8

FN7216.3

August 2, 2007

used to adjust initial operating points, but they should be

replaced with fixed resistors for further testing.

adjustment. It is recommended that a coupling resistor be

installed in series with the control voltage and mounted

directly next to the EL6201 pin. This will keep the inevitable

high-frequency noise of the EL6201’s local environment from

propagating to the modulation source, and it will keep

parasitic capacitance at the EL6201 pin minimized.

Both inputs have several megahertz of bandwidth for analog

modulation. The output enable pin can be used to pass

digital modulation up to about 20Mbit/sec rates.

Power Dissipation Considerations

Supply current can be predicted by Equation1:

The 12mA quantity represents the operating DC current of

the EL6201. This is also the current drawn from the supply

typical 50% duty cycle of output pull-up current, and the fact

that the peak-to-peak output current is about twice the pull-

internal capacitances that must be slewed at the operating

frequency. The 1.6V offset is a curve fit to measured data.

The internal die temperature operating range is -40°C to

+125°C. Internal temperature is equal to the ambient

temperature plus power dissipated times the thermal

resistance of the mounted package,

θ

MSOP-8 package,

θ

has a

θ

Power-Down with the SOT-23 Package

The supply current of the EL6201 is low enough so that a

logic output can simply provide the supply current of the part

and effect power-down. This is most useful using the

EL6201 in the SOT-23 package, which has no enable pin.

RF Applications

The EL6201 can easily interface to reactive loads, and is

adequate as a short-range modulated transmitter.

Remembering that the output circuitry looks like current

sources, impedance matching becomes a matter of

transforming the load impedance to an appropriate load line

for the EL6201. Also important is maintaining correct DC

bias voltage on the output. Since the output will have a net

DC current, capacitor coupling would allow the DC level to

drift toward a supply rail and increase output harmonic

products. In cases where such harmonics are important,

Figure 25 shows coupling the EL6201 output to a 50

Ω load:

Digital Clock Applications

The EL6201 can be used as a digital clock source. If

digital supply with an inductor or resistor, whose value is

chosen to drop about 250mV. In this way logic noise can be

isolated by the series component and the EL6201 local

bypass.

The rise- and fall-time of the output will be equal to

smallest that can set an output rise-time, in the interest of

lowest dissipation.

The jitter is about 0.7% of period, RMS.

-

+

PIN

I

S

12mA

I

OUTp-p

+

4V

S

(

- 1.6V

) FREQ 8 10

-12

×

×

×

+

-------------------------------------------------------------------------------------------------

=

(EQ. 1)

EL6201

C1

C2

R1

R2

L

0.001µF

50

Ω

LOAD

FIGURE 25. TUNED INTERFACE TO 50

Ω LEAD

EL6201