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LT1076-5 5V Step-Down Switching Regulator FEATURES
n n n n n n n n
DESCRIPTION
The LT(R)1076-5 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-to-negative 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- and 7-lead TO220 packages with frequency pre-set at 100kHz and current limit at 2.6A. See Application Note 44 for design details.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
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- and 7-Lead Packages Only 9.5mA Quiescent Current Operates Up to 60V Input
APPLICATIONS
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5V Output Buck Converter Tapped Inductor Buck Converter with 4A Output at 5V Positive-to-Negative Converter
TYPICAL APPLICATION
Basic Positive Buck Converter
100H** 8V TO 40V VIN LT1076-5 SENSE GND VC R3 1.5k C2 0.033F VSW MBR340* 5V 1.8A * MBR330P MAY BE USED FOR VIN 25V ** COILTRONICS #100-1-52 HURRICANE #HL-AG210LL
+
C3 200F
+
C1 500F 25V
LT1076-5 TA01
VALUE MAY BE REDUCED TO 50H FOR OUTPUT LOADS BELOW 1.5A
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LT1076-5 ABSOLUTE MAXIMUM RATINGS
(Note 1)
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 6) ................................................35V LT1076HV-5 (Note 6) ...........................................45V
Sense Pin Voltage ............................................ -2V, 10V Maximum Operating Ambient Temperature Range LT1076C-5, LT1076HVC-5 ....................... 0C to 70C LT1076I-5, LT1076HVI-5 ..................... -40C to 85C Maximum Operating Junction Temperature Range LT1076C-5, LT1076HVC-5 ..................... 0C to 125C LT1076I-5, LT1076HVI-5 ................... -40C to 125C Maximum Storage Temperature ............ -65C to 150C Lead Temperature (Soldering, 10 sec) .................. 300C
PACKAGE/ORDER INFORMATION
FRONT VIEW 5 4 3 2 1 Q PACKAGE 5-LEAD PLASTIC DD VIN VSW GND VC FB/SENSE TAB IS GND FRONT VIEW 7 6 5 4 3 2 1 R PACKAGE 7-LEAD PLASTIC DD SHDN VC SENSE GND ILIM VSW VIN
ORDER PART NUMBER LT1076CQ-5
ORDER PART NUMBER LT1076CR-5
JC = 4C/W, JA = 30C/W
FRONT VIEW 5 4 3 2 1 T PACKAGE 5-LEAD PLASTIC TO-220 VIN VSW GND VC SENSE TAB IS GND
JC = 4C/W, JA = 30C/W
FRONT VIEW 7 6 5 4 3 2 1 T7 PACKAGE 7-LEAD PLASTIC TO-220 SHDN VC SENSE GND ILIM VSW VIN
TAB IS GND
ORDER PART NUMBER LT1076CT-5 LT1076HVCT-5 LT1076IT-5 LT1076HVIT-5
ORDER PART NUMBER LT1076CT7-5
LEADS ARE FORMED STANDARD FOR STRAIGHT LEADS, ORDER FLOW 06 JC = 4C/W, JA = 50C/W
JC = 4C/W, JA = 50C/W
Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
ELECTRICAL CHARACTERISTICS
SYMBOL Switch "On" Voltage (Note 2) Switch "Off" Leakage CONDITIONS ISW = 0.5A ISW = 2A VIN = 25V, VSW = 0 VIN = 25V, VSW = 0
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TJ = 25C. VIN = 25V, unless otherwise noted.
MIN
l l
TYP
MAX 1.2 1.7 150 250
UNITS V V A A
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LT1076-5 ELECTRICAL CHARACTERISTICS
SYMBOL Supply Current (Note 3) CONDITIONS VOUT = 5.5V, VIN 40V 40V < VIN < 60V VSHDN = 0.1V (Device Shutdown) (Note 9) Normal Mode Start-Up Mode (Note 4) ILIM = Open RLIM = 10k (Note 10) RLIM = 7k (Note 10)
l l l l l
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TJ = 25C. VIN = 25V, unless otherwise noted.
