BQ2000PWRG4

bq2000 www.ti.com SLUS138D – JANUARY 2008 – REVISED DECEMBER 2009 Programmable Multi-Chemistry Fast-Charge Management IC Check for Samples: bq2000 FEATURES 1 • • • • • • • • Safe Management of Fast Charge for NiCd, NiMH, or Li-Ion Battery Packs High-Frequency Switching Controller for Efficient and Simple Charger Design Pre-Charge Qualification for Detecting Shorted, Damaged, or Overheated Cells Fast-Charge Termination by Peak Voltage (PVD) for Nickel chemistries, Minimum Current for Li-Ion chemistries, Maximum Temperature, and Maximum Charge Time Selectable Top-Off Mode for Achieving Maximum Capacity in NiMH Batteries Programmable Trickle-Charge Mode for Reviving Deeply Discharged Batteries and for Postcharge Maintenance Built-in Battery Removal and Insertion Detection Sleep Mode for Low Power Consumption APPLICATIONS • • • Multi-Chemistry Charger Nickel Charger High-Power, Multi-Cell Charger GENERAL DESCRIPTION The bq2000 is a programmable, monolithic IC for fast-charge management of nickel cadmium (NiCd), nickel metal-hydride (NiMH), or lithium-ion (Li-Ion) batteries in single- or multi-chemistry applications. The bq2000 chooses the proper battery chemistry (either nickel or lithium) and proceeds with the optimal charging and termination algorithms. This process eliminates undesirable, undercharged, or overcharged conditions, and allows accurate and safe termination of fast charge Depending on the chemistry, the bq2000 provides a number of charge termination criteria: • Peak voltage, PVD (for NiCd and NiMH) • Minimum charge current (for Li-Ion) • Maximum temperature • Maximum charge time For safety, the bq2000 inhibits fast charge until the battery voltage and temperature are within user-defined limits. If the battery voltage is below the low-voltage threshold, the bq2000 uses trickle-charge to condition the battery. For NiMH batteries, the bq2000 provides an optional top-off charge to maximize the battery capacity. The integrated high-speed comparator allows the bq2000 to be the basis for a complete, high-efficiency battery charger circuit for both nickel-based and lithium-based chemistries. 8-Pin DIP or Narrow SOIC or TSSOP spacer between para and illustration Pin Names SNS Current-sense input SNS 1 8 MOD VSS System ground VSS 2 7 VCC LED Charge-status output BAT Battery-voltage input LED 3 6 RC TS Temperature-sense input BAT 4 5 TS RC Timer-program input VCC Supply-voltage input MOD Modulation-control output 1 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2008–2009, Texas Instruments Incorporated bq2000 SLUS138D – JANUARY 2008 – REVISED DECEMBER 2009 www.ti.com These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. PIN DESCRIPTIONS SNS Current-sense input Enables the bq2000 to sense the battery current via the voltage developed on this pin by an external sense-resistor connected in series with the battery pack VSS System Ground Connect to the battery’s negative terminal LED Charge-status output Open-drain output that indicates the charging status by turning on, turning off, or flashing an external LED, driven through a resistor. BAT Battery-voltage input Battery-voltage sense input. A simple resistive divider, across the battery terminals, generates this input. TS Temperature-sense input Input for an external battery-temperature monitoring circuit. An external resistive divider network with a negative temperature-coefficient thermistor sets the lower and upper temperature thresholds. RC Timer-program input Used to program the maximum fast charge-time, maximum top-off charge-time, hold-off period, trickle charge rate, and to disable or enable top-off charge. A capcitor from VCC and a resistor to ground connect to this pin. VCC Supply-voltage input Recommended bypassing is 10µF + 0.1µF to 