SM6781BV Ni-MH/Ni-Cd Battery Charger IC NIPPON PRECISION CIRCUITS INC. OVERVIEW FEATURES ■ PINOUT 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 (< 1µA) 8-pin VSOP package (Top view) pre lim ina ■ ry 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. ■ ■ ■ ■ ■ ■ TIME CHGN LEDN INH BATT NC VSS ORDERING INFORMATION Device Package SM6781BV 8-pin VSOP VDD PACKAGE DIMENSIONS (Unit: mm) TBD NIPPON PRECISION CIRCUITS—1 SM6781BV BLOCK DIAGRAM VDD DC Input TIME ina ry VDD CHGN Current Source Reference Regulators Timer Mode Selector CHG Driver VDD BATT Max/Min Cell-voltage Check A/D −∆V Function Block Timing Control Logic LEDN Battery Pack INH OSC Charge Control Logic LED Driver NC VSS lim PIN DESCRIPTION Name I/O Description 1 TIME I 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. 2 LEDN O 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. 3 BATT I Battery voltage detector input. Connect a high-impedance resistor voltage divider between the poles of the battery for voltage detection. 4 VSS – Ground 5 VDD – Supply 6 NC – No connection (must be open) 7 INH I Inhibit input Charging operation is stopped when HIGH. Charging recommences with the same charging parameters when INH goes LOW again. 8 CHGN O Charge control (open-drain output) High impedance output when charging current is flowing. LOW-level output when charging current stops. pre Number NIPPON PRECISION CIRCUITS—2 SM6781BV SPECIFICATIONS Absolute Maximum Ratings VSS = 0V Symbol Supply voltage range VDD Input voltage range VIN Storage temperature range Tstg Operating temperature range Topr Power dissipation PD Condition DC Characteristics 1 VDD = 4.0 to 5.5V, VSS = 0V, Ta = 25°C Parameter Symbol Rating Unit − 0.3 to 7.0 V − 0.3 to 7.0 V − 55 to 125 °C – 25 to 85 °C 150 mW ina ry Parameter Condition Rating Variation Unit Minimum battery voltage VMNV VBATT < VMNV charge cutoff or prohibition 0.6 ± 0.2 V Maximum battery voltage VMXV VBATT > VMXV charge cutoff or prohibition 2.0 ± 0.1 V DC Characteristics 2 Parameter lim VDD = 4.0 to 5.5V, VSS = 0V, Ta = 0 to 85°C unless otherwise noted Symbol Rating Condition Unit min typ max VDD 4.0 5.0 5.5 V VBATT 0 – VDD V INH HIGH-level input voltage VIH1 0.7 – – V INH LOW-level input voltage VIL1 – – 0.1 V TIME HIGH-level input voltage VIH2 VDD − 0.5 – – V TIME MID-level input voltage VIM (VDD/2) − 0.5 – (VDD/2) + 0.5 V TIME LOW-level input voltage VIL2 – – 0.5 V BATT −∆V detection voltage range VDET 1 – 2 V LEDN output pulse frequency fLED – 1 – Hz BATT standby voltage VSTB VDD − 1.5 – VDD − 0.5 V VDD supply voltage pre BATT input voltage VDD current consumption IDD VDD = 5V, no load – – 0.5 mA VDD standby current ISTB VDD = 5V, VBATT = VDD , no load – – 1 µA LEDN, CHGN sink current IOL VOL = VSS + 0.8V 10 – – mA INH, TIME input leakage current IL VINH = VTIME = VSS to VDD – – ±1 µA LEDN, CHGN output leakage current IOZ −5 – – µA NIPPON PRECISION CIRCUITS—3 SM6781BV Maximum Quick Charging Time VDD = 5V, Ta = 25°C min typ max Unit HIGH 192 240 288 min MIDDLE 96 120 144 min LOW 64 –∆V Detection Voltage VDD = 5V, Ta = 25°C min –∆V detection voltage – –∆V detection prohibit time VDD = 5V, Ta = 25°C min 720 80 96 min typ max Unit –4 – mV typ max Unit 900 1080 sec pre lim –∆V detection prohibit time ina ry TIME pin NIPPON PRECISION CIRCUITS—4 SM6781BV FUNCTIONAL DESCRIPTION Charging Flowchart Initialization (approx. 