MAX3273ETG+T Maxim Integrated Products, MAX3273ETG+T Datasheet - Page 8

• Manufacturer Part Number: MAX3273ETG+T
• Description: IC LASR DRVR 2.7GBPS 3.6V 24TQFN
• Manufacturer: Maxim Integrated Products
• Type: Laser Diode Driver (Fiber Optic)r

Specifications of MAX3273ETG+T

• Data Rate: 2.7Gbps
• Number Of Channels: 1
• Voltage - Supply: 3.14 V ~ 3.6 V
• Current - Supply: 30mA
• Current - Modulation: 60mA
• Current - Bias: 100mA
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 24-TQFN Exposed Pad
• Mounting Type: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX3273 laser driver consists of two main parts: a
high-speed modulation driver and a laser-biasing block
with automatic power control (APC). The circuit design
is optimized for both high-speed and low-voltage
(+3.3V) operation. To minimize the jitter of the input sig-
nal at speeds as high as 2.7Gbps, the device accepts
a differential CML clock signal for data retiming. When
LATCH is high, the input data is synchronized by the
clock signal. When LATCH is low, the input data is
directly applied to the output stage.
The output stage is composed of a high-speed differ-
ential pair and a programmable modulation current
source. Because the modulation output drives a maxi-
mum current of 60mA into the laser with an edge speed
of 59ps, large transient voltage spikes can be generat-
ed (due to the parasitic inductance of the laser). These
transients and the laser-forward voltage leave insuffi-
+3.3V, 2.5Gbps Low-Power Laser Driver
Figure 3. Functional Diagram
8
_______________________________________________________________________________________
DATA
R
MODSET
CLK
MODSET
EN
V
BG
MAX3273
Detailed Description
x160
D
R
BIASMAX
BIASMAX
Q
LATCH
0
1
MUX
V
CC
x190
APCFILT1
C
APCFILT
TIA
cient headroom for the proper operation of the laser dri-
ver if the modulation output is DC-coupled to the laser
diode. To solve this problem, the MAX3273’s modula-
tion output is AC-coupled to the cathode of a laser
diode. An external pullup inductor is necessary to DC-
bias the modulation output at V
isolates laser-forward voltage from the output circuitry
and the supply voltage V
gram is shown in Figure 3.
The MAX3273 modulation output is optimized for dri-
ving a 25Ω load. Modulation current swings of 75mA
are possible, but because of minimum power-supply
and jitter requirements at 2.5Gbps, the specified maxi-
mum modulation current is limited to 60mA. To inter-
face with the laser diode, a damping resistor (R
required for impedance matching. An RC-shunt net-
work might also be necessary to compensate for the
laser-diode parasitic inductance, thereby improving the
APCFILT2
I
APCSET
DETECTOR
FAILURE
I
MOD
APCSET
OUT-
OUT+
BIAS
MD
R
L
L
L
APCSET
P1
P1
P2
FAIL
V
CC
V
CC
25Ω
C
D
CC
I
MD
R
. A simplified functional dia-
D
CC
. Such a configuration
I
500pF
BIAS
V
CC
D
) is