FX589P datasheet(4/18 Pages) CMLMICRO

4 / 18 page

Application Information

XTAL

XTAL/CLOCK

ClkDivA

ClkDivB

RxDCacq

PLLacq

Doc1

Doc2

Tx OUT

Tx ENABLE

Tx PS

Tx DATA

Rx DATA

Rx CLOCK

Tx CLOCK

Rx S/N

R 3

R 1

R 4

C 6

C 5

C 8

C 7

C 1

C 4

BIAS

V SS

Rx PS

Rx FEEDBACK

Rx SIGNAL IN

Rx HOLD

XTAL

XTAL/CLOCK

C 3

C 2

X 1

R 2

FX589P

External Components

Component

Value

Tolerance

Note 1

±5%

1.0M

Ω

±10%

Note 2

±10%

100k

Ω

±10%

Note 1

±10%

Note 5

100nF

±20%

1.0µF

±20%

22.0pF

±20%

Note 4

Note 3

Fig.2 Recommended External Components

2. R

3, R4 and C6 form the gain components for the Rx

Input signal. R

3 should be chosen as required by the

signal input level.

3. The FX589 can operate correctly with Xtal/Clock

frequencies of 1.0MHz to 8.2MHz (V

DD = 5.0V) and

1.0MHz to 5.0MHz (V

DD = 3.0V); see Table 1 for

examples. Operation of this device without a Xtal or

Clock input may cause device damage.

4. C

7 and C8 should both be 15.0nF for a data rate of

8kb/s, and inversely proportional to the data rate for

other data rates, e.g. 30.0nF at 4kb/s, 1.8nF at

64kb/s.

5. The value chosen for C

2 and C3 (including stray

capacitances) should be suitable for the applied V

and the frequency of X

As a guide: C

2 = C3 = 33.0pF at 1.0MHz falling to

18pF at the maximum frequency.

At 3 volts, C

2 = C3 = 33.0pF falling to 18pF at 5.0MHz.

The equivalent series resistance of X

1 should be less

than 2.0k

Ω falling to 150Ω at the maximum frequency.

Stray capacitance on the Xtal/clock circuit pins must

be minimised.

Notes

1. The RC network formed by R

1 and C1 is required

between the Tx Out pin and the input to the

modulator. This network, which can form part of any

dc level shifting and gain adjustment circuitry, forms

an important part of the transmit signal filtering.

The ground connection to the capacitor C

1 should be

positioned to give maximum attenuation of high-

frequency noise into the modulator.

The component values should be chosen so that the

product of the resistance (Ohms) and the capacitance

(Farads) is: BT of 0.3 = 0.34/bit rate (bits/second)

BT of 0.5 = 0.22/bit rate (bits/second).

Data Rate

BT = 0.3

BT = 0.5

(b/s)

R1 (k

Ω) C1 (pF)

R1 (k

Ω) C1 (pF)

4000

120

680

120

470

4800

100

680

100

470

8000

470

120

220

9600

390

470

16000

470

150

19200

100

180

120

32000

220

150

38400*

180

120

64000*

100

* V

>= 4.5V

Note that in all cases, the value of R

1 should be not less

than 47.0k

Ω and that the calculated value of C

1 includes

calculated parasitic (circuit) capacitances.

FX589P Datasheet(PDF) 4 Page - CML Microcircuits

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