LTC5100
3.3V, 3.2Gbps VCSEL Driver
FEATURES
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DESCRIPTIO
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155Mbps to 3.2Gbps Laser Diode Driver for VCSELs*
60ps Rise and Fall Times, 10ps Deterministic Jitter
Eye Diagram is Stable and Consistent Across
Modulation Range and Temperature
1mA to 12mA Modulation Current
Easy Board Layout, Laser can be Remotely Located
if Desired
No Input Matching or AC Coupling Components
Needed
On-Chip ADC for Monitoring Critical Parameters
Digital Setup and Control with I
2
C
TM
Serial Interface
Emulation and Set-Up Software Available**
Operates Standalone or with a Microprocessor
On-Chip DACs Eliminate External Potentiometers
Constant Current or Automatic Power Control
First and Second Order Temperature Compensation
On-Chip Temperature Sensor
Extensive Eye Safety Features
Single 3.3V Supply
4mm
×
4mm QFN Package
The LTC
®
5100 is a 3.2Gbps VCSEL driver offering an
unprecedented level of integration and high speed perfor-
mance. The part incorporates a full range of features to
ensure consistently outstanding eye diagrams. The data
inputs are AC coupled, eliminating the need for external
capacitors. The LTC5100 has a precisely controlled 50Ω
output that is DC coupled to the laser, allowing arbitrary
placement of the IC. No coupling capacitors, ferrite beads
or external transistors are needed, simplifying layout,
reducing board area and the risk of signal corruption. The
unique output stage of the LTC5100 confines the modula-
tion current to the ground system, isolating the high speed
signal from the power supply to minimize RFI.
The LTC5100 supports fully automated production with its
extensive monitoring and control features. Integrated 10-bit
DACs eliminate the need for external potentiometers. An on-
board 10-bit ADC provides the laser current and voltage,
as well as monitor diode current and temperature. Status
information is available from the I
2
C serial interface for feed-
back and statistical process control.
An internal digital controller compensates laser tempera-
ture drift and provides extensive laser safety features.
, LTC and LT are registered trademarks of Linear Technology Corporation.
I
2
C is a trademark of Philips Electronics N.V.
*Vertical Cavity Surface Emitting Laser
**Downloadable from www.linear.com
APPLICATIO S
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Gigabit Ethernet and Fibre Channel Transceivers
SFF and SFP Transceiver Modules
Proprietary Fiber Optic Links
TYPICAL APPLICATIO
3.3V
24LC00 EEPROM
IN SOT-23 PACKAGE
V
DD
SDA
SCL
DIGITAL
CONTROLLER
EN
FAULT
ADC
MD
3.2Gbps Electrical Eye Diagram
DAC
SRC
DAC
MODA
10nF
50Ω
1mA/DIV
IN
+
SERIALIZER
100Ω
IN
–
V
SS
+
MODB
ARBITRARY
DISTANCE
–
3.2Gbps
MODULATOR
5100 F01
WARNING: POTENTIAL EYE HAZARD.
SEE “EYE SAFETY INFORMATION”
Figure 1. VCSEL Transmitter with Automatic Power Control
sn5100 5100fs
U
50ps/DIV
5100 TA01
U
U
1
LTC5100
ABSOLUTE
(Note 1)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
SRC
V
DD
MD
EN
V
DD
, V
DD(HS)
............................................................. 4V
IN
+
, IN
–
(Cml_en = 1) (Note 6)
Peak Voltage ........... V
DD(HS)
– 1.2V to V
DD(HS)
+ 0.3V
Average Voltage...... V
DD(HS)
– 0.6V to V
DD(HS)
+ 0.3V
IN
+
, IN
–
(Cml_en = 0) (Note 4) .. –0.3V to V
DD(HS)
+ 0.3V
Cml_en = 0 (Note 4)
Peak Difference Between IN
+
and IN
–
..............
±2.5V
Average Difference Between IN
+
and IN
–
.......
