RF COMMUNICATIONS PRODUCTS
SA612A
Double-balanced mixer and oscillator
Product specification
Replaces data of September 17, 1990
IC17 Data Handbook
1997 Nov 07
Philips Semiconductors
Philips Semiconductors
Product specification
Double-balanced mixer and oscillator
SA612A
DESCRIPTION
The SA612A is a low-power VHF monolithic double-balanced mixer
with on-board oscillator and voltage regulator. It is intended for low
cost, low power communication systems with signal frequencies to
500MHz and local oscillator frequencies as high as 200MHz. The
mixer is a “Gilbert cell” multiplier configuration which provides gain
of 14dB or more at 45MHz.
The oscillator can be configured for a crystal, a tuned tank
operation, or as a buffer for an external L.O. Noise figure at 45MHz
is typically below 6dB and makes the device well suited for high
performance cordless phone/cellular radio. The low power
consumption makes the SA612A excellent for battery operated
equipment. Networking and other communications products can
benefit from very low radiated energy levels within systems. The
SA612A is available in an 8-lead dual in-line plastic package and an
8-lead SO (surface mounted miniature package).
PIN CONFIGURATION
D, N Packages
INPUT A 1
INPUT B 2
GND 3
OUTPUT A 4
8
7
6
5
V
CC
OSCILLATOR
OSCILLATOR
OUTPUT B
SR00098
Figure 1. Pin Configuration
APPLICATIONS
FEATURES
•
Low current consumption
•
Low cost
•
Operation to 500MHz
•
Low radiated energy
•
Low external parts count; suitable for crystal/ceramic filter
•
Excellent sensitivity, gain, and noise figure
ORDERING INFORMATION
DESCRIPTION
8-Pin Plastic Dual In-Line Plastic (DIP)
8-Pin Plastic Small Outline (SO) package (Surface-Mount)
•
Cordless telephone
•
Portable radio
•
VHF transceivers
•
RF data links
•
Sonabuoys
•
Communications receivers
•
Broadband LANs
•
HF and VHF frequency conversion
•
Cellular radio mixer/oscillator
TEMPERATURE RANGE
-40 to +85°C
-40 to +85°C
ORDER CODE
SA612AN
SA612AD
DWG #
SOT97-1
SOT96-1
BLOCK DIAGRAM
8
V CC
VOLTAGE
REGULATOR
OSCILLATOR
7
6
5
GROUND
1
2
3
4
SR00099
Figure 2. Block Diagram
1997 Nov 07
2
853-0391 18662
Philips Semiconductors
Product specification
Double-balanced mixer and oscillator
SA612A
ABSOLUTE MAXIMUM RATINGS
SYMBOL
V
CC
T
STG
T
A
PARAMETER
Maximum operating voltage
Storage temperature
Operating ambient temperature range SA612A
RATING
9
-65 to +150
-40 to +85
UNIT
V
°C
°C
AC/DC ELECTRICAL CHARACTERISTICS
T
A
=25°C, V
CC
= 6V, Figure 3
SYMBOL
V
CC
f
IN
f
OSC
PARAMETER
Power supply voltage range
DC current drain
Input signal frequency
Oscillator frequency
Noise figured at 45MHz
Third-order intercept point at 45MHz
Conversion gain at 45MHz
R
IN
C
IN
RF input resistance
RF input capacitance
Mixer output resistance
(Pin 4 or 5)
RF
IN
=-45dBm
14
1.5
3
1.5
TEST CONDITION
LIMITS
Min
4.5
2.4
500
200
5.0
-13
17
Typ
Max
8.0
3.0
UNIT
V
mA
MHz
MHz
dB
dBm
dB
kΩ
pF
kΩ
DESCRIPTION OF OPERATION
The SA612A is a Gilbert cell, an oscillator/buffer, and a temperature
compensated bias network as shown in the equivalent circuit. The
Gilbert cell is a differential amplifier (Pins 1 and 2) which drives a
balanced switching cell. The differential input stage provides gain
and determines the noise figure and signal handling performance of
the system.
