DESCRIPTION

The LTM®8074 is a 40VIN, 1.2A continuous, 1.75A peak, step-down µModule® (power module) regulator. The Silent Switcher architecture minimizes EMI while delivering high efficiency at frequencies up to 2.2MHz. Included in the package are the switching controller, power switches, inductor, and all support components. Operating over an input voltage range of 3.2V to 40V, the LTM8074 supports an output voltage range of 0.8V to 12V and a switching frequency range of 200kHz to 2.2MHz, each set by a single resistor. Only the input and output filter capacitors are needed to finish the design.The low profile package enables utilization of unused space on the bottom of PC boards for high density point of load regulation. The LTM8074 is packaged in a thermally enhanced, compact over-molded ball grid array (BGA) package suitable for automated assembly by standard surface mount equipment. The LTM8074 is RoHS compliant.

 

FEATURES

Low Noise Silent Switcher® Architecture

CISPR22 Class B Compliance

Wide Input Voltage Range: 3.2V to 40V

Wide Output Voltage Range: 0.8V to 12V

1.2A Continuous Output Current at 24VIN, 5VOUT,

TA = 85°C

1.75A Peak Output Current at 3.3VOUT

Selectable Switching Frequency: 200kHz to 2.2MHz

External Synchronization

Configurable as an Inverter

4mm × 4mm × 1.82mm BGA Package

 

APPLICATIONS

Automotive Battery Regulation

Power for Portable Products

Distributed Supply Regulation

Industrial Supplies

Wall Transformer Regulation

 

OPERATION

The LTM8074 is a stand-alone non-isolated step-down switching DC/DC power supply that can deliver up to 1.75A at 3.3VOUT. At lower VOUT the output current capability may be higher. The continuous current is determined by the internal operating temperature. It provides a precisely regulated output voltage programmable via one external resistor from 0.8V to 12V. The input voltage range is 3.2V to 40V. Given that the LTM8074 is a step-down converter, make sure that the input voltage is high enough to support the desired output voltage and load current. A simplified Block Diagram is given above.

The LTM8074 contains a current mode controller, power switching elements, power inductor and a modest amount of input and output capacitance. The LTM8074 is a fixed frequency PWM regulator. The switching frequency is set by simply connecting the appropriate resistor value from the RT pin to GND.

The RUN pin is used to place the LTM8074 in shutdown, reducing the input current to a few µA.

To enhance efficiency, the LTM8074 automatically switches to Burst Mode operation in light or no load situations. Between bursts, all circuitry associated with controlling the output switch is shut down reducing the input supply current to just a few µA.

The oscillator reduces the LTM8074’s operating frequency when the voltage at the FB pin is low. This frequency fold back helps to control the output current during start-up and overload.

The TR/SS node acts as an auxiliary input to the error amplifier. The voltage at FB servos to the TR/SS voltage until TR/ SS goes above 0.77V. Soft-start is implemented by gen erating a voltage ramp at the TR/SS pin using an external capacitor which is charged by an internal constant current. Alternatively, driving the TR/SS pin with a signal source or resistive network provides a tracking function. Do not drive the TR/SS pin with a low impedance voltage source.

The LTM8074 contains a power good comparator which trips when the FB pin is at about 90% to 110% of its regulated value. The PG output is an open-drain transistor that is off when the output is in regulation, allowing an external resistor to pull the PG pin high. The PG signal is valid when VIN is above 3.2V. If VIN is above 3.2V and RUN is low, PG will drive low.

The LTM8074 is equipped with a thermal shutdown that inhibits power switching at high junction temperatures. The activation threshold of this function is above the maxi mum temperature rating to avoid interfering with normal operation, so prolonged or repetitive operation under a condition in which the thermal shutdown activates may damage or impair the reliability of the device.