Philips sa676 DATASHEETS

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 = 2.4k 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.
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 (50
source) Conversion power gain Matched 14.5dBV step–up 10 17 dB
RF input resistance Single–ended 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 50source 44 dB Limiter gain 50source 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 = 2k
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
1
)
f1 = 45.0; f2 = 45.06MHz Input RF level = –52dBm
–10 dBm
50 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 50, 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, 1.5k 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/VIN
1993 Dec 15
6–131
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