ML3356 Ver la hoja de datos (PDF) - LANSDALE Semiconductor Inc.

Número de pieza

componentes Descripción

Fabricante

ML3356

Wideband FSK Receiver

LANSDALE Semiconductor Inc. 

ML3356

LANSDALE Semiconductor, Inc.

Legacy Applications Information

Figure 5. Application with Fixed Bias on Data Shaper

RF In

1:2

0.01

Data Out

5.0 V

18 k

Car. Det. Out

0 V or 4.0 V 3.3 k

130 k

15 k

10 k

10 k

390 k

3.0 k

3.3 k

0.1 470

pF

18 k

20

19

RF Input Ground

18

Data

Output

17

Comp(+)

16

15

Comp(–) Squelch

Status

14

13

Squelch Demod

Control Out

12

Demod

Filter

11

Quad

Input

ML3356

150 pF

RF

OSC

OSC RF

Mixer

Limiter Limiter Limiter Quad

Gnd

EM.

COL. VCC

Out

VCC

Input

Bias Bias

Bias

1

2

3

4

5

6

7

8

9

10

5.0 V

15 pF

5.6 pF fO

0.01

+ 5.0 to + 12 V 0.01

Bead

4.0 V

330

0.1

Cer. Fil.

10.7 MHz

330

0.01

0.01

0.01

Bead

0.1

180

82

APPLICATION NOTES (continued)

Shielding, which includes the placement of input and output

components, is important in minimizing electrostatic or elec-

tromagnetic coupling. The ML3356 has its pin connections

such that the circuit designer can place the critical input and

output circuits on opposite ends of the chip. Shielding is nor-

mally required for inductors in tuned circuits.

The ML3356 has a separate VCC and ground for the RF and

IF sections which allows good external circuit isolation by

minimizing common ground paths.

Note that the circuits of Figures 1 and 2 have RF, Oscillator,

and IF circuits predominantly referenced to the plus supply

rails. Figure 5, on the other hand, shows a suitable means of

ground referencing. The two methods produce identical results

when carefully executed. It is important to treat Pin 19 as a

ground node for either approach. The RF input should be

‘‘grounded’’ to Pin 1 and then the input and the mixer/oscilla-

tor grounds (or RF VCC bypasses) should be connected by a

low inductance path to Pin 19. IF and detector sections should

also have their bypasses returned by a separate path to Pin 19.

VCC and RF VCC can be decoupled to minimize feedback,

although the configuration of Figure 2 shows a successful

implementation on a common 5.0 V supply. Once again, the

message is: define a supply node and a ground node and return

each section to those nodes by separate, low impedance paths.

The test circuit of Figure 2 has a 3 dB limiting level of 30

µV which can be lowered 6 db by a 1:2 untuned transformer at

the input as shown in Figures 5 and 6. For applications that

require additional sensitivity, an RF amplifier can be added,

but with no greater than 20 db gain. This will give a 2.0 to 2.5

µV sensitivity and any additional gain will reduce receiver

dynamic range without improving its sensitivity. Although the

test circuit operates at 5.0 V, the mixer/oscillator optimum per-

formance is at 8.0 V to 12 V. A minimum of 8.0 V is recom-

mended in high frequency applications (above 150 MHz), or in

PLL applications where the oscillator drives a prescaler.

Page 4 of 9

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