Bench Talk

(Source: sommart– stock.adobe.com)

Efficiency, efficiency, efficiency. That's all engineers talk about now. Sometimes, it's a good idea to look past that to discover the best solution for a design. Low-dropout (LDO) voltage regulators deserve some attention in these cases. Today’s LDO voltage regulators have some unique advantages. In this blog, we will examine the key benefits that LDOs offer for low-power portable devices and secondary supplies in microcontroller and FPGA designs.

For a consumer handheld device or an industrial control sensor unit that needs, say, 100mA, you might select AA lithium primary batteries like Energizer L91. This battery would supply 3000mA-hours, or 30 hours, at our 100mA draw. Putting two batteries in series would yield a 3.4V maximum and 2.8V minimum output after 30 hours. A fixed voltage LDO for a 2.5V supply might have a dropout voltage of 0.18V, so there is a good margin there. When designing for low-power applications, we need as much battery life as possible. So, if we are using just 18mW for the regulator, we get an exact ±1% voltage. The efficiency may not be as good as a switching regulator, but it is a much simpler and more reliable design with some significant advantages. Let’s take, for example, the advantages of a Nisshinbo NR1600 Series SMT LDO Voltage Regulator. This family offers fixed (1.0V to 3.6V) and adjustable (1.0V to 4.8V) output voltages at up to 500mA output current. The NR1600 comes in a tiny DFN1212-6-GK 1.2 x 1.2 x 0.4mm package (Figure 1). There are distinct advantages here.

Figure 1: The NR1600 regulator is housed in a very small DFN package. (Source: Mouser Electronics)

The first and most prominent benefits are simplicity and reliability. The small size and low component count needed for this LDO circuit means higher reliability and lower cost—for parts, inspection, inventory, and board layout.

The second gain is a programmable soft start. Too often, engineers do not take system turn-on as a crucial point. At turn-on startup, the inrush current to the output capacitor and the entire circuit can be problematic. It can disturb the battery source or protection circuity or cause interference due to a noise spike that is difficult to track down. Soft is better. It's less stressful on all components.

The NR1600 has a 160mA typical startup inrush current limit, adding adjustable soft start timing from zero to about 1.7ms, set with a single capacitor, for even better startup control. For applications that require startup sequencing, a power-good output and a chip-enabled input allow easy configuration for sequential supply soft startup of two regulators (Figure 2).

Figure 2: Circuit block diagram of the NR1600 LDO regulator. (Source: Mouser Electronics)

The chip takes a quiescent current of only 80µA. You can turn off the enable when the supply is unnecessary and go into a very low-power sleep condition. The NR1600 also features an output noise voltage of just V_SET x 30µV_rms. Regulation is excellent too. At room temperature, it is ±1%, and over -40°C to +85°C, it is just 3 percent, or 54mV for a 1.8V device.

Additionally, the chip has a ripple rejection of 75dB at 1kHz and a +165°C thermal shutdown function. Under voltage lockout is standard. An optional discharge function is an output pull-down when the chip enable is off, during thermal shutdown, or undervoltage lockout. A FET (32W) is used to remove any leftover charge. Applications for the NR1600 include portable consumer devices and communications equipment, low-power industrial control equipment, and any design requiring multiple power rails. This device should be used anywhere where small size and reliability are factors.

While efficiency has long-been the name of the game when it comes to low-power design, simplicity and reliability are additional factors that position LDO voltage regulators in an advantageous place. The NR1600 series LDO voltage regulators from Nisshinbo Micro Devices stand out for their compact size, reliability, and efficient performance. Ideal for a wide range of applications from consumer electronics to industrial controls, these regulators represent a blend of simplicity and technological advancement that meets the needs of modern power supply designs.

Jim Harrison is an electronics engineer and has held senior design engineering positions with industrial automation and scientific instrumentation companies since 1989. In 2004 he moved to writing and was a Sr. Editor with Hearst Business Media, Electronics Products Magazine for 14 years. He is now a consultant with Lincoln Technology Communications.