Isolated Voltage/Current Detectors

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The ACPL-K370 and ACPL-K376 are voltage/current threshold detection optocouplers. The ACPL-K376 is a low-current version of the ACPL-K370. To obtain lower current operation, the ACPL-K376 uses a high-efficiency AlGaAs LED which provides higher light output at lower drive currents. The devices utilize threshold sensing input buffer ICs which permit control of threshold levels over a wide range of input voltages with a single external resistor.

The input buffer incorporates several features: hysteresis for extra noise immunity and switching immunity, a diode bridge for easy use with ac input signals, and internal clamping diodes to protect the buffer and LED from a wide range of over-voltage and over-current transients. Because threshold sensing is done prior to driving the LED, variations in optical coupling from the LED to the detector will have no effect on the threshold levels.

The ACPL-K370's input buffer IC has a nominal turn on threshold of 3.8 volts (VTH+) and 2.77 mA (ITH+). The buffer IC for the ACPL-K376 was designed to permit a lower input current. The nominal turn on threshold for the ACPL-K376 is 3.8 volts (VTH+) and 1.32 mA (ITH+), which reduces power dissipation by 52%.

The high gain output stage features an open collector output providing both TTL compatible saturation voltages and CMOS compatible breakdown voltages.

By combining several unique functions in a single package, the user is provided with an ideal component for industrial control computer input boards and other applications where a predetermined input threshold level is desirable.


  • ±5% voltage detection accuracy
  • 1140 Vpeak wide AC or DC detection range
  • User configurable single/dual detection levels
  • Built-in hysteresis improve noise immunity
  • 1.32 mA very low threshold current (ACPL-K376)
  • Logic compatible output
  • 2 V to 18 V wide output supply voltage
  • –40ºC to +105ºC operating temperature range
  • Stretched SO8 package with 8 mm creepage and clearance
  • Safety and regulatory approval (pending):
    -IEC/EN/DIN EN 60747-5-5: 1140 Vpeak working insulation voltage
    -UL 1577: 5000 Vrms/1min double protection rating
    -CSA: Component Acceptance Notice #5
  • Options available are:
    060 = IEC/EN/DIN EN 60747-5-2 Option
    500 = Tape/Reel Package Option (1 K min.)
    XXXE = Lead Free Option


  • Limit switch sensing
  • Low voltage detector
  • AC mains and DC link voltage detection
  • Relay contact monitor
  • Relay coil voltage monitor
  • Current sensing
  • Microprocessor interfacing
  • Telephone ring detection

Lifecycle Status


Substance Compliance

  • RoHS
    Pb & Pb-free options available
Specification Value
Lifecycle Active
Distrib. Inventory Yes
CMR (min.) (V/µs) 600.0
Vcm (V) 140.0
Hysteresis (mA) 1.2
Hysteresis Uom mA
RoHS6 Compliant Pb & Pb-free options available
Package Stretched SO8
Product Type AC / DC to Logic Interface
Prop Delay (tPHL) Max. (µs) 15.0
Prop Delay tPHL Uom µs
Prop Delay (tPLH) Max. (µs) 40.0
Prop Delay tPLH Uom µs
VDD2 (V) 20.0
UL Insulation Rating Viso (VRMS) 5000.0
IEC Maximum Working Insulation Voltage Viorm (VPEAK) 1140.0
Hysteresis (mA) 1.2 mA
Prop Delay (tPHL) Max. (µs) 15 µs
Prop Delay (tPLH) Max. (µs) 40 µs
Application Note2 i
Brochures1 i
Options Data Sheet3 i
Product Change Notice (PCN)2 i
Regulatory Certificate1 i
Reliability Data Sheet4 i
Selection Guide2 i
Technical Notes1 i
White Papers1 i
FAQs1 i
Promotional Material1 i


Isolated Voltage/Current Detectors


Isolated Voltage/Current Detectors


Isolated Voltage/Current Detectors