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SA676DK ,Low-voltage mixer FM IF systemFeatures and benefits Low power consumption: 3.5 mA typical at 3 V Mixer input to > 100 MHz Mixe ..
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SA676DK
Low-voltage mixer FM IF system
1. General 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.
2. Features and benefits Low power consumption: 3.5 mA typical at 3V Mixer input to > 100 MHz Mixer conversion power gain of 17 dB at 45 MHz XTAL oscillator effective to 100 MHz (LC oscillator or external oscillator can be used at
higher frequencies) 102 dB of IF amplifier/limiter gain2 MHz IF amp/limiter small signal bandwidth Temperature compensated logarithmic Received Signal Strength Indicator (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 exceeds 2000 V HBM per JESD22-A114 and 1000 V CDM per
JESD22-C101 Latch-up testing is done to JEDEC Standard JESD78 Class II, Level B
3. Applications Cordless telephones
SA676
Low-voltage mixer FM IF system
Rev. 3 — 19 July 2012 Product data sheet
NXP Semiconductors SA676
Low-voltage mixer FM IF system
4. Ordering information
5. Block diagram
Table 1. Ordering information
Tamb= 40 C to +85C
SA676DK/01 SA676DK SSOP20 plastic shrink small outline package; 20 leads;
body width 4.4 mm
SOT266-1
NXP Semiconductors SA676
Low-voltage mixer FM IF system
6. Pinning information
6.1 Pinning
6.2 Pin description
Table 2. Pin description
RF_IN 1 RF input
RF_IN_DECOUPL 2 RF input decoupling pin
OSC_OUT 3 oscillator output
OSC_IN 4 oscillator input
RSSI_OUT 5 RSSI output
VCC 6 positive supply voltage
AUDIO_FEEDBACK 7 audio amplifier negative feedback terminal
AUDIO_OUT 8 audio amplifier output
RSSI_FEEDBACK 9 RSSI amplifier negative feedback terminal
QUADRATURE_IN 10 quadrature detector input terminal
LIMITER_OUT 11 limiter amplifier output
LIMITER_DECOUPL 12 limiter amplifier decoupling pin
LIMITER_DECOUPL 13 limiter amplifier decoupling pin
LIMITER_IN 14 limiter amplifier input
GND 15 ground; negative supply
IF_AMP_OUT 16 IF amplifier output
IF_AMP_DECOUPL 17 IF amplifier decoupling pin
IF_AMP_IN 18 IF amplifier input
IF_AMP_DECOUPL 19 IF amplifier decoupling pin
MIXER_OUT 20 mixer output
NXP Semiconductors SA676
Low-voltage mixer FM IF system
7. Functional description
The SA676 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 MHz with 90 dB of gain. The gain/bandwidth distribution is optimized for 455 kHz,
1.5 k source applications. The overall system is well-suited to battery operation as well
as high performance 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 L/C 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 k resistor permitting direct connection to a
455 kHz ceramic filter. The input resistance of the limiting IF amplifiers is also 1.5 k. 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 dB of gain and 4.5 MHz bandwidth.
To achieve optimum linearity of the log signal strength indicator, there must be a 12 dBV
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
(IF_AMP_OUT) and the interstage network. The overall gain will then be 90 dB with 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 k with a
rail-to-rail output.
A log signal strength indicator completes the circuitry. The output range is greater than dB and is temperature compensated. This signal drives an internal op amp. The 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.
Remark: dBV = 20log VO/VI.
NXP Semiconductors SA676
Low-voltage mixer FM IF system
8. Limiting values
9. Thermal characteristics
10. Static characteristics
Table 3. Limiting values
In accordance with the Absolute Maximum Rating System (IEC 60134).
VCC supply voltage - 7 V
Tstg storage temperature 65 +150 C
Tamb ambient temperature operating 40 +85 C
Table 4. Thermal characteristics
Zth(j-a) transient thermal impedance
from junction to ambient
SA676DK/01 (SSOP20) 117 K/W
Table 5. Static characteristics
VCC =3V; Tamb =25 C; unless specified otherwise.
