MX857B Equivalent & Substitute Parts

Part Overview

The MX857B is a voltage level translator manufactured by IXYS Integrated Circuits Division, designed for unidirectional signal translation between different voltage domains. This 8-SOIC package device operates with VCCA ranging from 3V to 5.5V and VCCB from 7.5V to 20V, featuring differential output configuration. The product is classified as obsolete, making equivalent and substitute parts necessary for ongoing system support and new design implementations.

Key Parameters

Parameter	Value
Manufacturer Part Number	MX857B
Manufacturer	IXYS Integrated Circuits Division
Category	Logic
Package / Case	8-SOIC (0.154", 3.90mm Width)
Translator Type	Voltage Level
Channel Type	Unidirectional
Number of Circuits	1
Channels per Circuit	1
Voltage - VCCA	3V ~ 5.5V
Voltage - VCCB	7.5V ~ 20V
Output Type	Differential
Operating Temperature	-40°C ~ 85°C (TA)
Mounting Type	Surface Mount
Product Status	Obsolete
Moisture Sensitivity Level (MSL)	1 (Unlimited)
REACH Status	REACH Unaffected

Substitute Part Grouping Explanation

Substitution for the MX857B is determined by the following critical parameters:

Primary Substitution Criteria:

Translator Type: Voltage Level
Channel Type: Unidirectional
Number of Circuits: 1
Channels per Circuit: 1
Output Type: Differential or compatible output configuration
Operating Temperature Range: Minimum -40°C ~ 85°C
Mounting Type: Surface Mount
REACH Compliance: REACH Unaffected

The substitute parts identified fall into two functional categories based on output type compatibility:

Category 1 - Buffer/Non-Inverting Logic Translators (74AUP1T34 Series): These parts provide push-pull output configuration with reduced voltage supply ranges (1.1V ~ 3.6V) compared to the original MX857B. These are suitable for applications where the lower voltage supply range is acceptable and push-pull output meets functional requirements.

Category 2 - Voltage Level Translators with Extended Voltage Ranges (74AXP1T Series, FXLP34 Series, NLSV1T240): These parts maintain voltage level translation functionality with unidirectional, single-channel architecture. The 74AXP1T series operates at 0.7V ~ 2.75V, while FXLP34 and NLSV1T240 operate at 1V ~ 3.6V and 0.9V ~ 4.5V respectively.

Package variations (5-TSSOP, 5-X2SON, 6-XSON, 6-UFDFN, 6-MicroPak) represent different physical form factors suitable for different PCB layout requirements while maintaining functional equivalence.

Parameter Comparison

Parameter	MX857B	74AUP1T34GW,125	74AUP1T34GXH	74AXP1T125GNH	74AXP1T34GNH	FXLP34FHX	NLSV1T240MUTBG
Translator Type	Voltage Level	Buffer, Non-Inverting	Buffer, Non-Inverting	Voltage Level	Buffer, Non-Inverting	Voltage Level	Voltage Level
Channel Type	Unidirectional	-	-	Unidirectional	-	Unidirectional	Unidirectional
Number of Circuits	1	1	1	1	1	1	1
Channels per Circuit	1	1	1	1	1	1	1
Output Type	Differential	Push-Pull	Push-Pull	Tri-State	Push-Pull	Non-Inverted	Tri-State, Inverted
Voltage - Supply (VCCA)	3V ~ 5.5V	1.1V ~ 3.6V	1.1V ~ 3.6V	0.7V ~ 2.75V	0.7V ~ 2.75V	1V ~ 3.6V	0.9V ~ 4.5V
Voltage - Supply (VCCB)	7.5V ~ 20V	-	-	1.2V ~ 5.5V	-	1V ~ 3.6V	0.9V ~ 4.5V
Operating Temperature	-40°C ~ 85°C	-40°C ~ 125°C	-40°C ~ 125°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C	-40°C ~ 85°C
Mounting Type	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount	Surface Mount
Product Status	Obsolete	Active	Active	Obsolete	Obsolete	Active	Obsolete
RoHS Status	-	ROHS3 Compliant	-	ROHS3 Compliant	ROHS3 Compliant	-	ROHS3 Compliant
REACH Status	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected	REACH Unaffected	-	REACH Unaffected

Engineering Selection Recommendations

For Active Product Status Priority: The 74AUP1T34GW,125 and 74AUP1T34GXH are recommended as primary substitutes due to active product status and ROHS3 compliance. These parts are manufactured by Nexperia USA Inc. and NXP USA Inc. respectively, with substantial inventory availability. The 74AUP1T34GW,125 offers automotive-grade qualification (AEC-Q100) for applications requiring automotive standards.

