lt3507a Linear Technology Corporation, lt3507a Datasheet

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... Frequency foldback and thermal shutdown provide protection against fault conditions. The LT3507A provides higher output cur- rent than available with the LT3507. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation ...

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... For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 2 (Note 1) DRIVE Pin ...................................................................5V Operating Junction Temperature Range (Notes 2, 5) LT3507AE, LT3507AI ......................... –40°C to 125°C LT3507AH .......................................... –40°C to 150°C Storage Temperature Range .................. –65°C to 150°C Lead Temperature (Soldering, 10 sec) TSSOP Only ...................................................... 300°C ...

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... 200µA PGOOD PGOOD V Rising TRK/ 1mA VINSW Duty Cycle = 15 (Note 6) SW1 SW1 Duty Cycle = 15 1.5A (Note 6) SW2 I = 1.5A SW2 LT3507A , 17V, unless BOOST2 BOOST3 MIN TYP MAX UNITS µA 0.01 %/V 20 µA 30 µA 1.8 0.9 1.1 ...

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... The LT3507AI is guaranteed to meet performance specifications from –40°C to 125°C junction temperature. The LT3507AH is guaranteed over the full –40°C to 150°C operating junction temperature range. High junction temperatures degrade operating lifetimes. Operating lifetime is derated at junction temperatures greater than 125° ...

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... TEMPERATURE (°C) Frequency vs V (Foldback) FB 1200 R = 40. 25°C A 1000 800 600 400 200 0 150 0 0.2 0.4 0.6 0.8 V (V) FB LT3507A Switch V vs Switch Current, CESAT Channels 1, 2 and 3 0 25°C A 0.5 CHANNELS 2 AND 3 0.4 0.3 0.2 0 0.5 1 1.5 1.5 1.8 I (A) SW 3507A G02 Frequency 2.5 2.0 1.5 1.0 ...

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... LT3507A TYPICAL PERFORMANCE CHARACTERISTICS RUN Threshold vs Temperature 1.2 1.0 0.8 0.6 0.4 0.2 0.0 –50 –30 – 110 130 TEMPERATURE (°C) 3507A G10 Minimum On-Time vs I 250 200 150 100 –40° Voltage Drop vs I IN1 INSW 0. 25°C A 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0.00 0 0.2 0.4 0.6 0.8 150 I (mA) ...

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... OUT RUN1, RUN2, RUN3: The RUN pins are used to shut down the individual switching regulators. When all three RUN pins are low, the LT3507A shuts down and draws less than 1µA from V SW1, SW2, SW3: The SW pins are the outputs of the internal power switches ...

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... CHANNEL SHUTDOWN SLOPE SLAVE OSC CLK + – 0. PGOOD GND ONE OF THREE STEP-DOWN REGULATORS Figure 1. LT3507A Block Diagram with Typical External Components 8 V IN1 CLK1 INT REG MASTER CLK2 AND REF OSC CLK3 THERMAL SHUTDOWN UNDERVOLTAGE DETECTION + 0.9V – ...

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... Operation can be best understood by refer- ring to the Block Diagram (Figure 1). If the RUN pins are tied to ground, the LT3507A is shut down and draws <1µA from the input source tied to V any of the RUN pins are driven above 1V, the internal bias circuits turn on, including the internal regulator, reference, and master oscillator ...

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... The increased peak inductor current in pulse-skipping will also stress the switch transistor at high voltages and high switching frequency. If the LT3507A is allowed to pulse-skip and the input voltage is greater than 20V, then the switching frequency must be kept below 1.1MHz to prevent damage to the LT3507A ...

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... This gives 203 the peak-to-peak ripple current in the inductor: 93.8 ( 58.0 ΔI = 1– 40.2 30.0 where f is the switching frequency of the LT3507A and L 23.0 is the value of the inductor. The peak inductor and switch 18.0 current is: 14.3 11 SWPK LPK 9 ...

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... L • OUT The low ESR and small size of ceramic capacitors make them the preferred type for LT3507A applications. Not all ceramic capacitors are the same, however. Many of the higher value capacitors use poor dielectrics with high temperature and voltage coefficients. In particular, Y5V and Z5U types lose a large fraction of their capacitance with applied voltage and at temperature extremes ...

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... The minimum operating voltage of an LT3507A applica- tion is limited by the internal undervoltage lockout and by the maximum duty cycle. The boost circuit also limits the minimum input voltage for proper start-up. If the input voltage ramps slowly, or the LT3507A turns on when LT3507A PART NUMBER ...

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... BOOST Converter with Backup Output Regulator There is another situation to consider in systems where the output will be held high when the input to the LT3507A is absent. If the V to float, then the LT3507A’s internal circuitry will pull its quiescent current through its SW pin. This is acceptable 1 ...

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... LT3507A Figure 5. Diode D4 Prevents a Shorted Input from Discharging a Backup Battery Tied to the Output Input Capacitor Selection Bypass the input of the LT3507A circuit with a 10µF or higher ceramic capacitor of X7R or X5R type. The following paragraphs describe the input capacitor considerations in more detail. ...

