SCEU021A November   2019  – August 2021 TXB0101 , TXB0102 , TXB0104

 

  1.   Trademarks
  2. 1Introduction
    1. 1.1 Features
      1. 1.1.1 TXB Family
    2. 1.2 Hardware Description
      1. 1.2.1 Headers
      2. 1.2.2 Voltage Supply
      3. 1.2.3 Bypass Capacitors
      4. 1.2.4 OE Select
      5. 1.2.5 RC Loading
  3. 2Board Layout
  4. 3Schematic and Bill of Materials
    1. 3.1 Schematic
    2. 3.2 Bill of Materials
  5. 4Revision History

1.1.1 TXB Family

The TXB family uses two separate configurable power supply rails VCCA and VCCB with A ports tracking the VCCA supply and B ports tracking the VCCB supply. These devices are fully specified for partial-power-down applications using IOFF. The IOFF circuitry (SCEA026) disables the outputs, preventing damaging current backflow through the device when it is powered down. The VCC isolation feature ensures that if either VCC supply is powered down (0V), then the I/O ports are in a high-impedance state. Refer to the application note A guide to voltage translation with the TXB family for more on TXB family characteristics.

Weak driving capability is characteristic of auto-bidirectional translators, allowing the device output to be overridden by the external driver during a direction change, without the need for a separate DIR control pin. TXB devices are designed with buffered I/O architecture suitable for light load push-pull applications. During an edge transition, the One-shot (O.S) circuitry becomes active and lowers the effective output impedance. Once the transition is complete, the weak 4-kΩ buffer drives the output. During a DC state, only the series resistor drives the output, thus allowing the port to be overridden externally. Consequently, external pull-up or pull-down resistor values must be larger than 50-kΩ to avoid affecting VOH or VOL. Refer to the application note Effects of pull-up and pull-down resistors on TXB devices for further information.

Table 1-1 shows the comparison between the TXB, TXS and LSF Auto-Bidirectional families of TI.

Table 1-1 Auto-Bidirectional Families
MetricsTXBTXSLSF
Translation mechanismWeak buffered translationPassive translation with NMOS and internal pull-up resistorsPassive translation with NMOS and external pull-up resistors
Drive strengthVery low drive of 20ua due to 4K limiting bufferNo DC driveNo DC drive
Applications/ InterfacePush-pull applicationsOpen-drain applicationsPush-pull and open-drain applications
SpeedUp to 140MbpsUp to 24MbpsHigh speed up to 200Mbps
Translation flexibilityBuffered and fixed translation on A and B portsIntegrated pull-up resistors-reduces BOM cost of the system; Fixed translation on A and B portsFlexible translation due to external pull-up resistors
Frequency vs load balance trade-off
I/O portsA ports referenced to Vcca and B ports referenced to VccbA ports referenced to Vcca and B ports referenced to VccbA ports not referenced to Vcca, B ports not referenced to Vccb; allows multi-voltage translation
Edge- accelerationIntegrated one-shot edge acceleration circuitryIntegrated one-shot edge acceleration circuitryNo integrated one-shot acceleration circuitry
Vih/Vil requirementsDatasheet spec has Vih/Vil specificationsHas Vih /Vil spec but no RON for the FETNo Vih / Vil conditions, has RON specifications
Additional care-aboutVCCA<=VCCBVCCA<=VCCBVCCB>VCCA+0.8 V

TXB-EVM is shown in Figure 1-1. Table 1-2 shows the packages supported by the TXB-EVM.

Table 1-2 TXB-EVM Packages and Devices supported
DevicePackagePinsDevice Populated
TXB0101DCK (SC-70)6Yes
TXB0102DCU (VSSOP)8Yes
TXB0104 (TXB0104-Q1*)(1)PW (TSSOP)14No
RUT (UQFN)12Yes
TXB0108PW (TSSOP)20No
RGY (VQFN)20Yes
(1) -Q1 devices are not populated but can be supported.
GUID-31B1BC53-3AE8-49D8-8BE4-7FF2090B484D-low.gifFigure 1-1 TXB-EVM