MAX1649(1995) Ver la hoja de datos (PDF) - Maxim Integrated

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MAX1649
(Rev.:1995)

5V/3.3V or Adjustable, High-Efficiency, Low-Dropout, Step-Down DC-DC Controllers

Maxim Integrated 

5V/3.3V or Adjustable, High-Efficiency,

Low-Dropout, Step-Down DC-DC Controllers

V+

FB

DUAL-MODE™

COMPARATOR

MAX1649

50mV

MAX1651

SHDN

ERROR

OUT

COMPARATOR

REF

MINIMUM

Q OFF-TIME TRIG

ONE-SHOT

1.5V

REFERENCE

N

FROM V+

EXT

S

Q

MAXIMUM

TRIG ON-TIME Q

ONE-SHOT

F/F

R

CURRENT

CS

COMPARATOR

GND

™ Dual-Mode is a trademark of Maxim Integrated Products

Figure 2. Block Diagram

110mV

FROM V+

Shutdown Mode

When SHDN is high, the MAX1649/MAX1651 enter shut-

down mode. In this mode, the internal biasing circuitry is

turned off (including the reference) and the supply cur-

rent drops to less than 5µA. EXT goes high, turning off the

external MOSFET. SHDN is a logic-level input. Connect

SHDN to GND for normal operation.

Quiescent Current

In normal operation, the device's typical quiescent cur-

rent is 78µA. In an actual application, even with no load,

additional current is drawn to supply external feedback

resistors (if used) and the diode and capacitor leakage

currents. In the circuit of Figure 1, with V+ at 5V and

VOUT at 3.3V, typical no-load supply current for the

entire circuit is 90µA.

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