LT1319 Просмотр технического описания (PDF) - Linear Technology

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LT1319

Multiple Modulation Standard Infrared Receiver

Linear Technology 

LT1319

TYPICAL PERFORMANCE CHARACTERISTICS

Preamp Frequency Response vs

Input Capacitance

5

4 TA = 25°C

3

2

1

50pF

0

–1

10pF 30pF

–2

–3

–4

–5

100k

1M

10M

FREQUENCY (Hz)

100M

1319 G01

Preamp Highpass vs

Capacitance on FILT1

1000

TA = 25°C

100

10

1

Gain Stage Highpass vs

Capacitance on FILT2 or FILT2L

1000

TA = 25°C

100

10

0.1

100

1k

10k

100k

1M

HIGHPASS CORNER FREQUENCY (Hz)

1319 G02

1

1k

10k

100k

1M

10M

HIGHPASS CORNER FREQUENCY (Hz)

1319 G03

Preamp Output Noise vs

Input Capacitance

250

TA = 25°C

200

Input-Referred Noise vs

Lowpass Filter on PREOUT

20

TA = 25°C

RFILTER = 1k

15

FILTIN- or FILTINL- Referred

Threshold Voltage vs RT1

1.0

TA = 25°C

0.9

150

0.8

50pF

10

100

0.7

50

0

10k

30pF

10pF

100k

1M

10M

FREQUENCY (Hz)

100M

1319 G04

5

0

0.1

1

10

FILTER CUTOFF FREQUENCY (MHz)

1319 G05

0.6

0.5

20

30

RT1 (kΩ)

40

1319 G06

U

CIRCUIT DESCRIPTIO

The LT1319 is a general purpose low noise, high speed,

high gain, infrared receiver designed to easily provide IR

communications with portable computers, PDAs, desktop

computers and peripherals. The receiver takes the photo-

current from an infrared photodiode (Siemens BPW34FA

or Temic BPV22NF) and performs a current-to-voltage

conversion. After external filtering that is tailored for the

desired communication standard, two filter buffers are

provided. There are dual gain chains with nominal gain of

400V/V that feed internal comparators with hysteresis. The

comparator thresholds are set externally with a current into

the VTH pin. The high frequency comparator has a response

time of 25ns and is well-suited to high data rates.

4

The low frequency comparator responds in 60ns and is

useful for more modest data rates such as Sharp/Newton

and IRDA-SIR. The circuit also contains shutdown circuitry

to reduce power consumption. Rejection of ambient inter-

ference is accomplished with AC coupling loops around the

preamp and the two gain stages. The rejection frequency is

set with an internal resistor and an external capacitor to

ground. This feature allows changing of the break fre-

quency by simply switching in additional capacitors. To aid

in rejection of power supply noise there is internal supply

regulation and a fully differential topology after the filter

buffers.

1319fb

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