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LT1676 Dataheets PDF



Part Number LT1676
Manufacturers Linear Technology
Logo Linear Technology
Description Wide Input Range/ High Efficiency/ Step-Down Switching Regulator
Datasheet LT1676 DatasheetLT1676 Datasheet (PDF)

LT1676 Wide Input Range, High Efficiency, Step-Down Switching Regulator FEATURES s s s DESCRIPTIO s s s s s Wide Input Range: 7.4V to 60V 700mA Peak Switch Current Rating Adaptive Switch Drive Maintains Efficiency at High Load Without Pulse Skipping at Light Load True Current Mode Control 100kHz Fixed Operating Frequency Synchronizable to 250kHz Low Supply Current in Shutdown: 30µA Available in 8-Pin SO and PDIP Packages The LT®1676 is a wide input range, high efficiency Buck (step-down) sw.

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LT1676 Wide Input Range, High Efficiency, Step-Down Switching Regulator FEATURES s s s DESCRIPTIO s s s s s Wide Input Range: 7.4V to 60V 700mA Peak Switch Current Rating Adaptive Switch Drive Maintains Efficiency at High Load Without Pulse Skipping at Light Load True Current Mode Control 100kHz Fixed Operating Frequency Synchronizable to 250kHz Low Supply Current in Shutdown: 30µA Available in 8-Pin SO and PDIP Packages The LT®1676 is a wide input range, high efficiency Buck (step-down) switching regulator. The monolithic die includes all oscillator, control and protection circuitry. The part can accept input voltages as high as 60V and contains an output switch rated at 700mA peak current. Current mode control offers excellent dynamic input supply rejection and short-circuit protection. The LT1676 contains several features to enhance efficiency. The internal control circuitry is normally powered via the VCC pin, thereby minimizing power drawn directly from the VIN supply (see Applications Information). The action of the LT1676 switch circuitry is also load dependent. At medium to high loads, the output switch circuitry maintains high rise time for good efficiency. At light loads, rise time is deliberately reduced to avoid pulse skipping behavior. The available SO-8 package and 100kHz switching frequency allow for minimal PC board area requirements. , LTC and LT are registered trademarks of Linear Technology Corporation. U APPLICATIO S s s s s Automotive DC/DC Converters Telecom 48V Step-Down Converters Cellular Phone Battery Charger Accessories IEEE 1394 Step-Down Converters TYPICAL APPLICATIO VIN 8V TO 50V 1 5 VIN 2 SHDN VCC 3 VSW LT1676 FB 8 VC 7 220µH* MBR160 100µF 10V EFFICIENCY (%) + 39µF 63V 6 + 5V 400mA 36.5k 1% SYNC 2200pF 22k 100pF 12.1k 1% GND 4 *65T #30 ON MAGNETICS MPP #55030 1676 F01 Figure 1 U Efficiency vs VIN and ILOAD 90 80 70 60 50 40 VIN = 12V 30 20 1 VIN = 24V VIN = 36V VIN = 48V 10 ILOAD (mA) 1676 TA01 U 100 1000 1 LT1676 ABSOLUTE MAXIMUM RATINGS (Note 1) PACKAGE/ORDER INFORMATION TOP VIEW SHDN 1 VCC 2 VSW 3 GND 4 N8 PACKAGE 8-LEAD PDIP 8 7 6 5 VC FB SYNC VIN Supply Voltage ........................................................ 60V Switch Voltage ......................................................... 60V SHDN, SYNC Pin Voltage ........................................... 7V VCC Pin Voltage ....................................................... 30V FB Pin Voltage ........................................................... 3V Operating Junction Temperature Range LT1676C ................................................ 0°C to 125°C LT1676I ............................................ – 40°C to 125°C Storage Temperature Range ................. – 65°C to 150°C Lead Temperature (Soldering, 10 sec).................. 300°C ORDER PART NUMBER LT1676CN8 LT1676CS8 LT1676IN8 LT1676IS8 S8 PART MARKING 1676 1676I S8 PACKAGE 8-LEAD PLASTIC SO TJMAX = 125°C, θJA = 130°C/ W (N8) TJMAX = 125°C, θJA = 110°C/ W (S8) Consult factory for Military grade parts. The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 48V, VSW open, VCC = 5V, VC = 1.4V unless otherwise noted. SYMBOL VIN(MIN) IVIN IVCC VVCC PARAMETER Minimum Input Voltage q ELECTRICAL CHARACTERISTICS CONDITIONS MIN TYP 6.7 MAX 7.0 7.4 800 900 4.0 5.0 3.1 50 75 1.255 1.265 1500 1000 1500 170 220 0.01 UNITS V V µA µA mA mA V µA µA V V nA µmho µmho µA µA V %/V V/V Power Supplies VIN Supply Current VCC Supply Current VCC Dropout Voltage Shutdown Mode IVIN VC = 0V q 620 3.2 q q q VC = 0V (Note 2) VSHDN = 0V 2.8 30 Feedback Amplifier VREF IIN gm ISRC, ISNK VCL Reference Voltage q 1.225 1.215 400 200 60 45 1.240 600 FB Pin Input Bias Current Feedback Amplifier Transconductance Feedback Amplifier Source or Sink Current q ∆lc = ± 10µA q 650 100 2.0 Feedback Amplifier Clamp Voltage Reference Voltage Line Regulation Voltage Gain 12V ≤ VIN ≤ 60V q 200 ISW = 0.5A (Note 3) Duty Cycle = 0% q 600 1.0 1.5 1.0 1.25 Output Switch VON ILIM Output Switch On Voltage Switch Current Limit Control Pin Threshold Control Voltage to Switch Transconductance V A V A/V 0.55 0.9 0.70 1.1 2 Current Amplifier 2 U W U U W W W LT1676 ELECTRICAL CHARACTERISTICS The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VIN = 48V, VSW open, VCC = 5V, VC = 1.4V unless otherwise noted. SYMBOL Timing f Switching Frequency q PARAMETER CONDITIONS MIN 90 85 85 TYP 100 90 300 1.35 0.2 1.6 MAX 110 115 UNITS kHz kHz % ns V V/ns V/ns Maximum Switch Duty Cycle tON(MIN) Minimum Switch On Time VC Pin Boost Threshold dV/dt Below Threshold dV/dt Above Threshold Sync Function Minimum Sync Amplitude Synchronization Range SYNC Pin Input R SHDN Pin Function VSHDN Shutdown Mode Threshold High dV/dt Mode, RL = 50Ω (Note 4) Boost Operation q q q 1.5 130 40 0.5 2.2 250 V kHz kΩ V V V V q.


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