Two Programmable Buck Converters and Two Programmable Linear Voltage Regulators in a Single Package

Texas Instruments recently announced their new dual high-current buck converter and dual linear regulator all in a single IC.

Texas Instruments' LP87332D is being touted as a voltage regulator solution intended for meeting power management requirements of the platforms in industrial settings. Given all the goodies that this device offers, I personally can see this power solution being used in more than just industrial settings. According to the datasheet, this power management solution is available in only one package type: a 28-pin 5 × 5 mm VQFN (very thin QFN) package. Sure, 28 pins may initially seem like a lot of pins for a voltage regulator solution, but keep in mind that this device offers four voltage regulation solutions: two high-current buck converters, and two linear voltage regulators.

During my days as a solid-state drive (SSD) design engineer—which was a few years ago—the SSDs that I worked on required multiple voltage regulator solutions, including flavors of both DC/DC buck converters and linear voltage regulators. So, depending on present-day SSD designs and their design requirements, perhaps this TI device may be worth consideration as a possible candidate for power management.

Texas Instruments' LP87332D is a 28-pin device that offers two buck converters and two linear voltage regulators, with minimal external components. Circuit taken from the datasheet (PDF).

And, what makes this solution especially intriguing, and we'll discuss below, is that it's a truly programmable device via its I²C-compatible serial interface. As mentioned above, this IC is designed for industrial applications. Most industrial devices are expected to operate in the range of -40 to 105°C (AEC-Q100 Grade 2), while this device is able to operate in the range -40 to 125°C (AEC-Q100 Grade 1), a range typically reserved for devices used in automobiles, according to this TI website.

External Components

Texas Instruments appears to have provided a very thorough datasheet for this powerful (no pun intended) power management solution. TI has included recommendations for the required external filtering capacitors and the required inductors. As an example, the figure below shows us two options for recommended inductors.

Texas Instruments has provided, by way of the LP87332D datasheet, this recommended inductor table.

As a side note, it's very accommodating, and, in my opinion, very professional, when manufactures—such as TI—provide designers with a choice of inductors as opposed to, effectively, forcing designers to rely on a single-sourced part. So, nice work TI!

Buck Converters, Linear Regulators, and Programming

Buck Converters

The two buck converters in this IC have an input voltage range of 2.8 to 5.5 V, can provide output voltages ranging from 0.7 to 3.36 V, and can source up to 3 Amps (per converter). And while the switching frequency of these converters is 2 MHz, they can be synchronized, using an external clock, from 1 MHz up to 24 MHz, in 1-MHz steps. For more information on this topic, take a look at Section 7.3.2 (entitled Sync Clock Functionality) on page 17 of the datasheet.

The two buck converters can operate in PWM (pulse width modulation) mode, PFM (pulse frequency modulation) mode, or in AUTO mode, which means that the device automatically transitions between PWM and PFM modes depending on output current levels. As described in Section 7.3.1.2 (entitled Transition Between PWM and PFM Modes) on page 16 of the datasheet, PWM mode "optimizes efficiency at mid to full load at the expense of light-load efficiency," and PFM mode is utilized for reduced current consumption at lighter load current levels. If your design has both light- and heavy-current operational loads, and if one of your primary design requirements is to maximize power supply efficiencies, then you'll definitely want to consider using the AUTO mode. Its efficiency benefits are evident in the figure below.

The LP87332D's AUTO mode provides high buck converter efficiencies during light, medium, and heavy current loads. Plot taken from the datasheet (PDF).

 

Linear Regulators

The two low-dropout (LDO) linear regulators (LDO0 and LDO1) accept voltage inputs from 2.5 to 5.5 V, can provide output voltages from 0.8 to 3.3 V, and can supply output currents up to 300 mA per regulator.

 

Programming

Via the I2C interface programming aspect, the user can customize a whole host of features of this device, including:

• setting the output voltage of the buck converters and linear regulators;
• configuring the device's power-up sequence;
• enabling/disabling any of the converters/regulators;
• configuring the buck converters' operation mode (PWM, PFM, AUTO);
• and, enabling the buck converters' spread-spectrum mode for reducing EMI.

For more information on these programmable features and others, checkout Section 7.3 (entitled Feature Descriptions), on page 15, and Section 7.5 (entitled Programming) on page 35.

Layout Guidelines

TI has also been generous by providing layout guidelines including the following PCB layout example. For more information on layout hints and tips, review Section 10 (entitled Layout) on page 64 of the datasheet.

Board layout example of the LP87332D. Image taken from the datasheet (PDF).

Have you had a chance to use this new dual high-current buck converter and dual linear voltage regulator power management solution IC, from TI, in any of your designs? If so, leave a comment and tell us about your experiences.