SA614A

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© NXP B.V. 2014. All rights reserved.

Product data sheet

Rev. 4 — 14 February 2014

10 of 28

NXP Semiconductors

SA614A

Low power FM IF system

Audio out:

13.1 Circuit description

The SA614A is a very high gain, high frequency device. Correct operation is not possible

if good RF layout and gain stage practices are not used. The SA614A cannot be

evaluated independent of circuit, components, and board layout. A physical layout which

correlates to the electrical limits is shown in Figure 17. This configuration can be used as

the basis for production layout.

The SA614A is an IF signal processing system suitable for IF frequencies as high as

21.4 MHz. The device consists of two limiting amplifiers, quadrature detector, direct audio

output, muted audio output, and signal strength indicator (with log output characteristic).

The equivalent circuit is shown in Figure 4.

Figure 7 is the performance of the typical cellular radio application shown in Figure 6 with

45 MHz RF input and 455 kHz IF.

Fig 7.

Performance of the typical cellular radio application

AUDIO

RSSI (VOLTS)

THD + NOISE

NOISE

AM (80 % MOD)

aaa-009988

10

-120

-80

1

2

3

4

-60

-40

-20

(dB)

NOISE

AM (80 % MOD)

THD + NOISE

RSSI

(V)

-100

-80

-60

-40

-20

100

1 k

SA614A IF INPUT (μV) (1500 Ω)

SA602A RF INPUT (dBm) (50 Ω)

100 k

10 k

0