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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

v01.0711

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.

If the temperature stability performance similar to that shown in the plot “Vout and Vref vs. Temperature [1]” 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 follow these guide lines, the PADDLE should be grounded to the supply -VE terminal or

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

Under

the

HMC976LP3E

default

output

voltage

condition

(Vout

=

4.8V

and

maximum

output

current) the thermal protection circuitry limits

the output current to approximately 500μA. When the

ambient temperature rises to approximately +115°C. The output will be kept disabled, allowing to the regu-

lator to cool down, until the ambient temperature decreases by approximately

10°C. The thermal pro-

tection may cycle the output on and off, protecting the regulator from damage, dependant on the power

dissipation and ambient temperature. The thermal protection circuitry will act indirectly when a short circuit occurs at

the output. After the overload or the fault condition is removed/changed, the regulator output will return to the nominal

operation.

For reliable operation the “Absolute Maximum Ratings” must be complied with especially the maximum junction

temperature must not be exceeded. The board copper ground area and thermal dissipation should be taken into

account during board layout. The junction temperature for a given dissipation can be calculated from the equation

below

T T

P

j

a

d

ja

= +

×

























θ

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

Resistivity Junction to Ambient (°C/W).

⎟

⎠

⎞

⎜

⎝

⎛

−

⎟

⎠

⎞

⎜

⎝

⎛

−

⎟

⎠

⎞

⎜

⎝

⎛

−

⎟

⎠

⎞

⎜

⎝

⎛

=

1

17

.

1

*

32

.

0

1

9

.

18

*

1

17

.

1

1

Vout

Vout

R