VCC supply voltage 2.7 - 7.0 V
ICC supply current - 3.5 5.0 mA
NXP Semiconductors SA676
Low-voltage mixer FM IF system
11. Dynamic characteristics
[1] The generator source impedance is 50 , but the SA676 input impedance at IF_AMP_IN (pin 18) is 1500 . As a result, IF level refers
to the actual signal that enters the SA676 input (IF_AMP_IN, pin 18), which is about 21 dB less than the ‘available power’ at the
generator.
Table 6. Dynamic characteristics
Tamb =25 C; VCC=3 V; unless specified otherwise. RF frequency = 45 MHz+ 14.5 dBV RF input step-up. frequency= 455 kHz; R17= 2.4 k and R18= 3.3 k. RF level= 45 dBm; FM modulation=1 kHz with 5 kHz peak
deviation. Audio output with de-emphasis filter and C-message weighted filter. Test circuit Figure 9. 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.
Mixer/oscillator section (external LO = 220 mV RMS value) input frequency - 100 - MHz
fosc oscillator frequency - 100 - MHz noise figure at 45 MHz - 7.0 - dB
IP3I input third-order intercept point 50  source; =45.0MHz;f2=45.06MHz;
input RF level= 52 dBm 10 - dBm
Gp(conv) conversion power gain matched 14.5 dBV step-up 10 17 - dB  source - 2.5 - dB
Ri(RF) RF input resistance single-ended input - 8 - k
Ci(RF) RF input capacitance - 3.0 4.0 pF
Ro(mix) mixer output resistance MIXER_OUT pin 1.25 1.5 - k
IF section
Gamp(IF) IF amplifier gain 50  source - 44 - dB
Glim limiter gain 50  source - 58 - dB
AM AM rejection 30 % AM 1 kHz - 50 - dB
Vo(aud) audio output voltage gain of two 60 120 - mV
SINAD signal-to-noise-and-distortion ratio IF level 110 dBm - 17 - dB
THD total harmonic distortion - 55 - dB
S/N signal-to-noise ratio no modulation for noise - 60 - dB
Vo(RSSI) RSSI output voltage IF; R9=2k [1]
IF level = 110 dBm - 0.5 0.9 V
IF level = 50 dBm - 1.7 2.2 V
RSSI(range) RSSI range - 70 - dB
Zi(IF) IF input impedance IF_AMP_IN pin 1.3 1.5 - k
Zo(IF) IF output impedance IF_AMP_OUT pin - 0.3 - k
Zi(lim) limiter input impedance LIMITER_IN pin 1.3 1.5 - k
Zo(lim) limiter output impedance LIMITER_OUT pin - 0.3 - k
Vo(RMS) RMS output voltage LIMITER_OUT pin - 130 - mV
RF/IF section (internal LO)
SINAD signal-to-noise-and-distortion ratio system; RF level = 114 dBm - 12 - dB
NXP Semiconductors SA676
Low-voltage mixer FM IF system
12. Performance curves
NXP Semiconductors SA676
Low-voltage mixer FM IF system
NXP Semiconductors SA676
Low-voltage mixer FM IF system
NXP Semiconductors SA676
Low-voltage mixer FM IF system
13. Application information
NXP Semiconductors SA676
Low-voltage mixer FM IF system
[1] This value can be reduced when a battery is the power source.
[2] This is a 30 kHz bandwidth 455 kHz ceramic filter. All the characterization and testing are done with this
wideband filter. A more narrowband 15 kHz bandwidth 455 kHz ceramic filter that may be used as an
alternative selection is Murata CFUKG455KE4A-R0.
[3] R5 can be used to bias the oscillator transistor at a higher current for operation above 45 MHz.
Recommended value is 22 k, but should not be below 10k.
Table 7. SA676DK demo board component list

Partno	Mfg	Dc	Qty	Available	Descript
SA676DK	PH	N/a	4	avai	Low-voltage mixer FM IF system