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| TK65010 ADVANCED INFORMATION FEATURES s s s s Very Low Quiescent Current ( 5 A) Dual Comparator Outputs Single Monitor Input Miniature Package (SOT-23-5) s s s s BATTERY VOLTAGE MONITOR APPLICATIONS Battery Powered Systems Cellular Telephones Pagers Personal Communications Equipment DESCRIPTION The TK65010 battery voltage monitor is designed for portable battery powered systems where board space and cost are important design considerations. The proprietary monitoring architecture of the TK65010 allows two separate warning thresholds to be set utilizing a single resistor divider and single input pin. 01 S TK65010 VIN GND LBO The first warning indicator, a Low Battery Output (LBO), is intended to warn the battery powered system of a low battery condition. In such a condition, the LBO may be used to alert the system to illuminate a low battery indicator and to take appropriate action preparing for battery failure. The second warning indicator, a Dead Battery Output (DBO), is intended to be used by the system for shutdown purposes. The availability of the DBO allows the system to shut down in order to minimize deep discharge of the battery. VMON DBO BLOCK DIAGRAM The two warning indicators can be implemented utilizing the TK65010 and only two external components. VCC The TK65010 is available in a miniature 5-pin SOT-23-5 surface mount package. 710 mV LBO ORDERING INFORMATION VMON 700 mV TK65010 Tape/Reel Code GND DBO 690 mV TAPE/REEL CODE TL: Tape Left January 1999 TOKO, Inc. Page 1 TK65010 ABSOLUTE MAXIMUM RATINGS All Pins Except GND .................................................. 6 V Power Dissipation (Note 1) ....................................... TBD Storage Temperature Range ................... -55 to +150 C Operating Temperature Range ...................-20 to +80 C Junction Temperature ........................................... 150 C TK65010 ELECTRICAL CHARACTERISTICS VIN = 5 V, TA = Tj = Full Operating Temperature Range, unless otherwise specified. SYMBOL VIN VTH, LBO Vref, OA VTH, DBO VTH, LBO, HYST VTH, DBO, HYST IFB IQ VLBO VDBO PARAMETER Input Supply Range LBO Comparator Threshold OP-Amp Reference DBO Comparator Threshold LBO Comparator Hysteresis DBO Comparator Hysteresis Peak Feedback Current Quiescent Current Low Battery Threshold Dead Battery Threshold TEST CONDITIONS MIN 0.9 TYP MAX 6 UNITS V mV mV mV mV mV nA A V V 710 700 690 TBD TBD VMON = VTH, LBO -580 5 (Note 2) (Note 2) 1.1 0.9 Note 1: Power dissipation is 400 mW when mounted as recommended (200 mW In Free Air). Derate at 1.6 mW/C for operation above 25 C. Note 2: When using test circuit below. TEST CIRCUIT VIN BATTERY IN R1 301 K GND VMON LBO LOW BATTERY DBO DEAD BATTERY R2 1M Page 2 January 1999 TOKO, Inc. TK65010 THEORY OF OPERATION The circuit in Figure 1 illustrates a typical application utilizing the TK65010. The TK65010 differs from most voltage monitors due to the fact that two separate comparator thresholds can be set utilizing a single resistive divider and a single input pin. One comparator output is used as an early "low battery" warning. The second comparator can be used as a later "dead battery" warning. Under these conditions, current will be flowing into the VMON pin and will be limited to approximately 580 nA. As the battery voltage drops, the voltage on the VMON pin will drop proportionately. When the voltage on the VMON pin passes through approximately 710 mV, the output of the first comparator (LBO) will transition from a high to a low state. Shortly after the LBO output has been asserted, as the input voltage continues to drop, the magnitude of the current into the VMON pin will begin to proportionately decrease as the input voltage decreases. An op-amp feedback loop internal to the TK65010 will attempt to maintain the voltage on the VMON pin at a constant value of approximately 700 mV (thus, the plateau). As the battery voltage continues to drop, there comes a point where the feedback current decreases to approximately zero. A this point, the voltage on the VMON pin will resume a proportional drop with the input voltage. As the voltage on the VMON pin passes through approximately 690 mV, the second comparator output (DBO) will be asserted. For details on how to properly select the