19-1307; Rev 0a; 11/97
Step-Up/Down DC-DC Converter
in QSOP Package
The MAX1672 integrates a step-up DC-DC converter with a
linear regulator to provide step-up/down voltage conver-
sion. This device provides a constant output voltage for
inputs that vary above and below the output voltage. It has
a 1.8V to 11V input range and a preset 3.3V or 5V output.
The output can also be set from 1.25V to 5.5V using two
resistors. Typical efficiency is 85%.
The MAX1672’s step-up/linear-regulator configuration per-
mits the use of a single, physically smaller inductor than
can be used with competing SEPIC and flyback configura-
tions. Switch current is also selectable, permitting the use
of smaller inductors in low-current applications. The linear
regulator also acts as a filter to reduce output ripple voltage.
The MAX1672 has a low 85µA quiescent supply current, which
is further reduced to 0.1µA in logic-controlled shutdown. The
output voltage is disconnected from the input in shutdown.
The MAX1672 also has a PGI/PGO low-battery detector.
The MAX1672 comes in a 16-pin QSOP package (same size
as a standard 8-pin SO). For a larger device that delivers more
output current, refer to the MAX710/MAX711. The preassem-
bled MAX1672 evaluation kit is available to speed designs.
3.3V and Other Low-Voltage
2-Cell to 4-Cell AA Alkaline
with AC Input Adapters
__________Typical Operating Circuit
1.8V TO 11V
o Step-Up/Down Voltage Conversion
o 1.8V to 11V Input Range
o 3.3V/5V or Adjustable Output Voltage Range
o Output Current:
300mA at 5V (VIN ≥ 2.5V)
150mA at 5V (VIN ≥ 1.8V)
o Smaller Inductor than SEPIC and Flybacks
o Load Disconnects from Input in Shutdown
o Supply Current from Battery:
o PGI/PGO Low-Battery Comparator
o 16-Pin QSOP Package
(same footprint as 8-pin SO)
o No External FETs Required
o Thermal and Short-Circuit Protection
0°C to +70°C
-40°C to +85°C
*Dice are tested at TA = +25°C.
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