MAX1674 Datasheet, PDF (12/12 Pages) Maxim Integrated Products – High-Efficiency, Low-Supply-Current, Compact, Step-Up DC-DC Converters

High-Efficiency, Low-Supply-Current,
Compact, Step-Up DC-DC Converters
Optional External Rectifier
Although not required, a Schottky diode (such as the
MBR0520) connected between LX and OUT allows
lower start-up voltages (Figure 10) and is recommend-
ed when operating at input voltages below 1.3V. Note
that adding this diode provides no significant efficiency
improvement.
PC Board Layout and Grounding
Careful printed circuit layout is important for minimizing
ground bounce and noise. Keep the IC’s GND pin and
the ground leads of the input and output filter capaci-
tors less than 0.2in (5mm) apart. In addition, keep all
connections to the FB and LX pins as short as possi-
ble. In particular, when using external feedback resis-
tors, locate them as close to the FB as possible. To
maximize output power and efficiency and minimize
output ripple voltage, use a ground plane and solder
the IC’s GND directly to the ground plane.
V_IN
47µF
R1
200Ω _BATT
LX
(MAX1676)
R3
OUT
MAX1674
MAX1675
FB
LBI _{MAX1676 SHDN}
R4
0.1µF
CLSEL
(MAX1676)
LBO
REF
GND
22µH
MBR0520
0.1µF
47µF
R2
100k
LOW-BATTERY
OUTPUT
Figure 10. Adding a Schottky Diode for Low Input Voltage
Operation
Chip Information
TRANSISTOR COUNT: 751
Package Information
12 ______________________________________________________________________________________