FEATURES
· Member of the Texas Instruments Widebus™
Family
· UBT™ Transceiver Combines D-Type Latches
and D-Type Flip-Flops for Operation in
Transparent, Latched, Clocked, or
Clock-Enabled Modes
· OEC™ Circuitry Improves Signal Integrity and
Reduces Electromagnetic Interference
· GTL Buffered CLKAB Signal (CLKOUT)
· Translates Between GTL/GTL+ Signal Levels
and LVTTL Logic Levels
· Supports Mixed-Mode (3.3 V and 5 V) Signal
Operation on A-Port and Control Inputs
· Equivalent to '16601 Function
· Ioff Supports Partial-Power-Down Mode
Operation
· Bus Hold on Data Inputs Eliminates the Need
for External Pullup/Pulldown Resistors on
A Port
· Distributed VCC 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)

DESCRIPTION/ORDERING INFORMATION
The SN74GTL16616 is a 17-bit UBT™ transceiver that provides LVTTL-to-GTL/GTL+ and GTL/GTL+-to-LVTTL
signal-level translation. Combined D-type flip-flops and D-type latches allow for transparent, latched, clocked,
and clocked-enabled modes of data transfer identical to the '16601 function. Additionally, this device provides for
a copy of CLKAB at GTL/GTL+ signal levels (CLKOUT) and conversion of a GTL/GTL+ clock to LVTTL logic
levels (CLKIN). This device provides an interface between cards operating at LVTTL logic levels and a backplane
operating at GTL/GTL+ signal levels. Higher-speed operation is a direct result of the reduced output swing
(<1 V), reduced input threshold levels, and OEC™ circuitry.
The user has the flexibility of using this device at either GTL (VTT = 1.2 V and VREF = 0.8 V) or the preferred
higher noise margin GTL+ (VTT = 1.5 V and VREF = 1 V) signal levels. GTL+ is the Texas Instruments derivative
of the Gunning Transceiver Logic (GTL) JEDEC standard JESD 8-3. The B port normally operates at GTL or
GTL+ signal levels, while the A-port and control inputs are compatible with LVTTL logic levels and are 5-V
tolerant. VREF is the reference input voltage for the B port. VCC (5 V) supplies the internal and GTL circuitry, while
VCC (3.3 V) supplies the LVTTL output buffers.
Data flow in each direction is controlled by output-enable (OEAB and OEBA), latch-enable (LEAB and LEBA),
and clock (CLKAB and CLKBA) inputs. The clock can be controlled by the clock-enable (CEAB and CEBA)
inputs. For A-to-B data flow, the device operates in the transparent mode when LEAB is high. When LEAB is low,
the A data is latched if CEAB is low and CLKAB is held at a high or low logic level. If LEAB is low, the A-bus data
is stored in the latch/flip-flop on the low-to-high transition of CLKAB if CEAB also is low. When OEAB is low, the
outputs are active. When OEAB is high, the outputs are in the high-impedance state. Data flow for B to A is
similar to that of A to B, but uses OEBA, LEBA, CLKBA, and CEBA.
This device is fully specified for partial-power-down applications using Ioff. The Ioff circuitry disables the outputs,
preventing damaging current backflow through the device when it is powered down.
Active bus-hold circuitry holds unused or undriven LVTTL inputs at a valid logic state. Use of pullup or pulldown
resistors with the bus-hold circuitry is not recommended.
To ensure the high-impedance state during power up or power down, OE should be tied to VCC through a pullup
resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.