0.22µF of decoupling capacitance near the pin. MOD Modulation-control output Push-pull output that controls the charging current to the battery. MOD switches high to enable charging current to flow and low to inhibit charging-current flow. 2 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): bq2000 bq2000 www.ti.com SLUS138D – JANUARY 2008 – REVISED DECEMBER 2009 FUNCTIONAL DESCRIPTION The bq2000 is a versatile, multi-chemistry battery charge control device. See Figure 1 for a functional block diagram and Figure 2 for a state diagram. TS Voltage Reference BAT OSC Voltage Comparators 3x ADC PVD ALU Clock Phase Generator Timer Charge Control LED Voltage Comparators MOD RC Internal OSC SNS VCC VSS Figure 1. Functional Block Diagram Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): bq2000 3 bq2000 SLUS138D – JANUARY 2008 – REVISED DECEMBER 2009 www.ti.com VCC Reset or Battery Replacement at any time 4.0 V < VCC < 6.0 V Charge Initialization VBAT < VSLP VMCV < VBAT < VSLP Battery Voltage (Voltage at BAT pin checked continuously. PVD checked at rate of MTO/128.) Sleep Mode Charge Qualification State VSLP < VBAT < VCC VBAT < VMCV VTS > VHTF Charge Suspended Battery Temperature (Temperature at TS pin checked continuously) VTS < VHTF VTS < VHTF VLBAT < VBAT < VMCV and VHTF < VTS < VLTF VBAT < VLBAT or VTS > VLTF VTS > VLTF Battery Conditioning Current Regulation VLBAT < VBAT and VHTF < VTS < VLTF PVD (after hold-off period), or VTS < VTCO or Time = MTO NO Trickle Maintenance Charge Top-Off Selected? VTS > VLTF Fast Charge State VTS > VLTF Time < MTO and VBAT reaches VMCV Voltage Regulation YES Current Taper (IBAT < Imin). or Time = 2 x MTO or VTS < VTCO VTS < VLTF and Time < MTO VTS > VHTF Top-Off Time = MTO VBAT ≥ VMCV Done VBAT ≥ VMCV VTS < VHTF Charge Suspended (See Note) VTS < VHTF VTS > VHTF and Time < MTO VCC Reset or Battery Replacement or Capacity Depletion (Li-lon) NOTE: If VTS < VTCO at any time, may only return to Trickle Maintenance Charge state and not to Top-Off. Figure 2. State Diagram 4 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): bq2000 bq2000 www.ti.com SLUS138D – JANUARY 2008 – REVISED DECEMBER 2009 ABSOLUTE MAXIMUM RATINGS (1) VALUE UNIT –0.3 to 7 V –0.3 to VCC V Operating ambient temperature –20 to 70 °C Storage temperature –40 to 125 °C 260 °C VCC VCC relative to VSS VT DC voltage applied on any pin, relative to VSS TOPR TSTG TSOLDER Soldering temperature (10 s max.) (1) Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional operation should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Exposure to conditions beyond the operational limits for extended periods of time may affect device reliability. DC THRESHOLDS (1) TA = TOPR; VCC = 5V ±20% (unless otherwise specified) PARAMETER TEST CONDITIONS TYPICAL TOLERANCE UNIT VTCO Temperature cutoff Voltage at the TS pin 0.225 × VCC ±5% V VHTF High-temperature fault Voltage at the TS pin 0.25 × VCC ±5% V VLTF Low-temperature fault Voltage at the TS pin 0.5 × VCC ±5% V VMCV Maximum cell voltage Voltage at the BAT pin 2.00 ±0.75% VLBAT Minimum cell voltage Voltage at the BAT pin 950 ±5% mV PVD BAT input change for PVD detection Voltage at the BAT pin 3.8 ±20% mV VSNSHI High threshold at SNS Voltage at the SNS pin 50 ±10 mV VSNSLO Low threshold at SNS Voltage at the SNS pin –50 ±10 mV VSLP Sleep-mode input threshold Voltage at the BAT pin VCC–1 ±0.5 V VRCH Recharge threshold Voltage at the BAT pin VMCV–0.1 ±0.02 V (1) V All voltages are relative to VSS except as noted. RECOMMENDED DC OPERATING CONDITIONS over operating free-air temperature range (unless otherwise noted) TEST CONDITIONS VCC Supply voltage ICC Supply current Exclusive of external loads ICCS Sleep current VBAT = VSLPM VTS Thermistor input VTS < 0.5 V prohibited VOH Output