UC2906 UC3906 Sealed Lead-Acid Battery Charger FEATURES • • • • DESCRIPTION Optimum Control for Maximum The UC2906 series of battery charger controllers contains all of the necessary Battery Capacity and Life circuitry to optimally control the charge and hold cycle for sealed lead-acid batteries. These integrated circuits monitor and control both the output voltage and curInternal State Logic Provides rent of the charger through three separate charge states; a high current Three Charge States bulk-charge state, a controlled over-charge, and a precision float-charge, or Precision Reference Tracks standby, state. Battery Requirements Over Optimum charging conditions are maintained over an extended temperature Temperature range with an internal reference that tracks the nominal temperature characControls Both Voltage and teristics of the lead-acid cell. A typical standby supply current requirement of only Current at Charger Output 1.6mA allows these ICs to predictably monitor ambient temperatures. • System Interface Functions • Typical Standby Supply Current of only 1.6mA Separate voltage loop and current limit amplifiers regulate the output voltage and current levels in the charger by controlling the onboard driver. The driver will supply up to 25mA of base drive to an external pass device. Voltage and current sense comparators are used to sense the battery condition and respond with logic inputs to the charge state logic. A charge enable comparator with a trickle bias output can be used to implement a low current turn-on mode of the charger, preventing high current charging during abnormal conditions such as a shorted battery cell. Other features include a supply under-voltage sense circuit with a logic output to indicate when input power is present. In addition the over-charge state of the charger can be externally monitored and terminated using the over-charge indicate output and over-charge terminate input. BLOCK DIAGRAM SLUS186 - SEPTEMBER 1996 ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage (+VIN). . . . . . . . . . . . . . . . . . . . . . . . . . . 40V Open Collector Output Voltages. . . . . . . . . . . . . . . . . . . 40V Amplifier and Comparator Input Voltages . . . -0.3V to +40V Over-Charge Terminate Input Voltage . . . . . . -0.3V to +40V Current Sense Amplifier Output Current . . . . . . . . . . 80mA Other Open Collector Output Currents. . . . . . . . . . . . 20mA Trickle Bias Voltage Differential with respect to VIN . . . -32V Trickle Bias Output Current . . . . . . . . . . . . . . . . . . . . -40mA Driver Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80mA Power Dissipation at TA = 25°C(Note 2) . . . . . . . . 1000mW Power Dissipation at TC = 25°C (Note 2) . . . . . . . . 2000mW Operating Junction Temperature . . . . . . . . -55°C to +150°C Storage Temperature . . . . . . . . . . . . . . . . . -65°C to +150°C Lead Temperature (Soldering, 10 Seconds) . . . . . . . 300°C Note 1: Voltages are referenced to ground (Pin 6). Currents are positive into, negative out of, the specified terminals. Note 2: Consult Packaging section of Databook for thermal limitations and considerations of packages. UC2906 UC3906 CONNECTION DIAGRAMS PLCC-20, LCC-20 (TOP VIEW) Q, L Packages PACKAGE PIN FUNCTION FUNCTION PIN N/C C/S OUT C/SC/S+ C/L N/C +VIN GROUND POWER INDICATE OVER CHARGE TERMINATE N/C OVER CHARGE INDICATE STATE LEVEL CONTROL TRICKLE BIAS CHARGE ENABLE N/C VOLTAGE SENSE COMPENSATION DRIVER SOURCE DRIVER SINK DIL-16, SOIC-16 (TOP VIEW) J or N Package, DW Package 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for TA = -40°C to +70°C for the UC2906 and 0°C to +70°C for the UC3906, +VIN = 10V, TA = TJ. PARAMETER TEST CONDITIONS UC2906 MIN UC3906 TYP MAX 1.6 2.5 MIN UNITS TYP MAX 1.6 2.5 mA Input Supply Supply Current +VIN = 10V +VIN = 40V Supply Under-Voltage Threshold +VIN = Low to High 4.2 Supply Under-Voltage Hysteresis 1.8 2.7 4.5 4.8 0.20 0.30 2.3 2.325 3 8 4.2 1.8 2.7 mA 4.5 4.8 V 0.20 0.30 V 2.3 2.330 V 3 8 mV Internal Reference (VREF) Voltage Level (Note 3) Measured as Regulating Level at Pin 13 w/ Driver Current = 1mA, TJ = 25°C Line Regulation +VIN = 5 to 40V 2.275 Temperature Coefficient 2.270 -3.9 -3.9 mV/°C Voltage Amplifier µA Input Bias Current Total Input Bias at Regulating Level -0.5 -0.2 -0.5 -0.2 Maximum Output Current Source -45 -30 -15 -45 -30 -15 µA Sink 30 60 90 30 60 90 µA Driver current = 1mA 50 65 50 65 Open Loop Gain dB Output Voltage Swing Volts above GND or below +VIN 0.2 0.2 V Note 3. The reference voltage will change as a function of power dissipation on the die according to the temperature coefficient of the reference and the thermal resistance, junction-to-ambient. 