Datasheet LTC3528, LTC3528B (Analog Devices) - 10

LTC3528/LTC3528B
OPERATION (Refer to Block Diagram) Burst Mode OPERATION
minimizing switching and quiescent current losses. Burst The LTC3528 will automatically enter Burst Mode opera- Mode output ripple, which is typically 1% peak-to-peak, tion at light load current and return to fixed frequency can be reduced by using more output capacitance (10µF PWM mode when the load increases. Refer to the Typical or greater). Performance Characteristics to see the output load Burst As the load current increases, the LTC3528 automatically Mode threshold vs VIN. The load at which Burst Mode leaves Burst Mode operation. Note that larger output ca- operation is entered can be changed by adjusting the pacitor values may cause this transition to occur at lighter inductor value. Raising the inductor value will lower the loads. The regulator will also leave Burst Mode operation if load current at which Burst Mode operation is entered. a load transient occurs which causes the inductor current In Burst Mode operation, the LTC3528 continues switch- to repeatedly reach current limit. Once the LTC3528 has left ing at a fixed frequency of 1MHz, using the same error Burst Mode operation and returned to normal operation, amplifier and loop compensation for peak current mode it will remain there until the output load is reduced below control. This control method minimizes output transients the Burst threshold. when switching between modes. In Burst Mode opera- Burst Mode operation is inhibited during start-up and tion, energy is delivered to the output until it reaches the until soft-start is done and VOUT is at least 0.24V greater nominal regulated value, then the LTC3528 transitions to than VIN. sleep mode where the outputs are off and the LTC3528 The LTC3528B features continuous PWM operation at consumes only 12µA of quiescent current from VOUT. Once 1MHz. At very light loads, the LTC3528B will exhibit pulse- the output voltage has drooped slightly, switching resumes skip operation. again. This maximizes efficiency at very light loads by 3528fd 10 Document Outline Features Applications Description Typical Application Absolute Maximum Ratings Pin Configuration order information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Revision History Related Parts