SA58640 NXP Semiconductors, SA58640 Datasheet - Page 3

• Manufacturer Part Number: SA58640
• Description: Low-voltage mixer FM IF system
• Manufacturer: NXP Semiconductors

Philips Semiconductors
8. Functional description
1.
9397 750 14161
Objective data sheet
dB(V) = 20log V
7.2 Pin description
o
/V
i.
Table 2:
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)
IF stages. If the IF filter or interstage network does not cause 12 dB(V) insertion loss, a
Symbol
RF IN+
RF IN DECOUPLING
OSC
OSC
RSSI OUT
V
AUDIO FEEDBACK
AUDIO OUT
RSSI FEEDBACK
QUADRATURE IN
LIMITER OUT
LIMITER DECOUPLING
LIMITER DECOUPLING
LIMITER IN
GND
IF AMP OUT
IF AMP DECOUPLING
IF AMP IN
IF AMP DECOUPLING
MIXER OUT
CC
OUT
IN
Pin description
Rev. 01 — 1 November 2004
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
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
1
insertion loss between the first and second
Low-voltage mixer FM IF system
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
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SA58640
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