VITESSE VSC7925KFL, VSC7925KF Datasheet

Preliminary Data Sheet

VITESSE

SEMICONDUCTOR CORPORATION

VSC7925

SONET/SDH 2.5Gb/s Laser Diode Driver

Features Applications

• Rise Times Less Than 100ps

• High Speed Operation (Up to 2.5Gb/s NRZ Data)

• Single-ended Inputs

• Single Supply

• Direct Access to Modulation and Bias FET’s

• Data Density Monitors

• On-Chip Reclocking Register

• 24-Pin Ceramic Package

• SONET/SDH at 622Mb/s, 1.244Gb/s, and

2.488Gb/s

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

General Description

The VSC7925 is a single 5V supply, 2.5Gb/s laser diode driver with direct access to the laser modulation
and bias FETs. Laser bias and modulation currents are set by external components allowing precision monitor­ing and setting of the current levels. Data density outputs are provided to allow the user to adjust the laser bias
in unbalanced data applications. Clock and data inputs have nominal 50
quency decoupling capacitors.P

Ω termination resistors and high fre-

VSC7925 Block Diagram

DIN

50Ω

**

NDIN*

10pF

CLK

50Ω

NCLK*

10pF

* Terminated to off-chip capacitor

** On-die components

**

**

**

DQ

VIP

VIB

DCC

DCC

MK
NMK

MIP

I

MOD

MIB

IOUT

NIOUT

IBIAS

I

BIAS

G52157-0, Rev 3.2 Page 1
05/01/01

© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012

Tel: (800) VITESSE • FAX: [phone] • Email: [e-mail]

Internet: www.vitesse.com

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, NDIN In 2 Data Input and Data Reference
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 4 Negative Voltage Rail
GND Pwr Pwr 6 Positive Voltage Rail
VIP In DC 1 Modulation Gate Node
MIP In DC 1 Modulation Source Node
VIB I n DC 1 Bias Gate Node
MIB In DC 1 Bias Source Node
IBIAS Out DC 1 Laser Bias Output (To Laser Cathode)
CLK, NCLK In 2 Clock Input and Clock Reference
DCC In DC 1 Duty Cycle Control, Leave Floating
T otal Pin s 24

Table 2: Absolute Maximum Ratings

VSC7925

Symbol Rating Limit

V
T

T

SS

J

STG

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

Table 3: High-Speed Inputs and ECL Outputs

Symbol Parameter Min Typ Max Units Conditions

V

IN

V

CM

V

OH

V

OL

Single-ended Input Voltage Swin g 300 1500 mV V
Differential Input Common Mode

Range
ECL Output High Voltage -1200 -500 mV 50Ω to -2.0V
ECL Output Low Voltage -2000 -1600 mV 50Ω to -2.0V

-3.3 -1.3 V V

= -2.5V

CM

= -5.2V

SS

Page 2 G52157-0, Rev 3.2

© VITESSE SEMICONDUCTOR CORPORATION • 741 Ca l le Pl an o • Camarillo, CA 93012

Tel: (800) VITESSE • FAX: [phone] • Email: [e-mail]

Internet: www.vitesse.com

05/01/01

Preliminary Data Sheet

VITESSE

SEMICONDUCTOR CORPORATION

VSC7925

SONET/SDH 2.5Gb/s Laser Diode Driver

Table 4: Recommended Operating Conditions

Symbol Parameter Min Typ Max Units Conditions

GND Positive Voltage Rail 0 V
V

SS

T

CASE KF

NOTE: (1) Lower limit of specification is ambient temperature and upper limit is case temperature.

Negative Voltage Rail -5.5 -5.2 -4.9 V
Operational Temperature9.0 pt -40 85 °C

Power dissipation = 1.3W
Ceramic Package

Table 5: Power Diss ipat ion

Symbol Parameter Min Typ Max Units Conditions

I
P

VSS

D

Power Supply Current (VSS)220mAI
Total Power Dissipat ion 1200 mW

= I

MOD

BIAS

VSS = -5.5V, I
R

= 25Ω to GND

LOAD

T able 6: Laser Driver DC Electrical Specifications

Symbol Parameter Min Typ Max Units Conditions

I

BIAS

I

MOD

V

V

V

IB

IP

OCM

Programmable Laser Bias Current 2 50 mA
Programmabl e Mo du la tio n Cu rr e nt 2 - 60 mA

+

V

Laser Bias Contr ol Voltage

Laser Modulation Control Voltage

Output Voltage Compliance

GND

-2.5V

SS

2.1

V

SS

2.1

VI

+

VI

VVSS = -5.2V

BIAS

MOD

= 50mA

= 60mA

= 0mA

= I

MOD

BIAS

= 0mA,

T able 7: Laser Driver AC Electrical Specifications

Symbol Parameter Min Typ Max Units Conditions

25Ω load, 20%-80%,

tR, t

F

t

SU

t

H

G52157-0, Rev 3.2 Page 3
05/01/01

Output Rise and Fall Times 100 ps

Data to Clock Setup Time 50 ps
Hold Time 50 ps

© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012

Tel: (800) VITESSE • FAX: [phone] • Email: [e-mail]

Internet: www.vitesse.com

15mA < I

= 20mA

I

BIAS

MOD

< 60mA,