LEDN output ina ry Quick charge Stop/Hold/INH=High Figure 1. CHGN state Depends on charge mode When the BATT input voltage is outside the permitted range, quick charge stops. At this point, the maximum quick charge time count and -V prohibit time counters also stop. When the BATT input voltage comes back within the permitted range, quick charge and timer stop conditions are released. When quick charge mode is restarted, the saved peak voltage data is reset (cleared to 0V). NIPPON PRECISION CIRCUITS--6 SM6781BV -V Detection Function A -V condition is detected when the BATT voltage (VBATT) falls 4mV (typ) or more below the peak battery voltage, at which point the battery is deemed to be fully charged and quick charge finishes (valid for 1V < VBATT < 2V). 4mV Figure 3. Battery voltage change -V Detection A/D Converter The A/D converter employs double integration A/D conversion, and converts samples taken approximately every 1.17 seconds. -V Detection Timing lim 490ms max 2 16 1 3 1.17sec Peak hold and compare 18.7sec The -V detection and peak voltage detection are determined by the average value of 16 A/D converted samples. Consequently, -V detection timing occurs approximately every 18 seconds (16-sample length). A/D convert - V detect pre Standby Mode Charge Inhibit (INH) Figure 4. -V detection and A/D convert When the BATT input voltage exceeds the standby voltage VSTB, the device enters standby mode. In this mode, the maximum charging time timer, -V detection prohibit timer, and peak voltage data are all reset to zero. At this time, the CHGN and LEDN outputs both become high impedance. When INH goes HIGH, charge mode operation stops. While INH is HIGH, the internal timer stops, CHGN goes LOW and LEDN outputs 1Hz pulse (LEDN flashes). When INH goes LOW, the SM6781BV is restored to the previous state and the internal timer restarts. If INH is connected to temperature switch (NPC SM6611), it realizes simple temperature control. ina ry Quick charge time - V detect Vpeak Cell voltage 15 16 Operation Stop Averaging Peak hold and compare NIPPON PRECISION CIRCUITS--7 SM6781BV BATT Input The voltage applied to the BATT input, used for battery voltage detection, is a voltage potential, derived by a voltage divider resistor network (100k or higher recommended) or other means, that represents the voltage of a single battery cell during charging. If a single cell only is under charge, a current limiting resistor (100k or higher is recommended) should be connected between the battery and BATT input. Current Source Ra N Rb BATT pin Ra =N-1 Rb N:Number of cells Figure 5. BATT connection example (multiple) Operating Mode vs. BATT Input Voltage Battery voltage [V] VDD - 0.5 VDD - 1.5 lim NG 2.0 1.0 0.6 NG 0 Conditions INH Battery check OK Yes No - CHGN output LOW High impedance LOW LOW LOW High impedance LOW HIGH LOW - Yes - Charging Operating Status pre Charging status Quick charge Quick charge hold Quick charge inhibit Quick charge finish Standby ina ry Current Source BATT pin 100k Figure 6. BATT connection example (single) Battery check Quick charge -V detect Standby mode Valid Valid Valid LEDN output Internal timer LOW (ON) 1Hz (pulsing) 1Hz (pulsing) High impedance (OFF) High impedance (OFF) Count Hold Hold Reset Reset NIPPON PRECISION CIRCUITS--8 SM6781BV TYPICAL APPLICATION CIRCUIT VBB 12V VDD 5V R5 1.8k 5 R3 100k SW1 R4 100k 2 1 4 lim Note that the above circuit is an example circuit to demonstrate the connections for device functions. Battery charger operation is not guaranteed. pre NIPPON PRECISION CIRCUITS--9 ina ry Q1 2SC945 IN OUT VSS Q2 2SD525 R2 4/5W ICHG = 5V VBEQ2 = 5 - 0.65 4 ICHG R6 33k Q3 2SC945 R7 100k R1 5.1k 78L05 5 - VBEQ2 R2 SM6781BV VDD CHGN 8 7 6 3 CPU or Temperature switch (SM6611) LEDN TIME INH NC VSS BATT R9 200k R10 200k R9 =N-1 R10 N= Number of cells SM6781BV NIPPON PRECISION CIRCUITS INC. reserves the right to make changes to the products described in this data sheet in order to improve the design or performance and to supply the best possible products. Nippon Precision Circuits Inc. assumes no responsibility for the use of any circuits shown in this data sheet, conveys no license under any patent or other rights, and makes no claim that the circuits are free from patent infringement. Applications for any devices shown in this data sheet are for illustration only and Nippon Precision Circuits Inc. makes no claim or warranty that such applications will be suitable for the use specified without further testing or modification. The products described in this data sheet are not intended to use for the apparatus which influence human lives due to the failure or malfunction of the products. Customers are requested to comply with applicable laws and regulations in effect now and hereinafter, including compliance with export controls on the distribution or dissemination of the products. Customers shall not export, directly or indirectly, any products without first obtaining required licenses and approvals from appropriate government agencies. NIPPON PRECISION CIRCUITS INC. 4-3, Fukuzumi 2-chome Koto-ku, Tokyo 135-8430, Japan Telephone: +81-3-3642-6661 Facsimile: +81-3-3642-6698 http://www.npc.co.jp/ Email: sales@npc.co.jp NP0026AE 2001.01 pre NIPPON PRECISION CIRCUITS INC. lim NIPPON PRECISION CIRCUITS--10 ina ry |
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