DC/DC Controller offers margining, tracking and PLL capability

Milpitas, CA Linear Technology introduces the LTC3770, a synchronous step-down DC/DC controller with fast transient response, high output accuracy, integrated tracking and sequencing functions, and output margining capability. The LTC3770's constant on-time, valley current mode architecture, combined with a 50nsec typical minimum on-time, allows the control loop to respond instantly to load steps. The LTC3770 uses current mode control and can operate without a sense resistor by sensing the voltage drop across the synchronous power MOSFET. For systems where control of the maximum output current is important, a conventional sense resistor can be used in the source of the lower MOSFET. For either case the current limit is user-programmable, allowing optimum system efficiency and excellent control over the maximum output current.

The LTC3770 is capable of operating at very low duty cycles; outputs as low as 0.6V can be supplied from input voltages as high as 32V. The operating frequency is selected by a single external resistor. For applications that require constant-frequency operation, a phase lock loop allows the LTC3770 to be synchronized to an external clock.

The LTC3770 output voltage accuracy is specified at ±0.5% at room temp and ±0.67% from 0°C to 85°C. Tracking and sequencing functions allow the user to optimize the startup of multiple power supplies, and margining capability provides the user with the ability to stress the load circuitry with overvoltage and undervoltage conditions during production testing. An open-drain PGOOD output provides fault condition feedback.

Summary of LTC3770 features:
* Wide Input Range from 4V to 32V
* ±0.67% 0.6V Reference Voltage Accuracy
* Output Voltage Tracking Capability
* Programmable Margining
* Use of Sense Resistor is Optional
* True Current Mode Control
* Phase Lock Loop Frequency Synchronization

The LTC3770 is offered in two packages of 5mm x 5mm QFN and 28-lead SSOP. It is rated for operation from -40°C to 85°C. 1,000-piece price starts at $3.55.

Linear Technology Corporation, 1630 McCarthy Boulevard, Milpitas, CA 95035-7417. Tel: 1-800-4-LINEAR (for literature only), or go to the company's web site:

3770 Data sheet

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