ATR4255P-ILQY Datasheet ATR4255P-ILQY, ATR4255P-ILSY | P4-P6

4883B–AUDR–01/06

ATR4255P

Table 2-1. Pin Description

Pin Symbol Function

1MX1FMA1

mixer FM input A

2MX1FMB1

mixer FM input B

3 MX1AMB 1

mixer AM input B

4 GNDMX Ground 1

mixer, preamplifier AGC

5 FMAGC FM preamplifier AGC

6 AMVREG AM control voltage

7 AMAGC AM preamplifier AGC

8 AMPLPF AM AGC LP filter

9 METER Field strength output

10 ADJAC Adjacent channel detection output

11 MPX Multiplex signal

12 V57 5.7V reference voltage

13 OSCB Oscillator basis

14 OSCE Oscillator emitter

15 GNDOSC Oscillator ground

16 OSCOUT Oscillator output

17 EN 3-wire bus enable

18 CLK 3-wire bus clock

19 DATA 3-wire bus data

20 IF2OUT 2

IF amplifier output

21 INT Interrupt, stop signal

22 MX2LO 10.25 MHz input for 2

mixer

23 MX2OB 2

mixer output B

24 MX2OA 2

mixer output A

25 GND Ground

26 MX2IN 2

mixer input

27 V3P 3V reference for AMPIN, AMIFAGC, Control, IF2IN

28 IF2IN 2

IF amplifier input

29 V3 3V reference for IF1OUT, MX2IN

30 IF1OUT 1

IF amplifier output

31 DEV Deviation detect output, test output

32 OPLPF Operating point LPF

33 IF1AMI 1

IF AM amplifier input

34 SMUTE Soft mute control input

35 IFAGCH IF AGC LP filter high time

36 IFAGCL IF AGC LP filter low time constant

37 FILADJ Filter adjust

38 IF1FMI 1

IF FM amplifier input

39 IF1REF 1

IF and MX1OUT reference, MX1AMA, MX1AMB

40 MULTIP Multipath detection output

41 MX1AMA 1

mixer AM input A

42 VS Supply voltage

43 MX1OA 1

mixer output A

44 MX1OB 1

mixer output B

4883B–AUDR–01/06

ATR4255P

3. Functional Description

The ATR4255P implements an AM up/down-conversion reception path from the RF input signal

to the AM-demodulated audio frequency output signal, and for FM reception, a double-conver-

sion reception path from the RF input signal to the FM-demodulated multiplex signal (MPX). A

VCO and an LO prescaler for AM are integrated to generate the LO frequency for the 1

mixer.

Automatic gain control (AGC) circuits are implemented to control the preamplifier and IF stages

in the AM and FM reception path.

For improved FM performance, an integrated IF filter with adjustable bandwidth, a soft mute fea-

ture, and an automatic multipath noise cancellation (MNC) circuit are fully integrated. A powerful

set of sensors is provided for receiving condition analysis and stop signal generation.

Several register bits (bit 0 to bit 93) are used to control circuit operation and to adapt certain cir-

cuit parameters to the specific application. The control bits are organized in two 8-bit and three

24-bit registers that can be programmed by the 3-wire bus protocol. See Section

“3-wire Bus

Description” on page 19 for the bus protocol and the bit-to-register mapping. The meaning of the

control bits is described in the following sections.

3.1 Reception Mode

The IC can be operated in four different modes; modes AM, FM, Weather band (WB), and

Standby are selected by means of bits 92 and 93 as shown in Table 3-1.

In AM mode, the AM mixer, the AM RF-AGC and the 1

IF AM amplifier at pin 33 are activated.

The input of the 2

IF amplifier is connected to pin 28 and the output of the 2

IF amplifier is fed

to the AM demodulator. The output of the AM demodulator is available at MPX output pin 11.

In FM mode, the FM mixer, the FM RF-AGC and the 1

IF FM amplifier at pin 38 are activated.

The bandwidth of the output tank at pins 23 and 24 is increased and the input of the 2

amplifier can be switched between pins 23, 24 and 28. The output of the 2

IF amplifier is fed to

the integrated bandfilter and FM demodulator. The output of the FM demodulator is available at

MPX output, pin 11.

WB mode is similar to FM mode, but the input of the 2

IF amplifier is fixed to pin 28, the range

of the bandwidth control of the integrated band filter is shifted to lower bandwidth, and the gain

of the FM demodulator is increased.

In Standby mode, the mixers, IF amplifiers and AGC circuits are deactivated to reduce current

consumption.

Table 3-1. Operating Mode

AM/FM/Weather Channel Bit 93 Bit 92

Standby 0 0

FM 0 1

AM 1 0

Weather band (WB) 1 1

4883B–AUDR–01/06

ATR4255P

3.2 Test Mode

A special test mode is implemented for final production test only. This mode is activated by set-

ting bit 9 to “1”. This mode is not intended to be used in customer applications. For normal

operation, bit 9 has to be set to “0”. Bits 18 to 30 are deactivated in normal operation mode.

3.3 VCO

An oscillator circuit is implemented to build a VCO as proposed in the application schematic. The

VCO frequency is used to generate the LO frequency of the 1

mixer stages. The control voltage

of the VCO is usually generated by the PLL circuit ATR4256. The VCO signal is provided at the

buffered output pin 16 to be fed to the PLL circuit.

3.4 FM RF-AGC

The FM RF-AGC circuit includes a wideband level detector at the input, pin 1, of the FM mixer,

and an in-band level detector at the output of the FM IF amplifier (pin 30). The outputs of these

level detectors are used to control the current into the pin diode (see Figure 3-1) in order to limit

the signal level at the FM mixer input and the following stages. The maximum pin diode current

is determined by R115 and the time constant of the AGC control loop can be adjusted by chang-

ing the value of C111.

The AGC threshold level at the input of the FM mixer can be adjusted by bits 64 and 65 as

shown in

Table 3-3. The in-band AGC threshold referred to the FM mixer input (pin 1, pin 2)

depends on the gain of the FM IF amplifier and can be adjusted using bits 89 to 91.

Figure 3-1. FM RF-AGC Bit 92

Table 3-2. Test Mode

Mode Bit 9

Normal operation 0

Test mode 1

AGC B92

PIN Diode

VS Pin 42

Pin 5

C111

R115

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P24 P25-P27 P28-P30 P31-P33 P34-P34

ATR4255P-ILQY

Mfr. #:

Buy ATR4255P-ILQY

Manufacturer:

Microchip Technology / Atmel

Description:

RF Receiver COM.RADIO - AM/FM RECEIVER

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ATR4255P-ILQY

ATR4255P-ILQY

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