Philips SA625DK Datasheet

RF COMMUNICATIONS PRODUCTS

SA625

High performance low power mixer FM IF
system with high-speed RSSI

Product specification
Replaces data of November 3, 1992

IC17 Data Handbook

Philips Semiconductors

1997 Nov 07

Philips Semiconductors Product specification

High performance low power mixer FM IF system
with high-speed RSSI

DESCRIPTION

The SA625 is pin-to-pin compatible with the SA605, but has faster
RSSI rise and fall times. The SA625 is a high performance
monolithic low-power FM IF system incorporating a mixer/oscillator,
two limiting intermediate frequency amplifiers, quadrature detector,
muting, logarithmic received signal strength indicator (RSSI) with
fast rise and fall time, and voltage regulator. The SA625 combines
the functions of Signetics’ SA602A and SA624. The SA625 is
available in 20-lead SSOP (shrink small outline package).

For additional technical information please refer to application notes
AN1994, 1995 and 1996, which include example application
diagrams, a complete overview of the product and artwork for
reference.

FEATURES

•Fast RSSI rise and fall times

•Low power consumption: 5.8mA typical at 6V

•Mixer input to >500MHz

•Mixer conversion power gain of 13dB at 45MHz

•Mixer noise figure of 4.6dB at 45MHz

•XTAL oscillator effective to 150MHz (L.C. oscillator to 1GHz local

oscillator can be injected)

•102dB of IF Amp/Limiter gain

•25MHz limiter small signal bandwidth

•Temperature compensated logarithmic Received Signal Strength

Indicator (RSSI) with a dynamic range in excess of 90dB

•Two audio outputs - muted and unmuted

•Low external component count; suitable for crystal/ceramic/LC

filters

•Excellent sensitivity: 0.22µV into 50Ω matching network for 12dB

SINAD (Signal to Noise and Distortion ratio) for 1kHz tone with RF
at 45MHz and IF at 455kHz

•SA625 meets cellular radio specifications

PIN CONFIGURATION

MUTED AUDIO OUT

UNMUTED AUDIO OUT

QUADRATURE IN

•ESD hardened

APPLICA TIONS

•Digital cellular base stations

•High performance communications receivers

•Single conversion VHF/UHF receivers

•SCA receivers

•RF level meter

•Spectrum analyzer

•Instrumentation

•FSK and ASK data receivers

•Log amps

•Wideband low current amplification

•Digital cordless telephones

DK Package

RF

1

IN

RF BYPASS 2

XTAL OSC 3
XTAL OSC 4

MUTE

5

IN

6

V

CC

RSSI

7

OUT

8

9

10

Figure 1. Pin Configuration

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

SA625

SR00456

ORDERING INFORMATION

DESCRIPTION TEMPERATURE RANGE ORDER CODE DWG #

20-Pin Plastic Shrink Small Outline Package (SSOP) (Surface-mount) -40 to +85°C SA625DK

1997 Nov 07 853-1648 18664

2

SOT266-1

Philips Semiconductors Product specification

High performance low power mixer FM IF system
with high-speed RSSI

BLOCK DIAGRAM

20 19 18 17 16 15 14 13 12 11

IF
AMP

OSCILLATOR

EB

Figure 2. Block Diagram

SA625

LIMITER

RSSI

10987654321

SR00457

ABSOLUTE MAXIMUM RATINGS

SYMBOL PARAMETER RATING UNITS

T

V

θ

CC

STG

T

A

JA

Single supply voltage 9 V
Storage temperature range -65 to +150

Operating ambient temperature range SA625 -40 to +85
Thermal impedance DK package 117

°C/W

°C
°C

DC ELECTRICAL CHARACTERISTICS

VCC = +6V, TA = 25°C; unless otherwise stated.

LIMITS

SYMBOL PARAMETER TEST CONDITIONS SA625 UNITS

MIN TYP MAX

V

CC

I

CC

Power supply voltage range 4.5 8.0 V
DC current drain 4.55 5.8 6.75 mA
Mute switch input threshold

(ON)

(OFF) 1.0 V

1.7 V

1997 Nov 07

3

Philips Semiconductors Product specification

High performance low power mixer FM IF system
with high-speed RSSI

AC ELECTRICAL CHARACTERISTICS

TA = 25°C; VCC = +6V, unless otherwise stated. RF frequency = 45MHz + 14.5dBV RF input step-up; IF frequency = 455kHz; R17 = 5.1k; RF
level = -45dBm; FM modulation = 1kHz with ±8kHz peak deviation. Audio output with C-message weighted filter and de-emphasis capacitor.
Test circuit Figure 3. The parameters listed below are tested using automatic test equipment to assure consistent electrical characterristics.
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

