Datasheet

MAX9234/MAX9236/MAX9238
Hot-Swappable, 21-Bit, DC-Balanced LVDS
Deserializers
9
Maxim Integrated
MAX9234/MAX9236/MAX9238 vs.
MAX9210/MAX9220/MAX9222
The MAX9234/MAX9236/MAX9238 operate in DC-bal-
ance mode only. Pinouts are the same as the
MAX9210/MAX9220/MAX9222 except that pin 6 on the
MAX9234/MAX9236/MAX9238 is no connect (N.C.). DC
balance allows AC-coupling with series capacitors. The
MAX9234/MAX9236/MAX9238 are hot-swappable and
the input frequency can be changed on the fly, but oth-
erwise the specifications and functionality are the same
as the MAX9210/MAX9220/MAX9222 operating in DC-
balance mode. See Table 1.
Applications Information
Selection of AC-Coupling Capacitors
Voltage droop and the 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 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
LVDS receiver termination resistor (R
T
), the LVDS driver
output resistor (R
O
), and the series AC-coupling capac-
itors (C). The RC time constant for two equal-value
series capacitors is (C x (R
T
+ R
O
)) / 2 (Figure 10). The
RC time constant for four equal-value series capacitors
is (C x (R
T
+ R
O
)) / 4 (Figure 11).
R
T
is required to match the transmission line imped-
ance (usually 100Ω) and R
O
is determined by the LVDS
driver design (the minimum differential output resis-
tance of 78Ω for the MAX9209/MAX9211/MAX9213/
MAX9215 serializers is used in the following example).
This leaves the capacitor selection to change the sys-
tem time constant.
TxIN_, DCA_, AND DCB_ ARE DATA FROM THE SERIALIZER.
DCA0
DCB1DCA1
DCB2DCA2
CYCLE N + 1CYCLE NCYCLE N - 1
TxIN2TxIN6 TxIN3TxIN4TxIN5
TxIN9TxIN13 TxIN10TxIN11TxIN12
TxIN2TxIN3TxIN4DCA0 TxIN5TxIN6DCB0
TxIN9TxIN10TxIN11DCA1 TxIN12TxIN13DCB1
TxIN16TxIN17TxIN18DCA2 TxIN19TxIN20DCB2
TxIN0TxIN1
TxIN7TxIN8
TxIN14TxIN15TxIN16TxIN20 TxIN17TxIN18TxIN19
DCB0
RxCLK IN
RxIN1
RxIN0
RxIN2
TxIN1
TxIN8
TxIN15
TxIN0
TxIN7
TxIN14
+
-
Figure 9. Deserializer Serial Input
0.8V
PWRDWN
RxCLK IN
RxOUT_
RxCLK OUT
RPDD
HIGH-Z
Figure 8. Power-Down Delay