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TPS61000 Datasheet(PDF) 16 Page - Texas Instruments |
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TPS61000 Datasheet(HTML) 16 Page - Texas Instruments |
16 / 25 page ![]() BAT OUT BAT L OUT 9 9 ± 9 L , ¦ 9 u ' u u OUT L OUT BAT V I I V 0.8 K K TRIP BAT REF V V 5 5 ± N ± V 0.5 V § · § · u : u ¨ ¸ ¨ ¸ © ¹ © ¹ TPS61000, TPS61001, TPS61002, TPS61003 TPS61004, TPS61005, TPS61006, TPS61007 SLVS279D – MARCH 2000 – REVISED AUGUST 2015 www.ti.com 10.2.2.2 Programming the Low Battery Comparator Threshold Voltage The current through the resistive divider should be about 100 times greater than the current into the LBI pin. The typical current into the LBI pin is 0.01 µA. The voltage across R2 is equal to the reference voltage that is generated on-chip, which has a value of 500 mV ±15 mV. The recommended value for R2 is therefore in the range of 500 k Ω. From that, the value of resistor R1, depending on the desired minimum battery voltage (VBAT), can be calculated using the following equation: (2) For example, if the low-battery detection circuit should flag an error condition on the LBO output pin at a battery voltage of 1 V, a resistor in the range of 500 k Ω should be chosen for R1. The output of the low battery comparator is a simple open-drain output that goes active low if the battery voltage drops below the programmed threshold voltage on LBI. The output requires a pullup resistor with a recommended value of 1M Ω, and should only be pulled up to the VOUT. If not used, the LBO pin can be left floating. 10.2.2.3 Inductor Selection The output filter of inductive switching regulators is a low pass filter of second order. It consists of an inductor and a capacitor, often referred to as storage inductor and output capacitor. To select an inductor, keep the possible peak inductor current below the current limit threshold of the power switch in your chosen configuration. For example, the current limit threshold of the TPS61006’s switch is 1100 mA at an output voltage of 3.3 V. The highest peak current through the inductor and the switch depends on the output load, the input (VBAT), and the output voltage (VOUT). Estimation of the maximum average inductor current can be done using the following equation: (3) For example, for an output current of 100 mA at 3.3 V, at least 515-mA current flows through the inductor at a minimum input voltage of 0.8 V. The second parameter for choosing the inductor is the desired current ripple in the inductor. Normally it is advisable to work with a ripple of less than 20% of the average inductor current. A smaller ripple reduces the magnetic hysteresis losses in the inductor as well as output voltage ripple and EMI. But in the same way, the regulation time at load change rises. In addition, a larger inductor increases the total system cost. With those parameters it is possible to calculate the value for the inductor: where • f is the switching frequency • ΔIL is the ripple current in the inductor, that is 20% x IL (4) In this example, the desired inductor has the value of 12 µH. With this calculated value and the calculated currents, it is possible to chose a suitable inductor. Care has to be taken that load transients and losses in the circuit can lead to higher currents as estimated in equation 3. Also, the losses in the inductor caused by magnetic hysteresis losses and copper losses are a major parameter for total circuit efficiency. The following inductors from different suppliers were tested. All work with the TPS6100x converter within their specified parameters: Table 3. Recommended Inductors VENDOR PART NUMBER DO1608P Series Coilcraft DS1608P Series DO3308 Series 16 Submit Documentation Feedback Copyright © 2000–2015, Texas Instruments Incorporated Product Folder Links: TPS61000 TPS61001 TPS61002 TPS61003 TPS61004 TPS61005 TPS61006 TPS61007 |
Similar Part No. - TPS61000_15 |
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Similar Description - TPS61000_15 |
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