Linear Technology announces the LTC7820, a high power fixed ratio charge pump DC/DC controller that eliminates the power inductor in a non-isolated intermediate bus converter. It enables up to a 50% reduction in circuit size and up to 4,000 W/in3 power density. The dc/dc controller drives external MOSFETs in voltage divider, doubler or inverter configurations with an efficiency of up to 99%. Its open loop fixed duty suits non-isolated intermediate bus applications in power distribution, datacom, telecom, high-end computing and industrial systems.
The controller operates from 6 to 72 V (80 V absolute max) input voltage range and can produce output currents in multiple 10s of amps, depending on the topology and choice of external components. It can be configured for a 2:1 step-down ratio from an input voltage up to 72 V. Two of the devices can be cascaded for a 4:1 step-down ratio. For even higher step-down ratios, such as a 6:1, the Dickson converter topology is recommended and is ideal for 54-V input to a 9 V output, requiring only a single device. The LTC7820 can also be configured for a 1:2 step-up ratio or a 1:1 inverter ratio from an input voltage as high as 36 V. External MOSFETs switch at a fixed frequency, programmable from 100 kHz to 1 MHz. The controller’s 1.1 Ω n-channel MOSFET gate drivers help maximize efficiency and drive multiple MOSFETs in parallel for higher power applications.
The LTC7820 controller monitors system voltage, current and temperature for faults, and uses a sense resistor for overcurrent protection. It stops switching and pulls the /FAULT pin low when a fault condition occurs. An onboard timer can be set for appropriate restart/retry times. The EXTVCC pin permits the LTC7820 to be powered from the lower voltage output of the converter or other available sources up to 40 V, reducing power dissipation and improving efficiency. Additional features include soft switching for low EMI, a power good output signal, undervoltage lockout and internal charge balance circuitry.
The LTC7820 is available in a 4 x 5 mm QFN-28 package. Extended and industrial temperature versions are available from –40°C to 125°C. The 1,000-piece price starts at $4.70 each. Linear Technology: www.linear.com/product/LTC7820.
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