SYMBOL PARAMETER TEST CONDITIONS

MIN TYP MAX

Mixer/Osc section (ext LO = 300mV)

f

IN

f

OSC

IF section

THD Total harmonic distortion -34 -42 dB

S/N Signal-to-noise ratio No modulation for noise 73 dB

Input signal frequency 500 MHz
Crystal oscillator frequency 150 MHz
Noise figure at 45MHz 5.0 dB
Third-order input intercept point f1 = 45.0; f2 = 45.06MHz -10 dBm
Conversion power gain Matched 14.5dBV step-up 10 13 15 dB

50Ω source -1.7 dB
RF input resistance Single-ended input 3.0 4.7 kΩ
RF input capacitance 3.5 4.0 pF
Mixer output resistance (Pin 20) 1.25 1.5 kΩ

IF amp gain 50Ω source 39.7 dB
Limiter gain 50Ω source 62.5 dB
Input limiting -3dB, R17 = 5.1k Test at Pin 18 -113 dBm
AM rejection 80% AM 1kHz 29 34 43 dB
Audio level, R10 = 100k 15nF de-emphasis 80 150 260 mV
Unmuted audio level, R11 = 100k 150pF de-emphasis 480 mV
SINAD sensitivity RF level -118dB 16 dB

IF RSSI output, R9 = 100kΩ

IF RSSI output rise time RF level = -28dBm 1.2 µs
(10kHz pulse, no 455kHz filter) IF frequency = 10.7MHz
(no RSSI bypass capacitor) RF level = -56dBm 1.2 µs

IF RSSI output fall time RF level = -28dBm 7.6 µs
(10kHz pulse, no 455kHz filter) IF frequency = 10.7MHz
(no RSSI bypass capacitor) RF level = -56dBm 2.0 µs

RSSI range R9 = 100kΩ Pin 16 90 dB
RSSI accuracy R9 = 100kΩ Pin 16 +1.5 dB
IF input impedance 1.40 1.6 kΩ
IF output impedance 0.85 1.0 kΩ
Limiter intput impedance 1.40 1.6 kΩ
Limiter output impedance 300 Ω
Limiter output level with no load 280 mV

1

IF level = -118dBm 0 160 650 mV

IF level = -68dBm 1.9 2.5 3.1 V

IF level = -18dBm 4.0 4.8 5.6 V

IF frequency = 455kHz

RF level = -56dBm 1.2 µs

RF level = -28dBm 1.1 µs

IF frequency = 455kHz

RF level = -56dBm 2.1 µs

RF level = -28dBm 7.3 µs

SA625

SA625

UNITS

RMS

RMS

1997 Nov 07

4

Philips Semiconductors Product specification

High performance low power mixer FM IF system
with high-speed RSSI

AC ELECTRICAL CHARACTERISTICS(Continued)

LIMITS

SYMBOL PARAMETER TEST CONDITIONS SA625 UNITS

MIN TYP MAX

IF section (continued)

Unmuted audio output resistance 58 kΩ
Muted audio output resistance 58 kΩ

RF/IF section (int LO)

Unmuted audio level 4.5V = VCC, RF level = -27dBm 450 mV
System RSSI output 4.5V = VCC, RF level = -27dBm 4.3 V

NOTE:

1. The generator source impedance is 50Ω, but the SA625 input impedance at Pin 18 is 1500Ω. As a result, IF level refers to the actual signal
that enters the SA625 input (Pin 8) which is about 21dB less than the ”available power” at the generator.

CIRCUIT DESCRIPTION

The SA625 is an IF signal processing system suitable for second IF
or single conversion systems with input frequency as high as 1GHz.
The bandwidth of the IF amplifier is about 40MHz, with 39.7dB(v) of
gain from a 50Ω source. The bandwidth of the limiter is about
28MHz with about 62.5dB(v) of gain from a 50Ω source. However,
the gain/bandwidth distribution is optimized for 455kHz, 1.5kΩ
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 5dB, conversion gain of
13dB, and input third-order intercept of -10dBm. The oscillator will
operate in excess of 1GHz in L/C tank configurations. Hartley or
Colpitts circuits can be used up to 100MHz for xtal configurations.
Butler oscillators are recommended for xtal configurations up to
150MHz.

The output of the mixer is internally loaded with 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. 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 can be added between the first IF output (Pin 16) and the
interstage network.

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
relationship to the internal signal, drives the other port of the
multiplier cell.

Overall, the IF section has a gain of 90dB. For operation at
intermediate frequencies greater than 455kHz, special care must be
given to layout, termination, and interstage loss to avoid instability.

The demodulated output of the quadrature detector is available at
two pins, one continuous and one with a mute switch. Signal
attenuation with the mute activated is greater than 60dB. The mute
input is very high impedance and is compatible with CMOS or TTL
levels.

A log signal strength completes the circuitry. The output range is
greater than 90dB and is temperature compensated. This log signal
strength indicator exceeds the criteria for AMPs or TACs cellular
telephone.

NOTE: dB(v) = 20log V

OUT/VIN

SA625

RMS

° phase

1997 Nov 07

5