lt1683 Linear Technology Corporation, lt1683 Datasheet
lt1683
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lt1683 Summary of contents
Page 1
... N-channel MOSFET switches. Current and voltage slew rates can be independently set to optimize harmonic content of the switching waveforms vs efficiency. The LT1683 can reduce high frequency harmonic power by as much as 40dB with only minor losses in efficiency. The LT1683 utilizes a dual output (push-pull) current mode architecture optimized for low noise topologies ...
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... R CSL 7 14 SHDN GND G PACKAGE 20-LEAD PLASTIC SSOP = 150°C, θ 110°C/ W JMAX JA LT1683EG LT1683IG , 16.9k 16.9k and REF VSL CSL T MIN TYP MAX UNITS ● 1.235 1.250 1.265 ● 250 1000 ● 0.012 0.03 %/V ● – 2.56 – ...
Page 3
... Sink IN are assured by design, characterization and correlation with statistical process controls. The LT1683I is guaranteed and tested over the – 40° to 125° operating temperature range. Note 4: Output gate drivers will be enabled at this voltage. The GCL voltage will also determine drivers’ activity. ...
Page 4
... LT1683 W U TYPICAL PERFOR A CE CHARACTERISTICS Feedback Voltage and Input Current vs Temperature 1.260 1.258 1.256 1.254 1.252 1.250 1.248 1.246 1.244 1.242 1.240 –50 – TEMPERATURE (°C) Feedback Overvoltage Shutdown vs Temperature 1.70 1.65 1.60 1.55 1.50 1.45 1.40 1.35 1.30 1.25 1.20 –50 – 100 125 150 TEMPERATURE (°C) ...
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... TEMPERATURE (°C) 1683 G13 Soft-Start Current vs Temperature 9.5 SS VOLTAGE = 0.9V 9.3 9.1 8.9 8.7 8.5 8.3 8.1 7.9 7.7 7.5 –50 – 100 125 150 TEMPERATURE (°C) 1683 G16 LT1683 CS Pin to V Pin Transfer C Function 1 25°C A 1.4 1.2 1.0 0.8 0.6 0.4 0 100 120 CS PIN VOLTAGE (mV) 1683 G11 Gate Drive A/B Low Voltage vs Temperature 0 ...
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... LT1683 CTIO S Part Supply V5 (Pin 5): This pin provides a 5V output that can sink or source 10mA for use by external components. V5 source current comes from V . Sink current goes to GND must be greater than 6.5V in order for this voltage regulation. If this pin is used, a small capacitor (<1µF) may be placed on this pin to reduce noise ...
Page 7
... 0.1V, the gate drivers will be immediately S turned off (no slew control 0.22V in addition to the drivers being turned off, V and SS will be discharged to ground (short-circuit protec- tion). This will hasten turn off on subsequent cycles. LT1683 . VSL and the input voltage. Longer times produce is the equivalent capaci- VA/B ...
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... LT1683 CTIO S FB (Pin 9): The feedback pin is used for positive voltage sensing the inverting input to the error amplifier. The noninverting input of this amplifier connects internally to a 1.25V reference. If the voltage on this pin exceeds the reference by 220mV, then the output drivers will immediately turn off the external MOSFETs (no slew control) ...
Page 9
... CSL CSL TO DRIVERS REGULATOR V REG – ERROR AMP + CONTROL – COMP + LT1683 R VSL R VSL CAP A GATE A C SLEW VB CAP B GATE B PGND CS + SENSE AMP – SUB GND 1683 SENSE 1683fb 9 ...
Page 10
... Com- pliance with EMI standards will be an easier task and will require fewer external filtering components. The LT1683 uses two external N-channel MOSFETs as the power switches. This allows the user to tailor the drive conditions to a wide range of voltages and currents. ...
Page 11
... If the sink or source current is greater than 300mA then the current will be limited. and SS C The V5 regulator also has internal current limiting that will only guarantee ±10mA output current. LT1683 , then the maximum gate IN and is approximately IN is too low to provide adequate voltage to turn ...
