National Semiconductor LM3691 Data Handbook Specifications Miniature 1A Step-Down DC-DC Converter for Portable Applications
Summary
The LM3691 is a miniature, high-accuracy step-down DC-DC converter designed to power ultra-low voltage circuits from single Li-Ion cells up to 1A. Operating reliably between 2.3V and 5.5V input ranges, the device features advanced ECO/PWM modes for exceptional efficiency and extended battery life in portable applications. This manual provides comprehensive details on its function, including application circuits, pin descriptions, micro SMD integration guidelines, and operational safety features. It is ideally suited for powering demanding low-voltage electronics like mobile phones, hand-held radios, and MP3 players.
Page 1 Text Content
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June 11, 2008
LM3691 High Accuracy, Miniature 1A, Step-Down DC-DC Converter for Portable Applications General Description Features The LM3691 step-down DC-DC converter is optimized for VOUT = 0.75V to 1.8V powering ultra-low voltage circuits from a single Li-Ion cell or
±1% DC output voltage precision
3 cell Ni MH/Ni Cd batteries. It provides up to 1A load current,
2.3 ≤ VIN ≤ 5.5V
over an input voltage range from 2.3V to 5.5V. There are sev-
4 MHz switching frequency
eral different fixed voltage output options available.
64 μA (typ.) quiescent current in ECO mode
LM3691 has a mode-control pin that allows the user to select
Forced PWM mode or ECO mode that changes modes be- 1A maximum load capability
tween gated PWM mode and PWM automatically depending Automatic ECO/PWM mode switching on the load. In ECO, LM3691 offers superior efficiency and
Mode Pin to select ECO/Forced PWM mode
very low Iq under light load conditions. ECO mode extends the
1 μH inductor, 4.7 μF input capacitor (0603(1608) case
battery life through reduction of the quiescent current during
size) and 4.7 μF output capacitor (0603(1608) case size)
light load conditions and system standby.
Current overload and thermal shutdown protections
The LM3691 is available in a 6–bump micro SMD package.
Only three tiny surface-mount external components
Only three external surface-mount components, a 1μH induc-
required (solution size less than 15 mm2)
tor, a 4.7 μF input capacitor and a 4.7μF output capacitor, are required.
Applications Mobile Phones Hand-Held Radios MP3 players Portable Hard Disk Drives
Efficiency vs. Output Current
Typical Application Circuit
(VOUT = 1.8V, ECO Mode)
FIGURE 1. Typical Application Circuit
© 2008 National Semiconductor Corporation www.national.com
Page Summary Contents For National Semiconductor LM3691 Data Handbook Specifications Miniature 1A Step-Down DC-DC Converter for Portable Applications
Manual Details
| Brand | National |
|---|---|
| Pages | 18 |
| File Size | 2.15 MB |
| Published | June 15, 2026 |
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Frequently Asked Questions
What is the required input voltage range?
The recommended input voltage range (VIN) is 2.3V to 5.5V.
How can I save power in low-load situations?
Set the Mode Pin for ECO mode, which significantly reduces quiescent current and extends battery life during light load conditions.
What external components are needed for installation?
You only need three external surface-mount components: a 1μH inductor, a 4.7μF input capacitor, and a 4.7μF output capacitor.
How do I enable or disable the device?
The EN pin is enabled when voltage exceeds 1.2V and remains in shutdown mode if voltage drops below 0.4V.