Datasheet

5 V
0.42” 0.84”
1.5” 1.5”
1.5”1.5”
0.84” 0.42”
Rcvr
Rcvr
Rcvr
Slot 2 Slot 3 Slot 19 Slot 20
Conn.
Conn. Conn. Conn.
1.5”
Rcvr
Slot 1
Conn.
0.42”
Drvr
1.5”
Slot 21
Conn.
0.42”
330 Ω
470 Ω
Z
O
†
5 V
330 Ω
470 Ω
Z
O
‡
†
Unloaded backplane trace natural impedence (Z
O
) is 45 Ω. 45 Ω to 60 Ω is allowed, with 50 Ω being ideal.
‡
Card stub natural impedence (Z
O
) is 60 Ω.
Rcvr
SN74VMEH22501A
www.ti.com SCES3620A –DECEMBER 2004–REVISED FEBRUARY 2010
Distributed-Load Backplane Switching Characteristics
The preceding switching characteristics tables show the switching characteristics of the device into the lumped
load shown in the parameter measurement information (PMI) (see Figure 1 and Figure 2). All logic devices
currently are tested into this type of load. However, the designer's backplane application probably is a distributed
load. For this reason, this device has been designed for optimum performance in the VME64x backplane as
shown in Figure 3.
Figure 3. VME64x Backplane
The following switching characteristics tables derived from TI-SPICE models show the switching characteristics
of the device into the backplane under full and minimum loading conditions, to help the designer better
understand the performance of the VME device in this typical backplane. See www.ti.com/sc/etl for more
information.
Driver in Slot 11, With Receiver Cards in All Other Slots (Full Load)
Switching Characteristics for Bus Transceiver Function
over recommended operating conditions (unless otherwise noted) (see Figure 3)
FROM TO
PARAMETER MIN TYP
(1)
MAX UNIT
(INPUT) (OUTPUT)
t
PLH
5.9 8.5
1A or 2A 1B or 2B ns
t
PHL
5.5 8.7
t
r
(2)
Transition time, B port (10%–90%) 9 8.6 11.4 ns
t
f
(2)
Transition time, B port (90%–10%) 8.9 9 10.8 ns
(1) All typical values are at V
CC
= 3.3 V, T
A
= 25°C. All values are derived from TI-SPICE models.
(2) All t
r
and t
f
times are taken at the first receiver.
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