Features and Benefits
- High Efficiency Operation (No Sense Resistor Required)
- Wide Input Voltage Range: 2.5V to 36V
- Current Mode Control Provides Excellent Transient Response
- High Maximum Duty Cycle (Typ 92%)
- ±1% Internal Voltage Reference
- ±2% RUN Pin Threshold with 100mV Hysteresis
- Micropower Shutdown: IQ = 10µA
- Programmable Switching Frequency (50kHz to 1MHz) with One External Resistor
- Synchronizable to an External Clock Up to 1.3 × fOSC
- User-Controlled Pulse Skip or Burst Mode® Operation
- Internal 5.2V Low Dropout Voltage Regulator
- Capable of Operating with a Sense Resistor for High Output Voltage Applications (VDS >36V)
- Small 10-Lead MSOP Package
The LTC3704 is a wide input range, current mode, positive-to-negative DC/DC controller that drives an N-channel power MOSFET and requires very few external components. Intended for low to high power applications, it eliminates the need for a current sense resistor by utilizing the power MOSFET’s on-resistance, thereby maximizing efficiency.
The IC’s operating frequency can be set with an external resistor over a 50kHz to 1MHz range, and can be synchronized to an external clock using the MODE/SYNC pin. Burst Mode operation at light loads, a low minimum operating supply voltage of 2.5V and a low shutdown quiescent current of 10µA make the LTC3704 ideally suited for battery-operated systems.
For applications requiring constant frequency operation, the Burst Mode operation feature can be defeated using the MODE/SYNC pin. Higher than 36V switch voltage applications are possible with the LTC3704 by connecting the SENSE pin to a resistor in the source of the power MOSFET.
The LTC3704 is available in the 10-lead MSOP package.
- SLIC Power Supplies
- Telecom Power Supplies
- Portable Electronic Equipment
- Cable and DSL Modems
- Router Supplies
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (2)
Demonstration circuit 524 is a positive input to negative output converter featuring the LTC3704 switching controller. The DC524 converts a 5V to 15V input to a –5.2V output and provides up to 2.5A of output current from 5V input. The converter operates at 300kHz with a high efficiency of 89%. The DC524 is set to operate in No RSENSE™ mode with input voltages up to 15V. However, DC524 can be modified for higher input voltages with an optional current sense resistor. The circuit features optional soft-start circuitry that can be enabled or disabled with a single jumper. Also, DC524 has a jumper to program either continuous or Burst Mode™ operation. The DC524 can be synchronized to an external clock of up to 400kHz.
Demonstration circuit 518 is a SLIC (Subscriber Line Interface Circuit) positive input to negative output converter featuring the LTC3704 switching controller. DC518 converts 4.5V to 15V input to –24V at 200mA and –70V at 200mA at its output. The demo board uses a transformer with the three primary side widings in parallel to generate three –24V outputs. By stacking the voltages on top of each other, –70V ±10% is obtained. The demo board operates at 200kHz with high efficiency of up to 92%.
Tools & Simulations
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Models for the following parts are available in LTspice:
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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.