2 UC2906 UC3906 ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for TA = -40°C to +70°C for the UC2906 and 0°C to +70°C for the UC3906, +VIN = 10V, TA = TJ. PARAMETER TEST CONDITIONS UC2906 MIN UC3906 TYP MAX 2.0 2.2 MIN UNITS TYP MAX 2.0 2.2 Driver Minimum Supply to Source Differential Pin 16 = +VIN, IO = 10mA Maximum Output Current Pin 16 to Pin 15 = 2V 25 Saturation Voltage 40 25 40 V mA 0.2 0.45 0.2 0.45 V 0.2 1.0 0.2 1.0 µA Current Limit Amplifier Input Bias Current Threshold Voltage Offset below +VIN Threshold Supply Sensitivity +VIN = 5 to 40V 225 250 275 0.03 0.25 225 250 275 mV 0.03 0.25 %/V Voltage Sense Comparator Threshold Voltage As a function of VREF, L1 = RESET 0.945 0.95 0.955 0.945 0.95 0.955 V/V As a function of VREF, L1 = SET 0.895 0.90 0.905 0.895 0.90 0.905 V/V Input Bias Current Total Input Bias at Thresholds -0.5 -0.2 -0.5 -0.2 µA Current Sense Comparator Input Bias Current Input Offset Current Input Offset Voltage Referenced to Pin 2, IOUT = 1mA Offset Supply Sensitivity +VIN = 5 to 40V 20 Offset Common Mode Sensitivity CMV = 2V to +VIN Maximum Output Current VOUT = 2V Output Saturation Voltage IOUT = 10mA 25 0.1 0.5 0.01 0.2 25 30 20 µA 0.1 0.5 0.01 0.2 µA 25 30 mV 0.05 0.35 0.05 0.35 %/V 0.05 0.35 0.05 0.35 %/V 40 25 0.2 0.45 0.99 1.0 1.01 -0.5 25 40 mA 0.2 0.45 V 0.99 1.0 1.01 V/V -0.2 -0.5 -0.2 µA 40 25 40 mA Enable Comparator Threshold Voltage As a function of VREF Input Bias Current Trickle Bias Maximum Output Current VOUT = +VIN − 3V Trickle Bias Maximum Output Voltage Volts below +VIN, IOUT = 10mA Trickle Bias Reverse Hold-Off Voltage +VIN = 0V, IOUT = -10µA 2.0 6.3 7.0 0.7 1.0 2.6 2.0 6.3 7.0 0.7 1.0 2.6 V V Over-Charge Terminate Input Threshold Voltage Internal Pull-Up Current At Threshold 1.3 10 1.3 V µA 10 Open Collector Outputs (Pins 7, 9, and 10) Maximum Output Current VOUT = 2V Saturation Voltage IOUT = 1.6mA 0.25 0.45 0.25 0.45 IOUT = 50µA 0.03 0.05 0.03 0.05 V VOUT = 40V 1 3 1 3 µA Leakage Current 2.5 3 5 2.5 5 mA V UC2906 UC3906 the charger a low current turn on mode. The output current of the charger is limited to a low-level until the battery reaches a specified voltage, preventing a high current charging if a battery cell is shorted. Figure 2 shows the state diagram of the charger. Upon turn on the UV sense circuitry puts the charger in state 1, the high rate bulkcharge state. In this state, once the enable threshold has been exceeded, the charger will supply a peak current that is determined by the 250mV offset in the C/L amplifier and the sensing resistor RS. Internal Reference Temperature Characteristic and Tolerance To guarantee full re-charge of the battery, the charger’s voltage loop has an elevated regulating level, VOC, during state 1 and state 2. When the battery voltage reaches 95% of VOC, the charger enters the over-charge state, state 2. The charger stays in this state until the OVERCHARGE TERMINATE pin goes high. In Figure 1, the charger uses the current sense amplifier to generate this signal by sensing when the charge current has tapered to a specified level, IOCT. Alternatively the over-charge could have been controlled by an external source, such as a timer, by using the OVER-CHARGE INDICATE signal at Pin 9. If a load is applied to the battery and begins to discharge it, the charger will contribute its full output to the load. If the battery drops 10% below the float level, the charger will reset itself to state 1. When the load is removed a full charge cycle will follow. A graphical representation of a charge, and discharge, cycle of the dual lever float charger is shown in Figure 3. OPERATION AND APPLICATION INFORMATION Dual Level Float Charger Operations The UC2906 is shown configured as a dual level float charger in Figure 1. All high currents are handled by the external PNP pass transistor with the driver supplying base drive to this device. This scheme uses the TRICKLE BIAS output and the charge enable comparator to give Figure 1. The UC2906 in a Dual Level Float Charger 4 UC2906 UC3906 OPERATION AND APPLICATION INFORMATION (continued) Design procedure 1.) Pick divider current, ID. Recommended value is 50µA to 100µA. 2.) RC = 2.3V ⁄ ID 3.) RA + RB = RSUM = ( VF − 2.3V )⁄ ID 4.) RD = 2.3VRSUM ⁄ (VOC − VF ) 5.) RA = (RSUM + RX ) (1 −2.3V ⁄ VT) where: RX = RCRD ⁄ (RC + RD) 6.) RB = RSUM − RA 7.) RS = 0.25V ⁄ IMAX 8.) RT = ( VIN − VT − 2.5V ) ⁄ IT Note:V12 = 0.95VOC V31 = 0.90VF IOCT = IMAX 10 For further design and application information see UICC Application Note U-104 Figure 2. State Diagram and Design Equations for the Dual Level Float Charger Explanation: Dual Level Float Charger output, in this