resistor divider, refer to the "Design Considerations" section. VIN BATTERY IN R1 301 K GND VMON LBO LOW BATTERY DBO DEAD BATTERY R2 1M IFB FIGURE 1 In a typical voltage monitor, which uses an external resistive divider for setting the voltage monitor threshold, the input bias current to the monitor pin is essentially zero. In this type of scenario, the voltage on the monitor input would be a resistively divided version of the battery voltage. The TK65010 introduces a small feedback current (IFB) which introduces a "plateau" into the transfer characteristics between the battery voltage and the voltage monitoring pin. The width of this plateau is dependent upon the current range of the feedback current (IFB) and the values of the external resistor network. Figure 2 illustrates the typical relationship between the battery voltage (VIN), the feedback current (IFB) and the voltage on the monitoring pin (VMON). In selecting a resistor divider network, there are typically two degrees of freedom when selecting values. The first criteria in selecting the divider is the ratio of the two resistors. Selecting the ratio defines the lower threshold of the voltage monitor (DBO). The second degree of freedom when selecting the resistor divider is the absolute resistance values. This second degree of freedom can be utilized to set a secondary monitoring threshold (LBO) greater than the first. Typically, when the battery voltage is relatively high, the voltage on the VMON pin of the TK65010 will be a resistively divided version of the battery voltage minus the offset. The magnitude of the offset voltage will be dependent upon the resistor values comprising the external divider and the magnitude of the feedback current flowing into the IFB pin. January 1999 TOKO, Inc. VLBO VIN VDBO 700 mV VMON 580 nA IFB 0 nA LBO DBO FIGURE 2 Page 3 TK65010 PIN DESCRIPTION SUPPLY VOLTAGE PIN (VIN) This pin is the positive power supply for the TK65010. Current draw from the positive supply is typically 5 A. GNOUND PIN (GND) The pin provides the ground connection for the IC. VOLTAGE MONITORING PIN (VMON) This pin is the voltage monitoring pin of the TK65010. When the voltage on this pin is less than approximately 710 mV, the LBO signal will be asserted. When the voltage on this pin is less than approximately 690 mV, the DBO pin will be asserted. This pin is also connected to the negative input of a high-gain op-amp. The op-amp will attempt to maintain the voltage on this pin at 700 mV. However, the current-sink capability of this pin is limited to the range of 0 to 580 nA. LOW BATTERY OUTPUT PIN (LBO) This active-low pin will be asserted when the voltage on the VMON pin is less than approximately 710 mV; otherwise the LBO pin will not be asserted. DEAD BATTERY OUTPUT PIN (DBO) This active-low output will be asserted when the voltage in the VMON pin is less than approximately 690 mV; otherwise the DBO pin will not be asserted. Page 4 January 1999 TOKO, Inc. TK65010 DESIGN CONSIDERATIONS In order to design a voltage monitor utilizing the TK65010, the two external resistors comprising the resistor divider must be properly selected. Selecting the ratio of the resistors will establish the lower monitoring threshold (DBO). Selecting the value of the R1 will establish the upper monitoring threshold (LBO) relative to the lower (DBO) threshold. The value of R2 will be dictated by the ratio R1/R 2 and the value of R1. For the following explanations, please refer to the circuit diagram of Figure 3. SETTING THE DBO THRESHOLD As mentioned above, the ratio of R1/R2 established the "dead battery" threshold. The dead battery comparator trips when the voltage on the VMON pin passes through approximately 690 mV and the current into the VMON pin is approximately zero. Given the required dead battery threshold, the ratio R1/R2 can be selected utilizing the following equation: DBO Threshold = 690 mV x (1 + R1/R2) or VIN RESISTOR TOLERANCE CONSIDERATIONS The tolerance of the LBO and DBO thresholds will have a significant dependence upon the tolerance of the resistive components used in the resistor divider. When utilizing the previously described equations for setting the LBO and DBO thresholds, it is possible that optimal values of the resistive elements R1 and R2 may be relatively