Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
6–129
1993 Dec 15 853-1726 11659
DESCRIPTION
The SA676 is a low-voltage monolithic FM IF system incorporating a
mixer/oscillator, two limiting intermediate frequency amplifiers,
quadrature detector, logarithmic received signal strength indicator
(RSSI), voltage regulator and audio and RSSI op amps. The SA676
is available in a 20-pin SSOP (shrink small outline package).
The SA676 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.
FEATURES
•Low power consumption: 3.5mA typical at 3V
•Mixer input to >100MHz
•Mixer conversion power gain of 17dB at 45MHz
•XTAL oscillator effective to 100MHz (L.C. oscillator or external
oscillator can be used at higher frequencies)
•102dB of IF Amp/Limiter gain
•2MHz IF amp/limiter small signal bandwidth
•Temperature compensated logarithmic Received Signal Strength
Indicator (RSSI) with a 70dB dynamic range
•Low external component count; suitable for crystal/ceramic/LC
filters
PIN CONFIGURATION
RF IN+
RF IN– DECOUPLING
OSCOUT
OSCIN
RSSI OUT
7
20 MIXER OUT
19
18 IF AMP IN
17
16 IF AMP OUT
15 GND
14 LIMITER IN
13
12
11 LIMITER OUT
VCC
DK Package
AUDIO FEEDBACK
8
RSSI FEEDBACK 9
QUADRATURE IN 10
IF AMP DECOUPLING
AUDIO OUT
IF AMP DECOUPLING
LIMITER DECOUPLING
LIMITER DECOUPLING
2
1
3
4
5
6
SR00514
Figure 1. Pin Configuration
•Audio output internal op amp
•RSSI output internal op amp
•Internal op amps with rail-to-rail outputs
•ESD protection: Human Body Model 2kV
Robot Model 200V
APPLICATION
•Cordless phones
ORDERING INFORMATION
DESCRIPTION TEMPERATURE RANGE ORDER CODE DWG #
20-Pin Plastic Shrink Small Outline Package (Surface-mount) -40 to +85°C SA676DK SOT266-1
BLOCK DIAGRAM
20 19 18 17 16 15 14 13 12 11
10987654321
RSSI
IF
AMP
EB
V
REG
OSCILLATOR
LIMITER
MIXER
QUAD
+– +–
AUDIO
SR00515
Figure 2. Block Diagram
Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
1993 Dec 15 6–130
ABSOLUTE MAXIMUM RATINGS
SYMBOL PARAMETER RATING UNITS
VCC Single supply voltage 7 V
TSTG Storage temperature range –65 to +150 °C
TAOperating ambient temperature range –40 to +85 °C
θJA Thermal impedance DK package 117 °C/W
DC ELECTRICAL CHARACTERISTICS
VCC = +3V, TA = 25°C; unless otherwise stated.
SYMBOL
PARAMETER
TEST CONDITIONS
LIMITS
UNITS
SYMBOL PARAMETER TEST CONDITIONS SA676 UNITS
MIN TYP MAX
VCC Power supply voltage range 2.7 7.0 V
ICC DC current drain 3.5 5.0 mA
AC ELECTRICAL CHARACTERISTICS
TA = 25°C; VCC = +3V, unless otherwise stated. RF frequency = 45MHz; +14.5dBV RF input step-up; IF frequency = 455kHz; R17 = 2.4kΩ
and R18 = 3.3kΩ; RF level = –45dBm; FM modulation = 1kHz with ±5kHz peak deviation. Audio output with de-emphasis filter and C-message
weighted filter. Test circuit Figure 3. The parameters listed below 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.
