|Category||Power Management => Regulators => Switching Regulators => Step-Up and Flyback|
|Title||Step-Up and Flyback|
|Description||LT1070, 5A, 40kHz High Efficiency Switching Regulator|
|Company||Linear Technology Corporation|
|Datasheet||Download LT1070 datasheet|
The LT ®1070/LT1071 are monolithic high power switching regulators. They can be operated in all standard switching configurations including buck, boost, flyback, forward, inverting and "Cuk". A high current, high efficiency switch is included on the die along with all oscillator, control and protection circuitry. Integration of all functions allows the to be built in a standard 5-pin T0-220 power package. This makes it extremely easy to use and provides "bust proof" operation similar to that obtained with 3-pin linear regulators. The LT1070/LT1071 operate with supply voltages from to 60V, and draw only 6mA quiescent current. They can deliver load power to 100W with no external power devices. By utilizing current mode switching techniques, they provide excellent AC and DC load and line regulation. The LT1070/LT1071 have many unique features not found even on the vastly more difficult to use low power control chips presently available. They use adaptive antisat switch drive to allow very wide ranging load currents with no loss in efficiency. An externally activated shutdown mode reduces total supply current to 50µA typical for standby operation. Totally isolated and regulated outputs can be generated by using the optional "flyback regulation mode" built into the LT1070/LT1071, without the need for optocouplers or extra transformer windings.
Wide Input Voltage Range: to 60V Low Quiescent Current: 6mA Internal 5A Switch (2.5A for LT1071) Very Few External Parts Required Self Protected Against Overloads Operates in Nearly All Switching Topologies Shutdown Mode Draws Only 50µA Supply Current Flyback Regulated Mode Has Fully Floating Outputs Comes in Standard 5-Pin TO-220 Package Can be Externally Synchronized (Consult Factory)
Logic Supply 10A 5V Logic ±15V Op Amp Supply Off-Line Converter to 200W Battery Upconverter Power Inverter or to Fully Floating Multiple Outputs For Lower Current Applications, See the LT1072
USER NOTE: This data sheet is only intended to provide specifications, graphs and a general functional description of the LT1070/LT1071. Application circuits are included to show the capability of the LT1070/LT1071. A complete design manual (AN19) should be obtained to assist in developing new designs. This manual contains a comprehensive discussion of both the LT1070 and the external components used with it, as well as complete formulas for calculating the values of these components. The manual can also be used for the LT1071 by factoring in the lower switch current rating. A second Application Note, AN25, which details off-line applications is available.
*ROUGH GUIDE ONLY. BUCK MODE POUT = 5A VOUT. SPECIAL TOPOLOGIES DELIVER MORE POWER **DIVIDE VERTICAL POWER SCALE BY 2 FOR LT1071
Supply Voltage LT1070/LT1071 (Note 40V LT1070HV/LT1071HV (Note 2).......................... 60V Switch Output Voltage LT1070HV/LT1071HV........................................ 75V Feedback Pin Voltage (Transient, 1ms)................ ±15VConsult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS The q denotes the specifications which apply over the full operating temperature
range, otherwise specifications are = 25°C. VIN = 0.5V, VFB = VREF, output pin open unless otherwise specified.
SYMBOL VREF IB gm PARAMETER Reference Voltage Feedback Input Current Error Amplifier Transconductance Error Amplifier Source or Sink Current Error Amplifier Clamp Voltage Reference Voltage Line Regulation AV IQ Error Amplifier Voltage Gain Minimum Input Voltage Supply Current Control Pin Threshold Normal/Flyback Threshold on Feedback Pin 3V VIN VMAX, = 0.6V Duty Cycle = 0
Operating Junction Temperature Range Commercial (Operating)....................... to 100°C Commercial (Short Circuit)................... to 125°C Industrial......................................... to 125°C Military (OBSOLETE)................. to 150°C Storage Temperature Range................ to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C
The q denotes the specifications which apply over the full operating temperature range, otherwise specifications are = 25°C. VIN = 0.5V, VFB = VREF, output pin open unless otherwise specified.
SYMBOL VFB PARAMETER Flyback Reference Voltage Change in Flyback Reference Voltage Flyback Reference Voltage Line Regulation Flyback Amplifier Transconductance (gm) Flyback Amplifier Source and Sink Current BV Output Switch Breakdown Voltage CONDITIONS IFB = 50µA
0.05 IFB 1mA IFB 50µA, 3V VIN VMAX (Note = 0.6V, IFB = 50µA (Source) = 0.6V, IFB = 50µA (Sink) 3V VIN VMAX, ISW LT1070 LT1071 Duty Cycle TJ 25°C Duty Cycle < 25°C Duty Cycle = 80% (Note 5) Duty Cycle TJ 25°C Duty Cycle < 25°C Duty Cycle = 80% (Note 5)Output Switch "On" Resistance (Note 4) Control Voltage to Switch Current Transconductance
Supply Current Increase During Switch "On" Time Switching Frequency
Maximum Switch Duty Cycle Flyback Sense Delay Time Shutdown Mode Supply Current Shutdown Mode Threshold Voltage 3V VIN VMAX, 0.05V 3V VIN VMAX
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Minimum switch "on" time for the LT1070/LT1071 in current limit is 1µs. This limits the maximum input voltage during short-circuit conditions, in the buck and inverting modes only, to 35V. Normal (unshorted) conditions are not affected. Mask changes are being implemented which will reduce minimum "on" time to 1µs, increasing maximum short-circuit input voltage above 40V. If the present LT1070/LT1071 (contact factory for package date code) is being operated in the buck or inverting mode at high input voltages and short-circuit conditions are expected, a resistor must be placed in series with the inductor, as follows: The value of the resistor is given by:
t = Minimum "on" time LT1070/LT1071 in current limit, f = Operating frequency VF = Forward voltage of external catch diode at ILIMIT = Current limit RL = Internal series resistance of inductor Note 3: VMAX = 55V for LT1070HV and LT1071HV to avoid switch breakdown. Note 4: Measured with in hi clamp, VFB = 0.8V. ISW = 4A for LT1070 and 2A for LT1071. Note 5: For duty cycles (DC) between 50% and 80%, minimum guaranteed switch current is given by ILIM DC) for the LT1070 and ILIM DC) for the LT1071.
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