high input MOD, IOH = 10 mA VOL Output low input MOD, LED, IOL = 10 mA IOZ High-impedance leakage current LED Isnk Sink current MOD, LED RMTO Charge timer resistor CMTO Charge timer capacitor MIN TYP MAX 4 5 6 V 0.5 1 mA 5 µA VCC V 0.5 UNIT VCC–0.4 V 0.2 V 5 µA 20 mA 2 250 kΩ 0.001 1 µF IMPEDANCE PARAMETER MIN TYP MAX UNIT RBAT Battery input impedance 10 MΩ RTS TS input impedance 10 MΩ RSNS SNS input impedance 10 MΩ TIMING TA = TOPR; VCC = 5 V ±20% (unless otherwise noted) PARAMETER dMTO MTO time-base variation fTRKL Pulse-trickle frequency MIN TYP –5% 0.9 MAX UNIT 5% 1 1.1 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): bq2000 Hz 5 bq2000 SLUS138D – JANUARY 2008 – REVISED DECEMBER 2009 www.ti.com Initiation and Charge Qualification The bq2000 initiates a charge cycle when it detects • Application of power to VCC • Battery replacement • Exit from sleep mode • Capacity depletion (Li-Ion only) Immediately following initiation, the IC enters a charge-qualification mode. The bq2000 charge qualification is based on battery voltage and temperature. If the voltage on the BAT pin is less than the internal threshold, VLBAT, the bq2000 enters the battery conditioning state. This condition indicates the possibility of a defective or shorted battery pack. In an attempt to revive a fully depleted pack, the bq2000 enables the MOD pin to trickle-charge at a rate of once every 1.0s. As explained in the section "Top-Off and Pulse-Trickle Maintenance Charge," the trickle pulse-width is user-selectable and is set by the value of the resistance connected between the RC pin and VSS. During charge qualification, the LED pin blinks at a 1Hz rate, indicating the pending status of the charger. Once battery conditioning (trickle charge) has raised the voltage on the BAT pin above VLBAT, the IC enters fast charge, if the battery temperature is within the VLTF to VHTF range. The BQ2000 will stay in the battery conditioning state indefinitely and will not progress to fast charge until the voltage on the BAT pin is above VLBAT and the temperature is within the VLTF and VHTF range. No timer is implemented during battery conditioning. Battery Chemistry The bq2000 detects the battery chemistry by monitoring the battery-voltage profile during the initial stage of the fast charge. If the voltage on the BAT pin rises to the internal VMCV reference, the IC assumes a Li-Ion battery. Otherwise, the bq2000 assumes a NiCd/NiMH chemistry. While in the fast charge state, the LED pin is pulled low (the LED is on). As shown in Figure 3, a resistor voltage-divider between the battery pack's positive terminal and VSS scales the battery voltage. A low-pass filter then smooths out this voltage to present a clean signal to the BAT pin. In a mixed-chemistry design, a common voltage-divider is used as long as the maximum charge voltage of the nickel-based pack is below that of the Li-Ion pack. Otherwise, different scaling is required. BAT+ 2 VSS bq2000 4 RB1 BAT RB2 Figure 3. Battery Voltage Divider and Filter Once the chemistry is determined, the bq2000 completes the fast charge with the appropriate charge algorithm (Table 1). The user can customize the algorithm by programming the device using an external resistor and a capacitor connected to the RC pin, as discussed in later sections. NiCd and NiMH Batteries Following charge qualification (which includes trickle charge, if required ), the bq2000 fast-charges NiCd or NiMH batteries using a current-limited algorithm. During the fast-charge period, it monitors charge time, temperature, and voltage for adherence to the termination criteria. This monitoring is further explained in later sections. Following fast charge, the battery is topped off, if top-off is selected. The charging cycle ends with a trickle