MAX9171_07 Datasheet, PDF (8/12 Pages) Maxim Integrated Products – Single/Dual LVDS Line Receivers with “In-Path” Fail-Safe

Single/Dual LVDS Line Receivers with
“In-Path” Fail-Safe
ESD Protection
ESD protection structures are incorporated on all pins
to protect against electrostatic discharges encountered
during handling and assembly. The receiver inputs of
the MAX9171/MAX9172 have extra protection against
static electricity. These pins are protected to ±13kV
without damage. The structures withstand ESD during
normal operation and when powered down.
The receiver inputs of these devices are characterized
for protection to the limit of ±13kV using the Human
Body Model.
Human Body Model
Figure 4a shows the Human Body Model, and Figure
4b shows the current waveform it generates when dis-
charged into a low-impedance load. This model con-
sists of a 100pF capacitor charged to the ESD test
voltage, which is then discharged into the test device
through a 1.5kΩ resistor.
Applications Information
Supply Bypassing
Bypass V_CC with high-frequency surface-mount ceram-
ic 0.1µF and 0.001µF capacitors in parallel, as close to
the device as possible, with the 0.001µF capacitor clos-
est to the device. For additional supply bypassing,
place a 10µF tantalum or ceramic capacitor at the point
where power enters the circuit board.
Differential Traces
Input trace characteristics affect the performance of the
MAX9171/MAX9172. Use controlled-impedance PCB
traces to match the cable characteristic impedance.
Eliminate reflections and ensure that noise couples as
common mode by running the differential traces close
together. Reduce skew by matching the electrical
length of traces.
Each channel’s differential signals should be routed
close to each other to cancel their external magnetic
field. Maintain a constant distance between the differ-
ential traces to avoid discontinuities in differential
impedance. Avoid 90° turns and minimize the number
of vias to further prevent impedance discontinuities.
Cables and Connectors
Transmission media typically have a controlled differen-
tial impedance of about 100Ω. Use cables and connec-
tors that have matched differential impedance to
minimize impedance discontinuities. Balanced cables
tend to pick up noise as common mode, which is
rejected by the LVDS receiver.
Termination
The MAX9171/MAX9172 require an external termination
resistor. The termination resistor should match the differ-
ential impedance of the transmission line. Termination
resistance values may range between 90Ω to 132Ω,
depending on the characteristic impedance of the
transmission medium.
When using the MAX9171/MAX9172, minimize the dis-
tance between the input termination resistors and the
MAX9171/MAX9172 receiver inputs. Use a single 1%
surface-mount resistor.
Board Layout
For LVDS applications, a four-layer PCB that provides
separate power, ground, LVDS signals, and output sig-
nals is recommended. Separate the input LVDS signals
from the output signals to prevent crosstalk. Solder the
exposed pad on the TDFN package to a pad connected
to the PCB ground plane by a matrix of vias. Connecting
the exposed pad is not a substitute for connecting the
ground pin. Always connect pin 5 on the TDFN pack-
age to ground.
HIGH-
VOLTAGE
DC
SOURCE
R_C 1MΩ
CHARGE-CURRENT
LIMIT RESISTOR
Cs
100pF
R_D 1500Ω
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
DEVICE
UNDER
TEST
Figure 4a. Human Body ESD Test Modules
I_P 100%
90%
Ir
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
AMPERES
36.8%
10%
0
0 _tRL
TIME
t_DL
CURRENT WAVEFORM
Figure 4b. Human Body Current Waveform
Chip Information
TRANSISTOR COUNT: 624
PROCESS: CMOS
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