MAX9240GTM+ Maxim Integrated, MAX9240GTM+ Datasheet - Page 42

• Manufacturer Part Number: MAX9240GTM+
• Description: Serializers & Deserializers - Serdes 28Bit GMSL Deserializer
• Manufacturer: Maxim Integrated

Specifications of MAX9240GTM+

• Rohs: yes

For the fault detection circuit, select the resistor’s power
rating to handle a short to the battery. In coax mode,
leave the unused line-fault inputs unconnected. To detect
the short-together case, refer to Application Note 4709:
GMSL Line-Fault Detection. Table 13A lists the mapping
for line-fault types.
The control and configuration inputs, except three-level
inputs, include a pulldown resistor to GND. External pull-
down resistors are not needed.
The I
resistor to provide a logic-high level. There are tradeoffs
between power dissipation and speed, and a compromise
may be required when choosing pullup resistor values.
Every device connected to the bus introduces some
capacitance even when the device is not in operation. I
specifies 300ns rise times (30% to 70%) for fast mode,
which is defined for data rates up to 400kbps (see the I
specifications in the AC Electrical Characteristics table
for details). To meet the fast-mode rise-time requirement,
choose the pullup resistors so that rise time t
R
nized if the transition time becomes too slow. The deserial-
izer supports I
mode) and 400kbps (I
AC-coupling isolates the receiver from DC voltages up to
the voltage rating of the capacitor. Capacitors at the seri-
alizer output and at the deserializer input are needed for
proper link operation and to provide protection if either
end of the cable is shorted to a battery. AC-coupling
blocks low-frequency ground shifts and low-frequency
common-mode noise.
Voltage droop and the digital sum variation (DSV) of trans-
mitted symbols cause signal transitions to start from dif-
ferent voltage levels. Because the transition time is fixed,
starting the signal transition from different voltage levels
causes timing jitter. The time constant for an AC-coupled
link needs to be chosen to reduce droop and jitter to an
acceptable level. The RC network for an AC-coupled link
consists of the CML/coax receiver termination resistor
(R
the series AC-coupling capacitors (C). The RC time con-
stant, for four equal-value series capacitors, is (C x (R
+ R
Maxim Integrated
PULLUP
TR
TR
6.25MHz to 100MHz, 25-Bit GMSL Deserializer for
), the CML/coax driver termination resistor (R
2
))/4. R
C and UART open-drain lines require a pullup
x C
Selection of AC-Coupling Capacitors
Choosing I
TD
BUS
2
C/UART rates up to 1Mbps (UART-to-I
and R
< 300ns. The waveforms are not recog-
Coax or STP Cable With Line Fault Detect
TR
2
C-to-I
2
are required to match the trans-
Internal Input Pulldowns
C/UART Pullup Resistors
2
C mode).
AC-Coupling
R
= 0.85 x
TD
), and
2
2
2
TD
C
C
C
mission line impedance (usually 100I differential and
50I single-ended). This leaves the capacitor selection
to change the system time constant. Use 0.2FF or larger
high-frequency surface-mount ceramic capacitors, with
sufficient voltage rating to withstand 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 deserializer uses an AVDD and DVDD of 1.7V to
1.9V. All inputs and outputs, except for the serial input,
derive power from an IOVDD of 1.7V to 3.6V that scales
with IOVDD. Proper voltage-supply bypassing is essen-
tial for high-frequency circuit stability. The GPI-to-GPO
delay is 0.35ms (max). Keep the time between GPI trans-
missions to a minimum 0.35ms.
Power-supply
Characteristics table are the sum of the currents from
AVDD, DVDD, and IOVDD. Typical currents from the
individual power supplies are shown in
Interconnect for CML typically has a differential imped-
ance of 100I. Use cables and connectors that have
matched differential impedance to minimize impedance
discontinuities. Coax cables typically have a characteris-
tic impedance of 50I (contact the factory for 75I opera-
tion).
used in the GMSL link.
Table 14. Typical Power-Supply Currents
(Using Worst-Case Input Pattern)
Table 15. Suggested Connectors and
Cables for GMSL
Rosenberger
JAE
Nissei
Rosenberger
PCLK (MHz)
SUPPLIER
Table 15
25
50
Power-Supply Circuits and Bypassing
lists the suggested cables and connectors
D4S10A-40ML5-Z
AVDD (mA)
59S2AX-400A5-Y
currents
CONNECTOR
GT11L-2S
25.1
33.3
MX38-FF
Cables and Connectors
shown
DVDD (mA)
Power-Supply Table
13.7
9.2
MAX9240
A-BW-Lxxxxx
Dacar 538
in
F-2WME
AWG28
CABLE
RG174
Table
the
IOVDD (mA)
14.
Electrical
10.3
13.3
TYPE
Coax
STP
STP
STP
42