±1.25V
MODA, MODB (Transmitter Disabled) .... –0.3V to 2.75V
MODA, MODB
(Transmitter Enabled) ............ V
DD(HS)
– 2.75V to 2.75V
EN, SDA, SCL, FAULT ..................... –0.3V to V
DD
+ 0.3V
MD, SRC ................................................... –0.3V to V
DD
Ambient Operating Temperature Range .. – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 125°C
ORDER PART
NUMBER
LTC5100EUF
12 V
SS
11 MODA
10 MODB
9
V
SS
16 15 14 13
V
SS
1
IN
+
2
IN
–
3
17
V
SS
4
5
FAULT
6
SDA
7
SCL
8
V
DD(HS)
UF PART MARKING
5100
UF PACKAGE
16-LEAD (4mm
×
4mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JA
= 37°C/W
EXPOSED PAD IS V
SS
(PIN 17)
MUST BE SOLDERED TO PCB GROUND PLANE
Consult LTC Marketing for parts specified with wider operating temperature ranges.
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C; V
DD
= V
DD(HS)
= 3.3V, I
S
= 24mA; I
M
= 12mA (I
MPP
= 24mA); 49.9Ω, 1%
resistor from SRC (Pin 14) to MODA (Pin 11); 50Ω, 1% load AC coupled to MODB (Pin 10); 10nF, 10% capacitor from SRC (Pin 14) to
V
SS
; Cml_en = 0, Lpc_en = 1, transmitter enabled, unless otherwise noted. Test circuit in Figure 5.
PARAMETER
Power Supply
V
DD
, V
DD(HS)
Operating Voltage
V
DD
+ V
DD(HS)
Quiescent Current,
Excluding the SRC Pin Current (Note 2)
V
DD
= 3.465V
Transmitter Disabled, Power_down_en = 1
Transmitter Enabled, Is_rng = Im_rng = 3
Impp = 24mA
High Speed Data Inputs (IN
+
and IN
–
Pins) (Test Circuit, Figure 5)
Input Signal Amplitude
Peak-to-Peak Differential Voltage (The Single-
Ended Peak-to-Peak Voltage is One Half the
Differential Voltage)
Cml_en = 0 (Note 4)
Cml_en = 0 (Note 5)
Cml_en = 0 (Note 5)
Is_rng = 0
Is_rng = 1
Is_rng = 2
Is_rng = 3
6
12
18
24
0
80 to 120
50
1.65
9
18
27
36
10
1.2
V
DD
–
200mV
500 to 2400
mV
P-P
4.5
54
mA
mA
q
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
3.135
TYP
3.3
MAX
3.465
UNITS
V
Common Mode Input Signal Range (Note 3)
Differential Input Resistance
Common Mode Input Resistance
Open-Circuit Voltage
SRC Pin Current, I
S
Full-Scale I
S
Current
V
DD(HS)
Minimum Operating Current (Note 7)
Resolution
SRC Pin Voltage Range
1/16 of Full-Scale I
S
Current
Bits
V
sn5100 5100fs
2
U
V
Ω
kΩ
V
mA
mA
mA
mA
W
U
U
W W
W
LTC5100
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C; V
DD
= V
DD(HS)
= 3.3V, I
S
= 24mA; I
M
= 12mA (I
MPP
= 24mA); 49.9Ω, 1%
resistor from SRC (Pin 14) to MODA (Pin 11); 50Ω, 1% load AC coupled to MODB (Pin 10); 10nF, 10% capacitor from SRC (Pin 14) to
V
SS
; Cml_en = 0, Lpc_en = 1, transmitter enabled, unless otherwise noted. Test circuit in Figure 5.
