LT1268BCQ#PBF

LT1268B/LT1268 7.5A, 150kHz Switching Regulators U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ Wide Input Voltage Range: 3.5V to 30V Low Quiescent Current: 7mA Internal 7.5A Switch Very Few External Parts Required Self-Protected Against Overloads Available in Standard and Surface Mount 5-Pin Packages Can Be Externally Synchronized (See LT1072 Data Sheet) The LT1268B and LT1268 are monolithic high power switching regulators. Identical to the popular LT1070, except for switching frequency (150kHz) and higher switch current, they can be operated in all standard switching configurations including buck, boost, flyback, and inverting. 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 LT1268 to be built in standard 5-pin power packages. This makes it extremely easy to use and provides “bust proof” operations similar to that obtained with 3-pin linear regulators. UO APPLICATI ■ ■ ■ ■ S High Efficiency Boost Converter PC Power Supply with Multiple Outputs Battery Upconverter Negative-to-Positive Converter The LT1268 operate with supply voltages from 3.5V to 30V and draw only 7mA quiescent current. By utilizing current mode switching techniques, it provides excellent AC and DC load and line regulation. USER NOTE: This data sheet is only intended to provide specifications, graphs, and a general functional description of the LT1268B/LT1268. Application circuits are included to show the capability of the LT1268B/LT1268. 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 LT1268B/LT1268 factoring in the higher switch current rating and higher operating frequency. The LT1268 use an adaptive anti-sat switch drive to allow very wide ranging load currents with no loss in efficiency. An externally activated shutdown mode reduces total supply current to 100µA typical for standby operation. UO TYPICAL APPLICATI Boost Regulator with 5.3V ±1% Output D2, D3† 1N4001 + C1 220µF 16V VIN Efficiency of 5.3V Boost Converter 100 L2 2µH, 5A** + C3 390µF 16V C5 0.02 VSW VOUT 5.3V ±1% 3.75A R1 4.043k 0.1% + LT1268B FB CASE GND VC C2 0.068 R3 220Ω *COILTRONICS CTX8-5-52 **COILTRONICS CTX2-5-52 † OPTIONAL. D2 AND D3 ARE USED TO INCREASE UNDERVOLTAGE LOCKOUT FROM 2.7V TO ≈4V. R2 1.24k 0.1% C4 390µF 16V VIN = 4.7V VIN = 5V 80 70 60 LT1268 • TA01 VIN = 5.3V 90 EFFICIENCY (%) L1 8µH, 5A* VIN 4.7V TO 5.3V D1 MBR1035 0 1 2 3 4 LOAD CURRENT (A) LT1268 • TA02 1 LT1268B/LT1268 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO Supply Voltage ....................................................... 30V Switch Output Voltage ............................................ 60V Feedback Pin Voltage (Transient, 1ms) ................ ±15V Operating Junction Temperature Range Operating ............................................... 0°C to 125°C Short-Circuit ......................................... 0°C to 140°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C FRONT VIEW 5 4 3 2 1 ORDER PART NUMBER VIN VSW GND FB VC LT1268CQ LT1268BCQ Q PACKAGE 5-LEAD DD TJMAX = 125°C, θJC = 2°C/ W, θJA = See Notes 5 and 6 FRONT VIEW VIN VSW GND FB VC 5 4 3 2 1 T PACKAGE 5-LEAD TO-220 TJMAX = 125°C, θJC = 2°C/W, θJA = 50°C/W ORDER PART NUMBER LT1268CT LT1268BCT Consult factory for Industrial and Military parts ELECTRICAL CHARACTERISTICS VIN = 15V, VC = 0.5V, VFB = VREF, switch pin open, unless otherwise noted. SYMBOL PARAMETER CONDITIONS VREF Reference Voltage Measured at Feedback Pin (Note 4) LT1268B Reference Voltage LT1268 IB Feedback Input Current MIN TYP MAX UNITS ● 1.235 1.224 1.244 1.244 1.253 1.264 V V ● 1.224 1.214 1.244 1.244 1.264 1.274 V V 350 750 1100 nA nA VFB = VREF ● gm Error Amplifier Transconductance Error Amplifier Source or Sink Current Error Amplifier Clamp Voltage AV ∆IC = ±25µA 6000 7000 µmho µmho 150 120 200 ● 350 400 µA µA 2.30 0.52 V V 0.03 %/V VC = 1.5V Hi Clamp, VFB = 1V Lo Clamp, VFB = 1.5V Reference Voltage Line Regulation 3V ≤ VIN ≤ VMAX, VC = 0.8V Error Amplifier Voltage Gain 0.9V ≤ VC ≤ 1.4V Minimum Input Voltage IQ 3000 2400 4400 ● 1.80 0.25 ● 500 ● Supply Current 3V ≤ VIN ≤ VMAX, VC = 0.6V Control Pin Threshold Duty Cycle = 0 BV Output Switch Breakdown Voltage 3V ≤ VIN ≤ VMAX, ISW = 1.5mA VSAT Output Switch-ON Resistance (Note 1, 3) TJ ≤ 100°C TJ ≤ 125°C 2 Switch Current Limit (Note 3, 6) 800 V/V 2.8 3.0 V 7 10 mA 1.08 1.25 0.7 0.5 0.9 ● ● 60 75 0.12 Control Voltage to Switch Current Transconductance ILIM 