Data Sheet

ADPL76030

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Rev.0

35 of 40

With a 100 k resistor in the keep-running mode, the ADPL76030 continues switching normally and regulates the

current into ground. With a 499 k resistor in latch-off mode, the ADPL76030 stops switching until the EN/UVLO pin is

pulled low and high to restart. With no resistor in the hiccup mode, the ADPL76030 enters low duty cycle auto-retry

operation. The 1.25 µA pull-down current discharges the SS pin to 0.2 V and then 12.5 µA pull-up current charges the

SS pin up. If the output short-circuit condition is not removed when the SS pin reaches 1.75 V, the 1.25 µA pull-down

current turns on again, initiating a new hiccup cycle. This continues until the fault is removed. Once the output short-

circuit condition is removed, the output has a smooth short-circuit recovery due to soft-start.

Loop Compensation

The ADPL76030 uses an internal transconductance error amplifier, the output of which, VC, compensates the control

loop. The external inductor, output capacitor, and the compensation resistor and capacitor determine the loop

stability.

The inductor and output capacitor are chosen based on performance, size, and cost. The compensation resistor and

capacitor on the VC pin are set to optimize control loop response and stability. For a typical voltage regulator

application, a 2.2 nF compensation capacitor on the VC pin is adequate, and a series resistor should always be used

to increase the slew rate on the VC pin to maintain tighter output voltage regulation during fast transients on the

input supply of the converter.

Efficiency Considerations

The power efficiency of a switching regulator is equal to the output power divided by the input power times 100%. It

is often useful to analyze individual losses to determine what is limiting the efficiency and which change produces

the most improvement. Although all dissipative elements in circuits produce losses, four main sources account for

most losses in ADPL76030 circuits:



DC I2R losses. These arise from the resistances of the MOSFETs, sensing resistor, inductor, and PC board traces,

and cause the efficiency to drop at high output currents.



Transition loss. This loss arises from the brief amount of time switch A or switch C spends in the saturated region

during switch node transitions. It depends upon the input voltage, load current, driver strength, and MOSFET

capacitance, among other factors.



INTVCC current. This is the sum of the MOSFET driver and control currents.



CIN and COUT loss. The input capacitor has the difficult job of filtering the large RMS input current to the regulator

in the buck region. The output capacitor has the difficult job of filtering the large RMS output current in the boost

region. Both CIN and COUT are required to have low ESR to minimize the AC I2R loss, and sufficient capacitance to

prevent the RMS current from causing additional upstream losses in fuses or batteries.



Other losses. Schottky diode DB and DD are responsible for conduction losses during dead time and light load

conduction periods. Inductor core loss occurs predominately at light loads. Switch A causes reverse recovery

current loss in the buck region, and switch C causes reverse recovery current loss in the boost region. When

making adjustments to improve efficiency, the input current is the best indicator of changes in efficiency. If a

change is made and the input current decreases, then the efficiency has increased. If there is no change in the

input current, then there is no change in efficiency.