LT1076-5 5V Step-Down Switching Regulator U DESCRIPTIO FEATURES ■ ■ ■ ■ ■ ■ ■ ■ 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 UO APPLICATI ■ ■ 5V Output Buck Converter Tapped Inductor Buck Converter with 4A Output at 5V Positive-to-Negative Converter UO ■ S TYPICAL APPLICATI 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. Basic Positive Buck Converter 100µH** † VIN 8V TO 40V 5V ≤1.8A VSW LT1076-5 MBR340* * MBR330P MAY BE USED FOR VIN ≤ 25V SENSE GND + ** COILTRONICS #100-1-52 HURRICANE #HL-AG210LL VC R3 1.5k C3 200µF C2 0.033µF † + VALUE MAY BE REDUCED TO 50µH FOR OUTPUT LOADS BELOW 1.5A C1 500µF 25V LT1076-5 TA01 1 LT1076-5 U U RATI GS W W W W AXI U U ABSOLUTE PACKAGE/ORDER I FOR ATIO 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 FRONT VIEW 7 6 5 4 3 2 1 ORDER PART NUMBER SHDN VC SENSE GND ILIM VSW VIN LT1076CR-5 R PACKAGE 7-LEAD PLASTIC DD 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 LT1076CT-5 LT1076HVCT-5 LT1076IT-5 LT1076HVIT-5 VIN VSW GND VC SENSE T PACKAGE 5-LEAD TO-220 FOR STRAIGHT LEADS, ORDER FLOW 06 TJMAX = 110°C, θJA = 130°C/W FRONT VIEW SHDN VC SENSE GND ILIM VSW VIN 7 6 5 4 3 2 1 LT1076CY-5 Y PACKAGE 7-LEAD TO-220 TJMAX = 110°C, θJA = 130°C/W Consult factory for Military grade parts. ELECTRICAL CHARACTERISTICS TJ = 25°C, VIN = 25V, unless otherwise noted. PARAMETER CONDITIONS Switch “On” Voltage (Note 1) ISW = 0.5A ISW = 2A Switch “Off” Leakage VIN = 25V, VSW = 0 VIN = VMAX, VSW = 0 (Note 6) Supply Current (Note 2) VOUT = 5.5V, VIN ≤ 40V 40V < VIN < 60V VSHDN = 0.1V (Device Shutdown) (Note 8) ● ● Minimum Supply Voltage Normal Mode Start-Up Mode (Note 3) ● ● Switch Current Limit (Note 4) ILIM = Open RLIM = 10k (Note 9) RLIM = 7k (Note 9) ● ● Maximum Duty Cycle 2 MIN TYP MAX UNITS 1.2 1.7 V V 150 250 µA µA 8.5 9.0 140 11 12 300 mA mA µA 7.3 3.5 8.0 4.8 V V 2 2.6 1.8 1.2 3.2 A A A 85 90 ● ● % LT1076-5 ELECTRICAL CHARACTERISTICS PARAMETER TJ = 25°C, VIN = 25V, unless otherwise noted. CONDITIONS Switching Frequency TJ ≤ 125°C VOUT = VSENSE = 0V (Note 4) ● Switching Frequency Line Regulation 8V ≤ VIN ≤ VMAX (Note 7) ● Error Amplifier Voltage Gain (Note 7) 1V ≤ VC ≤ 4V TYP MAX UNITS 90 85 100 110 120 kHz kHz kHz 0.1 %/ V 20 0.03 2000 Error Amplifier Transconductance (Note 7) Error Amplifier Source and Sink Current MIN Source (VSENSE = 4.5V) Sink (VSENSE = 5.5V) V/ V 3700 5000 8000 µmho 100 0.7 140 1.0 225 1.6 µA mA 3 5 8 kΩ 4.85 5 5.15 V % % Sense Pin Divider Resistance Sense Voltage VC = 2V ● Output Voltage Tolerance VOUT (Nominal) = 5V All Conditions of Input Voltage, Output Voltage, Temperature and Load Current ● ±0.5 ±1.0 ±2 ±3 8V ≤ VIN ≤ VMAX (Note 6) ● 0.005 0.02 Over Temperature ● 1.5 –4.0 V mV/°C 24 V Output Voltage Line Regulation VC Voltage at 0% Duty Cycle Multiplier Reference Voltage Shutdown Pin Current VSHDN = 5V VSHDN ≤ VTHRESHOLD (≅ 2.5V) Shutdown Thresholds Switch Duty Cycle = 0 Fully Shut Down 5 10 20 50 µA µA 2.2 0.1 2.45 0.30 2.7 0.5 V V Thermal Resistance Junction to Case 4 The ● 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. %/ V °C/ W 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 U PACKAGE DESCRIPTIO Dimensions in inches (millimeters) unless otherwise noted. R Package, 7-Lead Plastic DD 0.060 (1.524) 0.401 ± 0.015 (10.185 ± 0.381) 0.175 ± 0.008 (4.445 ± 0.203) 0.050 ± 0.008 (1.270 ± 0.203) 15° TYP ( +0.012 0.331 –0.020 +0.305 8.407 –0.508 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) ( +0.012 0.143 –0.020 +0.305 3.632 –0.508 0.050 ± 0.010 (1.270 ± 0.254) 0.030 ± 0.008 (0.762 ± 0.203) ) 0.050 ± 0.012 (1.270 ± 0.305) 0.022 ± 0.005 (0.559 ± 0.127) DD7 0693 T Package, 5-Lead TO-220 0.165 – 0.180 (4.293 – 4.572) 0.147 – 0.155 (3.734 – 3.937) DIA 0.390 – 0.415 (9.906 – 10.541) 0.045 – 0.055 (1.143 – 1.397) 0.230 – 0.270 (5.842 – 6.858) 0.570 – 0.620 (14.478 – 15.748) 0.460 – 0.500 (11.684 – 12.700) 0.330 – 0.370 (8.382 – 9.398) 0.620 (15.75) TYP 0.700 – 0.728 (17.780 – 18.491) 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) 0.057 – 0.077 (1.448 – 1.956) 0.135 – 0.165 (3.429 – 4.191) 0.028 – 0.038 (0.711 – 0.965) 0.155 – 0.195 (3.937 – 4.953) T5 (FORMED) 0694 Y Package, 7-Lead TO-220 0.390 – 0.410 (9.91 – 10.41) 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) 0.103 – 0.113 (2.62 – 2.87) 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) 0.026 – 0.036 (0.66 – 0.91) 0.045 – 0.055 (1.14 – 1.40) 4 Linear Technology Corporation 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 1630 McCarthy Blvd., Milpitas, CA 95035-7487 (408) 432-1900 ● FAX: (408) 434-0507 ● TELEX: 499-3977 LINEAR TECHNOLOGY CORPORATION 1994