ADN2531ACPZ-R2 Analog Devices Inc, ADN2531ACPZ-R2 Datasheet - Page 14

• Manufacturer Part Number: ADN2531ACPZ-R2
• Description: IC, LASER DIODE DRIVER, 11.3GBPS LFCSP16
• Manufacturer: Analog Devices Inc

Specifications of ADN2531ACPZ-R2

• Laser Driver Type: Laser Diode
• Supply Current: 36mA
• Bias Current: 100mA
• Modulation Current: 70mA
• Data Rate: 11.3Gbps
• Supply Voltage Range: 3V To 3.6V
• Driver Case Style: LFCSP
• No. Of Pins: 16
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

ADN2531
LOAD MISTERMINATION
Due to its excellent S22 performance, the ADN2531 can drive
differential loads that range from 5 Ω to 140 Ω. In practice, many
TOSAs have differential resistance not equal to 100 Ω. In this
case, with 100 Ω differential transmission lines connecting the
ADN2531 to the load, the load end of the transmission lines are
misterminated. This mistermination leads to signal reflections
back to the driver. The excellent back-termination in the ADN2531
absorbs these reflections, preventing their reflection back to the
load. This enables excellent optical eye quality to be achieved even
when the load end of the transmission lines is significantly mis-
terminated. The connection between the load and the ADN2531
must be made with 100 Ω differential (50 Ω single-ended)
transmission lines so that the driver end of the transmission
lines is properly terminated.
CROSSPOINT ADJUST
The crossing level in the output electrical eye diagram can be
adjusted between 35% and 65% using the crosspoint adjust (CPA)
control input. This can be used to compensate for asymmetry in
the laser response and to optimize the optical eye mask margin.
The CPA input is a voltage-control input, and a plot of eye cross-
point vs. CPA control voltage is shown in Figure 14 and Figure 15
in the Typical Performance Characteristics section. The equivalent
circuit for the CPA pin is shown in Figure 37. To disable the
crosspoint adjust function and set the eye crossing to 50%, the
CPA pin should be tied to V
POWER CONSUMPTION
The power dissipated by the ADN2531 is given by
where:
V
I
V
I
and IMODN pins when V
V
SUPPLY
BIAS
CC
MSET
IBIAS
is the power supply voltage.
is the bias current generated by the ADN2531.
P
is the average voltage on the IBIAS pin.
is the sum of the current that flows into the VCC, IMODP,
is the voltage applied to the MSET pin.
=
7kΩ
V
CC
×
V
Figure 37. Equivalent Circuit for CPA Pin
⎛
⎜
⎝
CC
V
MSET
5
8 .
CPA
+
7kΩ
BSET
I
SUPPLY
CC
.
= V
⎞
⎟
⎠
MSET
+
V
= 0 (see Table 1).
IBIAS
7kΩ
×
I
BIAS
Rev. 0 | Page 14 of 20
Considering V
V
To ensure long-term reliable operation, the ADN2531 junction
temperature must not exceed 150°C, as specified in Table 3. For
improved heat dissipation, the module case can be used as a
heat sink, as shown in Figure 38.
PACKAGE
A compact optical module is a complex thermal environment, and
calculations of device junction temperature using the junction-to-
ambient thermal resistance (θ
accurate results. The following equation, derived from the
model in Figure 39, can be used to estimate the IC junction
temperature:
wher
T
T
T
P is the ADN2531 power dissipation in wa
θ
the package.
θ
exposed paddle of the package.
T
at points inside the module, as shown in Figure 38. The thermo-
couples should be positioned to obtain an accurate measurement of
the temperatures of the package top and paddle. θ
are given in Table 2.
PCB
J-TOP
J-PAD
PAD
TOP
J
TOP
BSET
is the IC junction temperature in °C.
THERMAL COMPOUND
DIE
is the temperature at the package exposed paddle in °C
COPPER PLANE
is t
and T
T
e:
P
to IBIAS, the dissipated power becomes
is the thermal resistance from the IC junc
is the th
J
=
he temperature at the top of the package in °C.
=
V
P
Figure 39. Electrical Model for Thermal Calc ations
CC
PAD
×
ermal resistance from the IC junction to the
×
Figure 38. Typical Optical Module Structure
can be determined by measuring the tem
(
BSET
θ
⎛
⎜
⎝
J
V
−
P
/I
PAD
5
MSET
BIAS
8 .
VIAS
×
= 10 V/A as the conversion factor from
θ
+
T
J
TOP
I
−
T
TOP
SUPPLY
MODULE CASE
TOP
T
T
PAD
θ
JA
J
)
J
) of the package do not yield
−
+
T
θ
T
θ
PAD
T
J
J-PAD
PAD
J-TOP
PAD
⎞
⎟
⎠
T
+
TOP
+
V
IBIAS
θ
×
J
θ
−
TOP
T
J
tts.
TOP
×
−
PAD
⎛
⎜
⎝
10
V
ul
tion to the top of
+
V
BSET
THERMOCOUPLES
T
J-TOP
/
PAD
A
⎞
⎟
⎠
and θ
×
perature
.
θ
J
−
J-PAD
TOP