MP8124 – 500mA, LNB POWER SUPPLY AND CONTROL REGULATOR

MP8124 Rev. 1.0

www.MonolithicPower.com

13

11/11/2015

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PIN FUNCTIONS

Pin #

Name

Description

1

LINEDROP

the long coaxial cable. When LINEDROP is high, the LDO output increases by 1V.

LINEDROP cannot be left floating. Pull it to the BYPASS voltage for automatic 1V

voltage compensation after start-up.

2

EN

Regulator on/off control input. Apply a high level at EN to turn on the regulator;

apply a low level at EN to turn off the regulator. Connect EN to the input source

through a resistor divider for automatic start-up. Do NOT leave EN floating.

3

SW

Power switch output. SW is the drain of the internal MOSFET switch of the boost

stage. Connect the power inductor and output rectifier to SW.

4

PGND

Power ground.

5

BST

Internal LDO driver supply.

6

VBOOST

Internal LDO power input.

7

VOUT

Output voltage.

8

AGND

Analog ground.

9

TCAP

Soft start. Connect a capacitor from TCAP to ground to set a rise time for the

output voltage. The TCAP voltage is the feedback reference voltage and should be

placed far away from the noise source.

10

COMP

Compensation for the boost regulator.

11

BYPASS

Power bias for internal circuit. Connect a 0.22μF bypass capacitor for the internal

regulator.

12

VDD

Input power supply.

13

EXTM

External modulation input for 22kHz tone signal. EXTM is shaped inside the

MP8124 and transferred onto the output. Tie EXTM to ground if not used.

14

13V/18V

Select 13V or 18V as the output voltage. Use 18V for high levels and 13V for low

levels. Do NOT leave 13V/18V floating. Pull 13V/18V to the BYPASS voltage for an

automatic 18V output after start-up.