Document
SA58640
Low-voltage mixer FM IF system
Rev. 3 — 12 April 2011
Product data sheet
1. Introduction
The SA58640 was designed for cordless telephone applications in which efficient and economic integrated solutions are required and yet high performance is desirable. Although the product is not targeted to meet the stringent specifications of high performance cellular equipment, it will exceed the needs for analog cordless phones. The minimal amount of external components and absence of any external adjustments makes for a very economical solution.
2. General description
The SA58640 is a low-voltage monolithic FM IF system incorporating a mixer/oscillator, two limiting intermediate frequency amplifiers, quadrature detector, logarithmic RSSI, voltage regulator and audio and RSSI operational amplifiers. The SA58640 is available in a 20-pin SSOP package.
3. Features and benefits
Low power consumption: 5.0 mA typical at 5 V Mixer input to >100 MHz Mixer conversion power gain of 17 dB at 45 MHz Crystal oscillator effective to 100 MHz (LC oscillator or external oscillator can be used
at higher frequencies) 102 dB of IF amplifier/limiter gain 2 MHz IF amplifier/limiter small signal bandwidth Temperature compensated logarithmic RSSI with a 70 dB dynamic range Low external component count; suitable for crystal/ceramic/LC filters Audio output internal op amp RSSI output internal op amp Internal op amps with rail-to-rail outputs ESD protection: Human body model 2 kV; robot model 200 V
4. Applications
Cordless telephones
NXP Semiconductors
SA58640
Low-voltage mixer FM IF system
5. Ordering information
Table 1. Ordering information
Type number
Package
Name
Description
SA58640DK
SSOP20 plastic shrink small outline package; 20 leads; body width 4.4 mm
6. Block diagram
Version SOT266-1
MIXER_OUT IF_AMP_IN IF_AMP_OUT
LIM_IN LIM_DEC
IF_AMP_DEC IF_AMP_DEC
GND
LIM_DEC LIM_OUT
20 19
18 17
16 15
14 13 12 11
mixer
IF amp
OSCILLATOR RSSI
limiter SA58640
quad
12
E
B
3
4
VREG
5
6
audio
7
8
9
10
RF_IN_P
OSCOUT
RSSI_OUT
RF_IN_N_DEC
OSCIN
VCC
AUDIO_FB RSSI_FB AUDIO_OUT QUAD_IN
002aab125
Fig 1. Block diagram of SA58640
SA58640
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 3 — 12 April 2011
© NXP B.V. 2011. All rights reserved.
2 of 20
NXP Semiconductors
7. Pinning information
7.1 Pinning
SA58640
Low-voltage mixer FM IF system
RF_IN_P 1 RF_IN_N_DEC 2
OSCOUT 3 OSCIN 4
RSSI_OUT 5 VCC 6
AUDIO_FB 7 AUDIO_OUT 8
RSSI_FB 9 QUAD_IN 10
SA58640DK
20 MIXER_OUT 19 IF_AMP_DEC 18 IF_AMP_IN 17 IF_AMP_DEC 16 IF_AMP_OUT 15 GND 14 LIM_IN 13 LIM_DEC 12 LIM_DEC 11 LIM_OUT
002aab134
Fig 2. Pin configuration for SSOP20
7.2 Pin description
Table 2. Pin description
Symbol
Pin
RF_IN_P
1
RF_IN_N_DEC 2
OSCOUT
3
OSCIN
4
RSSI_OUT
5
VCC
6
AUDIO_FB
7
AUDIO_OUT 8
RSSI_FB
9
QUAD_IN
10
LIM_OUT
11
LIM_DEC
12
LIM_DEC
13
LIM_IN
14
GND
15
IF_AMP_OUT 16
IF_AMP_DEC 17
IF_AMP_IN
18
IF_AMP_DEC 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
SA58640
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 3 — 12 April 2011
© NXP B.V. 2011. All rights reserved.
3 of 20
NXP Semiconductors
SA58640
Low-voltage mixer FM IF system
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 kΩ 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 crystal configurations.
The output impedance of the mixer is a 1.5 kΩ resistor permitting direct connection to a 455 kHz ceramic filter. The input resistance of the limiting IF amplifiers is also 1.5 kΩ. 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 line.