The main features of the LT8607, functional block diagram, multiple application circuit analysis

Linear's LT8607 is a compact, high efficiency and high speed synchronous switching buck regulator with non-switching quiescent current of only 1.7μA, continuous supply of 750mA, input voltage from 3V to 42V, output ripple less than 10mVP-P, and efficiency greater than 93%, adjustable and synchronizable frequency 200kHz to 2.2MHz, mainly used in general-purpose buck converters and low EMI buck converters. This article introduces the main features of the LT8607, functional block diagrams, various application circuits, and the main features of the demo board DC2565A , measurement setup diagram, circuit diagram, bill of materials and PCB design.

The LT®8607 is a compact, high efficiency, high speedsynchronous monolithic step-down switching regulator that consumes only 1.7μA of non-switching quiescentcurrent. The LT8607 can deliver 750mA of conTInuouscurrent. Top and bottom power switches are included withall necessary circuitry to minimize the Low for Burst Mode operaTIon enables highefficiency down to very low output currents while keeping the output ripple below 10mVP-P. Internal compensaTIon with peak current mode topology allows the use of smallinductors and results in fast transient response and goodloop stability. /UV pin has an accurate 1V threshold and can be used to program VIN undervoltage lockout or toshut down the LT8607 reducing the input supply currentto 1μA. The PG pin signals when VOUT is within ±8.5% of the programmed output voltage as well as fault condiTIons.

The MSOP package includes a SYNC pin to synchronize to an external clock, or to select Burst Mode operationor pulse-skipping with or without spread spectrum; the TR/SS pin programs soft-start or tracking.

The main features of the LT8607:

Wide Input Voltage Range: 3.0V to 42V
Ultralow Quiescent Current Burst Mode® Operation:
<3μA IQ Regulating 12VIN to 3.3VOUT
Output Ripple <10mVP-P
High Efficiency 2MHz Synchronous Operation:
>93% Efficiency at 0.5A, 12VIN to 5VOUT
750mA Maximum Continuous Output
Fast Minimum Switch-On Time: 35ns
Adjustable and Synchronizable: 200kHz to 2.2MHz
Spread Spectrum Frequency Modulation for Low EMI
Allows Use of Small Inductors
Low Dropout
Peak Current Mode Operation
Accurate 1V Enable Pin Threshold
Internal Compensation
Output Soft-Start and Tracking
Small Thermally Enhanced 10-Lead MSOP Packageor 8-Lead 2mm.2mm DFN Package

LT8607 application:

General Purpose Step-Down Converter
Low EMI Step Down

Figure 1. Functional Block Diagram of the LT8607

Figure 2. LT8607 application circuit diagram (1)

Figure 3. LT8607 application circuit diagram (2)

Figure 4. LT8607 application circuit diagram (3)

Figure 5. LT8607 application circuit diagram (4)

Figure 6. LT8607 application circuit diagram (5)

Demo board DC2565A

Demonstration Circuit 2565A is a 42V, 0.75A micropowersynchronous step-down regulator featuring the LTR8607.

The demo board is designed for 5V output from a 5.5Vto 42V input. The wide input range allows a variety of input sources, such as automotive batteries and industrialsupplies. The LT8607 is a compact, high efficiency, high speed synchronous monolithic step-down switchingregulator that Consumptions less than 3μA of quiescentcurrent when output is regulated at 5V. Top and bottompower switches, compensation components and other necessary circuits are inside of the LT8607 to minimizeexternal components and simplify design.

The SYNC pin on the demo board is grounded by default for low ripple Burst ModeR operation. Move JP1 to PULSESKIPPING position can change the operation mode topulse-skipping operation. Once JP1 is on SPREAD SPECTRUMposition, VCC is applied to the SYNC pin for low EMI spread spectrum Operation. To synchronous to anexternal clock, move JP1 to SYNC and apply the external clock to the SYNC turret. Figure 1 shows the efficiency of the circuit.

The radiated EMI performances of the board (with EMI filter) are shown in Figure 2 and Figure 3. The red lines in Figure 2 and Figure 3 are CISPR25 Class 5 peak limit. To use the EMIfilter, the input An inductorL2, which is a 0Ω jumper on the board by defaultnow, can be added in the EMI filter to further reduce theconducted emission.

The LT8607 data sheet gives a complete description of the part, operation and application information. The datasheet must be read in conjunction with this demo manual for DC2565A.

Figure 7. Demo board DC2565A measurement setup diagram

Figure 8. Demo board DC2565A circuit diagram demo board DC2565A bill of materials:

Figure 9. Demo board DC2565A PCB design (1)

Figure 10. Demo board DC2565A PCB design (2)

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