SM6781BV 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. ■ ■ ■ ■ ■ ■ 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) TIME CHGN LEDN INH BATT NC SM6781BV 8-pin VSOP PACKAGE DIMENSIONS (Unit: mm) 0 to 10 ° 4.4 ± 0.2 Package + 0.1 .05 0.15 − 0 0.575TYP 3.1 ± 0.3 1.15 ± 0.05 Device VDD VSS ORDERING INFORMATION 0.5 ± 0.2 ■ 6.4 ± 0.3 ■ PINOUT 0.65 0.10 0.1 ± 0.05 FEATURES 0.22 ± 0.1 0.12 M SEIKO NPC CORPORATION —1 SM6781BV BLOCK DIAGRAM VDD DC Input VDD TIME 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 Charge Control Logic INH SW LED Driver OSC NC VSS PIN DESCRIPTION Number 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 or when INH is HIGH. 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 Charge 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. SEIKO NPC CORPORATION —2 SM6781BV SPECIFICATIONS Absolute Maximum Ratings VSS = 0V Parameter Symbol Condition Rating Unit Supply voltage range VDD − 0.3 to 7.0 V Input voltage range VIN − 0.3 to 7.0 V Storage temperature range Tstg − 55 to 125 °C Operating temperature range Topr – 25 to 85 °C Power dissipation PD 150 mW DC Characteristics 1 VDD = 4.0 to 5.5V, VSS = 0V, Ta = 25°C Parameter Symbol Condition Rating Variation Unit Minimum battery voltage VMNV VBATT < VMNV quick charge cutoff or prohibition 0.6 ± 0.2 V Maximum battery voltage VMXV VBATT > VMXV quick charge cutoff or prohibition 2.0 ± 0.1 V DC Characteristics 2 VDD = 4.0 to 5.5V, VSS = 0V, Ta = 0 to 85°C unless otherwise noted. Rating Parameter Symbol Condition Unit min typ max VDD supply voltage VDD 4.0 5.0 5.5 V BATT input voltage VBATT 0 – VDD V INH HIGH-level input voltage VIH1 VDD − 0.5 – – V INH LOW-level input voltage VIL1 – – 0.5 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 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 SEIKO NPC CORPORATION —3 SM6781BV Maximum Quick Charging Time VDD = 5V, Ta = 25°C TIME pin min typ max Unit HIGH 192 240 288 min MIDDLE 96 120 144 min LOW 64 80 96 min min typ max Unit – –4 – mV min typ max Unit 720 900 1080 sec –∆V Detection Voltage VDD = 5V, Ta = 25°C –∆V detection voltage –∆V detection prohibit time VDD = 5V, Ta = 25°C –∆V detection prohibit time SEIKO NPC CORPORATION —4 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 Abnormal battery voltage detection or INH = HIGH Battery voltage check start (Abnormal battery voltage detection at VBATT ≥ 2V or 0.6V > VBATT) Continuously battery voltage check operation Maximum quick charge time count stopped −∆V detection prohibit time count stopped Quick charge mode (−∆V detection prohibit condition) LEDN = LOW (ON) CHGN = High impedance Quick charge hold LEDN = High impedance (pulsing) CHGN = LOW Abnormal battery voltage detection or INH = HIGH NO −∆V detection prohibit time passed YES Quick charge mode (−∆V detection active condition) LEDN = LOW (ON) CHGN = High impedance NO − ∆V detection or Maximum quick charge time passed Abnormal battery voltage detection cleared (Return status in force before abnormal battery voltage detected) and INH = LOW Battery voltage check (Battery voltage: VBATT ≥ 2V or 0.6V > VBATT) CHGN = LOW (Quick charge current stop condition) YES NO INH = HIGH YES NO Peak voltage data clear YES Quick charge finished Battery voltage check stop LEDN = High impedance (OFF) CHGN = LOW Maximum quick charge time count restarted −∆V detection prohibit time count restarted Resume quick charge mode SEIKO NPC CORPORATION —5 SM6781BV Initialization The SM6781BV charging operation commences when power is applied or when a battery is inserted (standby mode released). When initialization finishes, the charging mode is determined by the BATT input voltage and the timer mode. Battery Voltage Check 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 resumed approximately 2.3 seconds after. When quick charge mode is restarted, the saved peak voltage data is reset (cleared to 0V). –∆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, abnormal