LM3691 Datasheet, PDF (1/18 Pages) National Semiconductor (TI) – High Accuracy, Miniature 1A, Step-Down DC-DC Converter for Portable Applications

June 11, 2008
LM3691
High Accuracy, Miniature 1A, Step-Down DC-DC Converter
for Portable Applications
General Description
The LM3691 step-down DC-DC converter is optimized for
powering ultra-low voltage circuits from a single Li-Ion cell or
3 cell NiMH/NiCd batteries. It provides up to 1A load current,
over an input voltage range from 2.3V to 5.5V. There are sev-
eral different fixed voltage output options available.
LM3691 has a mode-control pin that allows the user to select
Forced PWM mode or ECO mode that changes modes be-
tween gated PWM mode and PWM automatically depending
on the load. In ECO, LM3691 offers superior efficiency and
very low I_q under light load conditions. ECO mode extends the
battery life through reduction of the quiescent current during
light load conditions and system standby.
The LM3691 is available in a 6–bump micro SMD package.
Only three external surface-mount components, a 1μH induc-
tor, a 4.7 μF input capacitor and a 4.7μF output capacitor, are
required.
Features
■ ^V_OUT ^{= 0.75V to 1.8V}
■ ^{±1% DC output voltage precision}
■ ^{2.3 ≤ V}_IN ^{≤ 5.5V}
■ ^{4 MHz switching frequency}
■ 64 μA (typ.) quiescent current in ECO mode
■ ^{1A maximum load capability}
■ ^{Automatic ECO/PWM mode switching}
■ ^{Mode Pin to select ECO/Forced PWM mode}
■ 1 μH inductor, 4.7 μF input capacitor (0603(1608) case
size) and 4.7 μF output capacitor (0603(1608) case size)
■ ^{Current overload and thermal shutdown protections}
■ ^{Only three tiny surface-mount external components}
required (solution size less than 15 mm²)
Applications
■ ^{Mobile Phones}
■ ^{Hand-Held Radios}
■ ^{MP3 players}
■ ^{Portable Hard Disk Drives}
Typical Application Circuit
Efficiency vs. Output Current
(V_OUT = 1.8V, ECO Mode)
FIGURE 1. Typical Application Circuit
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