XR-2209M datasheet(5/20 Pages) EXAR

5 / 20 page

XR-2209

Rev. 2.02

PRECAUTIONS

The following precautions should be observed when

operating the XR-2209 family of integrated circuits:

Pulling excessive current from the timing terminals

will adversely affect the temperature stability of the

circuit.

minimize

this

disturbance,

recommended that the total current drawn from pin 4

be limited to

6mA. In addition, permanent damage

to the device may occur if the total timing current

exceeds 10mA.

Terminals 2, 3, and 4 have very low internal

impedance and should, therefore, be protected from

accidental shorting to ground or the supply voltage.

SYSTEM DESCRIPTION

The XR-2209 functional blocks are shown in the block

diagram given in

Figure 1. They are a voltage controlled

oscillator (VCO), and two buffer amplifiers for triangle and

squarewave outputs.

Figure 2 is a simplified XR-2209

schematic diagram that shows the circuit in greater detail.

The VCO is a modified emitter-coupled current controlled

multivibrator. Its oscillation is inversely proportional to the

value of the timing capacitor connected to pins 2 and 3,

and directly proportional to the total timing current IT. This

current is determined by the resistor that is connected

from the timing terminals (pin 4) to ground.

The triangle output buffer has a low impedance output

(10

W typ.) while the squarewave is an open-collector

type. An external bias input allows the XR-2209 to be

used in either single or split supply applications.

Square Wave

Output

VCC

Triangle Wave

VCC

I +

VEE

BIAS

TWO

SWO

XR-2209

Output

I-

5.1K

Figure 3. Test Circuit for Single Supply Operation

VCC

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