Data Sheet

LT8615

analog.com

Rev 0

17 of 31

APPLICATIONS INFORMATION

Achieving Ultralow Quiescent Current

To enhance efficiency at light loads, the LT8615 enters low ripple Burst Mode operation, which keeps the output

capacitor charged to the desired output voltage while minimizing the input quiescent current and minimizing output

voltage ripple. In Burst Mode operation, the LT8615 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

LT8615 consumes 1.7μA.

As the output load decreases, the frequency of single current pulses decreases (see Figure 36) and the percentage of

time the LT8615 is in sleep mode increases, resulting in much higher light load efficiency than for typical converters.

By maximizing the time between pulses, the converter quiescent current approaches 2.5µA for a typical application

when there is no output load. Therefore, to optimize the quiescent current performance at light loads, the current in

the feedback resistor divider must be minimized as it appears to the output as load current.

Figure 36. SW Burst Mode Frequency vs. Load

Figure 37. Full Switching Frequency Minimum Load vs. VIN in Pulse-Skipping Mode

L = XGL6060-152ME, 1.5µH

VIN = 12V

VOUT = 3.3V

LOAD CURRENT (mA)

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VOUT = 3.3V

fsw = 2MHz

PULSE-SKIP OPERATION

INPUT VOLTAGE (V)

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