LT3480 LINER [Linear Technology], LT3480 Datasheet
LT3480
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LT3480 Summary of contents
Page 1
... Low ripple Burst Mode operation maintains high effi ciency at low output currents while keeping output ripple below 15mV in a typical application. In addition, the LT3480 can further enhance low output current effi ciency by draw- ing bias current from the output when V Shutdown reduces input supply current to less than 1μ ...
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... V A PARAMETER Minimum Input Voltage V Overvoltage Lockout IN 2 (Note 1) Operating Temperature Range (Note 2) LT3480E ............................................... –40°C to 85°C LT3480I .............................................. –40°C to 125°C Storage Temperature Range ................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) (MSE Only) ....................................................... 300° ...
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... Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LT3480E is guaranteed to meet performance specifi cations from 0°C to 85°C. Specifi cations over the –40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. The LT3480I specifi ...
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... LT3480 TYPICAL PERFORMANCE CHARACTERISTICS Effi ciency 100 V = 12V 34V 24V NEC PLC-0745-5R6 800kHz OUT 50 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 LOAD CURRENT (A) 3480 G01 No Load Supply Current 120 V = 3.3V OUT 100 INPUT VOLTAGE (V) 3480 G04 Maximum Load Current 3 ...
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... FB PIN VOLTAGE (mV) RUN/SS Pin Current 3 RUN/SS PIN VOLTAGE (V) LT3480 Feedback Voltage 840 820 800 780 760 2500 –50 – TEMPERATURE (°C) 3480 G11 Minimum Switch On-Time 140 120 100 80 ...
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... LT3480 TYPICAL PERFORMANCE CHARACTERISTICS Error Amp Output Current –10 –20 –30 –40 –50 –200 –100 0 100 FB PIN ERROR VOLTAGE (V) 3480 G19 V Voltages C 2.50 2.00 CURRENT LIMIT CLAMP 1.50 1.00 SWITCHING THRESHOLD 0.50 0 –50 – 100 125 TEMPERATURE (°C) 3480 G22 Switching Waveforms; Transition ...
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... PG (Pin 7): The PG pin is the open collector output of an internal comparator. PG remains low until the FB pin is within 14% of the fi nal regulation voltage. PG output is valid when V FB (Pin 8): The LT3480 regulates the FB pin to 0.790V. Connect the feedback resistor divider tap to this pin. V (Pin 9): The V C amplifi ...
Page 8
... IN output is in regulation, allowing an external resistor to pull the PG pin high. Power good is valid when the LT3480 is enabled and V The LT3480 has an overvoltage protection feature which disables switching action when the V typical (36V minimum). When switching is disabled, the LT3480 can safely sustain input voltages up to 60V ...
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... Absolute Maximum Ratings of 9.76 the V and BOOST pins, and the operating mode. 8.66 IN The LT3480 can operate from input voltages up to 38V, Value T and safely withstand input voltages up 60V. Note that while V >38V (typical), the LT3480 will stop switching, allowing IN the output to fall out of regulation ...
Page 10
... A reasonable starting point for selecting the ripple current is: SW ΔI = 0.4(I L where I OUT(MAX) guarantee suffi cient output current, peak inductor current must be lower than the LT3480’s switch current limit (I ), and The peak inductor current is L(PEAK) where I L(PEAK) the maximum output load current, and ΔI ripple current. The LT3480’ ...
Page 11
... LT3480. A ceramic input capacitor combined with trace or Open cable inductance forms a high quality (under damped) tank circuit. If the LT3480 circuit is plugged into a live supply, the input voltage can ring to twice its nominal value, possibly exceeding the LT3480’s voltage rating. This situation is easily avoided (see the Hot Plugging Safety section). For space sensitive applications, a 2.2μ ...
Page 12
... LT3480 due to their piezoelectric nature. When in Burst Mode operation, the LT3480’s switching frequency depends on the load current, and at very light loads the LT3480 can excite the ceramic capacitor at audio frequencies, generating audible noise. Since the LT3480 operates at a lower current limit during Burst Mode ...
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... If the LT3480 circuit is plugged into a live supply, the input volt- age can ring to twice its nominal value, possibly exceeding the LT3480’s rating. This situation is easily avoided (see the Hot Plugging Safely section) ...
