Power Electronics

High Power, Eight-Channel I2C-Controlled PMIC for Portable Processor Systems

Linear Technology Corporation announces the LTC3589, a complete power management solution for portable processors such as i.MX, PXA, ARM, OMAP and other advanced portable microprocessor systems. The device features eight independent rails, with dynamic control and sequencing, in a compact QFN package. These rails supply power to the processor core, SDRAM, system memory, PC cards, always-on real time clock (RTC) and a variety of other functions. The LTC3589 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 (LDOs). Supporting the multiple regulators is a highly configurable power sequencing capability, dynamic voltage scaling output voltage control, a pushbutton interface controller, as well as regulator control via an I2C interface with extensive status reporting and an interrupt output.

The LTC3589's three constant frequency current-mode buck switching regulators are internally compensated and provide up to 1A, 1A and 1.6A output currents, and have complete I2C-control, including selectable switching frequencies of 2.25MHz 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 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 (minimizes output voltage ripple at light loads and optimizes dynamic slew control between voltage output set points).

The LTC3589's single inductor, synchronous buck-boost converter generates a user-programmable output voltage rail from 2.5V to 5V. Utilizing a proprietary switching algorithm, the buck-boost converter maintains high efficiency and low noise operation with input voltages above, below or equal to the regulated output rail. The buck-boost error amplifier uses a fixed 0.8V 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 LTC3589 also has four LDOs for low noise analog supplies, including three 250mA rails with different combinations of fixed, adjustable and I2C-selectable voltage options. The other LDO is an always-on 25mA supply with a resistor-programmable output voltage.

The LTC3589's versatile I2C serial port is used to control regulator enables, 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 pushbutton interface, pin inputs, or I2C interface.

The LTC3589 is available from stock in a thermally enhanced, low profile (0.75mm) 40-pin 6mm x 6mm exposed pad QFN package. 1000-piece pricing starts at $4.65 each for the E grade and $5.35 each for the I grade, both with operating junction temperature range of -40°C to +125°C. An H grade version with operating junction temperature of -40°C to +150°C is also available, priced starting at $5.70 each in 1000-piece quantities.

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