Features

• High Efficiency: Up to 95%
• No Current Sense Resistor Required
• Constant Frequency 530kHz Operation Allows Small Size, Surface Mount Inductors
• OPTI-LOOP® Compensation Minimizes C_OUT
• Selectable Burst Mode® Operation
• Minimum Start-Up Voltage as Low as 0.9V
• Synchronizable Between 400kHz and 750kHz
• Micropower Shutdown: 10µA
• Current Mode Operation for Excellent Line and Load Transient Response
• Soft-Start Reduces Supply Current Transients
• 1.5% Output Voltage Accuracy
• Uses Low Value, Small Size, Surface Mount Inductors
• Available in 10-Lead MSOP Package

Typical Application

Description

The LTC1700 is a current mode synchronous step-up DC/DC controller that drives external N-channel and P-channel power MOSFETs using a constant frequency PWM architecture. Current limiting is provided by sensing the voltage drop across the main MOSFET, eliminating the need of a sense resistor. This No R_SENSE technique helps the LTC1700 maintain high efficiency at heavy loads while Burst Mode operation ensures high efficiency at light loads, thus providing high efficiencies over a wide range of load currents.

The LTC1700 operates at a minimum input voltage as low as 0.9V. The device boasts a ±1.5% output voltage accuracy and consumes only 200µA of quiescent current. In shutdown, it only draws 10µA.

To prevent inductor current runaway, the duty cycle is limited to 90%. Overvoltage protection is also provided which shuts both the external MOSFETs off when tripped.

High constant operating frequency of 530kHz allows the use of small inductors and output capacitors. The LTC1700 can also be synchronized between 400kHz to 750kHz. Burst Mode operation is inhibited when the device is externally clocked or when the SYNC/MODE pin is pulled low to reduce noise and RF interference.