Page 14
... IN proper startup, the minimum input voltage is also limited by the boost circuit. If the input voltage is ramped slowly, or the LT3480 is turned on with its RUN/SS pin when the output is already in regulation, then the boost capacitor may not be fully charged. Because the boost capacitor is charged with the energy stored in the inductor, the circuit will rely on some minimum load current to get the boost circuit running properly ...
Page 15
... Output Voltage, Load Current and Boost Circuit 3480 FO5 Soft-Start = 30V The RUN/SS pin can be used to soft-start the LT3480, reduc- ing the maximum input current during start-up. The RUN/SS pin is driven through an external RC fi lter to create a voltage ramp at this pin. Figure 7 shows the start-up and shut-down waveforms with the soft-start circuit ...
Page 16
... Shorted and Reversed Input Protection If the inductor is chosen so that it won’t saturate excessively, an LT3480 buck regulator will tolerate a shorted output. There is another situation to consider in systems where the output will be held high when the input to the LT3480 is absent. This may occur in battery charging applications 16 D4 ...
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... Figure 10. A Well Chosen Input Network Prevents Input Voltage Overshoot and Ensures Reliable Operation when the LT3480 is Connected to a Live Supply Finally, keep the FB and V traces will shield them from the SW and BOOST nodes. The Exposed Pad on the bottom of the package must be soldered to ground so that the pad acts as a heat sink ...
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... LT3480 into an energized supply, the input network should be designed to prevent this overshoot. Figure 10 shows the waveforms that result when an LT3480 circuit is connected to a 24V supply through six feet of 24-gauge twisted pair. The fi rst plot is the response with a 4.7μF ceramic capacitor at the input ...
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... BOOST LT3480 RT 14k PG SYNC 40.2k FB GND f = 800kHz 2.5V Step-Down Converter OFF RUN/SS BOOST LT3480 RT 20k PG 56.2k SYNC FB GND f = 600kHz LT3480 V OUT 3. 0.47μF 4.7μH D 316k 100k 22μF 3480 TA03 V OUT 2. 1μF 4.7μH D1 215k 100k 47μF 3480 TA04 3480fb 19 ...
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... BOOST LT3480 RT 14k PG SYNC 11.5k FB GND 470pF f = 2MHz D: DIODES INC. DFLS240L L: SUMIDA CDRH4D22/HP-2R2 12V Step-Down Converter OFF RUN/SS BOOST LT3480 RT 26.1k PG SYNC 40.2k FB GND f = 800kHz V OUT 0.47μF 2.2μH D 536k 100k 22μF 3480 TA05 V OUT 12V 2A L 0.47μF 10μ ...
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... TYPICAL APPLICATIONS V IN 3.5V TO 27V 4.7μF 330pF D: DIODES INC. DFLS240L L: TAIYO YUDEN NP06DZB3R3M 1.8V Step-Down Converter RUN/SS BOOST ON OFF LT3480 RT 18.2k PG SYNC 68.1k FB GND f = 500kHz LT3480 V OUT 1. 0.47μF 3.3μH D 127k 47μF 100k 3480 TA08 3480fb 21 ...
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... LT3480 PACKAGE DESCRIPTION 3.50 0.05 1.65 0.05 2.15 0.05 (2 SIDES) 0.25 0.05 0.50 BSC 2.38 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-2). CHECK THE LTC WEBSITE DATA SHEET FOR CURRENT STATUS OF VARIATION ASSIGNMENT 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH ...
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... TYP 0.53 0.152 1.10 (.021 .006) (.043) MAX DETAIL “A” SEATING PLANE 0.17 – 0.27 (.007 – .011) 0.50 TYP (.0197) BSC LT3480 2.06 0.102 (.081 .004) 1.83 0.102 (.072 .004) 0.497 0.076 (.0196 .003 REF 3.00 0.102 (.118 .004) (NOTE 4) 0.86 (.034) REF 0 ...
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... OUT Step-Down DC/DC Converter Linear Technology Corporation 24 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 ● 1.2V Step-Down Converter OFF RUN/SS BOOST LT3480 RT 16.2k PG SYNC 68.1k FB GND f = 500kHz COMMENTS V : 3.6V to 36V OUT(MIN 3.3V to 80V OUT(MIN) DFN and 16-Pin TSSOP Packages ...