SN74GTLPH16927

18-BIT LVTTL-TO-GTLP BUS TRANSCEIVER

WITH SOURCE-SYNCHRONOUS CLOCK OUTPUTS

SCES413 OCTOBER 2002

POST OFFICE BOX 655303

DALLAS, TEXAS 75265

Member of the Texas Instruments
Widebus

Family

TI-OPC

Circuitry Limits Ringing on

Unevenly Loaded Backplanes

OEC

Circuitry Improves Signal Integrity

and Reduces Electromagnetic Interference

Bidirectional Interface Between GTLP
Signal Levels and LVTTL Logic Levels

GTLP Buffered SYSCLK Signal (SSCLK) for
Source-Synchronous Applications

LVTTL Interfaces Are 5-V Tolerant

Medium-Drive GTLP Outputs (50 mA)

LVTTL Outputs (24 mA/24 mA)

GTLP Rise and Fall Times Designed for
Optimal Data-Transfer Rate and Signal
Integrity in Distributed Loads

off

, Power-Up 3-State, and BIAS V

Support Live Insertion

Bus Hold on A-Port Data Inputs

Distributed V

and GND Pins Minimize

High-Speed Switching Noise

Latch-Up Performance Exceeds 100 mA Per
JESD 78, Class II

ESD Protection Exceeds JESD 22
2000-V Human-Body Model (A114-A)
200-V Machine Model (A115-A)
1000-V Charged-Device Model (C101)

description/ordering information

The SN74GTLPH16927 is a medium-drive, 18-bit bus transceiver that provides LVTTL-to-GTLP and
GTLP-to-LVTTL signal-level translation. The device allows for transparent and latched modes of data transfer.
Additionally, with the use of the clock-mode select (CMS) input, the device can be used in source-synchronous
and clock-synchronous applications. Source-synchronous applications require the skew between the clock
output and data output to be minimized for optimum maximum-frequency system performance. In order to
reduce this skew, a flexible setup-time adjustment (FSTA) feature is incorporated into the device that sets a
predetermined delay between the clock and data. The CMS and direction (DIR) inputs control the mode of the
device.

ORDERING INFORMATION

PACKAGE

ORDERABLE

PART NUMBER

TOP-SIDE

MARKING

TSSOP DGG

Tape and reel

SN74GTLPH16927GR

GTLPH16927

C to 85

TVSOP DGV

Tape and reel

SN74GTLPH16927VR

GL927

VFBGA GQL

Tape and reel

SN74GTLPH16927KR

GL927

Package drawings, standard packing quantities, thermal data, symbolization, and PCB design guidelines

are available at www.ti.com/sc/package.

2002, Texas Instruments Incorporated

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.

OEC, TI-OPC, and Widebus are trademarks of Texas Instruments.

DGG OR DGV PACKAGE

(TOP VIEW)

DIR

GND

A2
A3

A4
A5
A6

GND

A7
A8
A9

A10

A11

A12

GND

A13
A14
A15

A16
A17

GND

A18

CLKOUT

CKOE

FSTA
BIAS V

B1
GND
B2
B3
V

REF

B4
B5
B6
GND
B7
B8
B9
B10
B11
B12
GND
B13
B14
B15
CMS
B16
B17
GND
B18
SSCLK
SYSCLK

PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.

SN74GTLPH16927
18-BIT LVTTL-TO-GTLP BUS TRANSCEIVER
WITH SOURCE-SYNCHRONOUS CLOCK OUTPUTS

SCES413 OCTOBER 2002

POST OFFICE BOX 655303

DALLAS, TEXAS 75265

description/ordering information (continued)

The system clock (SYSCLK) and CLKOUT pins are LVTTL compatible, while the source-synchronous I/O is
GTLP compatible. The benefits include compensation for output-to-output skew coming from the driver itself,
and compensation for process skew if more than one driver is used. The device provides a high-speed interface
between cards operating at LVTTL logic levels and a backplane operating at GTLP signal levels. High-speed
(about three times faster than standard TTL or LVTTL) backplane operation is a direct result of GTLP's reduced
output swing (<1 V), reduced input threshold levels, improved differential input, OEC

circuitry, and TI-OPC

circuitry. Improved GTLP OEC and TI-OPC circuits minimize bus-settling time and have been designed and
tested using several backplane models. The medium drive allows incident-wave switching in heavily loaded
backplanes with equivalent load impedance down to 11

GTLP is the Texas Instruments derivative of the Gunning Transceiver Logic (GTL) JEDEC standard JESD 8-3.
The ac specification of the SN74GTLPH16927 is given only at the preferred higher noise-margin GTLP, but the
user has the flexibility of using this device at either GTL (V

= 1.2 V and V

REF

= 0.8 V) or GTLP (V

= 1.5 V

and V

REF

= 1 V) signal levels. For information on using GTLP devices in FB+/BTL applications, refer to TI

application reports, Texas Instruments GTLP Frequently Asked Questions,

literature number SCEA019, and

GTLP in BTL Applications, literature number SCEA017.

Normally, the B port operates at GTLP signal levels. The A-port and control inputs operate at LVTTL logic levels,
but are 5-V tolerant and are compatible with TTL and 5-V CMOS inputs. V

REF

is the B-port differential input

reference voltage.

