説明

The LT8619 is a compact, high efficiency, high speed synchronous monolithic step-down switching regulator that consumes only 6μA of quiescent current. The LT8619 can deliver 1.2A of continuous current. Top and bottom power switches are included with all necessary circuitry to minimize the need for external components. Low ripple Burst Mode operation enables high efficiency down to very low output currents while keeping the output ripple to 10mVP-P. A SYNC pin allows forced continuous mode operation synchronized to an external clock. Internal compensation with peak current mode topology allows the use of small inductors and results in fast transient response and good loop stability. The EN/UV pin has an accurate 1V threshold and can be used to program VIN undervoltage lockout or to shut down the LT8619, reducing the input supply current to below 0.6μA. The PG flag signals when VOUT is within ±7.5% of the programmed output voltage. The LT8619 is available in a small 16-lead MSOP and 10-lead 3mm × 3mm DFN packages with exposed pad for low thermal resistance.

 

特徴

Wide Input Voltage Range: 3V to 60V

Fast Minimum Switch-On Time: 30ns

Ultralow Quiescent Current Burst Mode Operation:

6μA IQ Regulating 12VIN to 3.3VOUT

10mVP-P Output Ripple at No Load

Synchronizable/Programmable Fixed Frequency Forced Continuous Mode Operation: 300kHz to 2.2MHz

High Efficiency Synchronous Operation:

92% Efficiency at 0.5A, 5VOUT from 12VIN

90% Efficiency at 0.5A, 3.3VOUT from 12VIN

Low Dropout: 360mV at 0.5A

Low EMI

Accurate 1V Enable Pin Threshold

Internal Soft-Start and Compensation

Power Good Flag

Small Thermally Enhanced 16-Lead MSOP Package and 10-Lead (3mm × 3mm) DFN Packages

自動車用AEC-Q100認定

 

アプリケーション

12V Automotive Systems

12V and 24V Commercial Vehicles

48V Electric and Hybrid Vehicles

工業用品

 

オペレーション

The LT8619 is a monolithic, constant frequency current mode step-down DC/DC converter. An oscillator, with frequency set using a resistor on the RT pin, turns on the internal top power switch at the beginning of each clock cycle. Current in the inductor then increases until the current comparator trips and turns off the top power switch. The peak inductor current at which the top switch turns off is controlled by the voltage on the internal VC node. The error amplifier servos the VC node by comparing the voltage on the FB pin with an internal 0.8V reference. When the load current increases, it causes a reduction in the feedback voltage relative to the reference leading the error amplifier to raise the VC voltage until the average inductor current matches the new load current. When the top power switch turns off, the bottom power switch turns on until the next clock cycle begins or inductor current falls to zero (Burst Mode operation or pulse-skipping mode). If overload conditions result in more than 1.8A flowing through the bottom switch, the next clock cycle will be delayed until the switch current returns to a safe level.

If the EN/UV pin is low, the LT8619 is shut down and draws less than 0.6µA from the input. When the EN/UV pin is above 1V, the switching regulator starts operation. First, the internal LDO powers up, followed by the switching regulator 200μs soft-start ramp. During the soft-start phase, the switcher operates in pulse-skipping mode and gradually switches to forced continuous mode when VOUT approaches the set point (if SYNC pin is forced high or connected to an external clock). Typically, upon EN/UV rising edge, it takes about 660μs for the switcher output voltage to reach regulation and PG to be asserted.

 

アプリケーション情報

超低静止電流の実現

To enhance efficiency at light loads, the LT8619 enters into Burst Mode operation, which keeps the output capacitor charged to the desired output voltage while minimizing the input quiescent current and output ripple voltage. In Burst Mode operation the LT8619 delivers single small pulses of current to the output capacitor followed by sleep periods where the output power is supplied by the output capacitor. While in sleep mode the LT8619 consumes less than 6μA.