Fixed Ratio High Power Inductorless (Charge Pump) DC/DC Controller
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Evaluation Kit ManualsDC2787A - Demo Manual
Features and Benefits
- Wide VIN Range: 10V to 72V (80V ABS Max)
- Soft Switching for Low Noise Operation
- Phase-Lockable Fixed Frequency 200kHz to 1.5MHz
- ±1% Output Voltage Accuracy
- RSENSE or DCR Current Sensing
- Programmable CCM, DCM, or Burst Mode® Operation
- CLKOUT Pin for Multiphase Operation
- Short Circuit Protected
- EXTVCC Input for Improved Efficiency
- Monotonic Output Voltage Start-Up
- Optional External Reference
- 32-Pin (5mm × 5mm) QFN
The LTC7821 uses a proprietary architecture that merges a soft switching charge pump topology with a synchronous step-down converter to provide superior efficiency and EMI performance compared to traditional switching architectures.
In a typical 48V to 12V application, efficiency of greater than 97% is attainable with the LTC7821 switching at 500kHz. The same efficiency can only be achieved with a traditional controller switching at one-third the frequency. Higher switching frequencies allow the use of smaller inductances that yield faster transient response and smaller solution size.
The LTC7821 can be easily paralleled to provide higher output currents with its accurate current sharing capability and frequency synchronization function.
- Intermediate Bus Converters
- High Current Distributed Power Systems
- Telecom, Datacom, and Storage Systems
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (2)
Demonstration circuit 2787A is a high efficiency, 4 phase, hybrid converter. It can deliver 12V/100A with the input voltage from 40V to 60V. The demo board features the LTC7821, which uses an architecture that merges a soft-switching switched-capacitor topology with a traditional step-down converter to provide superior efficiency compared to the traditional switching architectures. It offers a high efficiency/high density and cost effective solution for nonisolated intermediate bus applications in power distribution, datacom and telecom as well as emerging 48V automotive systems.
External MOSFETs switch at a 400kHz fixed frequency for this demo board and can be programmed from 200kHz to 1.5MHz. The LTC7821’s powerful 1Ω N-channel MOSFET gate drivers maximize efficiency and can drive multiple MOSFETs in parallel for higher power applications. Due to its current mode control architecture, multiple LTC7821 devices can be operated in a parallel, multiphase configuration with excellent current sharing and low output voltage ripple to enable much higher power applications. Other benefits include low EMI emissions due to a soft-switched front end and reduced MOSFET stress.
The LTC7821 design eliminates the inrush current typically associated with switched capacitor circuits by prebalancing the capacitors on start-up. The LTC7821 also 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. Additional features include ±1% output voltage accuracy over temperature, a clock output for multiphase operation, a power good output signal, short-circuit protection, monotonic output voltage start-up, optional external reference, undervoltage lockout and internal charge balance circuitry. The LTC7821 data sheet must be used in conjunction with this demo board manual.
Demonstration circuit 2513A is a high efficiency, high power density hybrid converter. It can deliver 12V/20A with an input voltage from 36V to 72V. This demo board features the LTC7821, which uses an architecture that merges soft-switching switched-capacitor topology with a traditional step-down converter to provide superior efficiency compared to the traditional switching architectures. It offers a high efficiency/high density and cost effective solution for non isolated intermediate bus applications in power distribution, datacom and telecom as well as emerging 48V automotive systems.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
Models for the following parts are available in LTspice:
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