Features
• Integrated Active Current-Limit Protection
• Thermal Shutdown
• Guaranteed Turn-On: 2mA Input Control Current
• 350VP Blocking Voltage
• 3750Vrms Input/Output Isolation
• Small Surface Mount Package
• Low Drive Power Requirements
• Arc-Free With No Snubbing Circuits
• No EMI/RFI Generation

Applications
• Telphony hook switch
• VoIP gateways, such as VoIP
• IP-PBXs
• Satellite and cable set-top boxes
• V.92 (and other standard) modems
• Fax machines
• Voicemail systems
• Embedded modems for POS terminals,
automated banking, remote metering, vending
machines, security, and surveillance
• Instrumentation
• Medical equipment—Patient/equipment isolation
• Aerospace
• Industrial controls

Description
The CPC1540 is a normally open (1-Form-A) Solid
State Relay with an integrated current limit feature
that can replace electromechanical relays while
enhancing the robustness of wireline-interface
applications.
Designed specifically to target the hook switch
telephony market, the CPC1540 has a load voltage
rating of 350V.
The relay is constructed using an efficient infrared
LED for actuation control and an integrated
monolithic die for the switch output. The die,
fabricated in a high-voltage dielectrically isolated
technology, comprises a photodiode array, switch
control with active current limiting circuitry, and
MOSFET switches. Active current-limit circuitry in
the CPC1540 provides a thermal shutdown feature,
offering excellent power-cross immunity for improved
survivability in harsh environments.
These enhancements greatly improve the robustness
of end systems using this device compared to
systems using relays without the integrated current
limit. In addition, the active current limit circuitry
enables the CPC1540 to pass FCC 68.302 and
other regulatory voltage surge requirements when
adequate overvoltage protection is provided. The
CPC1540 relay may be used in both AC and DC
applications.