lt3470a Linear Technology Corporation, lt3470a Datasheet
lt3470a
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lt3470a Summary of contents
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... With its wide input range 40V, the LT3470A can regulate a wide variety of power sources, from 2-cell Li-Ion batteries to unregulated wall transformers and lead-acid batteries. Quiescent current in regulation is just 35μ ...
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... BIAS Voltage .............................................................15V SW Voltage ................................................................V Maximum Junction Temperature LT3470AE, LT3470AI ......................................... 125°C Operating Temperature Range (Note 2) LT3470AE .............................................– 40°C to 85°C LT3470AI............................................ –40°C to 125°C Storage Temperature Range ................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) ................. 300°C ORDER INFORMATION LEAD FREE FINISH ...
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... Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LT3470AE 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 = 3V unless otherwise specifi ...
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... LT3470A TYPICAL PERFORMANCE CHARACTERISTICS Effi ciency 3.3V OUT TOKO D52LC 47μ 25° 12V 36V V = 24V 0 100 LOAD CURRENT (mA) 3470a G01 Top and Bottom Switch Current Limits (V = 0V) vs Temperature FB 600 550 500 450 ...
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... G10 = 100mA) Diode Leakage ( Temperature 100 125 –50 3470a G12 LT3470A T = 25°C unless otherwise noted 0V 100 125 –25 0 TEMPERATURE (°C) 3470a G09 (I = 50mA – 100 125 TEMPERATURE (° ...
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... LT3470A TYPICAL PERFORMANCE CHARACTERISTICS Switch V CESAT 700 600 500 400 300 200 100 0 0 100 200 SWITCH CURRENT (mA) Catch Diode Forward Voltage 1.0 0.8 0.6 0.4 0 100 200 CATCH DIODE CURRENT (mA) Minimum Input Voltage 25°C A 5.5 5.0 4.5 4 RUN/START IN 3.5 3 100 LOAD CURRENT (mA) 6 BOOST Pin Current ...
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... PIN FUNCTIONS SHDN (Pin 8): The SHDN pin is used to put the LT3470A in shutdown mode. Tie to ground to shut down the LT3470A. Apply 2V or more for normal operation. If the shutdown feature is not used, tie this pin to the V NC (Pin 7): This pin can be left fl oating, connected tied to GND ...
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... LT3470A BLOCK DIAGRAM 500ns ONE SHOT NC SHDN V REF 1.25V – R Qʹ – ENABLE + BURST MODE DETECT BIAS BOOST OUT C2 GND 3470a BD 3470af ...
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... Burst Mode Operation Figure 1. Operating Waveforms of the LT3470A Converting 12V to 5V Using a 33μH Inductor and 10μF Output Capacitor comparator trips and resets the latch causing the switch to turn off. While the switch is off, the inductor current ramps down through the catch diode. When both the bot- ...
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... Electrical Characteristics) such that the average induc- tor current equals the load current. For safe operation, it must be noted that the LT3470A cannot turn the switch on for less than ~150ns. If the inductor is small and the input voltage is high, the current through the switch may exceed safe operating limit before the LT3470A is able to turn off ...
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... With a high quality capacitor fi ltering the ripple current from the inductor, the output voltage ripple is determined by the delay in the LT3470A’s feedback comparator. This ripple can be reduced further by adding a small (typically 22pF) phase lead capacitor between the output and the feedback pin ...
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... If the LT3470A circuit is plugged into a live supply, the input volt- age can ring to twice its nominal value, possibly exceeding the LT3470A’s rating. This situation is easily avoided; see the Hot-Plugging Safely section ...
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... Figure 4. Diode D1 Prevents a Shorted Input from Discharging 200 250 a Backup Battery Tied to the Output; It Also Protects the Circuit from a Reversed Input. The LT3470A Runs Only When the Input is 3470a F03b Present Hot-Plugging Safely LT3470A = 40V. There is another situation to consider pin is allowed to fl oat and the IN ), then the LT3470A’ ...
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... SW and BOOST nodes. Figure 5 shows component placement with trace, ground plane and via locations. Include vias near the GND pin, or pad, of the LT3470A to help remove heat from the LT3470A to the ground plane. SHDN V ...
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... IN nominal input voltage, possibly exceeding the LT3470A’s rating and damaging the part. If the input supply is poorly controlled or the user will be plugging the LT3470A into an energized supply, the input network should be designed to prevent this overshoot. Figure 6 shows the waveforms that result when an LT3470A circuit is connected to a 24V supply through six feet of 24-gauge twisted pair. The fi ...
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... IMPEDANCE INDUCTANCE ENERGIZED DUE TO 6 FEET 24V SUPPLY (2 METERS) OF TWISTED PAIR 10μF 35V AI.EI. 0.1μF Figure 6: A Well Chosen Input Network Prevents Input Voltage Overshoot and Ensures Reliable Operation When the LT3470A is Connected to a Live Supply LT3470A V IN 10V/DIV 2.2μF I ...
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... C2: CE JMK316 BJ226ML-T L1: TOKO A914BYW-330M=P3 2.5V Step-Down Converter IN C3 0.47μF , 6.3V V BOOST IN L1 LT3470A 33μH OFF ON SHDN SW BIAS 22pF C1 FB 1μF GND C1: TDK C3216JB1H105M C2: TDK C2012JB0J226M L1: SUMIDA CDRH3D28 LT3470A V OUT 3.3V 250mA R1 324k C2 22μF R2 200k 3470a TA03 V OUT 5V 250mA R1 604k C2 22μF R2 200k 3470a TA04 V OUT 2 ...
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... OFF ON SHDN SW BIAS 22pF C1 FB 1μF GND C1: TDK C3216JB1H105M C2: TDK C2012JB0J226M L1: MURATA LQH32CN150K53 12V Step-Down Converter IN C3 0.22μF , 16V V BOOST IN L1 LT3470A 33μH OFF ON SHDN SW BIAS 22pF C1 FB 1μF GND C1: TDK C3216JB1H105M C2: TDK C3216JB1C106M L1: MURATA LQH32CN150K53 V OUT 1.8V 250mA R1 147k C2 22μF ...
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... DDB Package 8-Lead Plastic DFN (3mm × 2mm) (Reference LTC DWG # 05-08-1702 Rev B) 3.00 ±0.10 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6) PACKAGE OUTLINE 0.200 REF LT3470A R = 0.115 0.40 ± 0.10 TYP TYP 2.00 ±0.10 (2 SIDES) 0.56 ± 0.05 (2 SIDES) ...
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... LT3470A RELATED PARTS PART NUMBER DESCRIPTION LT1616 25V, 500mA (I ), 1.4MHz, High Effi ciency OUT Step-Down DC/DC Converter LT1676 60V, 440mA (I ), 100kHz, High Effi ciency OUT Step-Down DC/DC Converter LT1765 25V, 2.75A (I ), 1.25MHz, High Effi ciency OUT Step-Down DC/DC Converter LT1766 60V, 1. 200kHz, High Effi ciency ...