LT1076CT-5

LT1076-5 5V Step-Down Switching Regulator FEATURES s s s s s s s s DESCRIPTIO Fixed 5V Output 2A On-Board Switch 100kHz Switching Frequency 2% Output Voltage Tolerance Over Temperature Greatly Improved Dynamic Behavior Available in Low Cost 5-Lead Package Only 9.5mA Quiescent Current Operates Up to 60V Input APPLICATI s s S s 5V Output Buck Converter Tapped Inductor Buck Converter with 4A Output at 5V Positive-to-Negative Converter The LT1076-5 is a 2A fixed 5V output monolithic bipolar switching regulator which requires only a few external parts for normal operation. The power switch, all oscillator and control circuitry, all current limit components, and an output monitor are included on the chip. The topology is a classic positive “buck” configuration but several design innovations allow this device to be used as a positive-tonegative converter, a negative boost converter, and as a flyback converter. The switch output is specified to swing 40V below ground, allowing the LT1076-5 to drive a tapped inductor in the buck mode with output currents up to 4A. The LT1076-5 uses a true analog multiplier in the feedback loop. This makes the device respond nearly instantaneously to input voltage fluctuations and makes loop gain independent of input voltage. As a result, dynamic behavior of the regulator is significantly improved over previous designs. On-chip pulse by pulse current limiting makes the LT10765 nearly bust-proof for output overloads or shorts. The input voltage range as a buck converter is 8V to 60V, but a self-boot feature allows input voltages as low as 5V in the inverting and boost configurations. The LT1076-5 is available in a low cost 5-lead TO-220 package with frequency pre-set at 100kHz and current limit at 2.6A. See Application Note 44 for design details. TYPICAL APPLICATI 8V TO 40V Basic Positive Buck Converter 100µH** † VIN LT1076-5 SENSE GND VC R3 1.5k VSW MBR340* 5V ≤1.8A * MBR330P MAY BE USED FOR VIN ≤ 25V ** COILTRONICS #100-1-52 HURRICANE #HL-AG210LL † + C3 200µF C2 0.033µF + C1 500µF 25V LT1076-5 TA01 U VALUE MAY BE REDUCED TO 50µH FOR OUTPUT LOADS BELOW 1.5A UO UO 1 LT1076-5 ABSOLUTE AXI U RATI GS PACKAGE/ORDER I FOR ATIO FRONT VIEW 7 6 5 4 3 2 1 R PACKAGE 7-LEAD PLASTIC DD SHDN VC SENSE GND ILIM VSW VIN Input Voltage LT1076-5............................................................ 45V LT1076HV-5 ....................................................... 64V Switch Voltage with Respect to Input Voltage LT1076-5............................................................ 64V LT1076HV-5 ....................................................... 75V Switch Voltage with Respect to Ground Pin (VSW Negative) LT1076-5 (Note 5).............................................. 35V LT1076HV-5 (Note 5) ......................................... 45V Sense Pin Voltage ........................................... – 2V, 10V Maximum Operating Ambient Temperature Range LT1076C-5, LT1076HVC-5 ..................... 0°C to 70°C LT1076I-5, LT1076HVI-5 .................. – 40°C to 85°C Maximum Operating Junction Temperature Range LT1076C-5, LT1076HVC-5 ................... 0°C to 125°C LT1076I-5, LT1076HVI-5 ................ – 40°C to 125°C Maximum Storage Temperature .......... –65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ORDER PART NUMBER LT1076CR-5 TJMAX = 110°C θ WILL VARY FROM APPROXIMATELY 30°C/W WITH 2.8IN2 OF 1 OZ COPPER TO 70°C/W WITH 0.20IN2 OF 1 OZ COPPER. FRONT VIEW 5 4 3 2 1 T PACKAGE 5-LEAD TO-220 VIN VSW GND VC SENSE LT1076CT-5 LT1076HVCT-5 LT1076IT-5 LT1076HVIT-5 FOR STRAIGHT LEADS, ORDER FLOW 06 TJMAX = 110° C, θJA = 130°C/W FRONT VIEW 7 6 5 4 3 2 1 Y PACKAGE 7-LEAD TO-220 SHDN VC SENSE GND ILIM VSW VIN LT1076CY-5 TJMAX = 110°C, θJA = 130°C/W Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS PARAMETER Switch “On” Voltage (Note 1) Switch “Off” Leakage Supply Current (Note 2) CONDITIONS ISW = 0.5A ISW = 2A TJ = 25°C, VIN = 25V, unless otherwise noted. MIN q q TYP MAX 1.2 1.7 150 250 UNITS V V µA µA mA mA µA V V A A A % VIN = 25V, VSW = 0 VIN = VMAX, VSW = 0 (Note 6) VOUT = 5.5V, VIN ≤ 40V 40V < VIN < 60V VSHDN = 0.1V (Device Shutdown) (Note 8) Normal Mode Start-Up Mode (Note 3) ILIM = Open RLIM = 10k (Note 9) RLIM = 7k (Note 9) q q q q q 8.5 9.0 140 7.3 3.5 2 2.6 1.8 