Dual 4A outputs from a 42V-in low EMI, step-down regulator
The device’s architecture uses four internal input capacitors as well as two internal BST (high-side boost) and a single INTVCC capacitor to minimize the area of the hot loops – these are implemented with ceramic capcitors within the body of the package. Combined with very well controlled switching edges and an internal construction using copper pillars in place of bond wires and an integral ground plane, the LT8650S’s design greatly reduces EMI emissions. This improved EMI performance is not sensitive to PCB layout, simplifying design and reducing risk even when using two-layer PC boards. The LT8650S can easily pass the automotive CISPR 25, Class 5 peak EMI limits with a 2 MHz switching frequency over its entire load range. Spread spectrum frequency modulation is also available to lower EMI levels further.
The LT8650S’s synchronous rectification delivers efficiency as high as 94.6% with a switching frequency of 2 MHz. Its 3.0V to 42V input voltage range is suitable for automotive and industrial applications. The internal high efficiency switches can deliver up to 4A of continuous output current simultaneously and up to 6A peak loads on either channel to output voltages as low as 0.8V. The device’s Burst Mode operation ensures 6.2 µA of quiescent current (for both channels), for applications such as automotive always-on systems. A fast minimum on-time of 40nsec enables 2 MHz constant frequency switching from a 16V input to a 2V output, enabling designers to optimize efficiency while avoiding critical noise-sensitive frequency bands. The LT8650S’s 32-lead 4 x 6 mm LQFN package and high switching frequency keeps external inductors and capacitors small.
The LT8650S utilizes internal top and bottom high efficiency power switches with the necessary boost diodes, 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 10 mVP-P. For applications requiring very fast transient response or current sharing of the two channels, external VC pins are available. For the lowest noise operation, the LT8650S can be programmed to run in forced continuous mode over the entire load range with spread spectrum frequency modulation. Its switching frequency is programmable and synchronizable from 300 kHz to 3 MHz. Current mode topology enables fast transient response and excellent loop stability. Other features include a die temperature monitor, power good flags, output soft-start/tracking and thermal protection.
The LT8650SEV is packaged in a 4 x 6 mm LQFN package. An industrial temperature version, the LT8650SIV, is tested and guaranteed to operate from a –40°C to 125°C operating junction temperature. Pricing starts at $5.75 (1000).
Analog Devices/Linear Technology; www.linear.com/product/LT8650S
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