Fast, Wide Operating Range No RSENSE Step-Down DC/DC Controller
Features and Benefits
- No Sense Resistor Required
- True Current Mode Control
- Optimized for High Step-Down Ratios
- tON(MIN) <=100ns
- Extremely Fast Transient Response
- Stable with Ceramic COUT
- Dual N-Channel MOSFET Synchronous Drive
- Power Good Output Voltage Monitor (LTC1778)
- Adjustable On-Time (LTC1778-1)
- Wide VIN Range: 4V to 36V
- ±1% 0.8V Voltage Reference
- Adjustable Current Limit
- Adjustable Switching Frequency
- Programmable Soft-Start
- Output Overvoltage Protection
- Optional Short-Circuit Shutdown Timer
- Micropower Shutdown: IQ <30µA
- Available in a 16-Pin Narrow SSOP Package
The LTC1778 is a synchronous stepdown switching regulator controller optimized for CPU power. The controller uses a valley current control architecture to deliver very low duty cycles with excellent transient response without requiring a sense resistor. Operating frequency is selected by an external resistor and is compensated for variations in VIN.
Discontinuous mode operation provides high efficiency operation at light loads. A forced continuous control pin reduces noise and RF interference, and can assist secondary winding regulation by disabling discontinuous operation when the main output is lightly loaded.
Fault protection is provided by internal foldback current limiting, an output overvoltage comparator and optional short-circuit shutdown timer. Soft-start capability for supply sequencing is accomplished using an external timing capacitor. The regulator current limit level is user programmable. Wide supply range allows operation from 4V to 36V at the input and from 0.8V up to (0.9)VIN at the output.
- Notebook and Palmtop Computers, PDAs
- Distributed Power 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 DC378 is a synchronous step-down buck regulator using the LTC1778 No RSENSE switching regulator controller. The controller uses a valley current control architecture to deliver very low duty cycles without requiring a sense resistor. The demo board operates with a 5V to 25V supply voltage and provides a 2.5V@10A output.
Demonstration circuit DC385 is a high density synchronous step-down (buck) regulator using the LTC1778 No RSENSE switching regulator controller. This controller uses a valley current control architecture to deliver very low duty cycles without requiring a sense resistor. The demo board input voltage range is 5V to 25V and it provides 1.2V@6A at the output.
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.
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Models for the following parts are available in LTspice:
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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.