COVER STORY LTC3307B
The LTC3307B showcases Analog Devices ability to produce very small, high effi ciency, low noise, monolithic synchronous step-down DC/DC converters. Housed in a low profi le 12-lead LQFN package measuring just 2mm × 2mm × 0.74mm the device is still capable of delivering 3A of output current and operates from a 2.25V to 5.5V input supply. Using constant-frequency, peak current mode control at switching frequencies from 3MHz to 10MHz and minimum on-time as low as 22ns, this regulator achieves fast transient response with small external components. The Silent Switcher architecture minimizes EMI emissions whilst the LQFN packages exposed pad delivers low thermal resistance.
The LT8648S is ideal for applications with higher power demands, this synchronous step-down regulator features second generation Silent Switcher 2 architecture designed to minimize EMI emissions while delivering high effi ciency at high switching frequencies. The device includes the integration of input and boost capacitors to optimize all the fast current loops inside and make it easy to achieve specifi ed EMI performance by reducing layout sensitivity. This performance makes the LT8648S ideal for noise sensitive applications and environments.
The LT8648S features fast, clean, low overshoot switching edges that enable high effi ciency operation even at high switching frequencies, leading to a small overall solution. The device is housed in a LQFN36 package measuring 7 x 4mm and can deliver an impressive 15A output current.
4.8A capability. Again, Silent Switcher architecture is employed in the LTM8051 to minimize EMI while delivering high effi ciency at frequencies up to 3MHz and enabling the device to achieve compliance with radiated emissions limits to CISPR22 Class B and CISPR25 Class 5 standards (Fig. 6) Included in the LTM8051 μModule® package are the controllers, power switches, inductors, and other support components. This high level of integration minimises the number of external components required, simplifying circuit design, and reducing overall cost.
Figure 6. Radiated EMI Performance (CISPR22 Class B & CISPR25 Class 5 Peak Limits)
Figure 5. Radiated EMI Performance (CISPR25 Test with Class 5 Peak Limits)
The device features peak current mode control with a 25ns minimum on-time, this allows high step-down ratios even at high switching frequencies. External compensation can also be implemented allowing for fast transient response at high switching frequencies, the device also permits current sharing whilst the CLKOUT pin enables synchronizing other regulators to the LT8648S. The device has low radiated EMI emissions and can meet the requirements of CISPR25 Class 5 Peak Limits (Fig.5).
Figure 4. Effi ciency and Power Loss in Burst Mode Operation
The LTC3307B can be operated in forced continuous or pulse- skipping mode for low noise, or low ripple Burst Mode operation for high efficiency at light loads (Fig.4). The device regulates output voltages as low as 500mV and includes integrated output over-voltage protection, short- circuit protection, thermal shut-down, clock synchronization, and up to 100% duty-cycle operation for low dropout. The compact and efficient LTC3307B is suitable for a range of applications such as battery-powered devices, optical networking equipment, servers, automotive, industrial and communications equipment. They are also ideal for circuits using distributed point of load (POL) DC power systems or for power supplies in designs incorporating FPGA, ASIC, and microprocessors.
The LT8648S has 3 operation modes, Burst Mode enables low 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 also provided along with an accurate input voltage UVLO confi gurable threshold.
The device operates over a wide input voltage range from 3V to 40V, output voltages from 0.8V to 8V, and a switching frequency range from 300kHz to 3MHz which can be set by a single resistor. Only the bulk input and output fi lter capacitors are needed to fi nish the design.
The LTM8051 is packaged in a compact Ball Grid Array (BGA) package measuring 6.25mm × 11.25mm × 2.22mm and has a specifi ed operating temperature range from -40°C to +125°C.
Design Support
The Silent Switcher switching regulators from Analog Devices are backed up with various development boards and kits, these allow designers to evaluate the full capability and features of the parts whilst speeding up time to market.
Anglia offer support for power supply and other types of designs with free evaluation kits and samples of Analog Devices products via the EZYsample service which is available to all registered Anglia Live account customers. Anglia’s engineering team are also on hand, they have extensive experience of working with power supply related designs and are able to advise on best practice to meet both effi ciency and regulatory requirements. This expertise is available to support customers with all aspects of their designs, offering hands on design support along with access to Analog Devices vast resource of technical application notes and reference designs.
LTM8051 LT8648S
www.cieonline.co.uk
The LTM8051 is a quad 40VIN, 1.2A step-down μModule® regulator, the outputs can be paralleled in an array for up to
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Components in Electronics September 2021 9
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