Linear Technology LTC3589 power management IC

Linear Technology has announced the LTC3589, a power management solution for portable processors such as i.MX, PXA, ARM, OMAP and other portable microprocessor systems.

The device features eight independent rails, with dynamic control and sequencing, in a compact QFN package. The rails supply power to the processor core, SDRAM, system memory, PC cards, always-on real time clock and a variety of other functions.

The device contains three high current, high efficiency step-down regulators, a high current/high efficiency buck-boost regulator and four low noise, low dropout linear regulators. Supporting the multiple regulators is a configurable power sequencing capability, dynamic voltage scaling output voltage control, a push-button interface controller, as well as regulator control via an I²C interface with extensive status reporting and an interrupt output.

The three constant frequency current-mode buck switching regulators are internally compensated and provide up to 1, 1 and 1.6 A output, and have complete I²C control, including selectable switching frequencies of 2.25 or 1.125 MHz and phasing. The device’s power-on default frequency is 2.25 MHz with switch edge rate adjustment for reduced EMI.

Each buck has a dynamically controlled DAC-based input reference and an external feedback pin to set the nominal output voltage range. Three operating modes can be set using the I²C interface: pulse-skipping (supports 100% duty cycle), burst mode operation (advantageous for best efficiency at low output loads) or forced continuous (minimises output voltage ripple at light loads and optimises dynamic slew control between voltage output setpoints).

The single inductor, synchronous buck-boost converter generates a user-programmable output voltage rail from 2.5 to 5 V. Using a switching algorithm, the converter maintains high efficiency and low noise operation with input voltages above, below or equal to the regulated output rail.

The error amplifier uses a fixed 0.8 V reference and the output voltage is set by an external resistor divider. Burst mode operation is enabled through the I²C control registers. No external compensation components are required.

The device also has four LDOs for low noise analog supplies, including three 250 mA rails with different combinations of fixed, adjustable and I²C-selectable voltage options. The other LDO is an always-on 25 mA supply with a resistor-programmable output voltage.

The I²C serial port is used to control regulator, output voltage levels, dynamic voltage scaling and slew rate, operating modes and status reporting. Regulator start-up is sequenced by connecting regulator outputs to enable pins in the desired order or via the I²C port.

System power-on, power-off and reset functions are controlled by a push-button interface, pin inputs or I²C interface.