Philips Semiconductors
Product specification
SA676
Low-voltage mixer FM IF system
6129
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
10
9
8
7
6
5
4
3
2
1
RSSI
IF
AMP
E
B
VREG
OSCILLATOR
LIMITER
MIXER
QUAD
+
+
AUDIO
SR00515
Figure 2. Block Diagram
Philips Semiconductors
Product specification
SA676
Low-voltage mixer FM IF system
1993 Dec 15
6130
ABSOLUTE MAXIMUM RATINGS
SYMBOL
PARAMETER
RATING
UNITS
V
CC
Single supply voltage
7
V
T
STG
Storage temperature range
65 to +150
C
T
A
Operating ambient temperature range
40 to +85
C
JA
Thermal impedance
DK package
117
C/W
DC ELECTRICAL CHARACTERISTICS
V
CC
= +3V, T
A
= 25
C; unless otherwise stated.
SYMBOL
PARAMETER
TEST CONDITIONS
LIMITS
UNITS
SYMBOL
PARAMETER
TEST CONDITIONS
SA676
UNITS
MIN
TYP
MAX
V
CC
Power supply voltage range
2.7
7.0
V
I
CC
DC current drain
3.5
5.0
mA
AC ELECTRICAL CHARACTERISTICS
T
A
= 25
C; V
CC
= +3V, unless otherwise stated. RF frequency = 45MHz; +14.5dBV RF input step-up; IF frequency = 455kHz; R17 = 2.4k
and R18 = 3.3k
; 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 = 220mV
RMS
)
f
IN
Input signal frequency
100
MHz
f
OSC
Crystal oscillator frequency
100
MHz
Noise figure at 45MHz
7.0
dB
Thirdorder input intercept point (50
source)
f1 = 45.0; f2 = 45.06MHz
Input RF level = 52dBm
10
dBm
Conversion power gain
Matched 14.5dBV stepup
10
17
dB
50
source
+2.5
dB
RF input resistance
Singleended input
8
k
RF input capacitance
3.0
4.0
pF
Mixer output resistance
(Pin 20)
1.25
1.5
k
IF section
IF amp gain
50
source
44
dB
Limiter gain
50
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
Signaltonoise ratio
No modulation for noise
60
dB
IF RSSI output, R
9
= 2k
1
IF 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
k
IF output impedance
Pin 16
0.3
k
Limiter input impedance
Pin 14
1.3
1.5
k
Limiter output impedance
Pin 11
0.3
k
Limiter output voltage
Pin 11
130
mV
RMS
Philips Semiconductors
Product specification
SA676
Low-voltage mixer FM IF system
1993 Dec 15
6131
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 50
, but the SA676 input impedance at Pin 18 is 1500
. 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, 1.5k
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 1.5k
resistor permitting
direct connection to a 455kHz ceramic filter. The input resistance of
the limiting IF amplifiers is also 1.5k
. 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 10k
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
/V
IN
Philips Semiconductors
Product specification
SA676
Low-voltage mixer FM IF system
1993 Dec 15
6132
10
8
7
6
4
3
2
1
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
2.2
F +10% Tantalum
100nF +10% Monolithic Ceramic
10
F Tantalum (minimum) *
C26
C27
FLT 1
FLT 2
IFT 1
L1
L2
X1
R10
R5
100nF +10% Monolithic Ceramic
2.2
F Tantalum
Not Used in Application Board (see Note 8, pg 8)
8.2k +5% 1/4W Carbon Composition
44.545MHz Crystal ICM4712701
0.8
H 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
330
H TOKO 303LN-1130
C21
100nF +10% Monolithic Ceramic
2.2
F
* NOTE: This value can be reduced when a battery is the power source.
SR00516
Figure 3. SA676 45MHz Application Circuit
Philips Semiconductors
Product specification
SA676
Low-voltage mixer FM IF system
1993 Dec 15
6133
RF GENERATOR
CMESSAGE
HP339A DISTORTION
ANALYZER
SCOPE
DC VOLTMETER
V
CC
(+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 0.45
V 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 10-15
F 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 0.1
F 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 22k
, but should not
be below 10k
.
Philips Semiconductors
Product specification
SA676
Low-voltage mixer FM IF system
1993 Dec 15
6134
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. I
CC
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
SA676
Low-voltage mixer FM IF system
1993 Dec 15
6135
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
*50
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 = 117.6mVRMS
AUDIO
THD + NOISE
AM REJECTION
NOISE
SR00521
Figure 8. Sensitivity vs RF Level (+25
C)
Philips Semiconductors
Product specification
SA676
Low-voltage mixer FM IF system
1993 Dec 15
6136
VOL
T
AGE (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 - V
CC
= 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
mV
RMS
V
C
SR00523
Figure 10. Audio Output vs Temperature and Supply Voltage
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