Features

• Out-of-Phase Controllers Reduce Input Capacitance
  and Power Supply Induced Noise
• OPTI-LOOP® Compensation Minimizes C_OUT
• Power Good Output Monitors Both Outputs
• 5-Bit Mobile VID Control, V_OUT: 0.9V to 2.0V
• Dual N-Channel MOSFET Synchronous Drive
• ±1% Output Voltage Accuracy
• DC Programmed Fixed Frequency 150kHz to 300kHz
• Wide V_IN Range: 3.5V to 36V Operation
• Very Low Dropout Operation: 99% Duty Cycle
• Adjustable Soft-Start Current Ramping
• Foldback Output Current Limiting
• Latched Short-Circuit Shutdown with Defeat Option
• Output Overvoltage Protection
• Remote Output Voltage Sense
• Low Shutdown Current: 20µA
• 5V and 3.3V Standby Regulators
• Selectable Constant Frequency, Burst Mode® and
  Continuous Operation

Typical Application

Description

The LTC®1708 is a dual adjustable 5-bit VID programmable step-down switching regulator controller that drives all N-Channel power MOSFET stages. A constant frequency current mode architecture allows adjustment of the frequency up to 300kHz. Power loss and noise due to the ESR of the input capacitance are minimized by operating the two main controller output stages out of phase.

OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The precision 0.8V reference is compatible with future microprocessor generations, and a wide 3.5V to 30V (36V maximum) input supply range that encompasses all battery chemistries. A power good output indicates when the output voltages are within 7.5% of their programmed value.

A RUN/SS pin for each controller provides both soft-start and an optional timed, short-circuit shutdown. Other protection features include: internal foldback current limiting and an output overvoltage crowbar. The forced continuous control pin (FCB) can be used to inhibit BurstMode operation or to regulate a third, flyback output.