Features: • Members of the Texas Instruments SCOPETM Family of Testability Products
• Members of the Texas Instruments WidebusTM Family
• State-of-the-Art 3.3-V ABT Design Supports Mixed-Mode Signal Operation (5-V Input and Output Voltages With 3.3-V VCC)
• Support Unregulated Battery Operation Down to 2.7 V
• UBTTM (Universal Bus Transceiver) Combines D-Type Latches and D-Type Flip-Flops for Operation in Transparent, Latched, or Clocked Mode
• Bus-Hold Data Inputs Eliminate the Need for External Pullup Resistors
•B-Port Outputs of SN74LVT182502 Devices Have Equivalent 25- Series Resistors, So No External Resistors Are Required
• Compatible With the IEEE Standard 1149.1-1990 (JTAG) Test Access Port and Boundary-Scan Architecture
• SCOPETM Instruction Set
IEEE Standard 1149.1-1990 Required Instructions, Optional INTEST, and P1149.1A CLAMP and HIGHZ
Parallel Signature Analysis at Inputs With Masking Option
Pseudo-Random Pattern Generation From Outputs
Sample Inputs/Toggle Outputs
Binary Count From Outputs
Device Identification
Even-Parity Opcodes
• Packaged in 64-Pin Plastic Thin Quad Flat Packages Using 0.5-mm Center-to-Center SpacingsPinout
SpecificationsSupply voltage range, VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . .0.5 V to 4.6 V
Input voltage range, VI (see Note 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . .0.5 V to 7 V
Voltage range applied to any output in the high state or power-off state, VO (see Note 1) . .. .0.5 V to 7 V
Current into any output in the low state, IO: SN74LVT18502 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .128 mA
SN74LVT182502 (A port or TDO) . . . . . . . . . . . . . . . . . .128 mA
SN74LVT182502 (B port) . . . . . . . . . . . . . . . . . . . . . . . . .30 mA
Current into any output in the high state, IO (see Note 2): SN74LVT18502 . . . . . . . . . . . . . . . . . . . . . .64 mA
SN74LVT182502 (A port or TDO) . . . . . . .. .64 mA
SN74LVT182502 (B port) . . . . . . . . . . . . . ..30 mA
Input clamp current, IIK (VI < 0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . .50 mA
Output clamp current, IOK (VO < 0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50 mA
Maximum power dissipation at TA = 55°C (in still air) (see Note 3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 W
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65°C to 150°CDescriptionThe SN74LVT18502 and SN74LVT182502 scan test devices with 18-bit universal bus transceivers are members of the Texas Instruments SCOPETM testability integrated-circuit family. This family of devices supports IEEE Standard 1149.1-1990 boundary scan to facilitate testing of complex circuit-board assemblies. Scan access to the test circuitry is accomplished via the 4-wire test access port (TAP) interface.
Additionally, these devices SN74LVT18502 are designed specifically for low-voltage (3.3-V) VCC operation, but with the capability to provide a TTL interface to a 5-V system environment.
In the normal mode, these devices SN74LVT18502 are 18-bit universal bus transceivers that combine D-type latches and D-type flip-flops to allow data flow in transparent, latched, or clocked modes. They can be used either as two 9-bit transceivers or one 18-bit transceiver. The test circuitry can be activated by the TAP to take snapshot samples of the data appearing at the device pins or to perform a self test on the boundary-test cells. Activating the TAP in the normal mode does not affect the functional operation of the SCOPEE universal bus transceivers.
About SN74LVT18502, Data flow in each direction is controlled by output-enable (OEAB and OEBA), latch-enable (LEAB and LEBA), and clock (CLKAB and CLKBA) inputs. For A-to-B data flow, the device operates in the transparent mode when LEAB is high. When LEAB is low, the A-bus data is latched while CLKAB is held at a static low or high logic level. Otherwise, if LEAB is low, A-bus data is stored on a low-to-high transition of CLKAB. When OEAB is low, the B outputs are active. WhenOEAB is high, the B outputs are in the high-impedance state. B-to-A data flow is similar to A-to-B data flow but uses the OEBA, LEBA, and CLKBA inputs.
In the test mode, the normal operation of the SCOPETM universal bus transceivers is inhibited and the test circuitry is enabled to observe and control the I/O boundary of the device SN74LVT18502. When enabled, the test circuitry performs boundary-scan test operations according to the protocol described in IEEE Standard 1149.1-1990.
About SN74LVT18502, Four dedicated test pins are used to observe and control the operation of the test circuitry: test data input (TDI), test data output (TDO), test mode select (TMS), and test clock (TCK). Additionally, the test circuitry performs other testing functions such as parallel-signature analysis (PSA) on data inputs and pseudo-random pattern generation (PRPG) from data outputs. All testing and scan operations are synchronized to the TAP interface.
Active bus-hold circuitry is provided by SN74LVT18502 to hold unused or floating data inputs at a valid logic level.
The B-port outputs of SN74LVT182502, which are designed to source or sink up to 12 mA, include 25-W series resistors to reduce overshoot and undershoot.
The SN74LVT18502 and SN74LVT182502 are characterized for operation from 40°C to 85°C.
SN74LVT18502 Data Sheet
