Regulator designed for wide input voltage, low EMI applications

The LT8606/LT8607/LT8608 is a family of monolithic step-down regulators optimized for applications with a wide input voltage range, low EMI levels, and small solution size. All devices in the family are available in thermally enhanced 10-lead MSE and 8-lead 2 mm x 2 mm DFN packages, allowing them to fit into tight spaces. As shown in Table 1, they differ in their output current capability.

The low IQ of the LT8606/LT8607/LT8608 is essential in battery-powered applications where no-load current must be kept low. These devices feature a Burst Mode® feature that consumes only 2.5 μA of quiescent current from the input source even when the output voltage is regulated, thereby keeping the battery on standby as long as possible. The wide input voltage range of 3 V to 42 V meets the demanding requirements of industrial and automotive applications, which are characterized by the lack of a stable, high-quality voltage source. The three devices are available in a 10-lead MSE package and also have spread spectrum operation capabilities to meet ultra-low EMI radiation requirements.

Figure 1 shows a 5 V output supply based on the 10-pin LT8607 regulator. The input voltage extends up to 42 V, and the output is set to 5 V (at 750 mA) with a 2 MHz switching frequency. Only a few additional components are required to complete the solution, including inductor L1 and a few passive components.

Figure 1. The high efficiency LT8607 12 V to 5 V synchronous step-down converter .

As shown in Figure 2, this circuit can achieve a peak efficiency of 92.5%.

Figure 2. Efficiency vs. load current for a 12 VIN to 5 VOUT step-down converter based on the LT8606/LT8607/LT8608.

High efficiency and low idle current are very important features for battery-powered applications during light load operation and no-load standby mode . The 2.5 μA quiescent current and Burst Mode operation option of the LT8606/LT8607/LT8608 are ideal solutions for these requirements. Under light load and no-load conditions, LT8606/LT8607/LT8608-based converters gradually reduce the switching frequency, thereby reducing switching power losses and maintaining low output voltage ripple. Figure 3 shows the light load efficiency of the solution shown in Figure 1.

Figure 3. Efficiency and power dissipation vs. load current for the circuit in Figure 1.

In automotive, industrial, computing, and telecommunications environments, EMI/EMC compliance is required in addition to efficiency. Using higher switching frequencies can reduce solution size, but the trade-off is often increased EMI emissions.

The integrated MOSFETs, built-in compensation circuitry, and 2.2 MHz operating frequency of the LT8606/LT8607/LT8608 minimize solution size, but they also achieve excellent EMI performance due to advanced process technology. Spread spectrum mode operation of the switching frequency can further reduce EMI emissions. Figure 4 shows the CISPR 25 EMI test results for the solution shown in Figure 1.

Figure 4. CISPR 25 radiated EMI performance of the circuit shown in Figure 1.

The LT8606/LT8607/LT8608 are easy-to-use monolithic step-down regulators with integrated power MOSFETs and built-in compensation circuitry. These devices are optimized for applications that require a wide input voltage range and low EMI noise. The 2.5 μA quiescent current and Burst Mode operation option of these devices make them an ideal solution for battery-powered step-down converters, significantly extending battery standby time.

The switching frequency range of 200 kHz to 2.2 MHz makes them suitable for most low-power to micropower applications. The integrated MOSFETs together with the switching frequency capability up to 2.2 MHz significantly reduce the total solution size. The CISPR 25 scan results show their excellent radiated EMI performance, thus meeting the most stringent EMI standards.