MIN TYP 8.5 9.0 140 7.3 3.5 2 2.6 1.8 1.2 90 100 20
l
MAX 11 12 300 8.0 4.8 3.2
UNITS mA mA A V V A A A % kHz kHz kHz %/V V/V mho A mA k V % % %/V V mV/C V
Minimum Supply Voltage Switch Current Limit (Note 5)
Maximum Duty Cycle Switching Frequency TJ 125C VOUT = VSENSE = 0V (Note 5) Switching Frequency Line Regulation 8V VIN VMAX (Note 8) Error Amplifier Voltage Gain (Note 8) 1V VC 4V Error Amplifier Transconductance (Note 8) Error Amplifier Source and Sink Current Sense Pin Divider Resistance Sense Voltage Output Voltage Tolerance VC = 2V VOUT (Nominal) = 5V All Conditions of Input Voltage, Output Voltage, Temperature and Load Current 8V VIN VMAX (Note 7) Over Temperature Multiplier Reference Voltage Shutdown Pin Current Shutdown Thresholds Thermal Resistance Junction to Case Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: To calculate maximum switch "on" voltage at currents between low and high conditions, a linear interpolation may be used. Note 3: 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 4: Total voltage from VIN pin to ground pin must be 8V after startup for proper regulation. For TA < 25C, limit = 5V. Note 5: Switch frequency is internally scaled down when the sense pin voltage is less than 2.6V to avoid extremely short switch on times. During VSHDN = 5V VSHDN VTHRESHOLD ( 2.5V) Switch Duty Cycle = 0 Fully Shut Down Source (VSENSE = 4.5V) Sink (VSENSE = 5.5V)
l l
85 90 85
110 120 0.1 8000 225 1.6 8 5.15 2 3 0.02
0.03 2000 3700 100 0.7 3 5000 140 1.0 5 5 0.5 1.0 0.005 1.5 -4.0 24 5 2.2 0.1 10 2.45 0.30
l l l l
4.85
Output Voltage Line Regulation VC Voltage at 0% Duty Cycle
20 50 2.7 0.5 4
A A V V C/W
current limit testing, VSENSE is adjusted to give a minimum switch on time of 1ms. Note 6: Switch to input voltage limitation must also be observed. Note 7: VMAX = 40V for the LT1076-5 and 60V for the LT1076HV-5. Note 8: 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 9: Does not include switch leakage. Note 10:
ILIM
RLIM - 1k 5k
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LT1076-5 PACKAGE DESCRIPTION
Q Package 5-Lead Plastic DD Pak
(Reference LTC DWG # 05-08-1461)
.060 (1.524) TYP
.256 (6.502)
.060 (1.524)
.390 - .415 (9.906 - 10.541) 15 TYP
.165 - .180 (4.191 - 4.572)
.045 - .055 (1.143 - 1.397) +.008 .004 -.004 +0.203 0.102 -0.102
.060 (1.524)
.183 (4.648)
.330 - .370 (8.382 - 9.398)
.059 (1.499) TYP
(
)
.075 (1.905) .300 (7.620) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK +.012 .143 -.020 +0.305 3.632 -0.508 .067 (1.702) .028 - .038 BSC (0.711 - 0.965) TYP
.013 - .023 (0.330 - 0.584)
.095 - .115 (2.413 - 2.921) .050 .012 (1.270 0.305)
Q(DD5) 0502
(
)
.420
.080
.420 .276
.350 .205 .565
.325 .565
.320 .090 .067 .042 .067 .090 .042
RECOMMENDED SOLDER PAD LAYOUT NOTE: 1. DIMENSIONS IN INCH/(MILLIMETER) 2. DRAWING NOT TO SCALE
RECOMMENDED SOLDER PAD LAYOUT FOR THICKER SOLDER PASTE APPLICATIONS
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LT1076-5
R Package 7-Lead Plastic DD Pak
(Reference LTC DWG # 05-08-1462)