The SA612A is designed for optimum low power performance.
When used with the SA614A as a 45MHz cordless phone/cellular
radio 2nd IF and demodulator, the SA612A is capable of receiving
-119dBm signals with a 12dB S/N ratio. Third-order intercept is
typically -15dBm (that’s approximately +5dBm output intercept
because of the RF gain). The system designer must be cognizant of
this large signal limitation. When designing LANs or other closed
systems where transmission levels are high, and small-signal or
signal-to-noise issues not critical, the input to the SA612A should be
appropriately scaled.
1997 Nov 07
3
Philips Semiconductors
Product specification
Double-balanced mixer and oscillator
SA612A
TEST CONFIGURATION
0.5 to 1.3µH
22pF
5.5µH
V
CC
6.8µF
100nF
10nF
8
7
6
5
150pF
OUTPUT
1nF
10pF
34.545MHz THIRD OVERTONE CRYSTAL
612A
1.5 to
44.2µH
330pF
1
47pF
INPUT
220pF
100nF
0.209 to
0.283µH
2
3
4
120pF
SR00101
Figure 3. Test Configuration
8
V
CC
18k
6
7
25k
BUFFER
1.5k
4
1.5k
5
BIAS
BIAS
2
1
BIAS
1.5k
3
GND
1.5k
SR00102
Figure 4. Equivalent Circuit
1997 Nov 07
4
Philips Semiconductors
Product specification
Double-balanced mixer and oscillator
SA612A
Besides excellent low power performance well into VHF, the
SA612A is designed to be flexible. The input, output, and oscillator
ports can support a variety of configurations provided the designer
understands certain constraints, which will be explained here.
The RF inputs (Pins 1 and 2) are biased internally. They are
symmetrical. The equivalent AC input impedance is approximately
1.5k || 3pF through 50MHz. Pins 1 and 2 can be used
interchangeably, but they should not be DC biased externally. Figure
5 shows three typical input configurations.
The mixer outputs (Pins 4 and 5) are also internally biased. Each
output is connected to the internal positive supply by a 1.5kΩ
resistor. This permits direct output termination yet allows for
balanced output as well. Figure 6 shows three single-ended output
configurations and a balanced output.
The oscillator is capable of sustaining oscillation beyond 200MHz in
crystal or tuned tank configurations. The upper limit of operation is
determined by tank “Q” and required drive levels. The higher the Q
of the tank or the smaller the required drive, the higher the
permissible oscillation frequency. If the required L.O. is beyond
oscillation limits, or the system calls for an external L.O., the
external signal can be injected at Pin 6 through a DC blocking
capacitor. External L.O. should be 200mV
P-P
minimum to 300mV
P-P
maximum.
Figure 7 shows several proven oscillator circuits. Figure 7a is
appropriate for cordless phones/cellular radio. In this circuit a third
overtone parallel-mode crystal with approximately 5pF load
capacitance should be specified. Capacitor C3 and inductor L1 act
as a fundamental trap. In fundamental mode oscillation the trap is
omitted.
Figure 8 shows a Colpitts varacter tuned tank oscillator suitable for
synthesizer-controlled applications. It is important to buffer the
output of this circuit to assure that switching spikes from the first
counter or prescaler do not end up in the oscillator spectrum. The
dual-gate MOSFET provides optimum isolation with low current.
The FET offers good isolation, simplicity, and low current, while the
bipolar circuits provide the simple solution for non-critical
applications. The resistive divider in the emitter-follower circuit
should be chosen to provide the minimum input signal which will
assume correct system operation.
612A
612A
612A
1
INPUT
2
1
2
1
2
a. Single-Ended Tuned Input
b. Balanced Input (For Attenuation
of Second-Order Products)
c. Single-Ended Untuned Input
SR00103
Figure 5. Input Configuration
1997 Nov 07
5
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