High frequency and high efficiency, small size and low EMI? This voltage regulator is the best choice

The LT8653S is a dual-channel, 2 A, synchronous step-down regulator with an input voltage range of 3 V to 42 V. Based on Silent Switcher® 2 technology, the LT8653S can operate efficiently at high frequencies and has excellent EMI performance to meet the stringent requirements of automotive, industrial, computing, and communications environments.

The LT8653S integrates two independent regulator channels into a thermally enhanced 3 mm × 4 mm package. Each channel can simultaneously deliver 2 A of continuous output current and up to 3 A in pulsed load applications. The LT8653S supports Burst Mode® operation and requires only 6.2 µA of quiescent current when both outputs are in regulation, a key feature in battery-powered systems.

The LT8653S also offers forced continuous mode and spread spectrum frequency (SSFM) operation. SSFM mode reduces peak emissions near the fundamental operating frequency and harmonics by spreading the energy over a wider spectrum.

The LT8653S offers external compensation options that can be used to optimize transient response, or internal compensation can be used for simplicity. Fixed output options are also available, with two output voltage selectable pins that can generate 5 V, 3.3 V, and 1.8 V outputs without the need for external feedback resistors.

Figure 1 shows a dual-output step-down regulator application with low EMI and high efficiency using the LT8653S. The input voltage range is 5.8 V to 42 V, and the outputs are 5 V/2 A and 3.3 V/2 A. The switching frequency is set to 2 MHz. The internal regulator is powered by the 3.3 V output through the BIAS pin to reduce power consumption. Enabling Burst Mode operation (SYNC/MODE tied to GND) optimizes efficiency at light loads.

Figure 2 shows the radiated EMI of the regulator in Figure 1, which meets the stringent automotive CISPR 25 Class 5 radiated EMI specification. When the LT8653S switches at 2 MHz, the regulator achieves a peak efficiency of 94.8% at 12 V input and 5 V output, and 92.1% at 24 V input and 5 V output.

To minimize component count, the LT8653S has built-in internal loop compensation for most systems, but for designs that require optimized load transient performance, external compensation can be used to minimize output voltage offset and transient response time. Figure 3 shows a dual output regulator designed to optimize transient response.

Figure 4 shows the 5 V output (VOUT1) in response to a 0 A to 2 A load step. In this case, the VOUT deviation is less than 80 mV. This fast transient response combined with the high initial accuracy of the LT8653S can meet stringent VOUT tolerance requirements.

To further reduce component count, different fixed output voltages can be selected using pins D0 and D1 of the LT8653S, eliminating the need for external resistors to set the LT8653S output voltage. Depending on the selected combination of D0 and D1 pins, the internal feedback resistor divider is enabled and the FB pin can be directly connected to VOUT to regulate 5 V, 3.3 V, or 1.8 V output. By eliminating the need for an external resistor network, the overall solution size is small.

The total resistance of the internal feedback resistor divider is 12 MΩ, so the no-load quiescent current is much lower than that of a conventional circuit using an external resistor divider. The internal feedback resistor divider provides better regulation than an external divider, whose resistor errors typically affect accuracy. Figure 5 shows a dual-output regulator optimized for low parts count—the 5 V and 3.3 V outputs can be set by simply floating the D0 and D1 pins.

Silent Switcher 2 technology enables the LT8653S to operate at high frequencies while providing high efficiency and low EMI emissions. The LT8653S offers a wide input voltage range, low quiescent current, and integrates two 2 A regulator channels in a small 4 mm × 3 mm package, reducing the number of components and solution size. The LT8653S is small in size and has a low number of external components, allowing for flexible design for a variety of applications.