Hermetically Sealed, Transistor Output Optocouplers for Analog and Digital Applications

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The HCPL-257K is a highest reliability Class K two channel hermetically sealed optocoupler in a 16-Pin ceramic DIP package. Gold plated leads, Solder dipped leads and various lead form options are also available. See datasheet for details.

The product is capable of operation and storage over the full military temp range and may also be purchased as either commercial grade, with MIL-PRF-38534 Class Level H testing or from the DLA SMD 5962-87679. The device is manufactured and tested on a MIL-PRF-38534 certified line and included in the DLA Qualified Manufacturers List QML-38534 for Hybrid Microcircuits.

Each channel contains a GaAsP LED which is optically coupled to an integrated photon detector. Separate connections for the photodiodes and output transistor collectors improve the speed up to a hundred times that of a conventional phototransistor coupler by reducing the base-collector capacitance.

The device is suitable for wide bandwidth analog applications, as well as for interfacing TTL to LSTTL or CMOS. Current Transfer Ratio (CTR) is 9% min at IF = 16mA. The 18V Vcc capability will enable the designer to interface any TTL family to CMOS. The availability of the base lead allows optimized gain/bandwidth adjustment in analog applications. The shallow depth of the IC photodiode provides better radiation immunity than conventional phototransistor couplers.

This product is also available with the transistor base node connected to improve common mode immunity and ESD susceptibility. In addition, higher CTR minimums are available by special request.

Package styles for this die set in one, two or four channels are 8 and 16-Pin DIP thru hole, 16-Pin surface mount DIP flat pack, and 20 pad leadless ceramic chip carrier. Most devices are available with a variety of lead forms and plating options. See datasheet for details.

As the same die are used for each channel of each device listed in the datasheet, absolute max ratings, recommended operating conditions, electrical specifications, and performance characteristics shown in the datasheet figures are virtually identical for all parts. Occasional exceptions exist due to package variations and limitations and are as noted. Additionally, the same package assembly processes and materials are used in all devices. These similarities give justification for the use of data obtained from one part to represent other parts performance for reliability and certain limited radiation test results.


  • Highest Reliability, Two Channel, 16-Pin DIP
  • Performance Guaranteed from -55 degrees to 125 degrees C
  • MIL-PRF-38534 Class K, QML-38534
  • Dual Marked with Device Part Number and DLA Standard Microcircuit Drawing
  • High Radiation Immunity
  • Reliability Data
  • Five Hermetically Sealed Package Configurations
  • One and Four Channel Devices Available (different package)
  • 9 MHz Bandwidth
  • High Speed: Typically 400kBit/s
  • Open Collector Output
  • 2-18 V Vcc Range
  • 1500 Vdc Withstand Test Voltage


  • Military and Aerospace
  • High Reliability Systems
  • Transportation, Medical, and Life Critical Systems
  • Vehicle Command, Control
  • Line Receiver
  • Switching Power Supply
  • Voltage Level Shifting
  • Analog Signal Ground Isolation
  • Isolated Input Line Receiver
  • Isolated Output Line Driver
  • Logic Ground Isolation
  • Isolation for Test Equipment Systems
  • Harsh Industrial Environments

Lifecycle Status


Specification Value
Lifecycle Active
Distrib. Inventory No
CMR (min.) (V/µs) 1000.0
CTR Min. (%) 9.0
Data Rate 700 Kb/s
Package Hermetic 16 Pin DIP
Product Type Hermetic High Speed Transistor
Reliability Class MIL-PRF-38534 Class K
VDD2 (V) 2.0
Prop Delay (tPHL) Max. (µs) 2.0 µs
Prop Delay (tPLH) Max. (µs) 6.0 µs
IF Min. (mA) 12.0 mA
Bandwidth (MHz) 9 MHz
Application Note3 i
Data Sheet1 i
Design Guide1 i
Product Change Notice (PCN)4 i
Regulatory Certificate2 i
Reliability Data Sheet1 i
Specification1 i
White Papers1 i
Selection Guide1 i