Non-Isolated DC-DC Step-Down Converters with Integrated Inductors for Space-Constrained Applications
By Landa Culbertson, Mouser Electronics
If you’ve ever worked on an application that is tight on space, you know it’s not that easy to find solutions to help achieve your end goal. Detailed size information is not usually among the foremost of specifications. Your initial approach tends to be, “Oh, this looks perfect for my project!” followed sadly by, “But it’s too big.” Regarding non-isolated dc-dc buck, or step-down, converters, designers looking for small point-of-load solutions are having better luck these days. The latest trend is dc-dc converters with integrated inductors, providing minimum footprint and profile.
Integrated Inductor Benefits
Aside from reducing board space requirements, internal inductors also simplify the design effort by eliminating the loop compensation and magnetic selection process, as well as enhancing performance by shielding radiated noise.
Grossing nearly $7 billion in analog revenue in 2012, with an estimated 25% attributable to the Power Management Segment, Texas Instruments is definitely one of the key companies to look at when researching power solutions. TI certainly does not disappoint with their new portfolio of space-saving dc-dc converter modules with integrated inductors, shown in Table 1.
The TPS82K MicroSiP™ Modules (pictured) are truly stunning given the amount of integration that leads to no additional component requirements (Figure 1), including a total solution size of <7 mm2.
Figure 1. The TPS82K MicroSiP™ Modules do not require additional components.
The TPS84K SWIFT™ Power Modules collection of devices, which require as few as three external components, offers something for everyone. TPS84250 and TPS84259 are the latest introductions, and elegantly address the positive and negative voltage requirements of amplifiers, as shown in Figure 2.
Figure 2. The TPS84K SWIFT™ Power Modules require minimal external components, and support a variety of applications, including positive and negative voltage requirements.
SIMPLE SWITCHER® Nano Modules
The SIMPLE SWITCHER® Nano Modules (pictured) provide a 1 amp solution that requires only an input capacitor, an output capacitor, a VCON capacitor, and feedback resistors, and it fits in <35 mm2.
Table 1. Texas Instruments DC-DC Buck Converter Modules with Integrated Inductors
|Iout (A)||Part Number||Vin (V)||Vout (V)||Switching frequency (kHz)||Package||Package Size (mm)||Total Solution Size ((mm2)|
|TPSK MicroSiP™ Modules|
|0.5||TPS82695||2.3 – 4.35||2.5 – 2.9||4000||µSiP8||2.3 x 2.9 x 1.0||6.7|
|0.6||TPS82671||2.3 – 4.80||1.05 -1.86||5500||µSiP8||2.3 x 2.9 x 1.0||6.7|
|TPS84K SWIFT™ Power Modules|
|2||TPS84210||2.95-6.0||0.8 – 3.6||500 to 2000||QFN39||9 x 11 x 2.8||Not available|
|4||TPS84410||2.95-6.0||0.8 – 3.6||500 to 2000||QFN39||9 x 11 x 2.8||Not available|
|6||TPS84610||2.95-6.0||0.8 – 3.6||500 to 2000||QFN39||9 x 11 x 2.8||Not available|
|3||TPS84320||4.5 – 14.5||0.8 – 5.5||330 to 780||QFN47||9 x 15 x 2.8||Not available|
|6||TPS84621||4.5 – 14.5||0.6 – 5.5||250 to 780||QFN47||9 x 15 x 2.8||Not available|
|2.5||TPS84250||7.0 - 50||2.5 - 15||400 to 1000||QFN41||9 x 11 x 2.8||Not available|
|2||TPS84259||4.5 - 40||-3 to -17||700 to 900||QFN41||9 x 11 x 2.8||Not available|
|SIMPLE SWITCHER® Nano Modules|
|0.65||LMZ10500||2.7 – 5.5||0.6 – 3.6||2000||POS8||3 x 2.5 x 1.425 ||35|
|1||LMZ10501||2.7 -5.5||0.6 – 3.6||2000||POS8||3 x 2.5 x 1.425||35|
Though Enpirion is a relatively new name in power management (and recently acquired by Altera), they offer an impressive portfolio of dc-dc buck converters with integrated inductors aimed at size-constrained applications. Founded in 2001 by a team of power management experts from Bell Laboratories, Enpirion provides space-saving system-on-chip power solutions for 5-V (5300 family, Table 2) and 12-V (2300 family, Table 3) supply rails. Figure 3 shows a typical implementation diagram using Enpirion’s 400-mA dc-dc converter, EP5348UI, with a total solution size of just 21 mm2. Figure 4 shows a typical application using Enpirion’s 4A dc-dc converter, EN2340QI, which fits in <200 mm2. Note that the 12-V products feature switching frequency synchronization to an external clock. In a system with multiple converters, similar, but not matching switching frequencies can produce a disturbance called beat frequency phenomenon. The ability to synchronize the switching frequencies of the regulators prevents the formation of beat frequencies. In addition, frequency synchronization helps keep the EMI generated within the system to a predictable set of frequencies.