maintenance-charge that continues as long as the voltage on the BAT pin remains below VMCV. 6 Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): bq2000 bq2000 www.ti.com SLUS138D – JANUARY 2008 – REVISED DECEMBER 2009 Lithium-Ion Batteries The bq2000 uses a two-phase fast-charge algorithm for Li-Ion batteries (Figure 4). In phase one, the bq2000 regulates constant current until VBAT rises to VMCV. Once VBAT = VMCV, the device identifies the cell as a Li-ion, and changes the termination method from PVD to minimum current. The bq2000 then moves to phase two, regulates the battery with constant voltage of VMCV, and terminates when the charging current falls below the IMIN threshold or the timer expires (whichever happens first). A new charge cycle is started if the cell voltage falls below the VRCH threshold. Current IMAX Charge Qualification VMCV Voltage Fast Charge Phase 1 VLBAT Phase 2 Voltage Trickle Current IMIN Time Figure 4. Lithium-Ion Charge Algorithm During the current-regulation phase, the bq2000 monitors charge time, battery temperature, and battery voltage for adherence to the termination criteria. During the final constant-voltage stage, in addition to the charge time and temperature, it monitors the charge current as a termination criterion. There is no post-charge maintenance mode for Li-Ion batteries. Table 1 summarizes the charging process for both Nickel and Li-Ion batteries. Table 1. Charge Algorithm BATTERY CHEMISTRY CHARGE ALGORITHM 1. Charge qualification 2. Trickle charge, if required NiCd or NiMH (VBAT < VMCV always) 3. Fast charge (constant current) 4. Charge termination (peak voltage, maximum charge time = 1 MTO) 5. Top-off (optional) 6. Trickle charge 1. Charge qualification 2. Trickle charge, if required Li-Ion (VBAT ≤ VMCV ) 3. Fast charge (constant current) 4. Fast charge (constant voltage) 5. Charge termination (minimum current, maximum charge time = 2 MTO) FAST CHARGE TERMINATION Initial Hold-OFF Period The bq2000 incorporates a user programmable hold-off period to avoid premature fast charge termination that can occur with brand new cells at the very beginning of fast charge. The values of the external resistor and capacitor connected to the RC pin set the initial hold-off period. During this period, the bq2000 avoids early termination due to an initial peak in the battery voltage by disabling the peak voltage-detection (PVD) feature. This period is fixed at the programmed value of the maximum charge time (MTO) divided by 32. Submit Documentation Feedback Copyright © 2008–2009, Texas Instruments Incorporated Product Folder Link(s): bq2000 7 bq2000 SLUS138D – JANUARY 2008 – REVISED DECEMBER 2009 hold-off period = www.ti.com MTO 32 (1) Maximum Charge Time (NiCD, NiMH, and Li-Ion) The bq2000 sets the maximum charge-time through the RC pin. With the proper selection of external resistor and capacitor values, various time-out values may be achieved. If the timer expires while still in constant-current charging, the bq2000 assumes a Nickel chemistry and proceeds to top-off charge (if top-off is enabled) or trickle maintenance charge. Figure 5 shows a typical connection. 2 VSS VCC 7 bq2000 CMTO RC 6 RMTO Figure 5. Typical Connection for the RC Input The following equation shows the relationship between the RMTO and CMTO values and the maximum charge time (MTO) for the bq2000: MTO = RMTO ´ CMTO ´ 35,988 (2) MTO is measured in minutes, RMTO in ohms, and CMTO in farads. (Note: RMTO and CMTO values also determine other features of the device. See Table 4 and Table 5 for details. If, during fast charge, VTS > VLTF, then the timer is paused and the IC enters battery conditioning charge until VTS < VLTF. Since the IC is in the battery conditioning state, the LED flashes at the 1 Hz rate. Once VTS