LT8607的主要特性,功能框图,多种应用电路解析

Linear公司的LT8607是紧凑高效率和高速的同步开关降压稳压器,非开关静态电流仅为1.7μA,可连续提供750mA电流,输入电压从3V到42V,输出波纹小于10mVP-P,效率大于93%,可调和可同步频率200kHz到2.2MHz,主要用在通用降压转换器和低EMI降压转换器.本文介绍了LT8607主要特性,功能框图,多种应用电路,以及演示板DC2565A主要特性,测量建立图,电路图,材料清单和PCB设计图.

The LT®8607 is a compact, high efficiency, high speedsynchronous monolithic step-down switching regulatorthat 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 need for externalcomponents. Low ripple Burst Mode operation enables highefficiency down to very low output currents while keepingthe 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. The EN/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% ofthe programmed output voltage as well as fault conditions.

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

LT8607主要特性:

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应用:

General Purpose Step-Down Converter
Low EMI Step Down

图1.LT8607功能框图

图2.LT8607应用电路图(1)

图3.LT8607应用电路图(2)

图4.LT8607应用电路图(3)

图5.LT8607应用电路图(4)

图6.LT8607应用电路图(5)

演示板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 ofinput sources, such as automotive batteries and industrialsupplies. The LT8607 is a compact, high efficiency,high speed synchronous monolithic step-down switchingregulator that consumes 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 defaultfor 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 lowEMI spread spectrum operation. To synchronous to anexternal clock, move JP1 to SYNC and apply the externalclock to the SYNC turret. Figure 1 shows the efficiencyof the circuit.

The demo board has an EMI filter installed. The radiatedEMI performances of the board (with EMI filter) are shownin Figure 2 and Figure 3. The red lines in Figure 2 andFigure 3 are CISPR25 Class 5 peak limit. To use the EMIfilter, the input should be tied to VEMI, not VIN. 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 ofthe part, operation and application information. The datasheet must be read in conjunction with this demo manualfor DC2565A.

图7.演示板DC2565A测量建立图

图8.演示板DC2565A电路图
演示板DC2565A材料清单:

图9.演示板DC2565A PCB设计图(1)

图10.演示板DC2565A PCB设计图(2)