VITESSE VSC7923X, VSC7923KFL, VSC7923KF, VSC7923CA Datasheet

Preliminary Data Sheet

VITESSE

SEMICONDUCTOR CORPORATION

VSC7923

SONET/SDH 2.5Gb/s Laser Diode Driver

Features Applications

• Rise Times Less Than 100ps

• High Speed Operation (Up to 2.4Gb/s NRZ Data)

• Single-Ended or Differential Input Operation

• Single Power Supply

• Direct Access to Modulation and Bias FETs

• Data Density Monitors

• SONET/SD H at 622Mb/ s, 1.244Gb/s,

2.488Gb/s, 3.125Gb/s

• Full-Speed Fibre Channel (1.062Gb/s)

General Description

The VSC7923 is a single 5V supply, 2.4 Gb/s laser diode driver with direct access to the laser modulation and bias FET’s. Laser bias and modulation currents are set by external com ponents allowing precision monitoring and setting of the current levels. Data inputs accept ECL levels. Data density outputs are provided to allow the user to adjust the laser bias in high unbalanced data applications.

VSC7923 Block Diagram

NIOUTIOUT

DIN

VREF

VIP

VIB

MK

NMK

MIP

IBIAS

IMOD

MIB

G52203-0, Rev 3.0 Page 1 05/11/01

Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com

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VITESSE

SEMICONDUCTOR CORPORATION

Preliminary Data Sheet

SONET/SDH 2.5Gb/s Laser Diode Driver

Table 1: Signal Pin Reference

Signal Type Level # Pins Description

DIN In ECL 1 Data Input MK, NMK Out ECL 2 Data Density Differential Outputs NIOUT Out 1 Laser Modulation Current Output (Complementary) IOUT Out 1 Laser Modulation Current Output (To Laser Cathode)) VSS Pwr Pwr 5 Negative Voltage Rail GND Pwr Pwr 9 Positive Voltage Rail VIP In DC 1 Modulation Gate Node MIP In DC 1 Modulation Source Node VIB In DC 1 Bias Gate Node MIB In DC 1 Bias Source Node VREF In DC 1 Data Input Reference T otal Pin s 24

Table 2: Absolute Maximum Ratings

Symbol Rating Limit

V

SS

T

J

T

STG

Negative Power Supply Voltage VCC to -6.0V Maximum Junction Temperature -55°C to + 125°C Storage Temperature -65°C to +150°C

VSC7923

Table 3: Recommended Operating Conditions

Symbol Parameter Min Typ Max Units Conditions

GND Positive Voltage Rail — 0 — V VSS Negative Voltage Rail -5.5 -5.2 -4.9 V T

Cl

T

J

NOTES: (1) Lower limit of specification is ambient temperature and upper limit is case temperature. (2) See section “Calculation of the

Operational Temperature Junction Temperature ——125 °C

Maximum Case Temperature” for detailed maximum temperature calculations.

(1)

-40 — 85

(2)

°C Power dissipation = 1. 25W

Table 4: ECL Input and Outputs

Symbol Parameter Min Typ Max Units Conditions

V

IN

V

OH

V

OL

Page 2 G52203-0, Rev 3.0

Input Voltage Swing 300 — 800 mV Peak-to-peak, V ECL Output High Voltage -1200 ——mV 50Ω to -2.0V ECL Output Low Voltage ——-1600 mV 50Ω to -2.0V

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REF

= -2.0V

05/11/01

Preliminary Data Sheet

VITESSE

SEMICONDUCTOR CORPORATION

VSC7923

SONET/SDH 2.5Gb/s Laser Diode Driver

Table 5: Power Diss ipat ion

Symbol Parameter Min Typ Max Units Conditions

I

VSS

P

D

P

DMAX

Power Supply Current (VSS) ——220 mA VSS = -5.5V, I

= -5.5V, I

V

T otal Po wer Di ssi patio n ——1210 mW

Maximum Power Dissipation ——1815 mW

R V

I

BIAS

SS LOAD

SS

= -5.5V, I

= 50mA, I

= 25Ω to GND

T able 6: Laser Driver DC Electrical Specifications

Symbol Parameter Min Typ Max Units Conditions

I

BIAS

I

MOD

V

IB

IP

OCM

Programmable Laser Bias Current 2 — 50 mA — Programmable Modulation Current 2 — 60 mA

