9

For price, delivery and to place orders: Hittite Microwave Corporation, 2 Elizabeth Drive, Chelmsford, MA 01824

978-250-3343 tel • 978-250-3373 fax • Order On-line at www.hittite.com

Application Support: apps@hittite.com

HMC976LP3E

400mA LOW NOISE, HIGH PSRR

LINEAR VOLTAGE REGULATOR

v02.1112

Output Voltage Adjustment

The output voltage can be set from 1.8V to <4.8V by a resistor from pin 2 to the output pin 11 shown in

required, then any external resistor temperature coefficient is a critical parameter and should be better than 50ppm

and 1% tolerance. Please note that the temperature coefficient of the internal resistor feedback divider is 270ppm/°C.

Layout of PCB

The layout of the PCB should follow these guide lines, the PADDLE should be connected to ground with at least 5 vias

directly under the paddle to the bottom side ground plane. To ensure the noise and PSRR specifications are met,

the capacitors connecting to Pins 15, 11, 3 (see user application schematics), should be placed as close as possible

to the relevant pin and the ground connection should be as short as possible. Trace widths and via sizes should be

scaled to match the current drawn. The use of a large ground plane is recommended with a large number of ground

vias near the device to carry the ground.

Thermal Protection

The HMC976LP3E includes an integrated thermal protection circuit. If the junction temperature of the HMC976LP3E

reaches the maximum operating junction temperature (115°C max, 130°C typical) then the thermal protection circuit

temporarily disables the HMC976LP3E outputs (with ~500uA output current) until the junction temperature cools down

by approximately 10°C.

A typical reason for the increase of the junction temperature is an unexpected increase in current draw. By disabling

the outputs, the HMC976LP3E is in this case protecting the other devices on the PCB that it is supplying with current.

The thermal protection circuitry will also indirectly protect against a short circuit at the output. After the overload or the

fault condition is removed or changed, the regulator output returns to the nominal operation

tion temperature must not be exceeded. The junction temperature for a given dissipation can be calculated from the

equation below:

Where Tj=Junction Temperature (°C), Ta=Ambient Temperature (°C), Pd=Dissipated Power (W)

=Thermal

Resistivity Junction to Ambient (°C/W). Please refer to Table 2 for thermal resistance values.

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Information furnished by Analog Devices is believed to be accurate and reliable. However, no

responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other

rights of third parties that may result from its use. Specifications subject to change without notice. No

license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

Trademarks and registered trademarks are the property of their respective owners.

For price, delivery, and to place orders: Analog Devices, Inc.,

One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106

Phone: 781-329-4700 • Order online at www.analog.com

Application Support: Phone: 1-800-ANALOG-D