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... LT1683 U OPERATIO There is also an on chip thermal shutdown circuit that will turn off the outputs in the event the chip temperature rises to dangerous levels. Thermal shutdown has hysteresis that will cause a low frequency (<1kHz) oscillation to occur as the chip heats up and cools down. ...
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... The LT1683 provides control over two of the more impor- tant variables for controlling EMI with switching inductive loads: switch voltage slew rate and switch current slew rate ...
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... LT1683 U U APPLICATIO S I FOR ATIO This part creates a second higher frequency rolloff of harmonics that inversely depends on the slew time, the time that voltage or current spends between the off state and on state. This time is adjustable through the choice of the slew resistors, the external resistors to ground on the ...
Page 15
... When both FB and NFB pins are used, the W U LT1683 will act to prevent either output from going beyond its set output voltage. The highest output (lightest load) will dominate control of the regulator. This technique would prevent either output from going unregulated high at no load ...
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... LT1683 U U APPLICATIO S I FOR ATIO wanted to turn on at 20V with 2V of hysteresis: − • • µ • − • • µ − • Resistor values could be altered further by adding Zeners in the divider string ...
Page 17
... The gate drive’s RMS discharge current times voltage Because of the strong V component it is advantageous IN to operate the LT1683 at as low always recommended that package temperature be measured in each application. The part has an internal thermal shutdown to minimize the chance of IC destruc- tion but this should not replace careful thermal design ...
Page 18
... LT1683 U U APPLICATIO S I FOR ATIO There are a number of ways to choose the inductance value for L. We suggest as a starting point that L be selected such that the converter is continuous at I /4. If your minimum I OUT(MAX) OUT your components can handle higher peak currents then use a higher number ...
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... 4.1mH 2 = 110µ • • 100 kHz • 494 ∆I – N • the FET. In our case our assump- ON < 1Ω. LT1683 1683fb 19 ...
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... LT1683 U U APPLICATIO S I FOR ATIO for capacitance. However, noise depends more on the ESR of the capacitors. In addition lower ESR can also improve efficiency. Input capacitors must also withstand surges that occur during the switching of some types of loads. Some solid tantalum capacitors can fail under these surge conditions. ...
Page 21
... ON capabilities of the MOSFET package as well as overall efficiency needs of the converter. The LT1683 can handle a large range of gate charges. However at very large charge stability may be affected. The power dissipation in the MOSFET depends on several factors. The primary element is I device is on ...
Page 22
... LT1683 U U APPLICATIO S I FOR ATIO When the part is active the gate drives will be pulled low to less than 0.2V. When the part is off, the gate drives contain a 40k resistor in series with a diode to ground that will offer passive holdoff protection. If you are using some logic level MOSFETs this might not be sufficient ...
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... L2 10µH 10.0k 2.74k 8.66k C1, C2:SANYO 16TPC33 C3: MURATA GRM235Y5V106Z C4: NIPPON THCR60EIE226Z D1, D2, D3 IN4148 1k D4, D5, D6, D7 MBRS1100 L1, L2: COOPER DS50224 T1: COOPER CTX02-15542 7.40 – 8.20 7.8 – 8.2 (.291 – .323) 0.42 ±0.03 RECOMMENDED SOLDER PAD LAYOUT LT1683 1.25 ±0.12 5.3 – 5.7 0.65 BSC G20 SSOP 0204 1683fb 23 ...
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... LT1683 U TYPICAL APPLICATIO 6.9k 2N3904 11V 68µF 20V SHDN SYNC 1.5nF LT1683 16. 25k 3. VSL 25k 3. CSL 15nF 1nF SS GND 13 10nF RELATED PARTS PART NUMBER DESCRIPTION LT1533 Ultralow Noise 1A Switching Regulator LT1534 Ultralow Noise 2A Switching Regulator ...