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National Semiconductor Electronic Components Datasheet

74ETL16245 Datasheet

16 Bit Data Transceiver

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PRELIMINARY
May 1994
54 74ETL16245 16-Bit Data
Transceiver with Incident Wave Switching
General Description
The 54 74ETL16245 contains sixteen non-inverting bidirec-
tional buffers with TRI-STATE outputs designed with inci-
dent wave switching live insertion support and enhanced
noise margin for TTL backplane applications
Both the A and B ports include a bus hold circuit to latch the
output to the value last forced on that pin
The B port of this device includes 25X series output resis-
tors which minimize undershoot and ringing
Features
Y Supports the VME64 ETL specification
Y Functionally and pin compatible with industry standard
TTL 16245 SSOP pinout
Y Improved TTL-compatible input threshold range
Y High drive TTL-compatible outputs (IOH e b60 mA
IOL e 90 mA)
Y Supports 25X incident wave switching on the A port
Y BiCMOS design significantly reduces power dissipation
Y Distributed VCC and GND pin configuration minimizes
high-speed switching noise
Y 25X series-dampening resistor on B-port
Y Available in 48-pin SSOP and ceramic flatpak
Y Guaranteed output skew
Y Guaranteed simultaneous switching noise level and
dynamic threshold performance
Y Guaranteed latchup protection
Logic Symbol
Connection Diagram
Pin Assignment for
SSOP and Flatpak
TL F 11654 – 1
Pin Description
Pin Names
DIR
OE
An
Bn
Description
Transmit Receive Input
Output Enable Input (Active LOW)
Backplane Bus Data
Local Bus Data
TRI-STATE is a registered trademark of National Semiconductor Corporation
C1995 National Semiconductor Corporation TL F 11654
TL F 11654 – 2
RRD-B30M105 Printed in U S A


National Semiconductor Electronic Components Datasheet

74ETL16245 Datasheet

16 Bit Data Transceiver

No Preview Available !

Functional Description
The device uses byte-wide Direction (DIR) control and Out-
put Enable (OE) controls The DIR inputs determine the di-
rection of data flow through the device The OE inputs dis-
able the A and the B ports
The part contains active circuitry which keeps all outputs
disabled when VCC is less than 2 2V to aid in live insertion
applications
Logic Diagrams (Positive Logic)
Truth Table (Each 8-bit Section)
Inputs
OE DIR
LL
LH
HX
Operation
A Data to B Bus
B Data to A Bus
Isolation
TL F 11654–3
ETL’s Improved Noise Immunity
TTL input thresholds are typically determined by tempera-
ture-dependent junction voltages which result in worst case
input thresholds between 0 8V and 2 0V By contrast ETL
provides greater noise immunity because its input thresh-
olds are determined by current mode input circuits similar to
those used for ECL or BTL ETL’s worst case input thresh-
olds between 1 4V and 1 6V are compensated for temper-
ature voltage and process variations
TL F 11654 – 4
Incident Wave Switching
When TTL logic is used to drive fully loaded backplanes the
combination of low backplane bus characteristic imped-
ance wide TTL input threshold range and limited TTL drive
generally require multiple waveform reflections before a val-
id signal can be received across the backplane The VME
International Trade Association (VITA) defined ETL to pro-
vide incident wave switching which increases the data trans-
fer rate of a VME backplane and extends the life of VME
applications TTL compatibility with existing VME back-
planes and modules was maintained
Improved Input Threshold Characteristics of ETL
ABTC Worst Case VOUT – VIN
TL F 11654–5
ETL Worst Case VOUT – VIN
TL F 11654 – 6
2


Part Number 74ETL16245
Description 16 Bit Data Transceiver
Maker National
Total Page 10 Pages
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