EL6208 查看數據表（PDF） - Intersil

零件编号

产品描述 (功能)

生产厂家

EL6208

Dual Push-Pull Laser Driver Oscillator

Intersil 

EL6208

noise on the power lines is common. There needs to be a

lossy bead inductance and secondary bypass on the supply

side to control signals from propagating down the wires.

Figure 20 shows the typical connection.

L SERIES: 70Ω REACTANCE AT 300MHz

VS

GND

EL6208

0.1µF

CHIP

+5V

0.1µF

CHIP

FIGURE 20. RECOMMENDED SUPPLY BYPASSING

Also important is circuit-board layout. At the EL6208's

operating frequencies, even the ground plane is not

low-impedance. High frequency current will create voltage

drops in the ground plane. Figure 21 shows the output

current loops.

RFREQ

RAMP

SUPPLY

BYPASS

SOURCING CURRENT LOOP

GND

SINKING CURRENT LOOP

LASER

DIODE

FIGURE 21. OUTPUT CURRENT LOOPS

For the pushing current loop, the current flows through the

bypass capacitor, into the EL6208 supply pin, out the IOUT

pin to the laser, and from the laser back to the decoupling

capacitor. This loop should be small.

For the pulling current loop, the current flows into the IOUT

pin, out of the ground pin, to the laser cathode, and from the

laser diode back to the IOUT pin. This loop should also be

small.

Power Dissipation

With the high output drive capability, the EL6208 is possible

to exceed the +125°C “absolute-maximum junction

temperature” under certain conditions. Therefore, it is

important to calculate the maximum junction temperature for

the application to determine if the conditions need to be

modified for the oscillator to remain in the safe operating

area.

The maximum power dissipation allowed in a package is

determined according to Equation 1:

PDMAX

=

T----J---M-----A----X-----------T----A----M----A----X--

ΘJA

(EQ. 1)

where:

PDMAX = Maximum power dissipation in the package

TJMAX = Maximum junction temperature

TAMAX = Maximum ambient temperature

θJA = Thermal resistance of the package

The supply current of the EL6208 depends on the peak-to-

peak output current and the operating frequency which are

determined by resistors RAMP and RFREQ. The supply

current can be predicted approximately by Equation 2:

ISUP

=

3----1---.--2---5----m-----A------×-----1----k---Ω---

RAMP

+

-3---0----m-----A------×----1----k----Ω---

RFREQ

+

0.6 m A

(EQ. 2)

The power dissipation can be calculated from Equation 3:

PD = VSUP × ISUP

(EQ. 3)

Here, VSUP is the supply voltage. Figures 22 and provide a

convenient way to see if the device will overheat. The

maximum safe power dissipation can be found graphically,

based on the package type and the ambient temperature. By

using the previous equation, it is a simple matter to see if PD

exceeds the device's power derating curve. To ensure

proper operation, it is important to observe the

recommended derating curve shown in Figures 22 and . A

flex circuit may have a higher θJA, and lower power

dissipation would then be required.

JEDEC JESD51-3 LOW EFFECTIVE THERMAL

CONDUCTIVITY TEST BOARD

0.6

0.5 488mW

0.4

0.3

θJA 6=L+d25S6OCT-/2W3

0.2

0.1

0

0

25

50

75 85 100 125 150

AMBIENT TEMPERATURE (°C)

FIGURE 22. PACKAGE POWER DISSIPATION vs AMBIENT

TEMPERATURE

9

7374.1

August 10, 2007

Share Link: