Philips Semiconductors

Product specification

SA602A

Double-balanced mixer and oscillator

1997 Nov 07

3

BLOCK DIAGRAM

87

65

4

3

2

1

OSCILLATOR

VOLTAGE

REGULATOR

GROUND

V

CC

SR00069

Figure 2. Block Diagram

AC/DC ELECTRICAL CHARACTERISTICS

LIMITS

SYMBOL

PARAMETER

TEST CONDITIONS

SA602A

UNITS

MIN

TYP

MAX

Power supply voltage range

4.5

8.0

V

DC current drain

2.4

2.8

mA

Input signal frequency

500

MHz

Oscillator frequency

200

MHz

Noise figure at 45MHz

5.0

5.5

dB

Third-order intercept point

-13

-15

dBm

Conversion gain at 45MHz

14

17

dB

RF input resistance

1.5

k

Ω

RF input capacitance

3

3.5

pF

Mixer output resistance

(Pin 4 or 5)

1.5

k

Ω

DESCRIPTION OF OPERATION

The SA602A 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 SA602A is designed for optimum low power performance.

When used with the SA604 as a 45MHz cellular radio second IF and

demodulator, the SA602A is capable of receiving -119dBm signals

with a 12dB S/N ratio. Third-order intercept is typically -13dBm (that

is 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 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 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 1.5k

Ω

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.