PMIC solutions for portable application processor systems

The LTC3676 and LTC3676-1 contain four synchronous step down dc/dc converters for core, memory, I/O and SoC rails, plus three 300mA low dropout regulators for low noise analogue supplies, with dynamic control and sequencing. The LTC3676-1 configures a 1.5A buck regulator for source/sink and tracking operation to support ddr memory termination and also adds a VTTR reference output for ddr. These two pin features replace the LDO4 enable and feedback pins of the LTC3676. Supporting the multiple regulators is a highly configurable power sequencing capability, dynamic voltage scaling output voltage control, a pushbutton interface controller, plus regulator control via an I^²C interface with extensive status reporting and an interrupt output. The LTC3676's four constant frequency current mode buck switching regulators are internally compensated and provide up to 2.5 and 1.5A output currents, and have complete I^²C control, including selectable switching frequencies (2.25 or 1.125MHz) and phasing. The device's power on default frequency is 2.25MHz, with switch edge rate adjustment for reduced EMI. Each buck has a dynamically controlled d/a converter based output reference and an external feedback pin to set the nominal output voltage range. Three operating modes can be set using the I^²C interface. The LTC3676 also has four ldos for low noise analogue supplies, including three 300mA rails with different combinations of fixed and I^²C selectable voltage options; two of these regulators feature adjustable outputs. The other ldo is an always on 25mA supply with a resistor programmable output voltage.