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Dial Into Performance & Emulated Current Mode
A family of unique hassle-free products that are easy to design-in into a broad category of power conversion applications for fast, reliable switching power supply solution. If efficiency is important and large input to output voltage difference is needed, then....
The LM(2)557x switching regulators feature all of the functions necessary to implement an efficient, high voltage buck regulator using a minimum of external components.
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This easy to use regulator includes a N-channel MOSFET, with an output current capability of up to 3 Amps. The regulator control method is based upon current mode control utilizing an emulated current ramp. Current mode control provides inherent line volt age feed-forward, cycle-by-cycle current limiting and ease of loop compensation.
The use of an emulated control ramp reduces noise sensitivity of the pulsewidth modulation circuit, allowing reliable control of very small duty cycles necessary in high input to output voltage ratio applications.
The operating frequency is programmable from 50 kHz up to 1 MHz. An oscillator synchronization pin allows multiple LM(2)557x regulators to self-synchronize or to be synchronized to an external clock. Additional protection features include: current limit, thermal shutdown and remote shutdown capability.
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Features - Integrated 75 V (42 V) N-channel MOSFET
- Ultra-wide input voltage range
from 6 V…75 V (42 V) - Internal bias regulator
- Adjustable output voltage from 1.225 V
- 1.5 % feedback reference accuracy
- Current mode control with emulated inductor current ramp
- Single resistor oscillator frequency setting
- Oscillator synchronization input
- Programmable soft-start
- Shutdown / Standby input
- Wide bandwidth error amplifier
- Thermal Shutdown
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Family Benefits - Multiple products with similar pin out and characteristics but different VIN, IOUT options to solve multiple and/or changing problems
- Helps user implementing a very high reliability power supply that could be used with expensive loads through excellent Transient Response and Ultra Short Duty Cycle
- Emulated Peak Current Mode combines best features of previous SIMPLE SWITCHER regulators AND current high performance switching regulators
- Improved transient response
- Good line and load regulation
- Reduced noise sensitivity of PWM circuitry
- Ultra-low duty cycle
- Convert from very high VIN (75 V/42 V) to very low VOUT (1.225 V)
- Cycle-by-cycle current limiting
- Ease of loop compensation
- Allows inductor size optimization
- Protects the load
Higher, Programmable Switching Frequency fswitch = 50...500 kHz/1 MHz Gives the designer freedom in choosing external components Can minimize solution size or maximize efficiency Reduces EMI External or Self Clock Synchronization External synchronization helps reduce system noise and RF interference Self synchronization makes it simple to synchronize multiple regulators Thermal shutdown and remote shutdown
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