42V, 6A, synchronous step-down Silent Switcher 2 delivers 95% efficiency at 2MHz & ultralow EMI/EMC emissions
24 November 2017
Analog Devices, Inc., which recently acquired Linear Technology Corporation, announces the LT8640S, a 6A, 42V input synchronous step-down switching regulator. Its unique Silent Switcher® 2 architecture uses two internal input capacitors as well as internal BST and INTVCC capacitors to minimise the area of the hot loops.
Combined with very well controlled switching edges and an internal construction with an integral ground plane and the use of copper pillars in lieu of bond wires, the LT8640S’s design dramatically reduces EMI/EMC emissions. This improved EMI/EMC performance is not sensitive to board layout, simplifying design and reducing risk even when using two layer PC boards. The LT8640S can easily pass the automotive CISPR 25, Class 5 peak EMI limits with a 2MHz switching frequency over its entire load range. Spread spectrum frequency modulation is also available to lower EMI/EMC levels further.
The LT8640S’s synchronous rectification delivers efficiency as high as 95%, with a switching frequency of 2MHz. Its 3.4V to 42V input voltage range is ideal for automotive and industrial applications. The internal high efficiency switches can deliver up to 6A of continuous output current and peak loads of 7A to voltages as low as 0.97V. The LT8640S’s Burst Mode® operation offers only 2.5µA of quiescent current, well suited for applications such as automotive always-on systems, which need to extend operating battery life.
The LT8640S’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 on-time of only 30ns enables 2MHz constant frequency switching from a 16V input to a 1.5V output, enabling designers to optimise efficiency while avoiding critical noise-sensitive frequency bands. The LT8640S’s 24-lead, 4mm x 4mm LQFN package and high switching frequency keeps external inductors and capacitors small, providing a compact, thermally efficient footprint.
The LT8640S utilises 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 ripple below 10mVP-P.
For applications requiring the lowest noise operation, the LT8640S can be programmed to run in forced continuous mode over the entire load range. Its switching frequency is programmable and synchronisable from 200kHz to 3MHz. 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.
The LT8640SEV is packaged in a 4mm x 4mm LQFN package. An industrial temperature version, the LT8640SIV, is tested and guaranteed to operate from a –40°C to 125°C operating junction temperature. Pricing starts at $4.65 each for 1,000-piece quantities and both versions are available from stock. For more information, visit www.linear.com/product/LT8640S.
Summary of Features
- Silent Switcher® 2 Architecture
- - Ultralow EMI/EMC Emissions on Any PCB
- - Eliminates PCB Layout Sensitivity
- - Internal Capacitors for VIN, BST, INTVCC Reduce Radiated EMI
- - 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
- 6A Maximum Continuous, 7A Peak Output Current
- 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
- Safely Tolerates Inductor Saturation in Overload
- Adjustable & Synchronisable: 200kHz to 3MHz
- Output Soft-Start & Tracking
- Small 24-Lead 4mm × 4mm LQFN Package
Pricing shown is for budgetary use only and may differ due to local duties, taxes, fees and exchange rates.
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