Low drop out (LDO) regulators are
useful in noise-sensitive situations but, when used with DC-DC
converters, their PSRR performance is often lacking. ON Semiconductor
has announced the NCP16x series of LDOs that aim to improve PSRR
performance.
One regulator in particular that is arguably the most well known is the 7805 5V regulator, which has seen widespread use in devices dating back to the 80s! But such regulators often require an input voltage that is at least 2V above the desired output voltage and this often results in a large amount of energy dissipation (i.e., wasted energy). This is where LDO regulators became popular as their minimum input voltage can be very close to the output voltage (for example, the NCP1117 has a maximum dropout voltage of 1.2V).
As electronics progressed, the need for high-speed systems and sensitive analog measurements has made electronic circuits more susceptible to noise and fluctuations. This would not typically be a problem if an LDO is used to regulate a power source such as a battery or mains supply (typical ripple frequency of 50Hz). If the power input to an LDO was from a switch mode power supply (SMPS), however, then the input ripple can be a serious issue.
SMPSs have become very popular due to their incredible energy efficiencies (up to 97%) and, when combined with LDOs, the regulation advantages of the LDO can be combined with the voltage reduction advantages of the SMPS. However, SMPSs often operate well above 100kHz and at these frequencies LDOs are not particularly good at regulating, such fast ripples which can result in high-frequency ripples in power lines. Therefore, sensitive circuits (especially analog circuits), can pick up interference from the power line and cause problems.
So with this information in mind, let's take a look at ON Semiconductor's NCP16x series.
Introducing the NCP16x Series
On the 4th of June, ON Semiconductor announced their latest line of LDO regulators, the NCP16x series, that they tout as having the industry's best power supply rejection ratio (PSSR). This will help designers of analog circuits avoid the problem with noise when using LDOs with SMPS.But the NCP16x range are not the only LDOs with high PSSR performance as they are also releasing the NCV81x range, which are AEC-Q100 qualified. For those who are unaware, AEC-Q100 qualified parts are those that are suitable for use in the US automotive industry and fall specifically under stress tests for integrated circuits. The applications for the NCP16x range include
- Portable devices (think SMPS with lithium-ion batteries)
- Wireless applications
- Image sensor modules
The wide input voltage range of 1.9V to 5.5V with a fixed voltage output range of 1.2V to 5.3V ensures that you can find the regulator you need for your application. With an incredibly low voltage dropout of 80mV, designers could be able to extend the life of batteries and therefore provide longer life devices to consumers.
But the real highlighted feature of these LDOs is their patented technology that gives them superior PSSR performance up to 100kHz, which will help to protect sensitive analog circuits from ripple noise from a switch mode power supply.
The new LDOs are available in the following IC packages:
- TSOP-5
- XDFN-4
- WLCSP-4
“An LDO is still the best solution for low current applications and with the small size and now even higher levels of performance in PSRR and low noise, they are an ideal power management solution for noise sensitive RF and image sensor applications. As an example of this we have a growing collection of image sensor reference designs that use this new LDO family. The total system level application provided by ON Semiconductor enables engineers to quickly implement the highest image quality sensor solutions available on the market today.”
Have you worked with LDOs, especially in automotive applications? Have you had issues with PSSR in the past? Share your experiences in the comments below?
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