PARAMETER
Laser Bias Current, I
B
Full-Scale Current (Note 8)
Is_rng = 0
Is_rng = 1
Is_rng = 2
Is_rng = 3
SRC Pin and MODA, MODB Pin Currents Within
Specified Voltage Ranges
6 – I
M
12 – I
M
18 – I
M
24 – I
M
9 – I
M
18 – I
M
27 – I
M
36 – I
M
±25
10
122
±15625
3.81
±488
Ib_tc1 = 0, Ib_tc2 = 0
Transmitter Disabled, V
SRC
= 1.2V
Im_rng = 0
Im_rng = 1
Im_rng = 2
Im_rng = 3
6
12
18
24
9
18
27
36
±500
50
mA
mA
mA
mA
%
Bits
ppm/°C
ppm/°C
ppm/°C
2
ppm/°C
2
ppm/°C
µA
mA
mA
mA
mA
CONDITIONS
MIN
TYP
MAX
UNITS
ELECTRICAL CHARACTERISTICS
Absolute Accuracy
Resolution
Linear Tempco Resolution
Linear Tempco Range
Second Order Tempco Resolution
Second Order Tempco Range
Temperature Stability
Off-State Leakage
MODA, MODB Pin Current, I
M
Full Scale, Peak-to-Peak Modulation Current (Note 9)
Minimum Operating Current (Note 10)
Resolution (Note 11)
Current Stability
Voltage Range
Absolute Accuracy of the Modulation Current
Linear Tempco Resolution
Linear Tempco Range
Second Order Tempco Resolution
Second Order Tempco Range
Maximum Bit Rate
Modulation Current Rise and Fall Times
Deterministic Jitter, Peak-to-Peak (Note 12)
Random Jitter, RMS (Note 13)
Pulse Width Distortion
Automatic Power Control (Note 14)
Minimum Operating Current for the Monitor Diode
(Note 15)
Temperature Stability
Monitor Diode Bias Voltage (Note 16)
Imd_tc1 = 0, Imd_tc2 = 0
I
MD
≤
1600µA
20% to 80% Measured with K28.5 Pattern at
2.5Gbps
Measured with K28.5 Pattern at 3.2Gbps
Im_tc1 = 0, Im_tc2 = 0
Peak Transient Voltage on MODA and MODB
1/8 of Full-Scale Peak-to-Peak
Modulation Current
9
±500
1.2
±25
122
±15625
3.81
±484
3.2
60
10
1
10
20% of Full Scale
Monitor Diode Current
±500
1.45
ppm/°C
V
2.7
Bits
ppm/°C
V
%
ppm/°C
ppm/°C
ppm/°C
2
ppm/°C
2
Gbps
ps
ps
ps
RMS
ps
sn5100 5100fs
3
LTC5100
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C; V
DD
= V
DD(HS)
= 3.3V, I
S
= 24mA; I
M
= 12mA (I
MPP
= 24mA); 49.9Ω, 1%
resistor from SRC (Pin 14) to MODA (Pin 11); 50Ω, 1% load AC coupled to MODB (Pin 10); 10nF, 10% capacitor from SRC (Pin 14) to
V
SS
; Cml_en = 0, Lpc_en = 1, transmitter enabled, unless otherwise noted. Test circuit in Figure 5.
PARAMETER
Automatic Power Control (Note 14)
Temperature Compensation (Note 17)
Linear Tempco Resolution
Linear Tempco Range
254 • Imd_nom/1024
±32300
• Imd_nom/1024
10
Is_rng = 0
Is_rng = 1
Is_rng = 2
Is_rng = 3
9
18
27
36
±3%
of Full Scale
±25%
of Reading
Im_rng = 0
Im_rng = 1
Im_rng = 2
Im_rng = 3
9
18
27
36
±3%
of Full Scale
±25%
of Reading
3.5
±150mV ±10%
of Reading
Imd_rng = 0
Imd_rng = 1
Imd_rng = 2
Imd_rng = 3
ADC Code = 0
34
136
544
2176
1/8 of Full Scale
0.2
±25%
of Reading
Celsius
239
0.500
Is_rng = 0
Is_rng = 1
Is_rng = 2
Is_rng = 3
400
800
1200
1600
±30mV ±10%
of Reading
V
DD
Decreasing
2.8
150
V
mV
sn5100 5100fs
ELECTRICAL CHARACTERISTICS
CONDITIONS
MIN
TYP
MAX
UNITS
ppm/°C
ppm/°C
Bits
mA
mA
mA
mA
ADC
Resolution
Source Current Measurement, I
S
(SRC Pin Current)
Full Scale
Accuracy
Average Modulation Current Measurement, I
M
(Note 18)
Full Scale
mA
mA
mA
mA
Accuracy
Laser Diode Voltage Measurement
Full Scale
Accuracy
Monitor Diode Current Measurement (Note 19)
Full Scale
V
µA
µA
µA
µA
%
Zero Scale
Resolution Relative to Reading
Accuracy
Temperature Measurement
Full Scale
Sensitivity
Termination Resistor Voltage Measurement
Full Scale
°C
°C/LSB
mV
mV
mV
mV
Accuracy
Safety Shutdown, Undervoltage Lockout (UVLO)
Undervoltage Detection
Undervoltage Detection Hysteresis
4
LTC5100
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C; V
DD
= V
DD(HS)
= 3.3V, I
S
= 24mA; I
M
= 12mA (I
MPP
= 24mA); 49.9Ω, 1%
resistor from SRC (Pin 14) to MODA (Pin 11); 50Ω, 1% load AC coupled to MODB (Pin 10); 10nF, 10% capacitor from SRC (Pin 14) to
V
SS
; Cml_en = 0, Lpc_en = 1, transmitter enabled, unless otherwise noted. Test circuit in Figure 5.
