Level shifter (logic voltage-level translator)

01

Match the voltage rails and bus type

TI's TXS0108E datasheet describes an 8-bit non-inverting bidirectional level translator with two configurable supply rails: the A port tracks VCCA, which accepts 1.4–3.6 V, and the B port tracks VCCB, which accepts 1.65–5.5 V, with VCCA ≤ VCCB, allowing translation between any of the 1.5, 1.8, 2.5, 3.3 and 5 V nodes. It needs no direction-control signal and no power-supply sequencing — either rail can ramp first. [1]

It lists maximum data rates of 110 Mbps with push-pull drivers and 1.2 Mbps with open-drain drivers. [1]

TI's TXB0108 is also an 8-bit auto-direction translator but extends the A port down to 1.2 V (1.2–3.6 V, with 1.65–5.5 V on the B port and VCCA not above VCCB), so it can translate from 1.2 V nodes; if either supply is at ground, all outputs go high-impedance. [2]

For a single signal with a known direction, TI's SN74LVC1T45 is a one-bit dual-supply bus transceiver whose ports each run from 1.65 V to 5.5 V; a direction-control (DIR) input, referenced to VCCA, selects whether data passes from A to B or B to A, and its inputs must be held at a valid logic level to avoid excess supply current. [3]

Editorial note: if one side runs above the other's maximum (for example a 5 V signal into a 3.3 V-only part), put that rail on the higher-voltage port and confirm the VCCA ≤ VCCB rule. [1]

Give the supplier the voltages on each side, bus type (push-pull, open-drain, I²C, SPI, UART, GPIO), direction (fixed, bidirectional, auto), data rate, channel count, enable and power-up needs, ESD requirements on connector-facing pins, temperature range, package and quantity.

02

Check data rate, enable, protection and package

When the output-enable (OE) input is low, all TXS0108E outputs go high-impedance; to keep them Hi-Z during power-up or power-down, OE is tied to ground through a pull-down resistor sized to the driver's current-sourcing capability. Latch-up exceeds 100 mA per JESD 78 class II, A-port ESD exceeds 2,000 V HBM, 150 V MM and 1,000 V CDM, and the B port meets IEC 61000-4-2 at ±8 kV contact and ±6 kV air discharge. It is specified from −40 to 85 °C in TSSOP-20 (6.5 × 6.4 mm), VSSOP-20, two VQFN-20 sizes and a 2.5 × 3.0 mm ball-grid package. [1]

Editorial calculation: at 110 Mbps a bit lasts about 9.1 ns; at 1.2 Mbps about 833 ns. A 400 kHz I²C bus (2.5 µs per bit) sits within the open-drain rate. [1]

The SN74LVC1T45 lists maximum data rates of 420 Mbps translating 3.3 V to 5 V, 210 Mbps translating to 3.3 V, 140 Mbps to 2.5 V and 75 Mbps to 1.8 V, ±24 mA output drive at 3.3 V and 4 µA maximum supply current, with I(off) partial-power-down support. The TXB0108 lists 4 µA maximum supply current, ±15 kV HBM ESD on its B port (±8 kV HBM in the YZP DSBGA package) and packages from a 1.90 × 2.40 mm DSBGA to a 6.50 × 4.40 mm TSSOP-20. [3] [2]

Editorial calculation: the SN74LVC1T45's 75 Mbps limit when translating down to 1.8 V is about 18% of its 420 Mbps limit for 3.3 V to 5 V (75 ÷ 420), so check the rate at your lowest output rail, not the headline figure. [3]

Editorial note: place the IEC-rated port toward external connectors where ESD events enter. [1]

03

Cross-check against a second maker's translators

SG Micro publishes product pages for two auto-direction translators that give a second, non-TI set of values. The SGM4553 is a 2-bit non-inverting bidirectional translator for open-drain and push-pull lines: its A port runs from 1.65 V to 5.5 V and its B port from 2.3 V to 5.5 V, with VCCA ≤ VCCB, and it needs no direction-control signal and no specific power-up sequence. SG Micro lists data rates of 24 Mbps push-pull and 2 Mbps open-drain, names UART, I²C/SMBus and GPIO as applications, and states that when OE goes low all I/Os enter the high-impedance state, with an internal pull-down current source on OE once VCCA is powered. [4]

The SGM4554 is a 1-bit auto-direction translator with a push-pull output whose A port accepts 1.2 V to 5.0 V and whose B port accepts 1.65 V to 5.5 V, covering the 1.2, 1.5, 1.8, 2.5, 3.3 and 5 V nodes. Its OE input is referenced to VCCA and SG Micro says OE should be tied to GND through a pull-down resistor sized to the driver's current-source capability; it supports partial power-down, and the device enters power-down mode when either rail is low. [5]

Editorial calculation: the SGM4553's 24 Mbps push-pull limit is about 22% of the TXS0108E's 110 Mbps (24 ÷ 110), and one bit at 24 Mbps lasts about 41.7 ns. Its 2 Mbps open-drain limit (500 ns per bit) still covers a 400 kHz I²C bus at 2.5 µs per bit. [4] [1]

Editorial note: both SG Micro parts list −40 °C to +85 °C, the same range as the TXS0108E, so a wider temperature requirement has to be raised with the supplier rather than assumed. [4] [5] [1]

04

Open-drain, 1.2 V push-pull and DIR-pin translator types

SG Micro lists the SGM4553, SGM4554 and SGM4556 on its level-shifter page, and 3PEAK lists I²C level shifters including the TPT29306.

Three translator types appear in the reviewed data sheets: auto-direction translators for open-drain and push-pull buses (TXS0108E), auto-direction translators aimed at push-pull lines and lower 1.2 V rails (TXB0108), and direction-controlled bus transceivers with a DIR pin and higher drive (SN74LVC1T45). SG Micro's SGM4553 and SGM4554 are further auto-direction examples at 2 bits and 1 bit. [1] [2] [3] [4] [5]

Ask each supplier for the datasheet with rail ranges, data rates by driver type and output rail, enable or direction-control behaviour, ESD ratings and package options. [1]

05

A and B port buffers, direction sensing, output enable and ESD by port

Each block is described in the TXS0108E datasheet; the last column names the value to fix for your board.

06

TXS0108E rails, channels, data rate, enable, ESD and package as a quote checklist

The published values are the TXS0108E's, except that the data-rate row adds the SN74LVC1T45's 75–420 Mbps range for a direction-controlled part.

07

Send the rails, bus and package data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Rails: [V low side; V high side]
Bus: [push-pull; open-drain; I²C; SPI]
Direction: [auto; DIR; fixed]
Rate: [Mbps]
Channels: [count]
Enable/power-up: [OE; Hi-Z]
ESD/temp/package: [kV; °C; package]
Quantity: [units]

See manufacturer records Send an enquiry through CNFX