MAX1649_09 Datasheet, PDF (7/12 Pages) Maxim Integrated Products – 5V/3.3V or Adjustable, High-Efficiency, Low-Dropout, Step-Down DC-DC Controllers

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
V_OUT at 3.3V, typical no-load supply current for the
entire circuit is 90µA.
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