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... The RUN pins are used to place the individual switching regulators and the internal bias circuits in shutdown mode. When all three RUN pins are pulled low, the LT3507A is in shutdown mode and draws less than 1µA from the input supply. When any RUN pin is pulled high (>1.5V) the inter- nal reference, LDO and selected channel are all turned on ...

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... The circuits in Figure 7 show some examples of these. In each case channel 1 starts first, followed by channel 2, then channel 3. The sequence shown is not a requirement; the LT3507A can sequence the channels in any order. Note that these circuits sequence the outputs during start-up. When shut down the three channels turn off simultaneously. ...

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... OUTPUT VOLTAGE TRACKING The LT3507A allows the user to program how the output ramps up by means of the TRK/SS pins. Through these pins, any channel output can be set up to either coinci- dently or ratiometrically track any other channel output. ...

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... LDO will shut off ). V must be IN3 OUT1 reducing power consumption. This pull-up can be sourced from one of the LT3507A outputs provided that channel is and V are OUT2 OUT3 always on when the other channels are on. The output stage of the LDO will drive the NPN base from the BIAS voltage least 0 ...

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... V is connected to V INSW the LT3507A is operating, with a saturation voltage of about 0.3V high impedance when the LT3507A is in shutdown (all three RUN pins low). The programmable lockout is a pair of comparators with the trip level set at 1.2V. The OVLO comparator trips when the OVLO pin exceeds 1 ...

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... LT3507A cool. The exposed pad on the bottom of the package must be soldered to a ground plane. This ground should be tied to other copper layers below with thermal vias; these lay- ers will spread the heat dissipated by the LT3507A. Place I OUT I ...

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... In a compact layout the pass transistor will be located close to the LT3507A. The inductors will also dissipate some power due to their series resistance and they must be close to the LT3507A. All of these heat sources will increase the effective ambient temperature seen by the LT3507A. ...

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... P Q 0.2A   0.02W P     LDO 100 The total dissipation on the LT3507A is the sum of all these and is equal to 0.73W. Note that this is less than half of P DISS(MAX) components are: P DIODE1 = 1.6A P IND1 Similarly, P 0.36W and 0.2A(3.3V – 3V) = 0.06W ...

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... Coincident Tracking 49.9k 22µ IN1 IN2 IN3 INSW BOOST1 UVLO 0.22µF SW1 OVLO FB1 680pF D1 V PGOOD1 C1 15k PGOOD2 18.7k PGOOD3 LT3507A BOOST2 TRK/SS1 SW2 BOOST3 0.22µF FB2 1000pF SW3 V FB3 C2 680pF 24.3k TRK/SS2 0.01µF BIAS TRK/SS3 DRIVE RUN1 RUN2 FB4 2.2nF ...

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... TRK/SS1 PGOOD2 PGOOD3 BOOST 2 BIAS LT3507A SW2 DRIVE FB2 FB4 1000pF V TRK/SS4 C2 270pF BOOST3 RUN1 SW3 RUN2 SHDN RUN3 FB3 1000pF V RT/SYNC C3 GND 54. 800kHz SW LT3507A 3.4k UVLO = 19V V OUT2 100k PGOOD V BST 0.1µF L2 3.3µH V OUT2 1.8V 18.7k 1.8A 33µF D2 13.3k 15k V BST 0.1µF L3 2.2µH V OUT3 1.2V 15.0k 1.8A 47µ ...

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... LT3507A PACKAGE DESCRIPTION 5.50 ± 0.05 4.10 ± 0.05 3.00 REF 5.00 ± 0.10 PIN 1 TOP MARK (SEE NOTE 6) 7.00 ± 0.10 NOTE: 1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE M0-220 VARIATION WHKD 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 26 UHF Package 38-Lead Plastic QFN (5mm × 7mm) (Reference LTC DWG # 05-08-1701 Rev C) 5.15 ± ...

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... BSC 0.17 – 0.27 (.0067 – .0106) TYP 4. RECOMMENDED MINIMUM PCB METAL SIZE FOR EXPOSED PAD ATTACHMENT *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.150mm (.006") PER SIDE LT3507A 9.60 – 9.80* (.378 – .386) 4.75 REF (.187) 20 6.40 2.74 REF (.252) ( ...

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... IN2 IN3 INSW BOOST1 UVLO 0.1µF SW1 OVLO FB1 1000pF D1 PGOOD1 V C1 PGOOD2 13.3k 1.5nF PGOOD3 TRK/SS1 BOOST3 0.1µF BOOST2 SW3 0.1µF LT3507A FB3 SW2 1200pF FB2 V 2000pF 1.5nF C2 7.32k TRK/SS3 1.5nF V TRK/SS2 BIAS OUT2 DRIVE RUN1 RUN2 FB4 SHDN RUN3 ...