The LT8640 is a step-down regulator featuring Silent Switcher architecture that is designed to minimize EMI/EMC emissions while delivering high efficiency at frequencies up to 3MHz. Assembled in a 3mm × 4mm QFN, the monolithic construction with integrated power switches and inclusion of all necessary circuitry yields a solution with a minimal PCB footprint. An ultralow 2.5µA quiescent current – with the output in full regulation – enables applications requiring highest efficiency at very small load currents. Its 3.4V to 42V input voltage range makes it ideal for automotive, military and industrial applications.
The LT8640 from Linear Technology is a 5A, 42V input capable synchronous step-down switching regulator with a unique Silent Switcher™ architecture, combined with spread spectrum frequency modulation, which reduces EMI/EMC emissions by more than 25dB, even with switching frequencies in excess of 2MHz, enabling it to easily pass the automotive CISPR25, Class 5 peak limits.
Even with switching frequencies in excess of 2MHz, synchronous rectification delivers efficiency as high as 95% while Burst Mode operation keeps quiescent current under 2.5µA in no-load standby conditions. The 3.4V to 42V input voltage range of this device makes it ideal for a wide range of automotive and industrial applications.
The LT8640’s internal high efficiency switches deliver up to 5A of continuous output current and peak loads of 7A to voltages as low as 0.97V. The devices’s Burst Mode® operation keeps quiescent current under 2.5µA in no-load standby conditions, making it well suited for applications such as automotive “always-on” systems, which need to extend operating battery life. The LT8640’s unique design maintains a minimum dropout voltage of only 100mV at 1A under all conditions, enabling it to excel in scenarios such as automotive cold-crank.
Furthermore, a fast minimum top switch on-time of only 40ns enables 2MHz constant frequency switching from a 16V input to a 1.5V output, equipping designers to optimize efficiency while avoiding critical noise-sensitive frequency bands. The LT8640’s 20-lead 3mm x 4mm QFN package and high switching frequency keep external inductors and capacitors small, providing a compact, thermally efficient footprint.
The LT8640 utilizes internal top and bottom high efficiency power switches with the necessary boost diode, oscillator, control and logic circuitry integrated into a single die. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output voltage ripple below 10mVP-P at any load, from zero to full current.
Special design techniques and a new high speed process enable high efficiency over a wide input voltage range, and the LT8640’s current-mode topology enables fast transient response and excellent loop stability. Other features include internal compensation, a power good flag, output soft-start/tracking and thermal protection. Operation is safe in overload even with a saturated inductor.
Essential features are included and easy to use: An open-drain PG pin signals when the output is in regulation. The SYNC/MODE pin selects between Burst Mode, pulse-skipping, or spread spectrum mode, and also allows synchronization to an external clock. Soft-start and tracking functionality is accessed via the TR/SS pin. An accurate enable threshold can be set using the EN/UV pin and a resistor at the RT pin programs switch frequency.
The LT8640EUDC is packaged in a 3mm x 4mm QFN package and is priced at $4.35 each. An industrial temperature version, the LT8640IUDC, is tested and guaranteed to operate from a -40°C to 125°C operating junction temperature and is priced at $4.79 each.
An automotive temperature version, the LT8640HUDC, is tested and guaranteed to operate from a -40°C to 150°C operating junction temperature and is priced at $5.04 each. All pricing is for 1,000-piece quantities and all versions are available from stock.
The USA list pricing shown is for budgetary use only. International prices may differ due to local duties, taxes, fees and exchange rates.
For more information, visit www.linear.com/product/LT8640.
Summary of Features of the LT8640:
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Silent Switcher™ Architecture:
- Ultralow EMI/EMC Emissions
- Spread Spectrum Frequency Modulation
- High Efficiency at High Frequency
- Up to 96% Efficiency at 1MHz
- Up to 95% Efficiency at 2MHz
- Wide Input Voltage Range: 3.4V to 42V
- Ultralow Quiescent Current Burst Mode® Operation:
- 2.5µA IQ Regulating 12VIN to 3.3VOUT, Output Ripple < 10mVP-P
- Fast Minimum Switch-On Time: 40ns
- Low Dropout Under All Conditions: 100mV at 1A
- Safely Tolerates Inductor Saturation in Overload
- Adjustable & Synchronizable: 200kHz to 3MHz
- Peak Current Mode Operation
- Accurate 1V Enable Pin Threshold
- Internal Compensation
- Output Soft-Start & Tracking
- Small 18-Lead 3mm × 4mm QFN
Typical Application
Applications
- Automotive and Industrial Supplies
- General Purpose Step-Down
- GSM Power Supplies
Linear Technology (UK) Limited
Tel: +44 (0)1628 477066
E-mail: uksales@linear.com
Web site: www.linear.com
Website for product information: http://www.linear.com/product/LT8640
