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
Package
Name
SA58640DK
SSOP20
Description
plastic shrink small outline package; 20 leads; body width 4.4 mm
Version
SOT266-1
Type number
6. Block diagram
MIXER_OUT
IF_AMP_IN
IF_AMP_OUT
IF_AMP_DEC IF_AMP_DEC
GND
20
19
18
17
16
15
LIM_IN
LIM_DEC
LIM_DEC
LIM_OUT
14
13
12
11
mixer
IF amp
OSCILLATOR
RSSI
limiter
SA58640
quad
E
1
2
3
B
4
5
V
REG
6
7
audio
8
9
10
RF_IN_P
OSCOUT
RSSI_OUT
RF_IN_N_DEC
OSCIN
V
CC
AUDIO_FB
RSSI_FB
AUDIO_OUT
QUAD_IN
002aab125
Fig 1.
Block diagram of SA58640
SA58640
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Product data sheet
Rev. 3 — 12 April 2011
2 of 20
NXP Semiconductors
SA58640
Low-voltage mixer FM IF system
7. Pinning information
7.1 Pinning
RF_IN_P
RF_IN_N_DEC
OSCOUT
OSCIN
RSSI_OUT
V
CC
AUDIO_FB
AUDIO_OUT
RSSI_FB
1
2
3
4
5
6
7
8
9
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
SA58640DK
QUAD_IN 10
Fig 2.
Pin configuration for SSOP20
7.2 Pin description
Table 2.
Symbol
RF_IN_P
RF_IN_N_DEC
OSCOUT
OSCIN
RSSI_OUT
V
CC
AUDIO_FB
AUDIO_OUT
RSSI_FB
QUAD_IN
LIM_OUT
LIM_DEC
LIM_DEC
LIM_IN
GND
IF_AMP_OUT
IF_AMP_DEC
IF_AMP_IN
IF_AMP_DEC
MIXER_OUT
Pin description
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
SA58640
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Product data sheet
Rev. 3 — 12 April 2011
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 linearity of the log signal
strength indicator, there must be a 12 dBV
1
insertion loss between the first and second IF
stages. If the IF filter or interstage network does not cause 12 dBV insertion loss, a fixed
or variable resistor or an L pad for simultaneous loss and impedance matching can be
added between the first IF output (pin 16) and the interstage network. The overall gain will
then be 90 dB with 2 MHz bandwidth.
The signal from the second limiting amplifier goes to a Gilbert cell quadrature detector.
One port of the Gilbert cell is internally driven by the IF. The other output of the IF is
AC-coupled to a tuned quadrature network. This signal, which now has a 90° phase
relationship to the internal signal, drives the other port of the multiplier cell.
The demodulated output of the quadrature drives an internal op amp. This op amp can be
configured as a unity gain buffer, or for simultaneous gain, filtering, and second-order
temperature compensation if needed. It can drive an AC load as low as 10 kΩ with a
rail-to-rail output.
A log signal strength indicator completes the circuitry. The output range is greater than
70 dB and is temperature compensated. This signal drives an internal op amp. The
op amp is capable of rail-to-rail output. It can be used for gain, filtering, or second-order
temperature compensation of the RSSI, if needed.
1.
dBV = 20 log V
o
/ V
i
.
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
SA58640
Product data sheet
Rev. 3 — 12 April 2011
4 of 20
NXP Semiconductors
SA58640
Low-voltage mixer FM IF system
9. Limiting values
Table 3.
Limiting values
In accordance with the Absolute Maximum Rating System (IEC 60134).
Symbol
V
CC
T
stg
T
amb
Z
th
Parameter
supply voltage
storage temperature
ambient temperature
transient thermal impedance
operating
Conditions
Min
-
−65
−40
-
Max
7
+150
+85
117
Unit
V
°C
°C
K/W
10. Static characteristics
Table 4.
Static characteristics
T
amb
= 25
°
C; V
CC
= +5 V; unless otherwise specified.
[1]
Symbol
V
CC
I
CC
[1]
Parameter
supply voltage
supply current
Conditions
Min
4.5
-
Typ
-
5.0
Max
6.0
6.0
Unit
V
mA
RF frequency = 45 MHz; +14.5 dBV RF input step-up; IF frequency = 455 kHz; R17 = 2.4 kΩ and
R18 = 3.3 kΩ; RF level =
−45
dBm; FM modulation = 1 kHz with
±
5 kHz peak deviation. Audio output with
de-emphasis filter and C-message weighted filter. See
Figure 8 “45 MHz application circuit”.
The
parameters listed above are tested using automatic test equipment to assure consistent electrical
characteristics. The limits do not represent the ultimate performance limits of the device. Use of an
optimized RF layout will improve many of the listed parameters.
SA58640
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Product data sheet
Rev. 3 — 12 April 2011
5 of 20
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