MAX9249GCM/V+ Maxim Integrated Products, MAX9249GCM/V+ Datasheet - Page 29

• Manufacturer Part Number: MAX9249GCM/V+
• Description: IC SERIALIZER GMSL LVDS 48TQFP
• Manufacturer: Maxim Integrated Products

Specifications of MAX9249GCM/V+

• Function: Serializer
• Data Rate: 2.5Gbs
• Input Type: LVDS
• Output Type: Serial
• Voltage - Supply: 3 V ~ 3.6 V
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 48-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Number Of Outputs: -
• Number Of Inputs: -

Table 10. Line-Fault Mapping
Both I
tors to provide a logic-high level. There are trade-offs
between power dissipation and speed, and a compro-
mise made in choosing pullup resistor values. Every
device connected to the bus introduces some capaci-
tance even when the device is not in operation. I
specifies 300ns rise times to go from low to high (30% to
70%) for fast mode, which is defined for data rates up to
400kbps (see the I
Characteristics section for details). To meet the fast-
mode rise-time requirement, choose the pullup resistors
so that rise time t
The waveforms are not recognized if the transition time
becomes too slow. The MAX9249 supports I
rates up to 1Mbps.
AC-coupling isolates the receiver from DC voltages up
to the voltage rating of the capacitor. Four capacitors—
two at the serializer output and two at the deserializer
input—are needed for proper link operation and to pro-
vide protection if either end of the cable is shorted to a
high voltage. AC-coupling blocks low-frequency ground
shifts and low-frequency common-mode noise.
Voltage droop and the digital sum variation (DSV) of
transmitted symbols cause signal transitions to start
from different voltage levels. Because the transition time
is finite, starting the signal transition from different volt-
age levels causes timing jitter. The time constant for an
AC-coupled link needs to be chosen to reduce droop
REGISTER
ADDRESS
0x08
2
C/UART open-drain lines require pullup resis-
Selection of AC-Coupling Capacitors
Choosing I
______________________________________________________________________________________
R
D[3:2]
D[1:0]
BITS
2
= 0.85 x R
C specifications in the AC Electrical
Serializer with LVDS System Interface
2
C/UART Pullup Resistors
LFNEG
LFPOS
NAME
PULLUP
x C
VALUE
AC-Coupling
00
01
10
11
00
01
10
11
BUS
Gigabit Multimedia Serial Link
2
< 300ns.
C/UART
Negative cable wire shorted to battery
Negative cable wire shorted to ground
Normal operation
Negative cable wire open
Positive cable wire shorted to battery
Positive cable wire shorted to ground
Normal operation
Positive cable wire open
2
C
and jitter to an acceptable level. The RC network for an
AC-coupled link consists of the CML receiver termination
resistor (R
and the series AC-coupling capacitors (C). The RC time
constant for four equal-value series capacitors is (C x
(R
transmission line impedance (usually 100I). This leaves
the capacitor selection to change the system time con-
stant. Use at least 0.2FF high-frequency surface-mount
ceramic capacitors, with sufficient voltage rating to with-
stand a short to battery, to pass the lower speed reverse
control-channel signal. Use capacitors with a case size
less than 3.2mm x 1.6mm to have lower parasitic effects
to the high-speed signal.
The MAX9249 uses a V
1.9V, and a V
inputs and outputs on the MAX9249 derive power from a
V
voltage-supply bypassing is essential for high-frequency
circuit stability.
Interconnect for CML typically has a differential imped-
ance of 100I. Use cables and connectors that have
matched differential impedance to minimize impedance
discontinuities. Twisted-pair and shielded twisted-pair
cables tend to generate less EMI due to magnetic-field
canceling effects. Balanced cables pick up noise as
common mode rejected by the CML receiver. Table 11
lists the suggested cables and connectors used in the
GMSL link.
IOVDD
TD
+ R
of 1.7V to 3.6V, which scale with IOVDD. Proper
Power-Supply Circuits and Bypassing
TR
TR
))/4. R
), the CML driver termination resistor (R
LINE-FAULT TYPE
LVDSVDD
TD
and R
of 3.0V to 3.6V. All single-ended
AVDD
Cables and Connectors
TR
are required to match the
and V
DVDD
of 1.7V to
TD
29
),