Hybrid Step-Down Synchronous Controller
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Features and Benefits
- Low Profile, High Power Density, Capable of 500W+
- Soft Switching: 99% Peak Efficiency and Low EMI
- VIN Max for Voltage Divider (2:1): 72V
- VIN Max for Voltage Doubler (1:2)/Inverter (1:1): 36V
- Wide Bias VCC Range: 6V to 72V
- Soft Startup into Steady State Operation
- 6.5V to 40V EXTVCC Input for Improved Efficiency
- Input Current Sensing and Overcurrent Protection
- Wide Operating Frequency Range: 100kHz to 1MHz
- Output Short-Circuit/OV/UV Protections with Programmable Timer and Retry
- Thermally Enhanced 28-Pin 4mm × 5mm QFN Package
The LTC7820 is a fixed ratio high voltage high power switched capacitor/charge pump controller. The device includes four N-channel MOSFET gate drivers to drive external power MOSFETs in voltage divider, doubler or inverter configurations. The device achieves a 2:1 step-down ratio from an input voltage as high as 72V, a 1:2 step-up ratio from an input voltage as high as 36V, or a 1:1 inverting ratio from an input voltage up to 36V. Each power MOSFET is switched with 50% duty cycle at a constant pre-programmed switching frequency. System efficiency can be optimized to over 99%. The LTC7820 provides a small and cost effective solution for high power, non-isolated intermediate bus applications with fault protection.
The LTC7820 switching frequency can be linearly programmed from 100 kHz to 1MHz. The device is available in a thermally enhanced 28-lead QFN package with some no-connect pins for high voltage compatible pin spacing.
- Bus Converters
- High Power Distributed Power Systems
- Communications Systems
- Industrial Applications
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 (1)
Demonstration circuit 2543B is a high efficiency, high density, open loop charge pump (inductorless) DC/DC converter. This demo board is a voltage divider which achieves a 2:1 step-down ratio from an input voltage from 36V to 60V. The output voltage is a fixed ratio of half of the input voltage (VIN/2) and can supply a 10A load current. This demo board has the option to deliver a 20A maximum load with the addition of 15 chip capacitors.
The DC2543B provides a very high efficiency solution of 98.7% when converting 48VIN to 24VOUT at 10A. When configured for a 20A output, an efficiency of up to 98.4% is achievable for a 48VIN to 24VOUT at 20A.
The demo board features the LTC7820, a fixed ratio high voltage high power switched capacitor/charge pump controller in a 4mm × 5mm QFN package. Please see LTC7820 data sheet for more detailed information.
The DC2543B needs to be powered on with no load current or a very small load current (less than 50mA) with the default setup. Large load current can be applied after VO is established. The board offers a disconnect FET option which is controlled by the LTC7820 FAULT pin to disconnect the load during startup as shown in the schematic. Please refer to “Voltage Divider Prebalance Before Switching” section in the LTC7820 data sheet for more details regarding the startup of the voltage divider. The board also features some protection functions such as overcurrent and thermal shutdown to make it a reliable solution.
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.
To launch ready-to-run LTspice demonstration circuits for this part:
Step 1: Download and install LTspice on your computer.
Step 2: Click on the link in the section below to download a demonstration circuit.
Step 3: If LTspice does not automatically open after clicking the link below, you can instead run the simulation by right clicking on the link and selecting “Save Target As.” After saving the file to your computer, start LTspice and open the demonstration circuit by selecting ‘Open’ from the ‘File’ menu.
Models for the following parts are available in LTspice:
LTC7820 Companion Parts
Recommended Related Parts
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Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.