SIGE SE1000W Datasheet

50 Ω 50 Ω 50 Ω

R

LightChargerTM155 Mb/s Transimpedance Amplifier

Applications

§ SONET/SDH-based transmission systems, test
equipment and modules

§ OC-3 fibre optic modules and line termination

§ ATM and FDDI optical receivers

Features

§ Single +5 V power supply

§ Input noise current = 12 nA rms when used with a

0.5 pF detector

§ Transimpedance gain = 15 kΩ into a 50 Ω load
(single-ended)

§ On-chip automatic gain control gives input
current overload of 2.6 mA pk and max output
voltage swing of 300 mV pk-pk

§ 50 Ω single-ended or 100 Ω differential wire bond

selectable outputs

§ Bandwidth (-3 dB) = 150 MHz (min)

§ Wide data rate range = 10 Mb/s to 155 Mb/s

§ High input bias level = 2 V

§ Minimal external components, supply decoupling

only

§ Operating junction temperature range = -40°C to

+95°C

§ Equivalent to Nortel Networks AB52

Ordering Information

SE1000W

Final

Product Description

SiGe Semiconductor offers a portfolio of optical
networking ICs for use in high-performance optical
transmitter and receiver functions, from 155 Mb/s up
to 12.5 Gb/s.

SiGe Semiconductor’s SE1000W is a fully integrated,
silicon bipolar transimpedance amplifier; providing
wideband, low noise preamplification of signal current
from a photodetector. It features single-ended or
differential outputs, selectable by wire bond options,
and incorporates an automatic gain control
mechanism to increase dynamic range, allowing input
signals up to 2.6 mA peak. For differential outputs, a
decoupling capacitor on the supply is the only
external circuitry required.

Noise performance is optimized for 155 Mb/s
operation, with a calculated rms noise based

sensitivity of –41 dBm for 10
using a detector with 0.5 pF capacitance and a
responsivity of 0.95 A/W, with an infinite extinction
ratio source.

-10

bit error rate, achieved

Type Package Remark

SE1000W Bare Die Shipped in

Waffle Pack

Functional Block Diagram

Input

Current

GND or –ve supply

TZ_IN

SE1000
TzAmp
155 Mb/s

Bandgap
Reference

f

Tz Amp

Automatic Gain Control

Integrator Rectifier

Output
Driver

Power
Supply
Rejection

Wire bond option for single -ended operation

OUTP

OUTN

ACGND

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Bondpad Diagram

SE1000W

LightChargerTM155 Mb/s Transimpedance Amplifier

Final

VCC2

VCC1

TZ_IN

1

2

Top

View

3

7 6 5 4

VEE2 VEE1 VEE1 ACGND

10

VCC1

9

OUTP

8

OUTN

Bondpad Description

Pad No. Name Description

1 VCC2 Positive supply (+5.0 V), front end circuitry only.
2 VCC1
3 TZ_IN Input pad (connect to photodetector cathode).
4 VEE2

5 ACGND
6 VEE1
7 VEE1

8 OUTN Negative differential voltage output; leave unconnected for single-ended operation.

Positive supply (+5.0 V), pads 2 & 10 are connected on chip. Only one pad needs to
be bonded.

Negative supply (0V) – Note this is separate ground for the input stage, which is AC
coupled on chip. There is no DC current through this pad.
Bond option: Connected to external capacitor to ground for single-ended operation
(recommended 1 nF); unconnected for differential operation.
Negative supply (0V), pads 6 & 7are connected on chip. Only one pad needs to be
bonded.
Negative supply (0V), pads 6 & 7 are connected on chip. Only one pad needs to be
bonded.

9 OUTP Positive differential or single-ended voltage output.

10 VCC1

Positive supply (+5.0 V), pads 2 & 10 are connected on chip. Only one pad needs to
be bonded.

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LightChargerTM155 Mb/s Transimpedance Amplifier

Functional Description
Amplifier Front-End

The transimpedance front-end amplifies an input
current from a photodetector, at pin TZ_IN, to produce
an output voltage with the feedback resistor Rf
determining the level of amplification (see the
functional block diagram on page 1). An automatic
gain control loop varies this resistor, to ensure that
the output from the front-end does not saturate the
output driver stage that follows. This gain control
allows input signals of up to 2.6 mA peak.

The input pin TZ_IN is biased at 3 V below the supply
voltage VCC, allowing a photodetector to easily be
reverse biased by connecting the anode to ground,
and hence enabling single rail operation.

The front-end stage has its own supply pins, VCC2
(+5 V) and VEE2 (0 V), to achieve optimum noise
performance and maintain integrity of the high-speed
signal path. The remainder of the circuitry uses the
supply pins VCC1 (+5 V) and VEE1 (0 V).

Output driver stage

The output driver acts as a buffer stage, capable of
swinging up to 150 mVpk-pk into a 50 Ω load (or
300 mVpk-pk differential into a 100 Ω load). The

small output swings allow ease of use with low
voltage post amplifiers (e.g. 3.3 V parts).

The output can be configured in a differential or
single-ended mode. For differential operation, the pad
ACGND is not wire bonded and the circuit provides a
fully balanced 100 Ω output, on the pins OUTP and
OUTN. For single-ended operation, the ACGND pad
is required to be wire bonded to an external capacitor

SE1000W

Final

to ground (recommend 1 nF). Under these
circumstances, OUTP operates as a single-ended
50 Ω output. In both cases, increasing optical input
level gives a positive-going output signal on the
OUTP pin.

Automatic Gain Control (AGC)

The AGC circuit monitors the voltages from the output
driver and compares them to an internal reference
level produced via the on-chip bandgap reference
circuit. When this level is exceeded, the gain of the
front-end is reduced by controlling the feedback
resistor Rf.

A long time-constant integrator is used within the
control loop of the AGC with a typical low frequency
cut-off of 5 kHz.

Power Supply Rejection

An on-chip power supply rejection circuit is used to
achieve both single-ended and differential rejection
from the +5 V VCC rail.

This stable DC reference minimizes the variation in
the noise and bandwidth performance of the circuit
due to power supply variation of +4.7 V to +5.3 V.

The AC rejection ensures that performance is not
degraded by noise on the power supply. The circuit
achieves a power supply rejection on the outputs of
40 dB for both single-ended and differential operation,
up to 100 kHz. The use of external decoupling will
help to remove any unwanted signals at higher
frequencies.

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