Rainbow Electronics MAX1655 - Manual (Page 7)

MAX1649/MAX1651
5V/3.3V or Adjustable, High-Efficiency,
Low-Dropout, Step-Down DC-DC Controllers
_______________________________________________________________________________________ 7
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.
MAX1649
MAX1651
Q
MINIMUM
OFF-TIME
ONE-SHOT
TRIG
Q
MAXIMUM
ON-TIME
ONE-SHOT
TRIG
DUAL-MODE™
COMPARATOR
ERROR
COMPARATOR
CURRENT
COMPARATOR
110mV
Q S
R
FROM V+
FROM V+
CS
EXT
OUT
GND
REF
SHDN
FB V+
1.5V
REFERENCE
F/F
N
™ Dual-Mode is a trademark of Maxim Integrated Products
50mV
Figure 2. Block Diagram