SA58640 Datasheet, PDF (3/16 Pages) NXP Semiconductors – Low-voltage mixer FM IF system

Philips Semiconductors
SA58640
Low-voltage mixer FM IF system
7.2 Pin description
Table 2: Pin description
Symbol
Pin
RF IN+
1
RF IN DECOUPLING 2
OSC_OUT
3
OSC_IN
4
RSSI OUT
5
V_CC
6
AUDIO FEEDBACK
7
AUDIO OUT
8
RSSI FEEDBACK
9
QUADRATURE IN
10
LIMITER OUT
11
LIMITER DECOUPLING 12
LIMITER DECOUPLING 13
LIMITER IN
14
GND
15
IF AMP OUT
16
IF AMP DECOUPLING 17
IF AMP IN
18
IF AMP DECOUPLING 19
MIXER OUT
20
Description
positive RF mixer input
negative RF mixer input, decoupling
oscillator output (emitter)
oscillator input (base)
RSSI amplifier output
positive supply
audio amplifier negative input, feedback
audio amplifier output
RSSI amplifier negative input, feedback
quadrature detector input
limiter amplifier output
limiter decoupling
limiter decoupling
limiter amplifier input
ground
IF amplifier output
IF amplifier decoupling
IF amplifier input
IF amplifier decoupling
mixer output
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
strength indicator, there must be a 12 dB(V)¹ insertion loss between the first and second
IF stages. If the IF filter or interstage network does not cause 12 dB(V) insertion loss, a
1. dB(V) = 20log V_o/V_i.
9397 750 14161
Objective data sheet
Rev. 01 — 1 November 2004
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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