0.38 V 0.18 0.22 12 Duty Cycle = 50%, TJ ≤ 100°C Duty Cycle = 65%, TJ ≤ 100°C ● ● 7.50 6.50 V V Ω Ω A/V 15 14 A A LT1268B/LT1268 ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER ∆IIN ∆ISW Supply Current Increase During Switch-ON Time f Switching Frequency VIN = 15V, VC = 0.5V, VFB = VREF, switch pin open, unless otherwise noted. CONDITIONS MIN ● DCMAX Maximum Switch Duty Cycle Shutdown Mode Supply Current 3V ≤ VIN ≤ VMAX, VC = 0.05V Shutdown Mode Threshold Voltage 3V ≤ VIN ≤ VMAX MAX UNITS 25 45 mA/A 120 120 150 180 180 kHz kHz 65 85 92 % 100 500 µA 150 250 300 mV mV 100 50 ● The ● denotes specifications which apply over the full operating temperature range. Note 1: Measured with VC in hi clamp, VFB = 0.8V. Note 2: For duty cycles (DC) between 50% and 65%, minimum guaranteed switch current is given by ILIM = 6.25 (1.7 – DC). Note 3: Minimum current limit is reduced by 0.5A at 125°C. 100°C test limits are guaranteed by correlation to 125°C tests. Note 4: LT1268B reference voltage is specified at ±9mV to guarantee ±1% output voltage accuracy when 0.1% external resistors are used to set output voltage. To maintain output accuracy under load, load current should be taken from the case and the ground pin should be connected separately to output ground. See AN19 for details. Note 5: The Q package is intended for surface mount without a separate heat sink. See graph for thermal resistance as a function of the mounting area. This curve assumes no other heat dissipators adjacent to package. Note 6: Maximum switch current may be limited by package power dissipation, especially for the surface mount (Q) package. This package TYP has a thermal resistance of 20°C/W to 50°C/W (see graph). The following formula will allow an estimate of maximum continuous switch current as a function of power loss and duty cycle. See AN19 for more details. P RSW × DC IMAX = P = Power dissipation due to switch current RSW = Switch-ON resistance ≈ 0.15Ω DC = Switch duty cycle In a typical application where thermal resistance is 30°C/W, maximum power might be limited to 2W and power allocated to switch loss is 1.5W. For a duty cycle of 40%, this yields 1.5 = 5A 0.15 × 0.4 IMAX = Obviously, a combination of high thermal resistance and high duty cycle may restrict switch current to a value well below the 7.5A electrical limit. W U TYPICAL PERFOR A CE CHARACTERISTICS Switch Current Limit vs Duty Cycle Switch Saturation Voltage 12 –55°C 25°C 125°C 6 0 10 20 30 40 50 60 70 80 90 100 DUTY CYCLE (%) LT1268 • TPC01 60 TJ = 25°C 1.4 50 1.2 SINGLE-SIDED BOARD, 1oz COPPER 40 1.0 θ (°C/W) 18 0 Q Package Thermal Resistance 1.6 SWITCH SATURATION VOLTAGE (V) SWITCH CURRENT (A) 24 0.8 0.6 30 20 DOUBLE-SIDED BOARD, 1oz COPPER BOTTOM COPPER AREA >100cm2 0.4 10 0.2 0 0 0 1 2 3 4 5 6 7 8 SWITCH CURRENT (A) 9 10 0 LT1268 • TPC02 Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 25 10 15 20 5 TOP SURFACE COPPER AREA (cm2) 30 LT1268 • 603 3 LT1268B/LT1268 UO TYPICAL APPLICATI Boost Converter (5V TO 12V) 5V 20µH VIN VSW MBR1020 12V, 1.5A LT1268CT 10.7k FB GND + VC 1k 1000µF 25V 1.24k + 1µF LT1268 • TA03 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. 0.401 ± 0.015 (10.185 ± 0.381) 0.060 (1.524) 0.175 ± 0.008 (4.445 ± 0.203) 15° TYP Q Package 5-Lead DD ( +0.012 0.331 –0.020 +0.305 8.407 –0.508 0.059 (1.499) TYP ) 0.050 ± 0.008 (1.270 ± 0.203) ( +0.008 0.004 –0.004 +0.203 0.102 –0.102 ) 0.105 ± 0.008 (2.667 ± 0.203) ( +0.012 0.143 –0.020 +0.305 3.632 –0.508 0.067 ± 0.010 (1.702 ± 0.254) ) 0.380 – 0.420 (9.652 – 10.668) 0.139 – 0.153 (3.531 – 3.886) DIA T Package 5-Lead TO-220 0.022 ± 0.005 (0.559 ± 0.127) 0.032 ± 0.008 (0.813 ± 0.203) 0.079 – 0.135 (2.007 – 3.429) 0.560 – 0.650 (14.224 – 16.510) 0.169 – 0.185 (4.293 – 4.699) 0.460 – 0.500 (11.68 – 12.70) 0.866 – 0.913 (21.996 – 23.190) 0.050 ± 0.012 (1.270 ± 0.305) 0.035 – 0.055 (0.889 – 1.397) 0.620 ± 0.020 (15.75 ± 0.508) 0.700 – 0.728 (17.780 – 18.491) 0.970 – 1.050 (24.64 – 26.67) 0.057 – 0.077 (1.448 – 1.956) 4 Linear Technology Corporation 0.028 – 0.035 (0.711 – 0.889) 0.015 – 0.025 (0.381 – 0.635) 0.210 – 0.240 (5.334 – 6.096) 0.304 – 0.380 (7.722 – 9.652) 0.055 – 0.090 (1.397 – 2.286) 0.079 – 0.115 (2.007 – 2.921) 0.149 – 0.230 (3.785 – 5.842) 1268fs, sn1268 LT/GP 0194 10K REV 0 • PRINTED IN THE USA 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977  LINEAR TECHNOLOGY CORPORATION 1994