2

Worcester, Massachusetts 01615-0036 (508) 853-5000

115 Northeast Cutoff, Box 15036

www.allegromicro.com

A8285/A8287

LNB Supply and Control Voltage Regulator

Functional Block Diagram

22 kHz Tone

Detector

Internal

Regulator

Boost Converter

Charge

Pump

Clock

Divider

22 kHz

Tone

Generator

I C Interface

2

Output

Voltage

Select

Fault Monitor

Overcurrent

TSD

Undervoltage

VREG

BOOST

Feedback

33 µH

33 µF

EXTM

SDA

SCL

ADD

IRQ

100 mV

VIN

LX

100 nF

VCP

BOOST

OSC In

DISABLE

100 nF

LNB

220

Ω

6.8 nF

33 µH

220 nF

1.5 µF

TCAP

TOUT

TDI

10 nF

TDO

OSC

Overcurrent

VPUMP

220 nF

Overcurrent

15

Ω

100 µF

100 nF

C10

C1

L1

D1

C5

C2

C4

C3

R3 R4 R5

R6

C9

R2

C8

D2

C6

C7

L2

R1

Tracking

Regulator

GM

ID

Characteristics

Suggested Manufacturer

C1

33 μF, 25 V, esr < 200 mΩ, I

Nichicon, part number UHC1E330MET

C2, C5,C10

100 nF, 50 V, X5R or X7R

C4

100 μF, 35 V, esr < 75 mΩ, I

Nichicon, part number UHC1V101MPT

C3,C6

220 nF, 50 V, X5R or X7R

C7

1.5 μF, 50 V, X5R or X7R

C8

6.8 nF, 50 V; Y5V, X5R, or X7R

C9

10 nF (maximum), 50 V; Y5V, X5R, or X7R

R1

15

Ω, 1%, c W

R2

220

Ω, 1%, 2 W

R3-R6

Value determined by V

L1

33 μH, I

TDK, part number TSL0808-330K1R4

L2

33 μH, I

TDK, part number TSL0808-330K1R4

D1

1 A, 35 V or 40 V, Schottky diode

Various, part number 1N5819; Sanken, part number AW04

D2

1 A, 100 V, 1N4002

Tone detector and leads TDI and TDO are not provided in 16-pin package (A8285).