PARAMETER
Bias Current Limit, I
B(LIMIT)
Set Point Resolution
Set Point Range
Is_rng = 0
Is_rng = 1
Is_rng = 2
Is_rng = 3
Automatic Power Control Mode Only, Apc_en = 1
Expressed in % Over the Imd Set Point
Expressed in % Under the Imd Set Point
Time from the Fault Occurance to Reduction of
the Laser Bias Current to 10% of Nominal
I
OL
= 3.3mA
V
FAULT
= 2.4V
I
OL
= 3.3mA
V
FAULT
= 2.4V
I
OL
= 3.3mA
V
FAULT
= 2.4V
I
OH
= –3.3mA
I
OL
= 3.3mA
2.4
0.4
0.8
2
En_polarity = 0 (EN Active Low), V
EN
= 0V
En_polarity = 0 (EN Active Low), V
EN
= V
DD
En_polarity = 1 (EN Active High), V
EN
= 0V
En_polarity = 1 (EN Active High), V
EN
= V
DD
Time from Active Transition on EN to 95% of
Nominal Laser Power and 95% of Full Modulation.
First Time Transmission is Enabled After Power
On or with Rapid_restart_en = 0
Time from Active Transition on EN to 95% of
Nominal Laser Power and 95% of Full Modulation.
When Transmission is Re-Enabled After the First
Time and with Rapid_restart_en = 1
Time from Inactive Transition on EN to 5% of
Nominal Laser Power
10
–10
–10 to 10
–10 to 10
10
100
–425
–280
0.4
50
–50
100
%
%
µs
7
9
18
27
36
Bits
mA
mA
mA
mA
CONDITIONS
MIN
TYP
MAX
UNITS
ELECTRICAL CHARACTERISTICS
Optical Power Limit
Overpower Limit
Underpower Limit
Safety Shutdown Response Time
FAULT Output, Open-Drain Mode, Flt_drv_mode = 0
Output Low Voltage
Output High Leakage Current
Output Low Voltage
Output High Current
Output Low Voltage
Output High Current
Output High Voltage
Output Low Voltage
Input Low Voltage
Input High Voltage
Input Low Current
Input High Current
Input Low Current
Input High Current
Transmit Enable Time
0.4
10
0.4
V
µA
V
µA
V
µA
V
V
V
V
µA
µA
µA
µA
ms
FAULT Output, Open-Drain Mode with 330µA Internal Pull Up, Flt_drv_mode = 1
FAULT Output, Open-Drain Mode with 500µA Internal Pull Up, Flt_drv_mode = 2
FAULT Output, Complementary Drive Mode, Flt_drv_mode = 3
EN Input, Ib_gain or (Apc_gain in APC Mode) = 16, Im_gain = 4, Is_rng = 0, Im_rng = 0
Transmit Re-Enable Time
1
ms
Transmit Disable Time
Minimum Pulse Width Required to Clear
a Latched Fault
10
µs
µs
sn5100 5100fs
5
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