Preliminary Data Sheet
VITESSE
SEMICONDUCTOR CORPORATION
VSC7927
SONET/SDH 2.5Gb/s Laser Diode Driver
Features
• Rise Times of Less Than 100ps
• High Speed Operation
(Up to 2.5 Gb/s NRZ Data)
• Differential or Single-Ended Inputs
• Single Supply
• ECL-Compatible Clock and Data Inputs
• Direct Access to Modulation and Bias FETs
• Data Density Monito rs
• On-Chip Reclocking Register
• On-Chip Mux for Clocked or Non-clocked Applications
• On-Chip 50
Ω Input Termination: Clock and Data
General Description
The VSC7927 is a single 5V supply, 2.5 Gb/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 high unbalanced data applications. Clock and data inputs are differentially terminated to 50
Ω.
Applications
• SDH/SONET @ 622Mb/s, 1.244Gb/s, 2.488Gb/s
• Full Speed Fibre Channel (1.062Gb/s)
VSC7927 Block Diagram
DIN
DINTERM*
NDIN
CLK
CLKTERM*
NCLK
*Terminated to Off-chip Capacitor
**On Die Components
50 Ω
50 Ω
50 Ω
50 Ω
**
**
**
**
DQ
M
U
X
SEL
VIP
VIB
DCC
MK
NMK
MIP
I
MOD
MIB
IOUT
NIOUT
IBIAS
I
BIAS
G52201-0, Rev 3.0 Page 1
04/05/01
© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012
Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com
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 ECL 2 Data Input and Data Reference, On-chip 50Ω Termination
MK, NMK Out ECL 2 Data Density Differential Outputs
NIOUT Out
IOUT Out — 1 Laser Modulation Current Output (to Laser Cathode)
VSS Pwr Pwr 2 Negative Voltage Rail
GND Pwr Pwr 5 Positive Voltage Rail
VIP In DC 1 Modulation Gate Node
MIP In DC 1 Modulatio n Sou r ce 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 ECL 2 Clock Input and Clock Reference, On-chip 50Ω Termination
DINTERM In DC 1 Data Reference
CLKTERM In DC 1 Clock Reference
DCC In DC 1 Duty Cycle Control, Leave Floating
SEL In DC 1 Clk/Non-clk Data Select
T otal Pin s
—— 24
— 1 Laser Modulation Current Output (Complementary)
VSC7927
Table 2: Mux Select Logic Table
SEL Mode Select
V
SS
GND Non-clocked Data In
N/C Non-clocked Data In
Clocked Data In
Table 3: 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
Table 4: 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 = 1.3W
Page 2 G52201-0, Rev 3.0
© VITESSE SEMICONDUCTOR CORPORATION • 741 Ca l le Pl an o • Camarillo, CA 93012
Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com
Internet: www.vitesse.com
04/05/01/01
Preliminary Data Sheet
VITESSE
SEMICONDUCTOR CORPORATION
VSC7927
SONET/SDH 2.5Gb/s Laser Diode Driver
Table 5: High Speed Inputs and ECL Outputs
Symbol Parameter Min Typ Max Units Conditions
V
IN
V
CM
V
OH
V
OL
V
IN
Single-ended Input Voltage Swing 300 — 1500 mVp-p V
Differential Input Common Mode Range -2.3 — -1.3 V VSS = -5.2V
ECL Output High Vol tag e -1200 ——mV 50Ω to -2.0V
ECL Output Low Voltage ——-1600 mV 50Ω to -2.0V
On-Chip Terminations 35 — 65 Ω
CM
Table 6: Power Diss ipat ion
Symbol Parameter Min Typ Max Units Conditions
= -5.5V, I
V
I
P
VSS
D
Power Supply Current (VSS) ——120 mA
Total Power Dissipation ——700 mW
SS
0mA, MK/NMK open circuit
V
= -5.5V, I
SS
0mA, R
LOAD
MK/NMK terminated 50Ω to -2V
T able 7: 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 — 100 mA —
Programmable Modulation Current 2 — 100 mA
V
+
Laser Bias Control Voltage ——
Laser Modulation Control Voltage ——
Output Voltage Compliance —
GND -
3V
SS
2.1
V
+
SS
2.1
— VV
—
VI
VI
BIAS
MOD
SS
= 50mA
= 60mA
= -5.2V
= -2.0V
= I
MOD
BIAS
= I
MOD
= 25Ω to GND,
BIAS
=
=
T able 8: Laser Driver AC Electrical Specifications
Symbol Parameter Min Typ Max Units Conditions
25Ω load, 20%-80%,
tR, t
t
SU
t
H
F
Output Rise and Fall Times ——100 ps
Data to Clock Setup Time — 50 90 ps
Hold Time 20 50 — ps
20mA < I
= 60mA
I
BIAS
—
—
MOD
< 60mA,
Table 9: Package Thermal Specifications
Symbol Parameter Min Typ Max Units Conditions
θ
JCC
G52201-0, Rev 3.0 Page 3
04/05/01
Thermal Resistance from Junction-to-Case — 25 — ° C/W Ceramic Package
© VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012
Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com
Internet: www.vitesse.com
VITESSE
SEMICONDUCTOR CORPORATION
Preliminary Data Sheet
SONET/SDH 2.5Gb/s Laser Diode Driver
VSC7927
Calculation of the Maximum Case Temperature
The VSC7927 is designed to operate with a maximum junction temperature of 125° C. The rise from the
case to junction is determined by the power dissip ation of the dev ice. The power dissipation is determine d by
the V
current plus the operating I
SS
MOD
and I
BIAS
currents.
The power of the chip is determined by the following formula:
P
= (-VSS * ISS) + ((V
D
IOUT – VSS
) * I
MOD
For example with:
V
SS
I
MOD
I
BIAS
V
IBIAS
V
IOUT
P
D
P
D
=- 5 . 2 V
=4 0 m A
=2 0 m A
=- 2 . 0 V
=- 2 . 0 V
= (-5.2 * 150mA) + ((5.2 - 2.0) * 40mA) + ((5.2-- 2.0) * 20mA)
= 780mW + 128mW + 64mW = 972mW
) + ((V
IBIAS – VSS
) * I
BIAS
)
θ
The thermal rise from junction-to-case is
* PD. For the ceramic package, θ
JC
mal rise is:
25° C/W * 972W = 24.3°C
The maximum case temperature is:
125° C – 24.3° C = 100.7°C
The absolute maximum power dissipation of the device is at:
V
I
MOD
I
BIAS
V
IBIAS
V
IOUT
P
D
P
D
SS
=- 5 . 5 V
=6 0 m A
=5 0 m A
=0 V
=0 V
= (5.5 * 150mA) + (5.5 * 60mA) + (5.5mA * 50mA)
= 1.43W
This will net a maximum junction to case thermal rise of: 1.43W * 25° C/W = 35.8°C
This situation will allow maximum case temperature of: 35.8°C – 58° C = 89.2°C
= 25° C/W. Thus the ther-
JCP
Page 4 G52201-0, Rev 3.0
© VITESSE SEMICONDUCTOR CORPORATION • 741 Ca l le Pl an o • Camarillo, CA 93012
Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com
Internet: www.vitesse.com
04/05/01/01