High Efficiency Switching Surge Stopper
Features and Benefits
- VOUT Clamp Stops High Voltage Input Surges
- 100% Duty Cycle Pass-Through Mode During Normal Operation
- Switches During Overvoltage or Overcurrent Transients and Faults and During Startup
- High Efficiency Switching Enables Long Duration Surge Protection and High Output Currents
- Wide VIN Range: 4V to 140V (150V Abs Max)
- Adjustable Output Voltage Clamp Up to 60V
- Adjustable Output Overcurrent Protection
- RSENSE or Inductor DCR Current Sensing Power Inductor Reduces Input EMI in Normal Mode
- Adjustable Soft-Start for Inrush Current Limiting
- Programmable Fault Timer
- Open-Drain Fault Warning Indicator
- 2.7% Retry Duty Cycle During Faults
- Adjustable Switching Frequency: 50kHz to to 900kHz
- Adjustable Input Voltage Turn-On Threshold
- Adjustable Input Overvoltage Lockout Threshold
- 20-Pin 4mm × 5mm QFN and TSSOP Packages
The LTC7862 high efficiency switching surge stopper protects loads from high voltage transients. High efficiency switching allows high output currents, small solution sizes, and high reliability. During an input overvoltage event, the LTC7862 controls the gates of two external N-channel MOSFETs to act as a switching DC/DC step-down regulator. This maintains the output voltage at a safe value, allowing the loads to continue to operate through the input overvoltage event. During normal operation, the LTC7862 turns on the top external N-channel MOSFET continuously, passing the input voltage through to the output, with minimal voltage drop. Using a fast peak current comparator, the LTC7862 also limits the maximum output current to protect against overcurrent and short-circuit faults.
An adjustable timer limits the time that the LTC7862 can spend switching during an overvoltage, overcurrent, or startup condition. When the timer expires, the external MOSFETs are turned off for a cooldown period and then the LTC7862 restarts. By strictly limiting how long the LTC7862 can switch, when the power loss is relatively high, the components and thermal design can be optimized for normal pass-through operation while still safely operating through high voltage input surges and/or overcurrent events.
- Automotive/Avionic/Industrial Surge Protection
- Automotive Load Dump Protection
- Vehicle Power Including ISO7637
- Military Power Including MIL1275
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (1)
Demonstration circuit 2674A is a 140V high efficiency switching surge stopper featuring the LTC7862. The board operates from an input voltage range of 8V to 140V, and provides a 8V to 34V output from 0A to 10A. Its output voltage is programmed to be clamped at 34V (typical) with a minimum ride-through duration of 500ms to allow the load to operate through the input overvoltage events. Its output current is limited to protect against output short-circuit faults. A soft-start feature is utilized to control its output voltage slew rate at start-up and input voltage transients. This feature reduces current surge and output voltage overshoot. The demonstration board is able to achieve low insertion drop (210mV typical) by utilizing the low RDS(ON) N-channel MOSFETs and low DCR inductor. This board also includes optional reverse polarity protection circuit which protects the downstream loads up to −40V. The demonstration circuit is suitable for a wide range of automotive, industrial, and telecom applications.
The LTC7862 high efficiency switching surge stopper protects loads from input high voltage transients. During an input overvoltage event, the LTC7862 controls the gate of two external N-channel MOSFETs and operate as a switching DC/DC step-down regulator. The output voltage is maintained at a safe level, allowing the loads to continue to operate through the input overvoltage events.
During normal operation, the LTC7862 turns on the top external N-channel MOSFET continuously, passing the input voltage through to the output with minimal voltage drop. The LTC7862 also limits the maximum output current to protect against overcurrent and short-circuit faults. A programmable timer limits the time that the LTC7862 can spend switching during an overvoltage, overcurrent, or startup condition. When the timer expires, the external MOSFETs are turned off for a cooldown period and then the LTC7862 restarts. The timer limits how long the LTC7862 can switch when the power loss is relatively high, the components and thermal design can be optimized for normal pass-through operation.
The LTC7862 data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with this demo manual for DC2674A. Proper board layout is essential for maximum thermal and electrical performance. See the data sheet sections for details. The LTC7862 is available in 20-lead TSSOP and QFN packages and two operating junction temperature grades: industrial (−40°C to 125°C) and high temperature automotive (−40°C to 150°C).
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
Models for the following parts are available in LTspice:
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.