SYMBOL
PARAMETER
TEST CONDITIONS
LIMITS
UNITS
SYMBOL
PARAMETER
TEST
CONDITIONS
MIN TYP MAX
UNITS
Mixer/Osc section (ext LO = 220mVRMS)
fIN Input signal frequency 100 MHz
fOSC Crystal oscillator frequency 100 MHz
Noise figure at 45MHz 7.0 dB
Third–order input intercept point (50Ω
source) f1 = 45.0; f2 = 45.06MHz
Input RF level = –52dBm –10 dBm
Conversion power gain Matched 14.5dBV step–up 10 17 dB
50Ω source +2.5 dB
RF input resistance Single–ended input 8 kΩ
RF input capacitance 3.0 4.0 pF
Mixer output resistance (Pin 20) 1.25 1.5 kΩ
IF section IF amp gain 50Ω source 44 dB
Limiter gain 50Ω source 58 dB
AM rejection 30% AM 1kHz 50 dB
Audio level Gain of two 60 120 mV
SINAD sensitivity IF level –110dBm 17 dB
THD Total harmonic distortion –55 dB
S/N Signal–to–noise ratio No modulation for noise 60 dB
IF RSSI output, R9 = 2kΩ1IF level = –110dBm 0.5 .90 V
IF level = –50dBm 1.7 2.2 V
RSSI range 70 dB
IF input impedance Pin 18 1.3 1.5 kΩ
IF output impedance Pin 16 0.3 kΩ
Limiter input impedance Pin 14 1.3 1.5 kΩ
Limiter output impedance Pin 11 0.3 kΩ
Limiter output voltage Pin 11 130 mVRMS
Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
1993 Dec 15 6–131
AC ELECTRICAL CHARACTERISTICS (Continued)
SYMBOL PARAMETER TEST CONDITIONS LIMITS UNITS
MIN TYP MAX
RF/IF section (int LO)
System SINAD sensitivity RF level = –114dBm 12 dB
NOTE:
1. The generator source impedance is 50Ω, but the SA676 input impedance at Pin 18 is 1500Ω. As a result, IF level refers to the actual signal
that enters the SA676 input (Pin 18) which is about 21dB less than the “available power” at the generator.
CIRCUIT DESCRIPTION
The SA676 is an IF signal processing system suitable for second IF
systems with input frequency as high as 100MHz. The bandwidth of
the IF amplifier and limiter is at least 2MHz with 90dB of gain. The
gain/bandwidth distribution is optimized for 455kHz, 1.5kΩ 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 7.0dB, conversion gain of
17dB, and input third-order intercept of –10dBm. The oscillator will
operate in excess of 100MHz in L/C tank configurations. Hartley or
Colpitts circuits can be used up to 100MHz for xtal configurations.
The output impedance of the mixer is a 1.5kΩ resistor permitting
direct connection to a 455kHz ceramic filter. The input resistance of
the limiting IF amplifiers is also 1.5kΩ. With most 455kHz ceramic
filters and many crystal filters, no impedance matching network is
necessary. The IF amplifier has 44dB of gain and 5.5MHz
bandwidth. The IF limiter has 58dB of gain and 4.5MHz bandwidth.
To achieve optimum linearity of the log signal strength indicator,
there must be a 12dB(v) insertion loss between the first and second
IF stages. If the IF filter or interstage network does not cause
12dB(v) 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 90dB with 2MHz 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 2nd-order temperature
compensation if needed. It can drive an AC load as low as 10kΩ
with a rail-to-rail output.
A log signal strength indicator completes the circuitry. The output
range is greater than 70dB 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 2nd-order
temperature compensation of the RSSI, if needed.
NOTE: dB(v) = 20log VOUT/VIN
Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
1993 Dec 15 6–132
108764321 5 9
20 19 18 17 16 14 13 12 11
15
RSSI
IF
AMP
MIXER QUAD
RSSI
OUTPUT AUDIO
C14
IFT1
C10
C9
C8
C7
C6 X1
L2
VCC
C5
C2
C1
L1
C18
C15
C17
FLT2
C23 C21
R17
2.4k
FLT1
51pF NPO Ceramic
220pF NPO Ceramic
5-30pF trim cap
1nF Ceramic
10.0pF NPO Ceramic
10pF NPO Ceramic
100nF +10% Monolithic Ceramic
100nF +10% Monolithic Ceramic
100nF +10% Monolithic Ceramic
100nF +10% Monolithic Ceramic
2.2µF +10% Tantalum
100nF +10% Monolithic Ceramic
10µF Tantalum (minimum) *
C26
C27
FLT 1
FLT 2
IFT 1
L1
L2
X1
R10
R5
100nF +10% Monolithic Ceramic
2.2µF Tantalum
Not Used in Application Board (see Note 8, pg 8)
8.2k +5% 1/4W Carbon Composition
44.545MHz Crystal ICM4712701
0.8µH nominal TOKO 292CNS-T1038Z
Ceramic Filter Murata SFG455A3 or equiv
Ceramic Filter Murata SFG455A3 or equiv
C1
C2
C5
C6
C7
C8
C9
C10
C12
C14
C15
C17
C18
Application Component List
45MHz
INPUT
LIMITER
VREG
OSCILLATOR
+– +–
C12
C26 R18
3.3k
R19
11k
C27
R10
R11
10k
10k
C19
C23
390pF +10% Monolithic Ceramic
100nF +10% Monolithic Ceramic
R11 10k +5% 1/4W Carbon Composition
R17
R18 2.4k +5% 1/4W Carbon Composition
3.3k +5% 1/4W Carbon Composition
R19 11k +5% 1/4W Carbon Composition
SA676DK Demoboard
C19
390pF
330nH Coilcraft UNI-10/142-04J08S
330µH TOKO 303LN-1130
C21 100nF +10% Monolithic Ceramic
2.2µF
* NOTE: This value can be reduced when a battery is the power source.
