DESCRIPTION

The LTM4632 is an ultrathin triple output step-down power μModule (power module) regulator that provides a complete power solution for DDR-QDR4 SRAM. Operating from a 3.6V to 15V input voltage, the LTM4632 supports two ±3A output rails, both sink and source capable, for VDDQ and VTT, plus a 10mA low noise reference VTTR output. Both VTT and VTTR tracks are equal to VDDQ/2. Housed in a 6.25mm × 6.25mm × 1.82mm LGA and 6.25mm × 6.25mm × 2.42mm BGA packages, the LTM4632 includes the switching controller, power FETs, inductors, and support components. Alternatively, the power μModule can also be configured as a two-phase single ±6A output VTT. Only a few ceramic input and output capacitors are needed to complete the design.

The LTM4632 supports selectable Burst Mode operation (CH1 only) and output voltage tracking for supply rail sequencing. Its high switching frequency and current mode control enable a very fast transient response to line and load changes without sacrificing stability.

Fault protection features include overvoltage input, overcurrent and overtemperature protection.

The LTM4632 is available with a SnPb (BGA) or RoHS compliant terminal finish.

 

FEATURES

Complete DDR-QDR4 SRAM Power Solution,Including VDDQ, VTT, VTTR (or VREF)

Solution in 0.5cm2 (Dual-Sided PCB)

Wide Input Voltage Range: 3.6V to 15V

3.3V Input Compatible with VIN Tied to INTVCC

0.6V to 2.5V Output Voltage Range

Dual ±3A DC Output Current with Sink and Source Capability

±1.5%, ±10mA Buffered VTTR = VDDQ/2 Output

3A VDDQ + 3A VTT or Dual Phase Single 6A VTT

±1.5% Maximum Total Output Voltage Regulation Error Over Load, Line, and Temperature

Current Mode Control, Fast Transient Response

External Frequency Synchronization

Multiphase Parallelable with Current Sharing

Selectable Burst Mode® Operation

Overvoltage Input and Overtemperature Protection

Power Good Indicator

Ultrathin 6.25mm × 6.25mm × 1.82mm LGA and 6.25mm × 6.25mm × 2.42mm BGA Packages

 

APPLICATIONS

DDR Memory Power Supply

General Purpose Point-of-Load Conversion

Telecom, Networking, and Industrial Equipment

 

OPERATION

The LTM4632 is a dual output standalone nonisolated switch mode DC/DC power supply for DDR-QDR4 SRAM memory supplies and bus termination. It can deliver two output rails which could both sink and source 3A DC current with few external input and output ceramic capacitors, plus a 10mA buffered VTTR (VREF) reference voltage which equals to one half of VDDQIN voltage.

Two or more module outputs can be easily paralleled to achieve a single VTT output with a higher sink and source current capability. Up to 8 phases can be paralleled to run simultaneously with a good current sharing guaranteed by current mode control loop.

This module provides precisely regulated output voltage (VOUT1) programmable via one external resistor from 0.6V to 2.5V over 3.6V to 15V input voltage range. With INTVCC tied to VIN, this module is able to operate from 3.3V input.

The LTM4632 has an integrated a dual constant on-time valley current mode regulator, power MOSFETs, inductor, and other supporting discrete components. The typical switching frequency is internally set to 1MHz. For switching noise-sensitive applications, the μModule can be externally synchronized to a clock within ±30% of the set frequency.

With current mode control and internal feedback loop compensation, the LTM4632 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 limiting. An internal overvoltage and undervoltage comparators pull the open-drain PGOOD output low if the output feedback voltage exits a ±8% window around the regulation point. Furthermore, an input overvoltage protection been utilized by shutting down both power MOSFETs when VIN rises above 17.5V to protect internal devices.

Pulling the RUN pin below 1V forces the controller into its shutdown state, turning off both power MOSFETs and most of the internal control circuitry. At light load currents, Burst Mode operation can be enabled to achieve higher efficiency compared to continuous current mode (CCM) by setting MODE pin to INTVCC. The TRACK/SS pin is used for power supply tracking and soft-start programming.