For Extended Voltage Range Applications: The FXLP34FHX manufactured by Fairchild Semiconductor maintains voltage level translation functionality with symmetric voltage supply ranges (1V ~ 3.6V for both VCCA and VCCB) and active product status. This part is suitable for applications where the original MX857B's extended VCCB range (7.5V ~ 20V) is not required.

For Obsolete Product Continuation: When the original MX857B voltage specifications (VCCA 3V ~ 5.5V, VCCB 7.5V ~ 20V) are critical, the 74AXP1T125GNH provides voltage level translation with VCCB range extending to 5.5V, though this remains below the original specification. Circuit redesign or alternative voltage regulation may be necessary for applications requiring the full original voltage range.

Compliance Considerations: All recommended active substitutes maintain REACH Unaffected status. ROHS3 compliance is available with 74AUP1T34 series and 74AXP1T series parts, supporting modern regulatory requirements.

Frequently Asked Questions (FAQ)

Q: Can the 74AUP1T34GW,125 directly replace the MX857B?

A: The 74AUP1T34GW,125 provides equivalent unidirectional, single-channel translation functionality with active product status and superior inventory availability. However, the voltage supply range differs significantly (1.1V ~ 3.6V versus MX857B's 3V ~ 5.5V VCCA and 7.5V ~ 20V VCCB). Direct replacement is feasible only if your application operates within the 74AUP1T34GW,125 voltage specifications. Output type differs (push-pull versus differential), requiring circuit validation.

Q: What is the difference between the 74AUP1T34 and 74AXP1T34 series?

A: The 74AUP1T34 series operates at 1.1V ~ 3.6V supply voltage with push-pull output, while the 74AXP1T34 series operates at lower voltage (0.7V ~ 2.75V) with push-pull output and higher output current (12mA versus 4mA). Both are unidirectional, single-channel translators. The 74AXP1T34 series is obsolete, while 74AUP1T34 remains active.

Q: Are package variations (5-TSSOP, 5-X2SON, 6-XSON) functionally equivalent?

A: Yes, package variations represent different physical form factors for the same functional device. The 5-TSSOP, 5-X2SON, and 6-XSON packages contain identical logic functionality. Package selection depends on PCB layout constraints, thermal requirements, and manufacturing capabilities. All maintain surface mount mounting type and equivalent electrical performance.

Q: Does the FXLP34FHX support the full voltage range of the MX857B?

A: No. The FXLP34FHX operates with symmetric voltage supply (1V ~ 3.6V for both VCCA and VCCB), which does not support the MX857B's extended VCCB range of 7.5V ~ 20V. The FXLP34FHX is suitable for applications where both voltage domains operate within 1V ~ 3.6V.

Q: What does "Unidirectional" mean in the context of these translators?

A: Unidirectional translators support signal translation in one direction only, from input to output. This differs from bidirectional translators which support simultaneous two-way communication. The MX857B and all listed substitutes are unidirectional devices.

Q: Is the NLSV1T240MUTBG a suitable replacement?

A: The NLSV1T240MUTBG provides voltage level translation with unidirectional, single-channel architecture and symmetric voltage supply (0.9V ~ 4.5V). However, it is obsolete and features tri-state inverted output, differing from the MX857B's differential output. This part is suitable only if your application requires tri-state inverted output and operates within the specified voltage range.

Q: What is the significance of "Active" versus "Obsolete" product status?

A: Active products have ongoing manufacturing support, guaranteed availability, and continued technical support from manufacturers. Obsolete products have ceased production and may have limited remaining inventory. For new designs, active products (74AUP1T34GW,125, 74AUP1T34GXH, FXLP34FHX) are preferred. For legacy system support, obsolete substitutes may be necessary if inventory remains available.

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