Datasheet HMC976LP3E (Analog Devices) - 9

HMC976LP3E
v02.1112
400mA LOW NOISE, HIGH PSRR LINEAR VOLTAGE REGULATOR Output Voltage Adjustment
The default output voltage is 4.8V this configuration “HMC976LP3E 4.8V User Application Schematic”. The output voltage can be set to 5V by a ground on HV pin 5 “HMC976LP3E 5V User Application Schematic”. 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 “HMC976LP3E 3.3V User Application Schematic”. The value of the resistor is given by the equation below. ⎛⎛Vout ⎞ ⎞ ⎜⎜ ⎟ −1⎟*18.9 ⎝⎝ 1.17 ⎠ ⎠ 1 R = (Kohms) ⎛⎛Vout ⎞ ⎞ 1− 0.32*⎜⎜ ⎟ −1⎟ ⎝⎝ 1.17 ⎠ ⎠ If the temperature stability performance similar to that shown in the plot “Vout=5V and Vref vs. Temperature” is 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 fol ow these guide lines, the PADDLE should be connected to ground with at least 5 vias T 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 M 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. G - S IN
Thermal Protection
N 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 IO temporarily disables the HMC976LP3E outputs (with ~500uA output current) until the junction temperature cools down IT by approximately 10°C. D N A typical reason for the increase of the junction temperature is an unexpected increase in current draw. By disabling O 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 R C E W For reliable long term operation the “Recommended Operating Condition” must be fol owed and the maximum junc- tion temperature must not be exceeded. The junction temperature for a given dissipation can be calculated from the O equation below: P   T =T +  P ×θ j a     d ja     Where Tj=Junction Temperature (°C), Ta=Ambient Temperature (°C), Pd=Dissipated Power (W) θ ja =Thermal Resistivity Junction to Ambient (°C/W). Please refer to Table 2 for thermal resistance values. InfoFro ma r p tion rfiucre nis, d he e d lbiv y e An raly a og n Ded t viceo p s is la be clie o eved rtd o e b re sa: H ccur iattti e te M and re ilicarbloew . a Ho ve C wever, onro For price, delivery, and to place orders: Analog Devices, Inc., responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other poration, 2 Elizabeth Drive, Chelmsford, MA 01824 One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106 9 978-250-3343 tel • 978-250-3373 fax • O rights of third parties that may result from its use. Specifications subject to change without notice. No rd P e h r O one n : 7-lin 81- e a 329-t w 47 w 0 w.h 0 • O it rd teite r o .nc li o n m license is granted by implication or otherwise under any patent or patent rights of Analog Devices. e at www.analog.com Application S Trademarks and registered trademarks are the property of their respective owners. upport: apps@ A h p i p tliti c te ati .ocom n Support: Phone: 1-800-ANALOG-D