RT5047A

Copyright © 2016 Richtek Technology Corporation. All rights reserved.

is a registered trademark of Richtek Technology Corporation.

DS5047A-01

November

2016

www.richtek.com

13

Table 1

SEL Pin Status

LNB Output Voltage

0

13.3V

1

18.3V

Tone Generation

The RT5047A provides the tone generation function, please refer to the Figure 2. Set the TONE pin with 22kHz logic

signal, the LNB linear regulator output will carry a 22kHz, 700mV peak to peak signal for DiSEqC 1.x communication.

It can meet base-band timings of 500

s (±100s) for a one-third bit PWK coded signal period on a nominal 22kHz

(±20 %).

TONE

signal

0V

3.3V

13.3V or

18.3V

700m

V

LNB

TONE signal

detect time

VLNB close

TONE after

TONE signal

detect time

VLNB output

TONE when

TONE signal

rise up

Figure 2. Tone Generation Options

Pull-Down Rate Control

The output linear stage provides approximately 40mA

of pull-down capability. This ensures that the output

volts are ramped from 18.3V to 13.3V in a reasonable

amount of time.

Over-Current Disable Time

If the LNB output current exceeds 550mA, typical, for

more than 45ms, then the LNB output will be disabled

and device enters a TON = 45ms/TOFF = 1800ms

routine. It will be returned to normal operation after a

successful soft-start process.

Inrush Current

At start-up or during a LNB reconfiguration event, a

transient surge current above the normal DC operating

level can be provided by the IC. This current increase

can be as high as 550mA, typical, for as long as

required, up to a maximum of 45ms.

OCP1=1000mA

25ms

OCP2=550mA

20ms

If loading is 1000mA

1800ms

OCP1=1000mA

25ms

OCP2=550mA

20ms

OCP1=250mA

25ms

OCP2=138mA

20ms

If LNB is shorted to GND

1800ms

OCP1=250mA

25ms

OCP2=138mA

20ms