U2762B

Rev. A3, 10-Jun-98

Preliminary Information

2 (9)

Pin Description

1

2

3

4

5

6

7

8

10

9

27

22

21

20

18

19

17

12

11

28

25

26

23

24

Mix out

A2 in

A2 REF

Data out

Com Nin

A1 in

GND2

Com in

A1 REF

RSSI

NC

Lim1 in

Lim1 REF

Lim1 out

GND3

Lim2 in

GND1

A2 out

Lim2 REF

LO in

LO REF

16

15

14

13

13960

SL in

DEM out

DEM NTank

DEM Tank

Figure 2. Pinning

Pin

Symbol

Function

1

NC

Not connected

2

RSSI

Signal-strength indicator

3

A1 REF

RF reference

4

A1 in

RF input

5

GND2

IF ground

6

Mix out

Mixer output

7

IF and AF power supply

8

A2 in

IF amplifier A2 input

9

A2 REF

IF amplifier A2 reference

10

Data out

Data output

11

Com Nin

Comparator reference

12

Com in

Comparator input / slicer output

13

SL in

Slicer input

14

DEM out

Demodulator output

15

16

DEM

NTank

Quadrature filter

17

Lim2 REF Limiter2 reference

18

Lim2 in

Limiter2 input

19

GND3

IF and AF Ground

20

Lim1 out

Limiter1 output

21

Lim1 REF Limiter1 reference

22

Lim1 in

Limiter1 input

23

IF power supply 1

24

A2 out

IF amplifier A2 output

25

GND1

RF ground

26

LO in

Local oscillator input

27

LO REF

Local oscillator reference

28

RF power supply

Functional Description

RF Amplifier / Mixer

The RF amplifier / mixer down-converts the antenna

signal to the IF frequency. It has asymmetrical RF and IF

ports. The LO input includes an amplifier for good sensi-

tivity and can be used in a symmetrical- as well as an

asymmetrical configuration.

IF Amplifier A2

An additional gain stage enables an application-specific

insertion point for IF filtering.

Limiter 1 / 2

The two-stage limiting amplifier is designed to be

directly coupled to low-cost 10.7-MHz ceramic IF filters

in front of each stage. The total dynamic range is 65 dB.

Demodulator

The quadrature demodulator in the receiving path

contains an internal 7-pF quadrature capacitor to couple

the IF signal to the external tank providing the 90-degree

phase shift. The tank may be either an LC-tank circuit or

an alignment-free discrete ceramic resonator.

Bit-Slicer Amplifier and Comparator

The bit-slicer limits the baseband signal. Furthermore it

eliminates the DC-offset by an AC-coupled lowpass filter

to the demodulator output. A second lowpass filter

recovers the exact comparator threshold value of the

bit-slicer’s output. The time constants of both lowpass

filters can be selected independently from each other to

optimize power-up timing.