battery voltage is detected, or INH is HIGH. Hi-Z CHGN Low Quick charge Stop/Hold/INH=High 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 LEDN Low Quick charge Abnormal battery voltage detect Stop/Hold, INH = High Figure 2. LEDN state Quick Charge Termination Quick charge finishes when either –∆V voltage is detected or the maximum charging time has elapsed. SEIKO NPC CORPORATION —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 Vpeak − ∆V detect Quick charge time Figure 3. Battery voltage change –∆V Detection A/D Converter The A/D converter employs dual slope A/D conversion, and converts samples taken approximately every 2.34 seconds. –∆V Detection Timing The –∆V detection and peak voltage detection are determined by the average value of 8 A/D converted samples. Consequently, –∆V detection timing occurs approximately every 18 seconds (8-sample length). 490ms max 8 2 1 7 3 8 Operation A/D convert Stop 2.34sec Averaging − ∆V detect Peak hold and compare 18sec 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 quick 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. Note that the saved peak voltage data (– ∆V) is reset (cleared to 0V). If INH is connected to temperature switch (NPC SM6611), it realizes simple temperature control. SEIKO NPC CORPORATION —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 (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 VDD Valid VDD − 0.5 VDD − 1.5 NG 2.0 Valid Valid 1.0 0.6 NG 0 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 SEIKO NPC CORPORATION —8 SM6781BV TYPICAL APPLICATION CIRCUIT (2 cells) VBB 12V R1 5.1kΩ 78L05 Q1 2SC945 IN OUT VSS 5V VBEQ2 Q2 2SD525 ICHG = R2 4Ω5W = 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 R4 100kΩ 2 1 4 VDD CHGN LEDN INH TIME NC VSS BATT 8 7 6 3 R8 200kΩ C1 1000pF R9 200kΩ R8 =N−1 R9 N= Number of cells Note that the above circuit is an example circuit to demonstrate the connections for device functions. Battery charger operation is not guaranteed. SEIKO NPC CORPORATION —9 SM6781BV Please pay your attention to the following points at time of using the products shown in this document. The products shown in this document (hereinafter “Products”) are not intended to be used for the apparatus that exerts harmful influence on human lives due to the defects, failure or malfunction of the Products. Customers are requested to obtain prior written agreement for such use from SEIKO NPC CORPORATION (hereinafter “NPC”). Customers shall be solely responsible for, and indemnify and hold NPC free and harmless from, any and all claims, damages, losses, expenses or lawsuits, due to such use without such agreement. NPC reserves the right to change the specifications of the Products in order to improve the characteristic or reliability thereof. NPC makes no claim or warranty that the contents described in this document dose not infringe any intellectual property right or other similar right owned by third parties. Therefore, NPC shall not be responsible for such problems, even if the use is in accordance with the descriptions provided in this document. Any descriptions including applications, circuits, and the parameters of the Products in this document are for reference to use the Products, and shall not be guaranteed free from defect, inapplicability to the design for the mass-production products without further testing or modification. Customers are requested not to export or re-export, directly or indirectly, the Products to any country or any entity not in compliance with or in violation of the national export administration laws, treaties, orders and regulations. Customers are requested appropriately take steps to obtain required permissions or approvals from appropriate government agencies. SEIKO NPC CORPORATION 1-9-9, Hatchobori, Chuo-ku, Tokyo 104-0032, Japan Telephone: +81-3-5541-6501 Facsimile: +81-3-5541-6510 http://www.npc.co.jp/ Email: [email protected] NC0026CE 2006.04 SEIKO NPC CORPORATION —10