large. Since large resistive components are not always available with tight tolerances, an alternate method can be used for applications where tighter tolerances are required. The purpose of the resistor divider connected between the Battery Input and the VMON pin is twofold. The first purpose is to appropriately select the divider ratio such that the DBO threshold is set to the desired level. The second purpose is to select the absolute resistor values such that the LBO threshold is set to an appropriate level relative to the DBO threshold. Effectively, an attenuated voltage source with a relatively large output impedance is driving the VMON pin. This scenario is illustrated in Figure 4. R1/R2 = (DBO Threshold - 690 mV) / 690 mV SETTING THE LBO THRESHOLD R1 VMON R2 The threshold of the LBO comparator will be at a value greater than the DBO threshold. The value of resistor value R1 dictates the difference between the LBO and DBO thresholds as follows: LBO Threshold = DBO Threshold x 1.029 + R1 x 580 nA or R1 = (LBO Threshold - DBO Threshold x 1.029) / 580 nA VIN BATTERY IN GND R1 VMON DBO DEAD BATTERY R2 LBO LOW BATTERY R1 x R2 R1 + R2 VMON + VIN x R2 R1 + R2 FIGURE 4 IFB FIGURE 3 January 1999 TOKO, Inc. Page 5 TK65010 DESIGN CONSIDERATIONS (CONT.) The resistor divider consisting of R1/R2 can be scaled downward by a factor scale factor (K) to utilize smaller resistor values K x R1 and K x R2 (K < 1). By adding an additional series resistor, which can be dependent upon the scale factor (K) and the resistor values comprising the divider, the VMON pin will effectively see the same voltage source and drive impedance as illustrated in Figure 4. The three-resistor attenuator is illustrated below in Figure 5. VIN K x R1 (1- K) x R1 x R2 R1 + R2 VMON K x R2 R1 x R2 R1 + R2 VMON + VIN x R2 R1 + R2 FIGURE 5 Page 6 January 1999 TOKO, Inc. TK65010 APPLICATIONS INFORMATION VIN LBO LOW BATTERY Li-ion CELL R1 715 K GND VMON DBO DEAD BATTERY R2 215 K Low Battery Threshold = 3.5 V Dead Battery Threshold = 3.0 V FIGURE 6: BASIC BATTERY MONITOR +5 V BATTERY VOLTAGE R1 1.23 M VIN LBO LOW BATTERY GND VMON DBO DEAD BATTERY R2 90.9 K Low Battery Threshold = 11.0 V Dead Battery Threshold = 10.0 V FIGURE 7: HIGH VOLTAGE MONITOR +5 V BATTERY VOLTAGE R1 1M VIN LBO LOW BATTERY GND VMON DBO DEAD BATTERY R2 73.2 K 13 K Low Battery Threshold = 11.1 V Dead Battery Threshold = 10.1 V FIGURE 8: HIGH VOLTAGE MONITOR WITH 3-RESISTOR ATTENUATOR January 1999 TOKO, Inc. Page 7 TK65010 PACKAGE OUTLINE Marking Information Marking xxx SOT-23-5 0.7 TK65010 Marking 1.0 (0.6) 5 4 (0.6) 1.6 e 0.95 e' e 0.95 1.90 1 2 3 0.4 +0.15 - 0.05 e 0.95 Recommended Mount Pad e 0.95 0.1 M 2.9 1.3 max +0.1 +0.15 - 0.05 (0.8) 1.1 e1 2.4 0 - 0.1 0.15 0.1 Dimensions are shown in millimeters Tolerance: x.x = 0.2 mm (unless otherwise specified) Toko America, Inc. Headquarters 1250 Feehanville Drive, Mount Prospect, Illinois 60056 Tel: (847) 297-0070 Fax: (847) 699-7864 TOKO AMERICA REGIONAL OFFICES Midwest Regional Office Toko America, Inc. 1250 Feehanville Drive Mount Prospect, IL 60056 Tel: (847) 297-0070 Fax: (847) 699-7864 Western Regional Office Toko America, Inc. 2480 North First Street , Suite 260 San Jose, CA 95131 Tel: (408) 432-8281 Fax: (408) 943-9790 Eastern Regional Office Toko America, Inc. 107 Mill Plain Road Danbury, CT 06811 Tel: (203) 748-6871 Fax: (203) 797-1223 Semiconductor Technical Support Toko Design Center 4755 Forge Road Colorado Springs, CO 80907 Tel: (719) 528-2200 Fax: (719) 528-2375 Visit our Internet site at http://www.tokoam.com The information furnished by TOKO, Inc. is believed to be accurate and reliable. However, TOKO reserves the right to make changes or improvements in the design, specification or manufacture of its products without further notice. TOKO does not assume any liability arising from the application or use of any product or circuit described herein, nor for any infringements of patents or other rights of third parties which may result from the use of its products. No license is granted by implication or otherwise under any patent or patent rights of TOKO, Inc. Page 8 (c) 1999 Toko, Inc. All Rights Reserved IC-xxx-TKxxxxx 0798O0.0K 0 - 15 2.8 0.3 max January 1999 TOKO, Inc. Printed in the USA |
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