MSK5030 Ver la hoja de datos (PDF) - M.S. Kennedy

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componentes Descripción

Fabricante

MSK5030

HIGH EFFICIENCY, 4 AMP STEP-DOWN SWITCHING REGULATORS

M.S. Kennedy 

APPLICATION NOTES CONT'D

MODES OF OPERATION:

Under heavy loads, the MSK 5030 operates in full PWM mode. Each pulse from the oscillator sets the internal PWM latch that

turns on the high-side MOSFET. As the high-switch turns off, the synchronous rectifier latch is set. 60ns later the low-side

MOSFET turns on until the start of the next clock cycle or until the inductor current crosses zero. Under fault conditions the current

exceeds the ±100mV current-limit threshold and the high-side switch turns off.

At light loads the inductor current does not exceed the 30mV threshold set by the minimum-current comparator. When this

occurs, the MSK 5030 goes into idle mode, skipping most of the oscillator pulses in order to reduce the switching frequency and

cut back gate-charge losses. The oscillator is gated off at light loads because the minimum-current comparator immediately resets

the high-side latch at the start of each cycle. Refer to Table 1 for the operational characteristics.

OPERATIONAL CHARACTERISTICS

ENABLE

LOAD

DESCRIPTION

0

X

DEVICE DISABLED

1

LOW <10%

PULSE SKIPPING MODE DISCONTINUOUS INDUCTOR CURRENT

1

MED <30%

PULSE SKIPPING MODE CONTINUOUS INDUCTOR CURRENT

1

HIGH >30%

CONSTANT FREQ. PWM MODE CONTINUOUS INDUCTOR CURRENT

TABLE 1

TYPICAL 3.3V APPLICATION CIRCUIT

4

Rev. E 6/02

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