Linear Technology – Power management for Li-Ion/polymer cell systems

The device features seven independent rails, with I2C control, flexible sequencing and fault monitoring in a 28mm2 QFN package.

The LTC3675 contains four high-efficiency synchronous step-down regulators, a high-current/high-efficiency buck-boost regulator, a synchronous boost regulator, a dual-string 40V-LED driver and an always-on LDO.

Pushbutton on/off/reset control, precision enable inputs and a power-on reset output provide flexible and reliable power-up sequencing.

The LTC3675’s I2C interface provides complete regulator control, status reporting and a maskable interrupt output.

Quiescent current is 16uA with all DC/DCs off to maximise battery run time.

The LTC3675’s four constant-frequency current-mode buck-switching regulators are internally compensated, providing up to 1A and 500mA output currents, respectively, with complete I2C control.

Further, the buck power stages can be paralleled to deliver up to twice the output current with a single inductor.

The buck regulators can operate in two different modes.

In pulse-skipping mode, the regulator will skip pulses at light loads, but will operate at a constant frequency of 2.25MHz at higher loads.

In Burst Mode operation, the regulator will burst at light loads for best efficiency and at higher loads will operate in constant frequency PWM mode for lowest noise performance.

I2C may be used to control the device, enabling mode of operation, feedback-regulation voltage and switch slew rate.

The bucks have forward- and reverse-current limiting, soft-start to limit inrush current during start-up, short-circuit protection and slew-rate control for lower radiated EMI.

The LTC3675’s buck-boost regulator is a 2.25MHz voltage mode regulator designed to deliver up to 1A load current for a typical programmed output voltage of 3.3V.

The regulator can be enabled via its enable pin or via I2C.

The mode of operation (Burst Mode or PWM), feedback regulation voltage and switch slew rate can all be controlled via I2C.

The buck-boost regulator also features forward current limiting, soft-start to limit inrush current during start-up, short-circuit protection and slew-rate control for lower radiated EMI.

The LTC3675’s boost regulator is designed to deliver up to 1A load current for a programmed output voltage of up to 5V.

Boost DC/DC enable, mode of operation (Burst Mode or PWM), feedback regulation voltage and switch slew rate can all be controlled via I2C.

The boost regulator has forward and reverse current limiting, soft start to limit inrush current during start-up, short-circuit protection, slew-rate control for lower radiated EMI and true output disconnect when in shutdown.

The LTC3675’s constant-frequency, current-mode 40V LED driver can regulate up to 25mA of current through each of two series 10-LED strings.

LED enable, 60dB brightness control and up/down gradation are programmed using I2C.

The LED driver can be configured as a general-purpose high-voltage boost converter with a 1.6A (typ) switch current limit.

Given its high duty cycle operation, it can boost from below 3V to up to 40V output at 55mA.

The LTC3675 is available in a thermally enhanced 0.75mm 44-pin 4 x 7mm QFN package.

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