Features

• Ultralow Quiescent Current:
  2.8μA I_Q Regulating 12V_IN to 3.3V_OUT
• Fixed Output Voltages: 5V
  2.2μA I_Q Regulating 12V_IN to 5V_OUT
• Low Ripple Burst Mode® Operation:
  Output Ripple < 15mV_P-P
• Wide Input Voltage Range: 4.3V to 38V
• 1.3A 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: I_Q = 700nA
• Power Good Flag
• Soft-Start Capability
• Internal Compensation
• Output Voltage: 1.19V to 30V
• Small Thermally Enhanced 10-Lead MSOP Package

Typical Application

Description

The LT®3971A is an adjustable frequency monolithic buck switching regulator that accepts a wide input voltage range up to 38V. Low quiescent current design consumes only 2.8μA of supply current while regulating with no load. Low ripple Burst Mode operation maintains high efficiency at low output currents while keeping the output ripple below 15mV in a typical application. An internally compensated current mode topology is used for fast transient response and good loop stability. A high efficiency 0.33Ω switch is included on the die along with a boost Schottky diode and the necessary oscillator, control and logic circuitry. An accurate 1V threshold enable pin can be used to shut down the LT3971A, reducing the input supply current to 700nA. A capacitor on the SS pin provides a controlled inrush current (soft-start). A power good flag signals when V_OUT reaches 91% of the programmed output voltage. The LT3971A is available in a small 10-lead MSOP package with an exposed pad for low thermal resistance.

The LT3971A and LT3971A-5 have a more accurate reference voltage compared to the LT3971 and LT3971-5. The LT3971A-5 also has specified V_OUT pin current and ABSMAX current. These characteristics are important for USB applications.