SA602A_15 Datasheet, PDF (4/19 Pages) NXP Semiconductors – Double-balanced mixer and oscillator

NXP Semiconductors
SA602A
Double-balanced mixer and oscillator
7. Functional description
The SA602A is a Gilbert cell, an oscillator/buffer, and a temperature-compensated bias
network as shown in Figure 3. The Gilbert cell is a differential amplifier (IN_A and IN_B
pins) that drives a balanced switching cell. The differential input stage provides gain and
determines the noise figure and signal handling performance of the system.
18 kΩ
6
7
25 kΩ
buffer
1.5 kΩ
4
1.5 kΩ
5
BIAS
BIAS
2
1
BIAS
1.5 kΩ
3
GND
1.5 kΩ
aaa-013205
Fig 3. Equivalent circuit
The SA602A is designed for optimum low-power performance. When used with the
SA604A as a 45 MHz cellular radio second IF and demodulator, the SA602A is capable of
receiving 119 dBm signals with a 12 dB S/N ratio. Third-order intercept is typically
13 dBm (that is approximately +5 dBm 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 are not critical, the input to the SA602A should be appropriately
scaled.
Besides excellent low-power performance well into VHF, the SA602A is designed to be
flexible. The input, RF mixer output and oscillator ports support various configurations
provided the designer understands certain constraints, which are explained here.
The RF inputs (IN_A and IN_B pins) are biased internally. They are symmetrical. The
equivalent AC input impedance is approximately 1.5 k  3 pF through 50 MHz. IN_A and
IN_B pins can be used interchangeably, but they should not be DC biased externally.
Figure 4 shows three typical input configurations.
SA602A
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 3 — 27 May 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
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