LT1977EFE#TR Linear Technology, LT1977EFE#TR Datasheet
LT1977EFE#TR
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LT1977EFE#TR Summary of contents
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... Industrial Power Systems ■ Distributed Power Systems ■ Battery-Powered Systems , LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode is a registered trademark of Linear Technology Corporation. *Protected by U.S. Patents including 6498466, 6531909. **See Burst Mode Operation section for conditions U TYPICAL APPLICATIO 14V to 3.3V Step-Down Converter with 100µ ...
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LT1977 ABSOLUTE AXI U RATI GS (Note SHDN, BIAS, SW, PG....................................... 60V IN BOOST Pin Above SW ............................................ 35V BOOST Pin Voltage ................................................. 68V SYNC PGFB, FB ................................................ 6V SS Operating JunctionTemperature ...
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ELECTRICAL CHARACTERISTICS temperature range, otherwise specifications are at T unless otherwise noted. SYMBOL PARAMETER Switch On Resistance (Note 9) Switching Frequency Maximum Duty Cycle Minimum SYNC Amplitude SYNC Frequency Range SYNC Input Impedance I C Current Threshold (Note 10) CSS ...
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LT1977 W U TYPICAL PERFOR A CE CHARACTERISTICS FB Voltage 1.30 1.29 1.28 1.27 1.26 1.25 1.24 1.23 1.22 1.21 1.20 –50 – 100 125 TEMPERATURE (°C) 1977 G01 SHDN Pin Current 5 25°C ...
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W U TYPICAL PERFOR A CE CHARACTERISTICS Switch Peak Current Limit 3.5 3.0 2.5 2.0 1.5 –50 –25 – 100 125 TEMPERATURE (°C) 1977 G10 Switch On Voltage (V ) CESAT 500 450 400 350 300 T ...
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LT1977 W U TYPICAL PERFOR A CE CHARACTERISTICS Dropout Operation 4 3.3V OUT BOOST DIODE = DIODES INC B1100 3.5 LOAD CURRENT = 250mA 3.0 2.5 LOAD CURRENT = 1.25A 2.0 1.5 1.0 0 2.5 3 ...
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CTIO S voltage on the PGFB pin drops below V discharged rapidly to 0V and PG will be active low with a 200µA sink capability. If the C pin is clamped (Power Good T condition) ...
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LT1977 W BLOCK DIAGRA V IN INTERNAL REF 4 UNDERVOLTAGE LOCKOUT BIAS THERMAL 10 SHUTDOWN SYNC 14 SHDN + 15 SHDN COMP – 1. SOFT-START FOLDBACK DETECT FB – 12 ERROR AMP + 1.25V ...
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W BLOCK DIAGRA power from the V pin, but if the BIAS pin is connected external voltage higher than 3V bias power will be drawn from the external source (typically the regulated output voltage). This improves efficiency. ...
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LT1977 U U APPLICATIO S I FOR ATIO LT1977 SOFT-START 500kHz FOLDBACK OSCILLATOR DETECT – ERROR AMP + Figure 2. Feedback Network Table 2 OUTPUT R1 VOLTAGE R2 NEAREST (1%) (V) (kΩ, 1%) (kΩ) 2.5 100 100 3 100 140 ...
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U U APPLICATIO S I FOR ATIO INPUT CAPACITOR Step-down regulators draw current from the input supply in pulses. The rise and fall times of these pulses are very fast. The input capacitor is required to reduce the voltage ripple ...
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LT1977 U U APPLICATIO S I FOR ATIO triangular with a typical value of 200mA to calculate this is: Output capacitor ripple current (RMS OUT RIPPLE ...
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U U APPLICATIO S I FOR ATIO The LT1977 is able to maintain peak switch current limit over the full duty cycle range by using patented circuitry to cancel the effects of slope compensation on peak switch current without affecting ...
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... After making an initial choice, consider the secondary things like output voltage ripple, second sourcing, etc. Use the experts in the Linear Technology’s applications department if you feel uncertain about the final choice. They have experience with a wide range of inductor types and can tell you about the latest developments in low profile, surface mounting, etc ...
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U U APPLICATIO S I FOR ATIO low value such that the current doesn’t continue to ratchet higher. When the FB pin voltage is abnormally low thereby indicating some sort of short-circuit condition, the oscil- lator frequency will be reduced. ...
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LT1977 U U APPLICATIO S I FOR ATIO Example: For V = 3.3V 12V OUT IN ( µ + ⎛ ⎞ 125 µ + µ + ⎜ ⎟ ...
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U U APPLICATIO S I FOR ATIO must weigh the importance of each specification in choos- ing the best diode for the application. The use of so-called “ultrafast” recovery diodes is gener- ally not recommended. When operating in continuous mode, ...
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LT1977 U U APPLICATIO S I FOR ATIO In addition to the shutdown feature, the LT1977 has an undervoltage lockout function. When the input voltage is below 2.4V, switching will be disabled. The undervoltage lockout threshold doesn’t have any hysteresis ...
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U U APPLICATIO S I FOR ATIO the user to generate a delayed signal after the power good threshold is exceeded. Referring to Figure 2, the PGFB pin is the positive input to a comparator whose negative input is set ...
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LT1977 U U APPLICATIO S I FOR ATIO a limited amount of drive capability and is susceptible to noise during start-up and Burst Mode operation. If erratic operation occurs during these conditions a small filter capacitor from the PGOOD pin ...
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U U APPLICATIO S I FOR ATIO Boost current loss OUT OUT = P BOOST V IN Quiescent current loss (0.0015 (0.003 OUT R ...
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LT1977 U U APPLICATIO S I FOR ATIO power. In questionable cases a prototype supply should be built and exercised to verify acceptable operation. 2. The simultaneous requirements of high V high f can result in an unacceptably short minimum ...
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... DIMENSIONS ARE IN 3. DRAWING NOT TO SCALE Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen- tation that the interconnection of its circuits as described herein will not infringe on existing patent rights system is assumed ...
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... I < 1µA, TSSOP16E 3.3V to 60V 100µA, I < 1µA, TSSOP16E 36V 0.8V 670µ OUT(MIN LT/LT 0805 REV A • PRINTED IN USA © LINEAR TECHNOLOGY CORPORATION 2004 < 15µA, < 6µA, < 1µA, SD < 1µA, < 1µA, SD < 20µA, 1977fa ...