200ms) Maximum quick charge time count start −∆V detection prohibit time count start Abnormal battery voltage detection 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 ina ry Supply applied Standby mode released 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 NO −∆V detection prohibit time passed lim YES Quick charge mode (−∆V detection active condition) LEDN = LOW (ON) CHGN = High impedance NO Abnormal battery voltage detection cleared (Return status in force before abnormal battery voltage detected) − ∆V detection or Maximum quick charge time passed YES Battery voltage check (Battery voltage: VBATT ≥ 2V or 0.6V > VBATT) CHGN = LOW (Quick charge current stop condition) YES NO Peak voltage data clear Maximum quick charge time count restarted −∆V detection prohibit time count restarted Abnormal battery voltage detection cleared pre Quick charge finished Battery voltage check stop LEDN = High impedance (OFF) CHGN = LOW NIPPON PRECISION CIRCUITS—5 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 ina ry 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). –∆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 Quick charge Stop/Hold/INH=High lim Low Figure 1. CHGN state 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. Hi-Z LED OFF Depends on charge mode pre Low Approximately 200ms Power ON or Standby mode cancel Figure 2. LEDN output Quick Charge Termination Quick charge finishes when either –∆V voltage is detected or the maximum charging time has elapsed. 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 Cell voltage ina ry Vpeak − ∆V detect Quick charge time 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 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). 490ms max 16 1 2 3 15 16 Operation A/D convert Stop 1.17sec Averaging − ∆V detect pre Peak hold and compare 18.7sec Peak hold and compare Figure 4. –∆V detection and A/D convert Standby Mode 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. Charge Inhibit (INH) 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. NIPPON PRECISION CIRCUITS—7 SM6781BV BATT Input ina ry The voltage applied to the BATT input, used for battery voltage detection, is a voltage potential, derived by a voltage divider resistor network (100kΩ 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 (100kΩ or higher is recommended) should be connected between the battery and BATT input. Current Source Current Source BATT pin Ra 100kΩ N BATT pin Rb Ra =N−1 Rb N:Number of cells Figure 5. BATT connection example (multiple) Figure 6. BATT connection example (single) Operating Mode vs. BATT Input Voltage Battery voltage [V] Battery check Quick charge −∆V detect Standby mode lim VDD − 0.5 Valid VDD − 1.5 NG 2.0 Valid Valid 1.0 0.6 NG 0 pre Charging Operating Status Conditions Charging status Battery check OK CHGN output LEDN output Internal timer INH Quick charge LOW Yes High impedance LOW (ON) Count Quick charge hold LOW No LOW 1Hz (pulsing) Hold Quick charge inhibit HIGH – LOW 1Hz (pulsing) Hold Quick charge finish LOW Yes LOW High impedance (OFF) Reset – – High impedance High impedance (OFF) Reset Standby NIPPON PRECISION CIRCUITS—8 SM6781BV TYPICAL APPLICATION CIRCUIT VBB 12V 78L05 ina ry R1 5.1kΩ Q1 2SC945 IN Q2 2SD525 OUT VSS 5V VBEQ2 R2 4/5W ICHG = = 5 − VBEQ2 R2 5 − 0.65 4 ICHG VDD 5V R6 33kΩ R5 1.8kΩ Q3 2SC945 R7 100kΩ CPU or Temperature switch (SM6611) SM6781BV 5 R3 100kΩ SW1 1 4 LEDN INH TIME NC VSS BATT 8 7 6 3 lim R4 100kΩ 2 CHGN VDD R9 200kΩ R10 200kΩ R9 =N−1 R10 N= Number of cells pre Note that the above circuit is an example circuit to demonstrate the connections for device functions. Battery charger operation is not guaranteed. NIPPON PRECISION CIRCUITS—9 pre lim ina ry 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. 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: [email protected] NP0026AE 2001.01 NIPPON PRECISION CIRCUITS—10