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ISL6292DCR4-T Datasheet(PDF) 10 Page - Renesas Technology Corp |
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ISL6292DCR4-T Datasheet(HTML) 10 Page - Renesas Technology Corp |
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10 / 13 page  ISL6292D FN9166 Rev.0.00 Page 10 of 13 July 2004 End-of-Charge (EOC) Current The end-of-charge current IMIN sets the level at which the charger indicates the end of the charge with the STAT1 and STAT2 pins, as shown in Figure 4. The charger terminates at this moment. The IMIN is set in two ways, by connecting a resistor between the IMIN pin and ground, or by connecting the IMIN pin to the V2P8 pin. When programming with the resistor, the IMIN is set in the equation below. (EQ. 6) where RIMIN is the resistor connected between the IMIN pin and the ground. When connected to the V2P8 pin, the IMIN is set to 1/10 of IREF, except when the IREF pin is shorted to GND. Under this exception, IMIN is 5mA. Charge Current Thermal Foldback Over-heating is always a concern in a linear charger. The maximum power dissipation usually occurs at the beginning of a charge cycle when the battery voltage is at its minimum but the charge current is at its maximum. The charge current thermal foldback function in the ISL6292D frees users from the over-heating concern. Figure 5 shows the current signals at the summing node of the current error amplifier CA in the Block Diagram. IR is the reference. IT is the current from the Temperature Monitoring block. The IT has no impact on the charge current until the internal temperature reaches approximately 100°C; then IT rises at a rate of 1 A/°C. When IT rises, the current control loop forces the sensed current ISEN to reduce at the same rate. As a mirrored current, the charge current is 100,000 times that of the sensed current and reduces at a rate of 100mA/°C. For a charger with the constant charge current set at 1A, the charge current is reduced to zero when the internal temperature rises to 110°C. The actual charge current settles between 100°C to 110°C. Usually the charge current should not drop below IMIN because of the thermal foldback. For some extreme cases if that does happen, the charger does not indicate end-of-charge unless the battery voltage is already above the recharge threshold. 2.8V Bias Voltage The ISL6292D provides a 2.8V voltage for biasing the internal control and logic circuit. This voltage is also available for external circuits such as the NTC thermistor circuit. The maximum allowed external load is 2mA. NTC Thermistor The ISL6292D uses two comparators (CP2 and CP3) to form a window comparator, as shown in Figure 7. When the TEMP pin voltage is “out of the window,” determined by the VTMIN and VTMAX, the ISL6292D stops charging and indicates a fault condition. When the temperature returns to the set range, the charger re-starts a charge cycle. The two MOSFETs, Q1 and Q2, produce hysteresis for both upper and lower thresholds. The temperature window is shown in Figure 6. IMIN 10000 VREF RIMIN ---------------- 0.8V RIMIN ---------------- 4 10 A = = FIGURE 5. CURRENT SIGNALS AT THE AMPLIFIER CA INPUT Temperature 100OC I R I T I SEN FIGURE 6. CRITICAL VOLTAGE LEVELS FOR TEMP PIN 3.0V V TMIN (1.50V) 0V Under Temp Over Temp TEMP Pin Voltage V TMIN- (1.286V) V TMAX (0.605V) V TMAX+ (0.660V) + - + - V2P8 TEMP GND 2.8V R2 R3 R4 R5 Q1 Q2 CP2 CP3 Under Temp Over Temp ISL6292D R U To TEMP Pin V TMIN V TMAX RT + - R1 Battery Removal CP1 V RMV FIGURE 7. THE INTERNAL AND EXTERNAL CIRCUIT FOR THE NTC INTERFACE |
Similar Part No. - ISL6292DCR4-T |
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