1.2 90 11 12 300 8.0 4.8 3.2 Minimum Supply Voltage Switch Current Limit (Note 4) Maximum Duty Cycle q 85 2 U W U U WW W LT1076-5 ELECTRICAL CHARACTERISTICS PARAMETER Switching Frequency CONDITIONS TJ = 25°C, VIN = 25V, unless otherwise noted. MIN q q TYP 100 20 0.03 2000 MAX 110 120 0.1 UNITS kHz kHz kHz %/ V V/ V µmho µA mA kΩ V % % %/ V V mV/°C V µA µA V V °C/ W TJ ≤ 125°C VOUT = VSENSE = 0V (Note 4) 8V ≤ VIN ≤ VMAX (Note 7) 1V ≤ VC ≤ 4V 90 85 Switching Frequency Line Regulation Error Amplifier Voltage Gain (Note 7) Error Amplifier Transconductance (Note 7) Error Amplifier Source and Sink Current Sense Pin Divider Resistance Sense Voltage Output Voltage Tolerance 3700 Source (VSENSE = 4.5V) Sink (VSENSE = 5.5V) 100 0.7 3 VC = 2V VOUT (Nominal) = 5V All Conditions of Input Voltage, Output Voltage, Temperature and Load Current 8V ≤ VIN ≤ VMAX (Note 6) Over Temperature q q q q 5000 140 1.0 5 5 ±0.5 ±1.0 0.005 1.5 –4.0 24 8000 225 1.6 8 5.15 ±2 ±3 0.02 4.85 Output Voltage Line Regulation VC Voltage at 0% Duty Cycle Multiplier Reference Voltage Shutdown Pin Current Shutdown Thresholds Thermal Resistance Junction to Case VSHDN = 5V VSHDN ≤ VTHRESHOLD (≅ 2.5V) Switch Duty Cycle = 0 Fully Shut Down 5 2.2 0.1 10 2.45 0.30 20 50 2.7 0.5 4 The q denotes specifications which apply over the full operating temperature range. Note 1: To calculate maximum switch “on” voltage at currents between low and high conditions, a linear interpolation may be used. Note 2: A sense pin voltage (VSENSE) of 5.5V forces the VC pin to its low clamp level and the switch duty cycle to zero. This approximates the zero load condition where duty cycle approaches zero. Note 3: Total voltage from VIN pin to ground pin must be ≥ 8V after startup for proper regulation. For TA < 25°C, limit = 5V. Note 4: Switch frequency is internally scaled down when the sense pin voltage is less than 2.6V to avoid extremely short switch on times. During current limit testing, VSENSE is adjusted to give a minimum switch on time of 1µs. Note 5: Switch to input voltage limitation must also be observed. Note 6: VMAX = 40V for the LT1076-5 and 60V for the LT1076HV-5. Note 7: Error amplifier voltage gain and transconductance are specified relative to the internal feedback node. To calculate gain and transconductance from the Sense pin (Output) to the VC pin, multiply by 0.44. Note 8: Does not include switch leakage. Note 9: ILIM ≈ RLIM – 1k 5k 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. 3 LT1076-5 PACKAGE DESCRIPTIO 0.060 (1.524) ( +0.012 0.331 –0.020 +0.305 8.407 –0.508 ) 0.050 ± 0.010 (1.270 ± 0.254) 0.030 ± 0.008 (0.762 ± 0.203) ( +0.012 0.143 –0.020 +0.305 3.632 –0.508 ) 0.390 – 0.415 (9.906 – 10.541) 0.460 – 0.500 (11.684 – 12.700) 0.057 – 0.077 (1.448 – 1.956) 0.390 – 0.410 (9.91 – 10.41) 0.103 – 0.113 (2.62 – 2.87) 0.026 – 0.036 (0.66 – 0.91) 0.045 – 0.055 (1.14 – 1.40) 4 Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 q FAX: (408) 434-0507 q TELEX: 499-3977 U Dimensions in inches (millimeters) unless otherwise noted. R Package, 7-Lead Plastic DD 0.401 ± 0.015 (10.185 ± 0.381) 0.175 ± 0.008 (4.445 ± 0.203) 15° TYP 0.050 ± 0.008 (1.270 ± 0.203) 0.059 (1.499) TYP ( +0.008 0.004 –0.004 +0.203 0.102 –0.102 ) 0.105 ± 0.008 (2.667 ± 0.203) 0.022 ± 0.005 (0.559 ± 0.127) 0.050 ± 0.012 (1.270 ± 0.305) DD7 0693 T Package, 5-Lead TO-220 0.147 – 0.155 (3.734 – 3.937) DIA 0.230 – 0.270 (5.842 – 6.858) 0.570 – 0.620 (14.478 – 15.748) 0.330 – 0.370 (8.382 – 9.398) 0.620 (15.75) TYP 0.700 – 0.728 (17.780 – 18.491) 0.165 – 0.180 (4.293 – 4.572) 0.045 – 0.055 (1.143 – 1.397) 0.152 – 0.202 0.260 – 0.320 (3.860 – 5.130) (6.604 – 8.128) 0.095 – 0.115 (2.413 – 2.921) 0.013 – 0.023 (0.330 – 0.584) 0.028 – 0.038 (0.711 – 0.965) 0.135 – 0.165 (3.429 – 4.191) 0.155 – 0.195 (3.937 – 4.953) T5 (FORMED) 0694 Y Package, 7-Lead TO-220 0.147 – 0.155 (3.73 – 3.94) DIA 0.169 – 0.185 (4.29 – 4.70) 0.045 – 0.055 (1.14 – 1.40) 0.235 – 0.258 (5.97 – 6.55) 0.560 – 0.590 (14.22 – 14.99) 0.620 (15.75) TYP 0.700 – 0.728 (17.78 – 18.49) 0.152 – 0.202 (3.86 – 5.13) 0.260 – 0.320 (6.60 – 8.13) 0.016 – 0.022 (0.41 – 0.56) 0.135 – 0.165 (3.43 – 4.19) 0.095 – 0.115 (2.41 – 2.92) 0.155 – 0.195 (3.94 – 4.95) Y7 0893 LT/GP 0794 5K REV A • PRINTE IN USA © LINEAR TECHNOLOGY CORPORATION 1994