LT4250LCS8 Integrated Circuit Chip 8-Lead SO Negative 48V Hot Swap Controller Circuit Breaker

The LT4250LCS8 is an eight pin negative 48 V hot swap controller that allows a board to be safely inserted into and removed from a live backplane. It operates from -18 V to -80 V and is pin compatible with the LT1640L and LT1640H, so an existing board layout can be upgraded without a redesign.

Inrush current and short circuit current limits are programmed separately, which lets the start-up ramp be gentle while the running fault limit stays tight enough to protect the pass transistor. The circuit breaker is designed to be immune to voltage steps and current spikes on the feed, so a transient on the backplane does not trip a healthy card.

Undervoltage lockout and overvoltage protection thresholds are set with external dividers, and the part includes a bell-core compatible on/off threshold so it works with the signalling used in central office equipment. The power good output can enable a downstream power module directly.

The H version provides an active high power good output and the L version an active low output, so either polarity of module enable can be driven without an inverter. This part is the PWRGD active low version, and the eight pin package keeps the controller close to the connector.

The LT4250LCS8 is the commercial grade part in the 8-Lead Plastic SOIC package, specified from 0 to 70 degrees C. It is RoHS compliant and lead free, every order ships with full traceability, and samples and volume pricing are available on request.

• Safe insertion into a live -48 V backplane
• Circuit breaker immune to voltage steps
• Programmable inrush current limit
• Programmable short circuit current limit
• Pin compatible with LT1640L and LT1640H
• Operates from -18 V to -80 V
• Programmable overvoltage protection
• Programmable undervoltage lockout
• Power good control output
• Bell-core compatible on/off threshold
• Eight pin footprint
• 8-Lead Plastic SOIC package
• RoHS compliant, lead free

• Central office switching
• -48 V distributed power systems
• Negative power supply control
• Hot board insertion
• Telecom line cards
• High availability servers

Typical use is a -48 V central office card where a backplane transient must not trip the breaker while a real board short must.

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