參數(shù)資料
型號(hào)： VSC7938
廠商： Vitesse Semiconductor Corporation.
英文描述： Laser Diode Driver with Automatic Power Control
中文描述： 激光二極管驅(qū)動(dòng)器，帶有自動(dòng)功率控制
文件頁(yè)數(shù)： 13/16頁(yè)
文件大?。?/td> 213K
代理商： VSC7938
VITESSE
Preliminary Data Sheet
VSC7938
SONET/SDH 3.125Gb/s
Laser Diode Driver with Automatic Power Control
G52349-0, Rev 3.0
01/20/01
Page 13
VITESSE
SEMICONDUCTOR CORPORATION
741 Calle Plano
Camarillo, CA 93012
Tel: (800) VITESSE
FAX: (805) 987-5896
Email: prodinfo@vitesse.com
Internet: www.vitesse.com
Applications Information
The following is a typical design example for the VSC7938 assuming 3.3V operation with APC.
Select a Laser
The Table 5 provides specifications for a typical communication-grade laser capable of operating at
2.5Gb/s.
Table 6: Typical Laser Characteristics
Select Resistor for APCSET
The monitor diode current is estimated by I
MD
= P
AVE
*
ρ
MON
= 6mW * 0.04mA/mW = 0.24mA. The I
MD
vs. R
APCSET
in
Typical Operating Characteristics
shows the resistor at APCSET should be 5k
.
Select Resistor for MODSET
To ensure some minimum extinction ratio over temperature and lifetime, assume an optimal extinction ratio
of 20 (13dB) at 25
°
C
. The modulation current may be calculated from the following equation:
I
MOD
= P
p-p
/
η
= 2 * P
AVE
* (r
e
-1) / (r
e
+1) /
η =
2 * 6mA * (20-1) / (20 + 1) / 0.4 = 27.1mA
The graph of I
MODSET
vs. R
MODSET
in
Typical Operating Characteristics
shows the resistor for MODSET
should be 8.5k
.
Select Resistor for BIASMAX
The maximum threshold current at +85
°
C and end of life must be determined. A graph of a typical laser
’
s
I
th
versus T
C
reveals a maximum threshold current of 30mA at 85
°
C
. Therefore, the maximum bias can be
approximated by:
I
BIASMAX
= I
TH-MAX
+ I
MOD
/ 2 = 30mA + 27.1mA / 2 = 43.6mA
The graph of I
BIASMAX
vs. R
BIASMAX
in
Typical Operating Characteristics
shows the resistor for BIASMAX
should be 5k
.
Wire Bonding
For best performance, gold ball-bonding techniques are recommended. Wedge bonding is not recom-
mended. For best performance and to minimize inductance keep wire bond lengths short.
PCB Layout Guidelines
Use high frequency PCB layout techniques with solid ground planes to minimize crosstalk and EMI. Keep
high speed traces as short as possible for signal integrity. The output traces to the laser diode must be short to
minimize inductance. Short output traces will provide best performance.
Symbol
Parameter
Value
Units
λ
P
AVE
I
th
ρ
MON
η
T
C
Wavelength
Average Optical Output Power
Threshold Current
Laser to Monitor Transfer
Laser Slope Efficiency
Operating Temperature Range
1310
6
6
0.04
0.4
nm
mW
mA
mA/mW
mW/mA
°
C
-40 to +85
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
VSC7938R0 制造商:VITESSE 制造商全稱:Vitesse Semiconductor Corporation 功能描述:Laser Diode Driver with Automatic Power Control
VSC7938W 制造商:VITESSE 制造商全稱:Vitesse Semiconductor Corporation 功能描述:Laser Diode Driver with Automatic Power Control
VSC7939 制造商:VITESSE 制造商全稱:Vitesse Semiconductor Corporation 功能描述:Laser Diode Driver with Automatic Power Control
VSC7939RP 制造商:VITESSE 制造商全稱:Vitesse Semiconductor Corporation 功能描述:Laser Diode Driver with Automatic Power Control
VSC7939W 制造商:VITESSE 制造商全稱:Vitesse Semiconductor Corporation 功能描述:Laser Diode Driver with Automatic Power Control
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