March 1997

ML4632

Fiber Optic LED Driver

BLOCK DIAGRAM

FEATURES

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Current Driven Output for accurate Launch Power

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Programmable output current from 20mA to 100mA

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Programmable temperature coefficient, 0 to 3300ppm/

°C

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High Efficiency Output Stage

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Programmable LED pre-bias current

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Low EMI/RFI Noise

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ECL or TTL inputs

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Optional Peaking circuit

APPLICATIONS

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IEEE 802.3, 10BASE-F

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IEEE 802.5 Fiber Optic Token Ring

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IEEE 802.4 Fiber Optic Token Bus

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Fiber Optic Data Communications and

Telecommunications

GENERAL DESCRIPTION

The ML4632 is a fiber optic LED driver suited for network

applications up to 20Mbps. The part is capable of driving

up to 100mA of current through a Fiber Optic LED from

an ECL or TTL level input signal. Its efficient output stage

provides a high current that can be programmed for

accurate absolute output level as well as automatic

temperature compensation. The combination of automatic

temperature compensation and a highly accurate current

driven design insures precise launch power.

The LED driver’s output stage provides fast, well matched

rise and fall times through a unique class B output stage

that burns supply current only when the LED is on. A

positive temperature coefficient of up to 3300ppm/

°C can

be programmed into the output current to compensate for

the negative temperature coefficient of the LED optical

output power. An optional peaking circuit may also be

employed.

The ECL and TTL inputs are ANDed so one can be used

for data and the other for an enable input. An ECL

compatible BIAS voltage is also provided for single ended

ECL applications.

ECLP

BUFFER

PEAK

DRIVER

PTAT

DRV

AMP

REF

+

–

14

1

2

13

8

4

9

12

10

11

5

3

6

7

ECLN

VBIAS

TTL

GND

PTAT

VREF

DRV

RTSET

LED

RPK

PEAK

1