BQ24400DR

bq24400 www.ti.com SLUS498A – SEPTEMBER 2001 – REVISED FEBRUARY 2010 Programmable NiCd/NiMH Fast-Charge Management IC Check for Samples: bq24400 FEATURES 1 • • • • • • • • Safe Management of Fast Charge for NiCd and NiMH 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), 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 • • Nickel Charger High-Power, Multi-Cell Charger 8-Pin DIP or Narrow SOIC or TSSOP GENERAL DESCRIPTION The bq24400 is a programmable, monolithic IC for fast-charge management of nickel cadmium (NiCd) and nickel metal-hydride (NiMH) in single or multi-cell applications. The bq24400 provides these charge termination criteria: • Peak voltage, PVD • Maximum temperature • Maximum charge time For safety, the bq24400 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 bq24400 uses trickle-charge to condition the battery. For NiMH batteries, the bq24400 provides an optional top-off charge to maximize the battery capacity. The integrated high-speed comparator allows the bq24400 to be the basis for a complete, high-efficiency battery charger circuit for nickel-based chemistries. 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 © 2001–2010, Texas Instruments Incorporated bq24400 SLUS498A – SEPTEMBER 2001 – REVISED FEBRUARY 2010 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 bq24400 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 capacitor 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 © 2001–2010, Texas Instruments Incorporated Product Folder Link(s): bq24400 bq24400 www.ti.com SLUS498A – SEPTEMBER 2001 – REVISED FEBRUARY 2010 FUNCTIONAL DESCRIPTION The bq24400 is a versatile, NiCd and NiMH 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 © 2001–2010, Texas Instruments Incorporated Product Folder Link(s): bq24400 3 bq24400 SLUS498A – SEPTEMBER 2001 – REVISED FEBRUARY 2010 www.ti.com VCC Reset or Battery Replacement at any time 4.0 V < VCC < 6.0 V Charge Initialization VBAT < VSLP Battery Voltage (Voltage at BAT pin checked continuously. PVD checked at rate of MTO/128.) Sleep Mode VMCV < VBAT < VSLP 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 Fast Charge State Top-Off Selected? VTS > VLTF YES 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 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 © 2001–2010, Texas Instruments Incorporated Product Folder Link(s): bq24400 bq24400 www.ti.com SLUS498A – SEPTEMBER 2001 – REVISED FEBRUARY 2010 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 ±2.5% 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 (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 = VSLP 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 © 2001–2010, Texas Instruments Incorporated Product Folder Link(s): bq24400 Hz 5 bq24400 SLUS498A – SEPTEMBER 2001 – REVISED FEBRUARY 2010 www.ti.com Initiation and Charge Qualification The bq24400 initiates a charge cycle when it detects • Application of power to VCC • Battery replacement • Exit from sleep mode Immediately following initiation, the IC enters a charge-qualification mode. The bq24400 charge qualification is based on battery voltage and temperature. If the voltage on the BAT pin is less than the internal threshold, VLBAT, the bq24400 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 bq24400 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 bq24400 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. Fast Charge (Current Regulation) Following charge qualification (which includes trickle charge, if required), the bq24400 begins fast charge fast 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. While in the fast charge state, the LED pin is pulled low (the LED is on). 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. Table 1 summarizes the charging process. Table 1. Charge Algorithm BATTERY CHEMISTRY CHARGE ALGORITHM 1. Charge qualification 2. Trickle charge, if required NiCd or NiMH Batteries (VBAT < VMCV always) 3. Fast charge (constant current) 4. Fast charge termination (peak voltage, maximum charge time = 1 MTO) 5. Top-off (optional) 6. Trickle charge FAST CHARGE TERMINATION Initial Hold-Off Period The bq24400 incorporates a user programmable hold-off period to avoid premature fast charge termination that can occur with brand new nickel 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 bq24400 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. MTO hold-off period = 32 (1) 6 Submit Documentation Feedback Copyright © 2001–2010, Texas Instruments Incorporated Product Folder Link(s): bq24400 bq24400 www.ti.com SLUS498A – SEPTEMBER 2001 – REVISED FEBRUARY 2010 Maximum Charge Time The bq24400 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 fast charge, the bq24400 proceeds to top-off charge (if top-off is enabled) or trickle maintenance charge. If top-off is enabled, the timer is reset on the completion of fast charge before beginning top-off charge. Figure 3 shows a typical connection. 2 VSS VCC 7 bq24400 CMTO RC 6 RMTO Figure 3. 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 bq24400: 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 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