SR00516
Figure 3. SA676 45MHz Application Circuit
Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
1993 Dec 15 6–133
RF GENERATOR
C–MESSAGE
HP339A DISTORTION
ANALYZER
SCOPE
DC VOLTMETER
VCC (+3)
45MHz
DE-EMPHASIS
FILTER
RSSI AUDIO
SA676 DEMOBOARD
SR00517
Figure 4. SA676 Application Circuit Test Set Up
NOTES:
1. C-message: The C-message and de-emphasis filter combination has a peak gain of 10 for accurate measurements. Without the gain, the
measurements may be affected by the noise of the scope and HP339A analyzer. The de-emphasis filter has a fixed -6dB/Octave slope
between 300Hz and 3kHz.
2. Ceramic filters: The ceramic filters can be 30kHz SFG455A3s made by Murata which have 30kHz IF bandwidth (they come in blue), or
16kHz CFU455Ds, also made by Murata (they come in black). All specifications and testing are done with the wideband filter.
3. RF generator: Set your RF generator at 45.000MHz, use a 1kHz modulation frequency and a 6kHz deviation if you use 16kHz filters, or
8kHz if you use 30kHz filters.
4. Sensitivity: The measured typical sensitivity for 12dB SINAD should be 0.45µV or –114dBm at the RF input.
5. Layout: The layout is very critical in the performance of the receiver. We highly recommend our demo board layout.
6. RSSI: The smallest RSSI voltage (i.e., when no RF input is present and the input is terminated) is a measure of the quality of the layout and
design. If the lowest RSSI voltage is 500mV or higher, it means the receiver is in regenerative mode. In that case, the receiver sensitivity
will be worse than expected.
7. Supply bypass and shielding: All of the inductors, the quad tank, and their shield must be grounded. A 10-15µF or higher value tantalum
capacitor on the supply line is essential. A low frequency ESR screening test on this capacitor will ensure consistent good sensitivity in
production. A 0.1µF bypass capacitor on the supply pin, and grounded near the 44.545MHz oscillator improves sensitivity by 2-3dB.
8. R5 can be used to bias the oscillator transistor at a higher current for operation above 45MHz. Recommended value is 22kΩ, but should not
be below 10kΩ.
Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
1993 Dec 15 6–134
6
5
4
3
2
–55 –35 –15 5 25 45 65 85 105 125
VCC = 2.7V
VCC = 3V
VCC = 5V
VCC = 7V
mA
°C
TEMPERATURE (°C)
ICC (mA)
SR00518
Figure 5. ICC vs Temperature and Supply Voltage
TEMPERATURE (°C)
18.00
17.75
17.50
17.25
17.00
16.75
16.50
16.25
16.00
–40 –30 –20 –10 0 10 20 30 40 50 60 70 80
2.7V
3V
7.0V
CONVERSION GAIN (dB)
SR00519
Figure 6. Conversion Gain vs Temperature and Supply Voltage
Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
1993 Dec 15 6–135
20
10
0
–10
–20
–30
–40
–50
–60
–70
–80
–66 –56 –46 –36 –26 –16 –6 4 14 24 34
FUND PRODUCT 3rd ORDER PRODUCT
*50Ω INPUT
IF OUTPUT POWER (dBm)
RF* INPUT LEVEL (dBm)
RF = 45MHz
IF = 455kHz
SR00520
Figure 7. Mixer Third Order Intercept and Compression
DECIBELS (dB)
5
–125 –115 –105 –95 –85 –75 –65 –55 –45 –35 –25
RF LEVEL (dBm)
0
–5
–10
–20
–25
–30
–35
–40
–45
–50
–55
–60
–65
VCC = 3V
RF = 45MHz
DEVIATION = ±5kHz
AUDIO LEVEL = 117.6mV RMS
AUDIO
THD + NOISE
AM REJECTION
NOISE
SR00521
Figure 8. Sensitivity vs RF Level (+25°C)
Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
1993 Dec 15 6–136
VOLTAGE (V)
2.1
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
–125 –115 –105 –95 –85 –75 –65 –55 –45
RF LEVEL (dBm)
+85°C
+27°C
–40°C
SR00522
Figure 9. RSSI vs RF Level and Temperature - VCC = 3V
300
–55 –35 –15 5 25 45 65 85 105 125
VCC = 2.7V
VCC = 3V
VCC = 5V
VCC = 7V
250
200
150
100
50
0
mVRMS
V
°C
SR00523
Figure 10. Audio Output vs Temperature and Supply Voltage
