Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
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 ef fective 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
DK Package
1
RF IN+
OSC
OUT
V
CC
2
3
4
IN
5
6
7
8
9
RF IN– DECOUPLING
OSC
RSSI OUT
AUDIO FEEDBACK
AUDIO OUT
RSSI FEEDBACK
QUADRATURE IN 10
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
APPLICA TION
•Cordless phones
20 MIXER OUT
19
IF AMP DECOUPLING
18 IF AMP IN
17
IF AMP DECOUPLING
16 IF AMP OUT
15 GND
14 LIMITER IN
13
LIMITER DECOUPLING
12
LIMITER DECOUPLING
11 LIMITER OUT
SR00514
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
MIXER
IF
AMP
OSCILLATOR
+–
EB
Figure 2. Block Diagram
RSSI
V
REG
AUDIO
LIMITER
+–
QUAD
10987654321
SR00515
1993 Dec 15 853-1726 11659
6–129
Philips Semiconductors Product specification
SYMBOL
PARAMETER
TEST CONDITIONS
UNITS
SA676Low-voltage mixer FM IF system
ABSOLUTE MAXIMUM RATINGS
SYMBOL PARAMETER RATING UNITS
V
CC
T
STG
T
A
θ
JA
DC ELECTRICAL CHARACTERISTICS
VCC = +3V, TA = 25°C; unless otherwise stated.
SYMBOL PARAMETER TEST CONDITIONS SA676 UNITS
V
CC
I
CC
Single supply voltage 7 V
Storage temperature range –65 to +150 °C
Operating ambient temperature range –40 to +85 °C
Thermal impedance DK package 117 °C/W
LIMITS
MIN TYP MAX
Power supply voltage range 2.7 7.0 V
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.
LIMITS
MIN TYP MAX
Mixer/Osc section (ext LO = 220mV
f
OSC
f
IN
Input signal frequency 100 MHz
Crystal oscillator frequency 100 MHz
Noise figure at 45MHz 7.0 dB
Third–order input intercept point (50Ω
source)
Conversion power gain Matched 14.5dBV step–up 10 17 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 = 2kΩ
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 mV
RMS
1
)
f1 = 45.0; f2 = 45.06MHz
Input RF level = –52dBm
–10 dBm
50Ω source +2.5 dB
IF level = –110dBm 0.5 .90 V
IF level = –50dBm 1.7 2.2 V
RMS
1993 Dec 15
6–130
Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
AC ELECTRICAL CHARACTERISTICS (Continued)
SYMBOL
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.
PARAMETER TEST CONDITIONS LIMITS UNITS
MIN TYP MAX
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 V
OUT/VIN
1993 Dec 15
6–131
Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
C26
R18
3.3k
R17
2.4k
C15
45MHz
INPUT
FLT1
C23
C21
20 19 18 17 16 14
IF
AMP
MIXER
OSCILLATOR
C1
L1
C2
C5
C8
C7
L2
C6
X1
+–
RSSI
C9
C10
15
V
REG
FLT2
R10
10k
C18
C17
13 12 11
LIMITER
QUAD
+–
R11
10k
C12
C27
2.2µF
C19
390pF
R19
11k
108764321 5 9
IFT1
C14
51pF NPO Ceramic
C1
220pF NPO Ceramic
C2
C5
C6
C7
C8
C9
C10
C12
C14
C15
C17
C18
C19
C21
* NOTE: This value can be reduced when a battery is the power source.
10% Monolithic Ceramic
100nF +
5-30pF trim cap
1nF Ceramic
10.0pF NPO Ceramic
10% Monolithic Ceramic
100nF +
µF Tantalum (minimum) *
10
10% Tantalum
2.2µF +
100nF +
10% Monolithic Ceramic
10pF NPO Ceramic
100nF +10% Monolithic Ceramic
100nF +10% Monolithic Ceramic
390pF +
10% Monolithic Ceramic
100nF +
10% Monolithic Ceramic
1993 Dec 15
RSSI
OUTPUT
V
CC
AUDIO
SA676DK Demoboard
Application Component List
C23
100nF +
C26
C27
FLT 1
FLT 2
IFT 1
L1
L2
X1
R5
R10
R11
R17
R18
R19
100nF +
2.2µF Tantalum
Ceramic Filter Murata SFG455A3 or equiv
Ceramic Filter Murata SFG455A3 or equiv
330µH TOKO 303LN-1130
330nH Coilcraft UNI-10/142-04J08S
0.8
44.545MHz Crystal ICM4712701
Not Used in Application Board (see Note 8, pg 8)
8.2k +
10k +
2.4k +
3.3k +
11k +
10% Monolithic Ceramic
10% Monolithic Ceramic
µH nominal TOKO 292CNS-T1038Z
5% 1/4W Carbon Composition
5% 1/4W Carbon Composition
5% 1/4W Carbon Composition
5% 1/4W Carbon Composition
5% 1/4W Carbon Composition
Figure 3. SA676 45MHz Application Circuit
6–132
SR00516
Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
RF GENERATOR
45MHz
V
(+3)
CC
DC VOLTMETER
SCOPE
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.
SA676 DEMOBOARD
RSSI AUDIO
DE-EMPHASIS
FILTER
C–MESSAGE
HP339A DISTORTION
ANALYZER
SR00517
1993 Dec 15
6–133
Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
mA
ICC (mA)
6
5
4
V
= 7V
CC
V
= 5V
CC
= 3V
V
CC
3
2
–55 –35 –15 5 25 45 65 85 105 125
V
= 2.7V
CC
TEMPERATURE (°C)
Figure 5. ICC vs Temperature and Supply Voltage
18.00
17.75
17.50
17.25
17.00
16.75
CONVERSION GAIN (dB)
16.50
3V
7.0V
2.7V
°C
SR00518
1993 Dec 15
16.25
16.00
–40 –30 –20 –10 0 10 20 30 40 50 60 70 80
TEMPERATURE (°C)
SR00519
Figure 6. Conversion Gain vs Temperature and Supply Voltage
6–134
Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
20
10
0
RF = 45MHz
IF = 455kHz
–10
–20
–30
*50Ω INPUT
–10
–20
–25
FUND PRODUCT
–40
IF OUTPUT POWER (dBm)
–50
–60
–70
–80
–66 –56 –46 –36 –26 –16 –6 4 14 24 34
3rd ORDER PRODUCT
RF* INPUT LEVEL (dBm)
SR00520
Figure 7. Mixer Third Order Intercept and Compression
5
0
–5
AUDIO
VCC = 3V
RF = 45MHz
DEVIATION = ±5kHz
AUDIO LEVEL = 117.6mV
RMS
1993 Dec 15
–30
DECIBELS (dB)
–35
–40
–45
–50
–55
–60
–65
–125 –115 –105 –95 –85 –75 –65 –55 –45 –35 –25
AM REJECTION
THD + NOISE
NOISE
RF LEVEL (dBm)
Figure 8. Sensitivity vs RF Level (+25°C)
6–135
SR00521
Philips Semiconductors Product specification
SA676Low-voltage mixer FM IF system
2.1
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
VOLTAGE (V)
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)
Figure 9. RSSI vs RF Level and Temperature - VCC = 3V
+85°C
+27°C
–40°C
SR00522
V
300
V
= 7V
250
200
RMS
150
mV
100
50
0
–55 –35 –15 5 25 45 65 85 105 125
CC
VCC = 5V
V
VCC = 2.7V
CC
= 3V
Figure 10. Audio Output vs Temperature and Supply Voltage
°C
SR00523
1993 Dec 15
6–136
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