case tied to the OC TERMINATE input, goes high. The charger changes to the float state and holds the battery voltage at VF. F. Here a load (>lMAX) begins to discharge the battery. G. The load discharges the battery such that the battery voltage falls below V31. The charger is now in state 1, again. A. Input power turns on, battery charges at trickle current rate. B. Battery voltage reaches VT enabling the driver and turning off the trickle bias output, battery charges at lMAX rate. C. Transition voltage V12 is reached and the charger indicates that it is now in the over-charge state, state 2. D. Battery voltage approaches the over-charge level VOC and the charge current begins to taper. E. Charge current tapers to lOCT. The current sense amplifier Figure 3. Typical Charge Cycle: UC2906 Dual Level Float Charger 5 UC2906 UC3906 OPERATION AND APPLICATION INFORMATION (continued) at the current sense output to prevent excessive power dissipation on the UC2906. Compensated Reference Matches Battery Requirements When the charger is in the float state, the battery will be maintained at a precise float voltage, VF. The accuracy of this float state will maximize the standby life of the battery while the bulk-charge and over-charge states guarantee rapid and full re-charge. All of the voltage thresholds on the UC2906 are derived from the internal reference. This reference has a temperature coefficient that tracks the temperature characteristic of the optimum-charge and hold levels for sealed lead-acid cells. This further guarantees that proper charging occurs, even at temperature extremes. A PNP Pass Device Reduces Minimum Input to Output Differential The configuration of the driver on the UC2906 allows a good bit of flexibility when interfacing to an external pass transistor. The two chargers shown in Figures 1 and 4 both use PNP pass devices, although an NPN device driven from the source output of the UC2906 driver can also be used. In situations where the charger must operate with low input to output differentials the PNP pass device should be configured as shown in Figure 4. The PNP can be operated in a saturated mode with only the series diode and sense resistor adding to the minimum differential. The series diode, D1, in many applications, can be eliminated. This diode prevents any discharging of the battery, except through the sensing divider, when the charger is attached to the battery with no input supply voltage. If discharging under this condition must be kept to an absolute minimum, the sense divider can be referenced to the POWER INDICATE pin, Pin 7, instead of ground. In this manner the open collector off state of Pin 7 will prevent the divider resistors from discharging the battery when the input supply is removed. Dual Step Current Charger Operation Figures 4, 5 and 6 illustrate the UC2906’s use in a different charging scheme. The dual step current charger is useful when a large string of series cells must be charged. The holding-charge state maintains a slightly elevated voltage across the batteries with the holding current, 1H. This will tend to guarantee equal charge distribution between the cells. The bulk-charge state is similar to that of the float charger with the exception that when V12 is reached, no over-charge state occurs since Pin 8 is tied high at all times. The current sense amplifier is used to regulate the holding current. In some applications a series resistor, or external buffering transistor, may be required Figure 4. The UC2906 in a Dual Step Current Charger 6 UC2906 UC3906 OPERATION AND APPLICATION INFORMATION (continued) Figure 5. State Diagram and Design Equations for the Dual Step Current Charger Explanation: Dual Step Current Charger A. Input power turns on, battery charges at a rate of IH + IMAX. B. Battery voltage reaches V12 and the voltage loop switches to the lower level VF. The battery is now fed with the holding current IH. C. An external load starts to discharge the battery. D. When VF is reached the charger will supply the full current IMAX + IH. E. The discharge continues and the battery voltage reaches V21 causing the charger to switch back to state 1. Figure 6. Typical Charge Cycle: UC2906 Dual Step Current Charger UNITRODE INTEGRATED CIRCUITS 7 CONTINENTAL BLVD. • MERRIMACK, NH 03054 TEL. 603-424-2410 • FAX 603-424-3460 7 IMPORTANT NOTICE Texas Instruments and its subsidiaries (TI) reserve the right to make changes to their products or to discontinue any product or service without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. TI warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. 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