LTC4268IDKD-1

LTC4268IDKD-1 is a Linear Technology (now Analog Devices) Power over Ethernet (PoE) Powered Device (PD) controller. It implements the IEEE 802.3af/at PoE interface for a PD, handling detection, classification, and power-path control to a PoE switch.
Key points:
- Function: detects a compliant PSE, classifies the PD, negotiates power, and drives/controls the PD power path via an external high-side switch MOSFET; provides protection and fault handling.
- Protections: overvoltage, reverse polarity, short-circuit/overcurrent, undervoltage lockout, and thermal protection; includes soft-start and fault/status outputs.
- Requirements: external high-side MOSFET (and typical support components) to carry PoE current; no on-chip full power path.
- Packaging/variants: -IDKD-1 denotes a specific industrial-temperature/packaging variant of the LTC4268 family. Check the datasheet for exact pinout and temperature range.
- Applications: PoE-powered devices such as IP cameras, VoIP phones, wireless access points, etc.
For detailed specs, pinout, and typical application circuits, refer to the LTC4268 datasheet.

Here are the key features of the LTC4268IDKD-1 (hot-swap/power-path protection device):
- Wide input voltage range suitable for telecom/industrial/applications (external MOSFET-based power path).
- External N-channel MOSFET drive: provides protected high-side power switching.
- Programmable current limit via sense resistor; overload protection with fast fault response.
- Slew-rate controlled inrush/pre-charge control for gentle capacitor charging.
- Overvoltage and undervoltage protection to guard against rail faults.
- Overcurrent/short-circuit protection with latched fault condition.
- Reverse-current protection and power-path blocking.
- Fault/status reporting: fault/status outputs for host MCU monitoring.
- Enable (ON/OFF) control and soft-start sequencing.
- Thermal protection with latch to prevent thermal runaway.
- Compact package variant (-IDKD) suitable for surface-mount designs.
Note: For exact electrical specs (limits, timings, pinout), refer to the LTC4268 datasheet for the -IDKD-1 variant.

- Pin count: 28 pins (28-lead package)
- Function: IEEE 802.3af/at Power over Ethernet (PoE) PD controller. It handles PD detection/classification and drives the external MOSFETs to control the PoE power path, including current/overload protection and power management for a PoE-powered device.

Manufacturer: Analog Devices, Inc. (ADI).
Kind of company: A multinational American semiconductor company that designs, manufactures, and markets integrated circuits, specializing in analog, mixed-signal, and digital signal processing ICs. It acquired Linear Technology in 2017 (the LTC product line originated there).

Typical applications for the LTC4268IDKD-1 are as a PoE PD controller (IEEE 802.3af/at) used in powered devices to negotiate, regulate, and protect power from a PoE source. Common use areas include:
- IP cameras and video phones
- Wireless access points and bridges
- PoE-powered LED lighting
- Industrial sensors, remote I/O, and automation equipment
- Security and access-control devices
- PoE switches/midspans and other 802.3af/at compliant PDs

LTC4268IDKD-1 is in a 28-pin QFN package with an exposed pad.