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55V, 1.2A (IOUT) Step-Down DC/DC Converter with Only 2.8µA Quiescent Current

Nov 24 2009 - MILPITAS, CA
  • Linear Technology Corporation announces the LT3991, a 1.2A, 55V step-down switching regulator with an integrated boost diode. Its Burst Mode® operation keeps quiescent current under 2.8µA in no load standby conditions. The LT3991's 4.3V to 55V input voltage range makes it ideal for automotive and industrial applications. Its internal 1.7A switch can deliver up to 1.2A of continuous output current to voltages as low as 1.19V. The LT3991's Burst Mode operation offers ultralow quiescent current, making it well suited for applications such as automotive or industrial systems that demand always-on operation and optimum battery life. Switching frequency is user programmable from 200kHz to 2MHz, enabling the designer to optimize efficiency while avoiding critical noise-sensitive frequency bands. The combination of its 10-lead 3mm× 3mm DFN or thermally enhanced MSOP packages and high switching frequency keep external inductors and capacitors small, providing a compact, thermally efficient footprint.


    The LT3991 utilizes a high efficiency 1.7A, 440mΩ switch, with the necessary boost diode, oscillator, control and logic circuitry integrated into a single die. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping output ripple below 15mVPK-PK. Special design techniques and a new high voltage process enable high efficiency over a wide input voltage range, and the LT3991's current mode topology enables fast transient response and excellent loop stability. Other features include a power good flag, soft-start capability, external clock synchronization and internal compensation.


    The LT3991EDD is packaged in a 3mm × 3mm DFN-10, and the LT3991EMSE is packaged in a thermally enhanced MSOP-10, priced starting at $2.95 each for 1,000 piece quantities. The LT3991IDD and LT3991IMSE are tested and guaranteed to operate from a –40ºC to 125ºC operating junction temperature and are priced at $3.28 each in 1,000 piece quantities. All versions are available from stock. For more information, visit www.linear.com.


    Summary of Features: LT3991


    • Ultralow Quiescent Current: 2.8µA IQ Regulating 12VIN to 3.3VOUT
    • Low Ripple Burst Mode® Operation: Output Ripple < 15mVP-P
    • Wide Input Voltage Range: 4.3V to 55V
    • 1.2A Maximum Output Current
    • Adjustable Switching Frequency: 200kHz to 2MHz
    • Synchronizable Between 250kHz to 2MHz
    • Fast Transient Response
    • Accurate 1V Enable Pin Threshold
    • Low Shutdown Current: IQ = 700nA
    • Power Good Flag
    • Soft-Start Capability
    • Internal Compensation
    • Saturating Switch Design: 0.44Ω On-Resistance
    • Output Voltage: 1.19V to 30V
    • Small Thermally Enhanced 10-Pin MSOP Package & (3mm × 3mm) DFN Packages

    2.8µA IQ, 55V Step-Down DC/DC Converter

    LT3991 PR Image

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