Dual 8A DC/DC µModule Regulator Is Easily Paralleled for 16A

2009-09-01

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Two Independent 8A Regulator Systems in a Single Package

The LTM4616 is a dual input, dual output DC/DC µModule regulator in a 15mm × 15mm × 2.8mm LGA surface mount package. Only a few external components are needed since the switching controller, MOSFETs, inductor and other support components are integrated within the tiny package.

Both regulators feature an input supply voltage range of 2.375V to 5.5V and an adjustable output voltage range of 0.6V to 5V with up to 8A of continuous output current (10A peak). For higher output current designs, the LTM4616 can operate in a 2-phase parallel mode allowing the part to deliver a total output current of 16A. The default switching frequency is set to 1.5MHz, but can be adjusted to either 1MHz or 2MHz via the PLLLPF pins. Moreover, CLKIN can be externally synchronized from 750kHz to 2.25MHz. The device supports output voltage tracking for supply rail sequencing. Safety features include protection against short circuit, overvoltage and thermal shutdown conditions.

Simple and Efficient

The LTM4616 can be used as completely independent dual switching regulators with different inputs and outputs or paralleled to provide a single output. Figure 1 shows a typical design for a 5V common input and two independent outputs, 1.8V and 1.2V. Figure 2 shows the efficiency of the circuit at both 5V and 3.3V inputs.

Figure 1. Dual output LTM4616 for a single 3.3V to 5V input, independent 1.8V and 1.2V outputs at 8A each

Figure 2. LTM4616 efficiency: dual output

Few external components are needed since the integrated output capacitors can accommodate load steps to the full 8A. Each output voltage is set by a single set resistor from FB1 (or FB2) to GND. In parallel operation, the FB pins can be tied together with a single resistor for adjustable output voltage.

Parallel Operation for Increased Output Current

You can double the maximum output current to 16A by running the two outputs in parallel as shown in Figure 3. Note that the FB pins share a single voltage-set feedback resistor that is half the value of the feedback resistor in the usual two output configuration. This is because the internal 10k top feedback resistors are in parallel with one another, making the top value 5k.

Figure 3. LTM4616 with 16A parallel operation

It is preferred to connect CLKOUT1 to CLKIN2 when operating from a single input voltage. This minimizes the input voltage ripple by running the two regulators out of phase with each other. If more than 16A output current is required, then multiple LTM4616 regulators can be configured for multiphase operation with up to 12 phases via the PHMODE pin. Figure 4 shows the expected efficiency of the parallel system at 5V and 3.3V inputs to 1.8V output. Note that the two regulators drive equal output current even during soft-start, as shown in Figure 5.

Figure 4. Efficiency: single 1.8V output

Figure 5. Balanced current sharing for even heat dissipation [5V_IN to 1.8V_OUT at 16A]

Conclusion

Whether you require a single 16A high current output or dual 8A outputs with sequencing, the LTM4616 provides a simple and efficient solution.

关于作者

Eddie Beville

Eddie Beville是电源模块设计经理，负责μModule®系列的设计和开发。Eddie拥有加州橘子郡查普曼大学电子工程技术学士学位。Eddie喜欢骑山地自行车、跆拳道和钓鱼。

Alan Chern

Alan Chern是凌力尔特（现为ADI公司的一部分）原助理设计工程师。他负责为uModule®电源产品的设计、测试、演示板生产和产品评估提供支持。此外，Alan还参与客户应用方面的工作并管理uModule电源产品的设计导入项目。Alan拥有圣何塞州立大学MBA学位和加州大学圣克鲁兹分校电气工程学士学位。