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© Koninklijke Philips Electronics N.V. 2004. All rights reserved.

Objective data sheet

Rev. 01 — 1 November 2004

3 of 16

Philips Semiconductors

SA58640

Low-voltage mixer FM IF system

7.2 Pin description

8.

Functional description

The SA58640 is an IF signal processing system suitable for second IF systems with input

frequency as high as 100 MHz. The bandwidth of the IF amplifier and limiter is at least

2 MHz with 90 dB of gain. The gain/bandwidth distribution is optimized for 455 kHz,

1.5 k

: source applications. The overall system is well-suited to battery operation as well

as and high quality products of all types.

The input stage is a Gilbert cell mixer with oscillator. Typical mixer characteristics include

a noise figure of 7.0 dB, conversion gain of 17 dB, and input third-order intercept of

10 dBm. The oscillator will operate in excess of 100 MHz in LC tank configurations.

Hartley or Colpitts circuits can be used up to 100 MHz for XTAL configurations.

The output impedance of the mixer is a 1.5 k

: resistor permitting direct connection to a

455 kHz ceramic filter. The input resistance of the limiting IF amplifiers is also 1.5 k

:. With

most 455 kHz ceramic filters and many crystal filters, no impedance matching network is

necessary. The IF amplifier has 44 dB of gain and 5.5 MHz bandwidth. The IF limiter has

58 dB of gain and 4.5 MHz bandwidth. To achieve optimum linearity of the log signal

IF stages. If the IF filter or interstage network does not cause 12 dB(V) insertion loss, a

Table 2:

Pin description

Symbol

Pin

Description

RF IN+

1

positive RF mixer input

RF IN

 DECOUPLING

2

negative RF mixer input, decoupling

3

oscillator output (emitter)

4

oscillator input (base)

RSSI OUT

5

RSSI amplifier output

6

positive supply

AUDIO FEEDBACK

7

audio amplifier negative input, feedback

AUDIO OUT

8

audio amplifier output

RSSI FEEDBACK

9

RSSI amplifier negative input, feedback

QUADRATURE IN

10

quadrature detector input

LIMITER OUT

11

limiter amplifier output

LIMITER DECOUPLING

12

limiter decoupling

LIMITER DECOUPLING

13

limiter decoupling

LIMITER IN

14

limiter amplifier input

GND

15

ground

IF AMP OUT

16

IF amplifier output

IF AMP DECOUPLING

17

IF amplifier decoupling

IF AMP IN

18

IF amplifier input

IF AMP DECOUPLING

19

IF amplifier decoupling

MIXER OUT

20

mixer output

1.