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TZA3041

Gigabit Ethernet/Fibre Channel laser drivers

Philips Electronics 

Philips Semiconductors

Gigabit Ethernet/Fibre Channel laser

drivers

Product specification

TZA3041AHL; TZA3041BHL;

TZA3041U

handbook, halfpaTgZe ERO, TONE

<1 nA

<1 nA

40 pF

LINEAR VOLTAGE TO

CURRENT CONVERTER

2.4 V

MGS905

GND

Fig.10 TZERO and TONE internal configuration.

Automatic laser shut-down and laser slow start

The laser modulation and bias currents can be rapidly

switched off when a HIGH level (CMOS) is applied to

pin ALS. This function allows the circuit to be shut-down in

the event of an optical system malfunction. A 25 kΩ

pull-down resistor defaults pin ALS to the non active state

(see Fig.11).

When a LOW level is applied to pin ALS, the modulation

and bias currents slowly increase to the desired values at

the typical time constants of τONE and τZERO, respectively.

This can be used to slow-start the laser.

Manual laser override

The automatic laser control function can be overridden by

connecting voltage sources to pins TZERO and TONE to

take direct control of the current sources for bias and

modulation respectively. The control voltages should

range from 1.4 to 3.4 V to swing the modulation current

over the range 1 to 60 mA and the bias current over the

range 1 to 90 mA. These current ranges are guaranteed.

Due to the tolerance range in the manufacturing process,

some devices may have higher current values than those

specified, as shown in Figs 12 and 13. Both figures show

that temperature changes cause a slight tilting of the linear

characteristic around an input voltage of 2.4 V.

Consequently, the manually controlled current level is

most insensitive to temperature variations at around this

value. Bias and modulation currents in excess of the

specified range are not supported and should be avoided.

Currents into or out of pins TZERO and TONE in excess of

10 µA must be avoided to prevent damage to the circuit.

handbook, halfpage

100 Ω

ALS

100 Ω

25 kΩ

GND

VCC(R)

MGS911

Fig.11 ALS input.

2002 Aug 13

10

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