DESCRIPTION

The LTM4608A is a complete 8A switch mode DC/DC power supply with ±1.75% total output voltage error. Included in the package are the switching controller, power FETs, inductor and all support components. Operating over an input voltage range of 2.7V to 5.5V, the LTM4608A supports an output voltage range of 0.6V to 5V, set by a single external resistor. This high efficiency design delivers up to 8A continuous current (10A peak). Only bulk input and output capacitors are needed to complete the design. The low profile package (2.82mm) enables utilization of unused space on the back side of PC boards for high density point-of-load regulation.The 0.630mm LGA pads with 1.27mm pitch simplify PCB layout by providing standard trace routing and via placement. The high switching frequency and current mode architecture enable a very fast transient response to line and load changes without sacrificing stability. The device supports frequency synchronization, programmable multiphase and/or spread spectrum operation, output voltage tracking for supply rail sequencing and voltage margining. Fault protection features include overvoltage protection, overcurrent protection and thermal shutdown. The LTM4608A is offered in 9mm × 15mm × 2.82mm LGA and 9mm × 15mm × 3.42mm BGA packages. The LTM4608A is available with SnPb (BGA) or RoHS compliant terminal finish.

 

FEATURES

Complete Standalone Power Supply

±1.75% Total DC Output Error (–55°C to 125°C)

2.7V to 5.5V Input Voltage Range

8A DC, 10A Peak Output Current

0.6V Up to 5V Output

Output Voltage Tracking and Margining

Power Good Tracks Margining

Multiphase Operation

Parallel Current Sharing

Onboard Frequency Synchronization

Spread Spectrum Frequency Modulation

Overcurrent/Thermal Shutdown Protection

Current Mode Control/Fast Transient Response

Selectable Burst Mode® Operation

Up to 95% Efficiency

Output Overvoltage Protection

9mm × 15mm × 2.82mm LGA and  9mm × 15mm × 3.42mm BGA Packages

 

APPLICATIONS

Telecom, Networking and Industrial Equipment

Storage Systems

Point of Load Regulation

 

OPERATION

The LTM4608A is a standalone nonisolated switch mode DC/DC power supply. It can deliver up to 8A of DC output current with few external input and output capacitors. This module provides precisely regulated output voltage programmable via one external resistor from 0.6V DC to 5.0V DC over a 2.7V to 5.5V input voltage.  The LTM4608A has an integrated constant frequency current mode regulator and built-in power MOSFET devices with fast switching speed. The typical switching frequency is 1.5MHz. For switching noise sensitive applications, it can be externally synchronized from 0.75MHz to 2.25MHz. Even spread spectrum switching can be implemented in the design to reduce noise.With current mode control and internal feedback loop compensation, the LTM4608A module has sufficient stability margins and good transient performance with a wide range of output capacitors, even with all ceramic output capacitors. Current mode control provides cycle-by-cycle fast current limit and thermal shutdown in an overcurrent condition. Internal overvoltage and undervoltage comparators pull the open-drain PGOOD output low if the output feedback voltage exits a ±10% window around the regulation point. Pulling the RUN pin below 1.3V forces the controller into its shutdown state, by turning off both M1 and M2 at low load current. The TRACK pin is used for programming the output voltage ramp and voltage tracking during start-up. See Applications Information.

The LTM4608A is internally compensated to be stable over all operating conditions. The Linear Technology µModule Power Design Tool is provided for transient and stability analysis. The FB pin is used to program the output voltage with a single external resistor to ground. Multiphase operation can be easily employed with the synchronization and phase mode controls. Up to 12 phases can be cascaded to run simultaneously with respect to each other by programming the PHMODE pin to different levels. The LTM4608A has clock in and clock out for poly phasing multiple devices or frequency synchronization. High efficiency at light loads can be accomplished with selectable Burst Mode operation using the MODE pin. These light load features will accommodate battery operation. Efficiency graphs are provided for light load operation in the Typical Performance Characteristics. Output voltage margining is supported, and can be programed from ±5% to ±15% using the MGN and BSEL pins. The PGOOD pin is disabled during margining