V

+

Laser Bias Control Voltage ——

Laser Modulation Control Voltage ——

Output Voltage Compliance

GND -

2.2V

——VV

SS

2.1

V

+

SS

2.1

—

VI

BIAS

MOD

SS

= 50mA

= 60mA

= -5.2V

MOD

OUT

= I

BIAS

= I

BIAS

= 60mA,

= 0V

= 0mA

= 0mA,

T able 7: Laser Driver AC Electrical Specifications

Symbol Parameter Min Typ Max Units Conditions

25Ω load, 20%-80%,

tR, t

F

Output Rise and Fall Times ——100 ps

15mA < I

= 20mA

I

BIAS

MOD

< 60mA,

Table 8: Package Thermal Specifications

Symbol Parameter Min Typ Max Units Conditions

θ

JCC

θ

JCMG

Thermal Resistance from Junction-to-Case — 25 — °C/W Ceramic Package Thermal Resistance from Junction-to-Case — 32 — °C/W Metal Glass Package

G52203-0, Rev 3.0 Page 3 05/11/01

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VITESSE

SEMICONDUCTOR CORPORATION

Preliminary Data Sheet

SONET/SDH 2.5Gb/s Laser Diode Driver

VSC7923

Calculation of the Maximum Case Temperature

The VSC7923 is designed to operate with a maximum junction temperature of 125°C. The rise from the case to junction is determined by the power dissipation of the device. The power dissipation is determined by the V current plus the operating I

The power of the chip is determined by the following formula:

P

=(-VSS * ISS) + ((V

D

For example with: V

SS

I

MOD

I

BIAS

V

IBIAS

V

IOUT

P

D

PD = 1144mW + 128mW + 64mW = 1.336W

MOD

and I

BIAS

currents.

– VSS) * I

IOUT

MOD

) + ((V

IBIAS

– VSS) * I

BIAS

= -5.2V = 40mA = 20mA = -2.0V = -2.0V

= 5.2 * 220mA) + ((5.2 - 2.0) * 40mA) + ((5.2-- 2.0) * 20mA)

)

SS

θ

The thermal rise from ju nctio n to case is

* PD. For the metal glass package, θJC = 32 °C/W. Thus the th er-

JC

mal rise is:

32°C/W * 1.336W = 42.7°C

The maximum case temperature is:

125°C – 42.7°C = 82.3°C

The absolute maximum power dissipation of the device is at:

V

SS

I

MOD

I

BIAS

V

IBIAS

V

IOUT

=-5.5V =60mA =50mA =0V =0V

= (5.5 * 220mA) + (5.5 * 60mA) + (5.5mA * 50mA)

P

D

= 1.815W

P

D

This will net a maximum junction to case thermal rise of: 1.815W * 32°C/W = 58°C

This situation will allow maximum case temperature of: 125°C – 58°C = 67°C

Page 4 G52203-0, Rev 3.0

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05/11/01

Preliminary Data Sheet

VITESSE

SEMICONDUCTOR CORPORATION

VSC7923

Input Termination Schemes

OV (GND)

1400 1400

X

DIN

VREF

X

4300 4300

-5.2V (VSS)

SONET/SDH 2.5Gb/s Laser Diode Driver

Figure 1: Input Structure

+

-

• Nominal VREF = -1.3V

• 1400, 4300 Ohm Resistor

on die, nominal values

Figure 2: Single Ended AC Coupled

GND

SOURCE

50 Ohms

GND GND

Figure 3: Differential AC Coupled

GNDGND

GND

-2V

50Ω

-2V

50Ω

0.1µF

GND

VREF

0.1µF

DIN

X

VREF

DIN

X X

+

-

VSS

GND

+

-

VSS

G52203-0, Rev 3.0 Page 5 05/11/01

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