This device is fully specified for live-insertion applications using I

off

, power-up 3-state, and BIAS V

. The I

off

circuitry disables the outputs, preventing damaging current backflow through the device when it is powered
down. The power-up 3-state circuitry places the outputs in the high-impedance state during power up and power
down, which prevents driver conflict. The BIAS V

circuitry precharges and preconditions the B-port

input/output connections, preventing disturbance of active data on the backplane during card insertion or
removal, and permits true live-insertion capability.

This GTLP device features TI-OPC circuitry, which actively limits the overshoot caused by improperly
terminated backplanes, unevenly distributed cards, or empty slots during low-to-high signal transitions. This
improves signal integrity, which allows adequate noise margin to be maintained at higher frequencies.

Active bus-hold circuitry holds unused or undriven LVTTL data inputs at a valid logic state. Use of pullup or
pulldown resistors with the bus-hold circuitry is not recommended.

When V

is between 0 and 1.5 V, the device is in the high-impedance state during power up or power down.

However, to ensure the high-impedance state above 1.5 V, the output-enable (OE) input should be tied to V

through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of
the driver.

SN74GTLPH16927

18-BIT LVTTL-TO-GTLP BUS TRANSCEIVER

WITH SOURCE-SYNCHRONOUS CLOCK OUTPUTS

SCES413 OCTOBER 2002

POST OFFICE BOX 655303

DALLAS, TEXAS 75265

terminal assignments

DIR

FSTA

BIAS VCC

GND

VCC

VREF

GND

A10

A11

B11

B10

A12

A13

GND

B13

B12

A14

A15

VCC

CMS

B15

B14

A16

A17

GND

B17

B16

A18

CLKOUT

CKOE

SYSCLK

SSCLK

B18

functional description

The SN74GTLPH16927 is a medium-drive (50 mA), 18-bit bus transceiver containing D-type latches and D-type
flip-flops for data-path operation in transparent or latched modes and can replace any of the functions shown
in Table 1. Data polarity is noninverting.

Table 1. SN74GTLPH16927 Bus-Transceiver Replacement Functions

FUNCTION

8 BIT

9 BIT

10 BIT

16 BIT

18 BIT

Transceiver

'245, '623, '645

'863

'861

'16245, '16623

'16863

Buffer/driver

'241, '244, '541

'827

'16241, '16244, '16541

'16825

Latched transceiver

'543

'16543

'16472

Latch

'373, '573

'843

'841

'16373

'16843

SN74GTLPH16927 bus transceiver replaces all above functions

Additionally, the device allows for conversion of the system clock (SYSCLK) to GTLP signal levels (SSCLK) and
LVTTL signal levels (CLKOUT). It also provides conversion of a GTLP source-synchronous clock to LVTTL
signal levels (CLKOUT).

The device allows for conversion of the LVTTL system clock (SYSCLK) to GTLP (SSCLK) and LVTTL
(CLKOUT) signal levels when used as the transmitter and GTLP source-synchronous clock (SSCLK) to LVTTL
(CLKOUT) signal levels when used as the receiver in source-synchronous applications. Source-synchronous
operation removes time-of-flight restrictions and allows for increased data throughput. CMS is used to switch
between system-synchronous mode and clock-synchronous mode. The clock output-enable (CKOE) input is
used to switch between latched and transparent mode.

Data flow in each direction is controlled by CKOE, clock (SYSCLK or SSCLK), DIR, and OE. OE controls the
18 bits of data. The CLKOUT/SSCLK buffered clock path for the A-to-B and B-to-A directions is controlled by
CKOE. In the data-isolation mode (OE high, CKOE low), A data can be stored in one register and/or B data can
be stored in the other register.

GQL PACKAGE

(TOP VIEW)

SN74GTLPH16927

18-BIT LVTTL-TO-GTLP BUS TRANSCEIVER

WITH SOURCE-SYNCHRONOUS CLOCK OUTPUTS

SCES413 OCTOBER 2002

POST OFFICE BOX 655303

DALLAS, TEXAS 75265

Function Tables

A-TO-B DIRECTION

INPUTS

OUTPUTS

MODE

CKOE

CMS

DIR

SYSCLK

SSCLK

CLKOUT

MODE

H or L

SYSCLK

Latched storage of A

SYSCLK

Clocked storage of A

Source

synchronous

SYSCLK

Clocked storage of A

synchronous

SYSCLK

Data isolation

Transparent transmission of A

Isolation

SYSCLK

Transmit SYSCLK

H or L

SYSCLK

Transmit SYSCLK

B-TO-A DIRECTION

INPUTS

OUTPUTS

MODE

CKOE

CMS

DIR

SYSCLK

SSCLK

CLKOUT

MODE

H or L

Input

SSCLK

Latched storage of B

Input

SSCLK

Clocked storage of B

Source

synchronous

Input

SSCLK

Clocked storage of B

synchronous

Input

SSCLK

Data isolation

H or L

Output

SYSCLK

Latched storage of B

Output

SYSCLK

Clocked storage of B

Clock

synchronous

Output

SYSCLK

Clocked storage of B

synchronous

Output

SYSCLK

Data isolation

Output

Transparent transmission of B

Output

Transparent transmission of B

Output

Isolation

Input

SSCLK

Receive SSCLK

H or L

Input

SSCLK

Receive SSCLK

Part Number SN74GTLPH16927