Features and Benefits
- Silent Switcher® Architecture
- Ultralow EMI Emissions
- Optional Spread Spectrum Modulation
- High Efficiency at High Frequency
- Up to 96% Efficiency at 1MHz, 12VIN to 5VOUT
- Up to 95% Efficiency at 2MHz, 12VIN to 5VOUT
- Wide Input Voltage Range: 3.4V to 42V
- 5A Maximum Continuous, 7A Peak Transient Output
- Ultralow Quiescent Current Burst Mode® Operation
- 2.5µA IQ Regulating 12VIN to 3.3VOUT
- Output Ripple < 10mVP-P
- Fast Minimum Switch On-Time: 30ns
- Low Dropout Under All Conditions: 100mV at 1A
- Forced Continuous Mode
- Adjustable and Synchronizable: 200kHz to 3MHz
- Output Soft-Start and Power Good
- Small 20-Lead 4mm × 3mm LQFN Package
- AEC-Q100 Qualified for Automotive Applications
The LT8636/LT8637 synchronous step-down regulator features Silent Switcher architecture designed to minimize EMI emissions while delivering high efficiency at high switching frequencies. Peak current mode control with a 30ns minimum on-time allows high step-down ratios even at high switching frequencies.
The LT8636’s ultralow 2.5µA quiescent current—with the output in full regulation—enables applications requiring highest efficiency at very small load currents. The LT8637 has external compensation to enable current sharing and fast transient response at high switching frequencies. A CLKOUT pin enables synchronizing other regulators to the LT8636/LT8637.
Burst Mode operation enables ultralow standby current consumption, forced continuous mode can control frequency harmonics across the entire output load range, or spread spectrum operation can further reduce EMI emissions. Soft-start and tracking functionality is accessed via the TR/SS pin, and an accurate input voltage UVLO threshold can be set using the EN/UV pin.
- Automotive and Industrial Supplies
- General Purpose Step-Down
Product Lifecycle Recommended for New Designs
This product has been released to the market. The data sheet contains all final specifications and operating conditions. For new designs, ADI recommends utilization of these products.
Evaluation Kits (1)
Demonstration circuit 3020A is a 42V, 5A (7A Peak) synchronous step-down Silent Switcher® with spread spectrum frequency modulation featuring the LT8637. The demo board is designed for 5V output from a 5.8V to 42V input. The wide input range allows a variety of input sources, such as automotive batteries and industrial supplies. The LT8637 is a compact, low emission, high efficiency, and high frequency synchronous monolithic stepdown switching regulator. The LT8637 is the same as the LT8636, except it has a VC pin for external compensation. This allows the customer to optimize the loop response, or to parallel multiple regulators for higher current applications. The proprietary Silent Switcher architecture minimizes electromagnetic emissions with simplified filter and reduced layout sensitivity. Selectable spread spectrum mode further improves EMI performance, making it perfect solution to the noise sensitive applications. The regulator’s ultralow 2.5μA quiescent current—with the output in full regulation—enables applications requiring highest efficiency at very light load currents, such as automotive and battery powered portable instruments.
Peak current mode control with minimum on-time of as small as 30ns allows high step-down conversion even at high frequency. The LT8637 switching frequency can be programmed either via oscillator resistor or external clock over a 200kHz to 3MHz range. The default frequency of demo circuit 3020A is 2MHz.
The SYNC/MODE pin on the demo board DC3020A is grounded (JP1 at BURST position) by default for low ripple Burst Mode® operation. To synchronize to an external clock, move the Jump JP1 to SYNC/FCM and apply the external clock to the SYNC terminal ON THE 3020A. In sync mode, the part runs in forced continuous mode. Without external clock applied, the SYNC/MODE pin is floating, and the part runs in forced continuous mode. This mode offers fast transient response and full frequency operation over a wide load range. Alternatively, move the Jump JP1 to the SPREAD-SPECTRUM, and the SYNC/MODE is tied to INTVCC, the part runs in forced continuous mode with spread spectrum function enabled.
The LT8637 data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with the demo manual for demo circuit 3020A. The layout recommendations for low EMI operation and best thermal performance are available in the data sheet section Low EMI PCB Layout and Thermal Considerations and Peak Output Current. Contact ADI applications engineer for support.
Tools & Simulations
LTpowerCAD® is a power supply design program which selects power stage components, provides detailed power efficiency, shows quick loop Bode plot stability and load transient analysis, and can export to LTspice for simulation.
Design tools for the following parts are available in LTpowerCAD:
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.