ISL80510/05: High Performance LDOs
1A/0.5A Linear Regulators
Power Supply Design - Points of Concern
Before we talk about LDOs or the ISL80510 specifically, let’s first talk a little about power supply design in general. Here are some major topics that most of the power supply designers are concerned about. Simple design means less external components and less design or debug time. To create a simple system, use devices that offer integrated functionality of needed circuitry. Ideally, the device should not provide features that are not needed, especially if those features require additional external components. Efficiency and solution size are other major points of concern in power supply design. Simple designs often have smaller solution sizes as well, while efficiency may be inversely proportional the solution size. Engineering support plays a very important role in power supply sales.
Intersil Low Dropout Regulators (LDOs)
Though some of the topics discussed on the previous slides may not be directly applicable to LDOs, Intersil LDOs offer leading performances to stand out in the market. They offer fast transient performance, best-in-class overall accuracy and very low dropout voltage. Some of the differentiating features offered are remote sense, adjustable monotonous soft-start, and adjustable current limit.
Using an LDO
Low dropout regulators are frequently used due to their simplicity, low external component count, low electrical noise, and low quiescent current (IQ). For low load currents, their power dissipation is manageable and their efficiency is approximately VOUT/VIN. If the source decreases in voltage with use, such as with a battery, the efficiency of an LDO will increase as the difference between the input voltage and output voltage reduces until the dropout voltage is reached. However, at high load currents or when the input voltage is significantly higher than the output voltage, the power dissipation can be unmanageable due to excessive heat and too much power drain on the rest of the system. Also, an LDO can only provide an output below the input voltage.
Here are typical loads and applications where LDO use plays an important role in the power supply chain. Common applications include medical instruments, test equipment, and routers.
Linear Regulators: Kinds of LDOs
LDOs can be divided into three major categories. First, general purpose LDOs, these LDOs use transistors as pass devices and are very inexpensive as they suffer from many disadvantages compared to modern LDOs. The second type of LDO uses a power MOSFET as a pass element to offer smaller dropout voltage. However, they don’t have other modern features and protection circuits. High performance LDOs use P-CH MOSFETs as pass elements to offer the best dropout voltage and they offer additional performance and protection features.
ISL80505 and ISL80510: High Performance LDOs
The ISL80510 and ISL80505 are high performance, low dropout and low cost LDOs for applications where a balance is needed between performance and cost. The ISL80510 is designed for loads up to 1A and offers the best trade-off between dropout, stability, and PSRR. The 130mV typical dropout results in less power dissipation, while the very flat PSRR response across a wide range of frequency helps maintain the low noise of the output. Features like the adjustable monotonous soft-start are ideal for powering digital components and devices with a power-on reset. It also has very fast transient response, excellent total DC accuracy, and overcurrent and overtemperature protection. Other key specifications are 2.2V to 6V input and up to 5.5V output.
The ISL80505 has all the same features of the ISL80510 but is intended for smaller loads up to 0.5A and has a slightly better input voltage range, dropout, and PSRR at those load levels.
Helpful Design Resources
At Intersil, we try to provide as much support as possible to our valued customers. Here is a list of some of the tools that customers can make use of during their quest for a high performance power supply design from Intersil.
ISL80510EVAL1Z Evaluation Board
The ISL80510EVAL1Z is a very simple and easy to use evaluation or demonstration board that we have developed for the ISL80510. It is a very small 30mm x 30mm board with easy power connections and is ideal to wire into an active design or to show the performance of the part. The load regulation, load transient, and PSRR are shown here. A detailed user’s guide is also available for this board.
The evaluation board also has jumpers to select all major VOUT normally needed in an actual application. For the ISL80505, simply de-solder the ISL80510 from the board and solder the ISL80505 in its place. The board will work equally well with either device.
ISL80136/138 – 40V Input 50mA and 150mA LDOs
On this slide, I would like to cover LDOs that could be complementary to the ISL80510 if needed for a high voltage application. The ISL80136 50mA LDO and the ISL80138 150mA LDO both have very small IQ and shutdown current. They operate from a 6V to 40V power supply rail and have 1% voltage reference accuracy. This is an ideal solution for high voltage, low current applications. Flat quiescent current performance is ideal for high temperature industrial applications.
Intersil LDO Family
Here is the parametric table of Intersil LDOs. We provide both single supply and split power supply LDOs for critical applications. Supported VIN range is from 1V to 40V and output current is from 0.05A to 3A.
In summary, low dropout regulators are ideal for applications that require low noise and a small for factor, but efficiency and power dissipation must be accounted for as well. The ISL80505 and ISL80510 provide excellent performance, including very low dropout and high total accuracy, as well as valuable features like monotonic soft-start and overcurrent protection.