- High Efficiency: Up to 95%
- No Current Sense Resistor Required
- Constant Frequency 530kHz Operation Allows Small Size, Surface Mount Inductors
- OPTI-LOOP® Compensation Minimizes COUT
- 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
The LTC®1700 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 RSENSETM 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.
- Cellular Telephones
- Wireless Modems
- RF Communications
- 2.5V to 3.3V, 2.5V to 5V Converters
- Battery-Powered Equipment
- Telecom/Network Systems
Demonstration Circuit DC349B demonstrates a synchronous step-up DC/DC converter using the LTC1700 controller. The LTC1700 is a current mode No RSENSE™ synchronous step-up controller with up to 95% efficiency. Applications include 2.5V to 3.3V or 5V converters, 2.5V to 5V converters, single cell Li-Ion to 5V applications or two cell AA to 3.3V or 5V applications. The LTC1700’s 550kHz operating frequency allows the use of small inductors and capacitors. The device can also be synchronized to frequencies between 400kHz to 750kHz. The DC349B provides output voltages of 3.3V or 5V (jumper selectable).