Figure 3. Enpirion’s 5-V, 400-mA system-on-chip switching dc-dc converter power solution fits in 21 mm2
Table 2. Enpirion 5300 Family of 5-V DC-DC Buck Converters with Integrated Inductors*
|Iout (A)||Part Number||Vin (V)||Vout (V)||Switching frequency (kHz)||Package||Package Size (mm)||Total Solution Size (mm2)|
|0.4||EP5348UI||2.5 - 5.5||0.60 - 3.3||9000||µQFN14||2 x 1.75 x 0.9||21|
|0.5||EP5352QI||2.4 - 5.5||1.20 - 3.3||4000||QFN20||4 x 5 x 1.1||36|
|0.6||EP5362QI||2.4 - 5.5||1.20 - 3.3||4000||QFN20||4 x 5 x 1.1||36|
|0.6||EP5368QI||2.4 - 5.5||0.60 - 3.3||4000||QFN16||3 x 3 x 1.1||21|
|0.8||EP5382QI||2.4 -5.5||1.20 - 3.3||4000||QFN20||4 x 5 x 1.1||36|
|0.8||EP5388QI||2.4 -5.5||0.60 - 3.3||4000||QFN16||3 x 3 x 1.1||28|
|1.0||EN5311QI||2.4 - 6.6||0.60 - 3.3||4000||QFN20||4 x 5 x 1.1||36|
*Higher current options up to 9A are available
Figure 4. Enpirion’s 12-V, 4-A system-on-chip switching dc-dc converter power solution fits in 191 mm2
Table 3. Enpirion 2300 Family of 12-V DC-DC Buck Converters with Integrated Inductors
|Iout (A)||Part Number||Vin (V)||Vout (V)||Frequency Synchronization||Package||Package Size (mm)||Total Solution Size ((mm2)|
|4||EN2340QI||4.5 – 14.0||0.75 - 5.0||Yes||QFN68||8 x 11 x 3.0||191|
|6||EN2360QI||4.5 – 14.0||0.6 - 5.0||Yes||QFN68||8 x 11 x 3.0||191|
|9||EN2390QI||4.5 – 14.0||0.6 - 5.0||Yes||QFN76||10 x 11 x 3.0||235|
|15||EN23F0QI||4.5 – 14.0||0.6 - 3.3||Yes||QFN92||13 x 12 x 3.0||325|
Over the last couple of years, Micrel has released a family of synchronous buck regulators notable for internal inductors and architectures that provide the benefits of a low dropout voltage regulator (LDO) including ease of use, fast transient response, high PSRR, low noise, and low quiescent current, while also providing high efficiency. As seen in Figure 5, Micrel’s devices, such as the MIC33050, require minimal external components and come in a variety of voltage and current options, all in the low-profile MLF package.
Figure 5. Micrel’s 600-mA switching dc-dc solution requires only three external capacitors
Size is relative, and though it appears there are now many sufficiently small dc-dc buck converter solutions available on the market, there is sure to be more integration to come, driven by the continued miniaturization of modern electronics.
Landa writes from Dallas, TX. She holds a BSEE, and has 18 years experience in the electronics industry, from tech startups to Fortune 500 companies.