.060 (1.524) TYP
.256 (6.502)
.060 (1.524)
.390 - .415 (9.906 - 10.541) 15 TYP
.165 - .180 (4.191 - 4.572)
.045 - .055 (1.143 - 1.397) +.008 .004 -.004 +0.203 0.102 -0.102
.060 (1.524)
.183 (4.648)
.330 - .370 (8.382 - 9.398)
.059 (1.499) TYP
(
)
.075 (1.905) .300 (7.620) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK .050 (1.27) BSC
.013 - .023 (0.330 - 0.584)
.095 - .115 (2.413 - 2.921) .050 .012 (1.270 0.305)
R (DD7) 0502
(
+.012 .143 -.020 +0.305 3.632 -0.508
)
.026 - .035 (0.660 - 0.889) TYP
.420 .420 .080 .276
.350 .205 .565
.325 .565
.320 .090 .050 .035 .050 .090 .035
RECOMMENDED SOLDER PAD LAYOUT NOTE: 1. DIMENSIONS IN INCH/(MILLIMETER) 2. DRAWING NOT TO SCALE
RECOMMENDED SOLDER PAD LAYOUT FOR THICKER SOLDER PASTE APPLICATIONS
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LT1076-5 PACKAGE DESCRIPTION
T Package 5-Lead Plastic TO-220 (Standard)
(Reference LTC DWG # 05-08-1421)
.147 - .155 (3.734 - 3.937) DIA .230 - .270 (5.842 - 6.858) .460 - .500 (11.684 - 12.700) .570 - .620 (14.478 - 15.748) .330 - .370 (8.382 - 9.398) .700 - .728 (17.78 - 18.491) .620 (15.75) TYP .165 - .180 (4.191 - 4.572)
.390 - .415 (9.906 - 10.541)
.045 - .055 (1.143 - 1.397)
SEATING PLANE .152 - .202 .260 - .320 (3.861 - 5.131) (6.60 - 8.13)
.095 - .115 (2.413 - 2.921) .155 - .195* (3.937 - 4.953) .013 - .023 (0.330 - 0.584)
BSC
.067 (1.70)
.028 - .038 (0.711 - 0.965)
.135 - .165 (3.429 - 4.191)
* MEASURED AT THE SEATING PLANE
T5 (TO-220) 0801
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LT1076-5 PACKAGE DESCRIPTION
T7 Package 7-Lead Plastic TO-220 (Standard)
(Reference LTC DWG # 05-08-1422)
.147 - .155 (3.734 - 3.937) DIA .230 - .270 (5.842 - 6.858) .460 - .500 (11.684 - 12.700) .570 - .620 (14.478 - 15.748) .330 - .370 (8.382 - 9.398) .620 (15.75) TYP .700 - .728 (17.780 - 18.491) .165 - .180 (4.191 - 4.572)
.390 - .415 (9.906 - 10.541)
.045 - .055 (1.143 - 1.397)
SEATING PLANE .152 - .202 .260 - .320 (3.860 - 5.130) (6.604 - 8.128) .050 (1.27) .026 - .036 (0.660 - 0.914)
.095 - .115 (2.413 - 2.921) .155 - .195* (3.937 - 4.953)
BSC
.135 - .165 (3.429 - 4.191)
.013 - .023 (0.330 - 0.584) *MEASURED AT THE SEATING PLANE
T7 (TO-220) 0801
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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.
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LT1076-5 RELATED PARTS
PART NUMBER LT1074/HV LT3430 LT1956 DESCRIPTION 4.4A (IOUT), 100kHz High Efficiency Step-Down DC/DC Converter 60V, 2.75A (IOUT), 200kHz High Efficiency Step-Down DC/DC Converter 60V, 1.2A (IOUT), 500kHz High Efficiency Step-Down DC/DC Converter COMMENTS VIN: 7.3V to 45V/64V, VOUT(MIN): 2.21V, IQ: 8.5mA, ISHDN: 10A, DD5/7, TO-2205/7 VIN: 5.5V to 60V, VOUT(MIN): 1.20V, IQ: 2.5mA, ISHDN: 25A, TSSOP16E VIN: 5.5V to 60V, VOUT(MIN): 1.20V, IQ: 2.5mA, ISHDN: 25A, TSSOP16E
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
LT 0407 REV C * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 1994

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