Point Of Load (POL) Solutions
For multiple power supply rails for MCU and FPGA
Point of load (POL) converters are a popular choice for applications that require multiple power rails demanded by the latest generation of Microprocessors, DSP or FGPA. These complex core IC increasingly require sophisticated power schemes, than often demand a large number of higher current, low Voltage power supply rails. Providing all the required power supply rails using a multi-channel PMIC means the power must be routed around the PCB from a central point, which can result in poor output regulation and complicated PCB layouts. Using a PMIC also localises the heat dissipation which can be problematic for thermal management.
These problems can be overcome by deploying several Point of load (POL) DC/DC Converters instead of a single PMIC, with each DC/DC providing a one supply rail and locating these DC/DC Converter IC close to where the power is required on the PCB. The resulting shorter PCB track lengths helps to improve VOUT stability and reduces EMI. The systems heat dissipation can also be spread more evenly around the PCB, which improves thermal management.
Torex specialises in simple, cost-effective, POL DC/DC Converters and this article shown how they can be used in typical application.
Using Point of Load Micro DC/DC Converters to power a Microprocessor or FPGA.
- Stable operation and reduction of CL and decoupling capacitors
- Small size / High efficiency / Good heat dispersion / Low EMI
- Power-up and shutdown sequence
|(1) Step-down DC/DC
||DC/DC with Integrated Inductor, PWM/PFM, 3MHz, 600mA
||DC/DC with Integrated Inductor, PWM/PFM, 2.4MHz, 2A
|(2) RESET IC
||Low Iq, Release delay with external Cd
(1) Step-down DC/DC for MPU / Memory / FPGA as POL
- Stable operation / small size / low EMI can be achieved by the placing Micro DC/DC (with integrated inductor) very close to the Point of Load. (XCL205/06, XCL211/12)
(2) Monitoring 5V input
- Monitor 5V input with the voltage detector. For start-up / shutdown sequence control and notification of voltage drop to MPU. (XC6119)
(3) Start-up / Shutdown sequence
- The RC delay to each CE terminal of the DC/DC and the CL discharge function make it easy to implement start-up / shutdown sequences. Drive the RC delays with the CMOS output type (XC6119C) voltage detector.
Benefit Of Point Of Load VS. PMIC
Typical PMIC Approach
Problems with using a PMIC
- Unstable operation due to long wiring and GND interference
- Therefore, many capacitors are required for each part
- Heat concentration and EMI from long wiring
Point Of Load Approach:
Benefit of POL and TOREX proposal
- Short wiring length by placement in the immediate vicinity, achieves stable operation and reduction of capacitors. Easy heat dissipation due to heat source separation, and reduced EMI
- By using the Inductor built-in Micro DC/DC, it can be easily placed in the immediate vicinity, and stable operation, lower EMI, and easier design are possible