Details, datasheet, quote on part number: DC2195B-B

The LT8609 family of step-down (buck) regulators from Linear Technology, now a part of ADI, can provide 2 A of continuous current with peak loads of 3 A of current. With a wide voltage input range from 3 V to 24 V or 42 V, the LT8609 consumes a very low 1.7 μA of non-switching quiescent current. This buck regulator is adjustable and synchronizable with a frequency range of 200 kHz to 2.2 MHz. The LT8609 is available in three types, with the standard having a fast switching edge speed, and can operate in both pulse-skipping mode and burst mode. The LT8609A has slower switch edges for lower EMI emissions. The LT8609B operates in pulse-skipping mode only and fast-switch edge speed. The LT8609 is ideal for GSM transceivers, low EMI requirements, and general purpose step-down applications.

CompanyLinear Technology Corporation
DatasheetDownload DC2195B-B datasheet
DC2195B-B photo

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Features, Applications
DEMO MANUAL 42V, 2A Micropower Synchronous Step-Down Regulator DESCRIPTION

Demonstration circuit 42V, 2A micropower synchronous step-down regulator featuring the LT8609/ LT8609A. There are two assembly versions. DC2195B-A is for the LT8609A and DC2195B-B is for the LT8609. The difference is the LT8609A has slower edge speeds for improved EMI at the expense of a small efficiency loss. The demo board is designed for 5V output from to 42V input. The wide input range allows a variety of input sources, such as automotive batteries and industrial supplies. The is a compact, high efficiency, high speed synchronous monolithic step-down switching regulator that consumes only 2.5A of quiescent current when output is regulated at 5V. Top and bottom power switches, compensation components and other necessary circuits are inside of the LT8609 to minimize external components and simplify design. The SYNC pin on the demo board is grounded by default for low ripple burst mode operation. Move JP1 to PULSE SKIPPING position can change the operation mode to pulseskipping operation. Once is on SPREAD SPECTRUM position, VCC is applied to the SYNC pin for low EMI spread spectrum operation. To synchronize to an external clock, move JP1 to SYNC and apply the external clock to the SYNC turret. Figure 1 shows the efficiency of the circuit. The demo board has an EMI filter installed. Under spread spectrum operation, the radiated EMI performances of the board (with EMI filter) are shown in Figures 2 and 3. The red lines in Figures 2 and 3 are CISPR25 Class 5 peak limit. To use the EMI filter, the input should be tied to VEMI, not VIN. An inductor L2, which a 0 jumper on the board by default now, can be added in the EMI filter to further reduce the conducted emission. This board is suitable for a wide range of automotive, telecom, industrial, and other general purpose applications. The LT8609/LT8609A data sheet gives a complete description of the part, operation and application information. The data sheet must be read in conjunction with this demo manual for DC2195B. Design files for this circuit board are available at

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SYMBOL VIN VOUT IOUT fSW EFE (LT8609A) EFE (LT8609) PARAMETER Input Voltage Range Output Voltage Maximum Output Current Switching Frequency Efficiency for DC2195B-A Efficiency for DC2195B-B

DC2195B is easy to set up to evaluate the performance of the LT8609/LT8609A. Refer to Figure 4 for proper measurement equipment setup and follow the procedure below: NOTE: When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. See Figure 5 for the proper scope technique. 1.Set an input power supply that is capable of 42V/2A. Then turn off the supply. 2.With power off, connect the supply to the input terminals VEMI and GND. 3.Turn on the power at the input. NOTE: Make sure that the input voltage never exceeds 42V. 4.Check for the proper output voltage of 5V. Turn off the power at the input. 5.Once the proper output voltage is established, connect a variable load capable of sinking 5V to the output terminals VOUT and GND. Set the current for 0A.

a. If efficiency measurements are desired, an ammeter can be put in series with the output load in order to measure the DC2195B's output current. b.A voltmeter can be placed across the output terminals in order to get an accurate output voltage measurement. 6.Turn on the power at the input. NOTE: If there is no output, temporarily disconnect the load to make sure that the load is not set too high. 7.Once the proper output voltage is again established, adjust the load and/or input within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other desired parameters. 8.An external clock can be added to the SYNC terminal when SYNC function is used (JP1 on the SYNC position). Please ensure that the chosen RT sets the LT8609/ LT8609A switching frequency to equal or below the lowest SYNC frequency. See the data sheet section, "Synchronization."

Figure 1. Efficiency vs Load Current at 12V Input 2MHz Switching Frequency

Figure 2. LT8609A Demo Circuit EMI Performance in CISPR25 Radiated Emission Test (VIN = 14V, VOUT = 5V, IOUT 2A, 2MHz Switching Frequency)


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The LT8609 family of step-down (buck) regulators from Linear Technology, now a part of ADI, can provide 2 A of continuous current with peak loads of 3 A of current. With a wide voltage input range from


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