LINEAR Hot Swap Controller with Integrated MOSFETs and Sensing Resistors - 5mm x 3mm DFN for Accurate Current Limiting and Load Current Monitoring in Tight Spaces - Design Note 466
Summary
Introducing a compact Hot Swap controller designed for safe and reliable power management in live backplane systems. This integrated circuit provides robust inrush current control, acts as a protective circuit breaker, and features soft-start capabilities across 2.9V to 26.5V voltages. The manual details the device's integration of an MOSFET and sense resistor into a small DFN package, enabling precise load monitoring (current and voltage) for designers needing high accuracy in minimal space. It is ideal for power electronics applications requiring maximum protection and reliability when boards are connected or disconnected.
Page 1 Text Content
Hot Swap Controller, MOSFET and Sense Resistor Are Integrated in a 5mm × 3mm DFN for Accurate Current Limit and Load Current Monitoring in Tight Spaces – Design Note 466 Vladimir Ostrerov Introduction Hot Swap controller fi ts easily onto boards operating in
In general, a Hot Swap™ controller provides two important the voltage range from 2.9V to 26.5V. A dedicated 12V functions to boards that can be plugged and unplugged version, LTC4217-12, is also available, which contains from a live backplane: preset 12V specifi c thresholds. Figure 1 shows how little space is required for a complete Hot Swap circuit.
• It limits the potentially destructive inrush current
when a board is plugged in. LTC4217 Features Figure 2 shows a simplifi ed block diagram of the LTC4217.
• It acts as a circuit breaker, with the maximum
The controller provides inrush current control and a 5%
current and maximum time at that current factored
accurate 2A current limit with foldback. For soft-start, an
into the breaker function.
internal current source charges the gate of the N-channel
Two of the components required to implement these MOSFET with 300V/s slew rate. Lower soft-start output functions, the power MOSFET and sense resistor, tend voltage slew rates can be set by adding an external gate to dominate the board real estate taken by the Hot Swap capacitor. circuit. The LTC®4217 saves space by combining these two
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks components with a Hot Swap controller in a 16-pin 5mm × of Linear Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.
3mm DFN package (or 20-lead TSSOP). This 2A integrated
SENSE
VIN VOUT
RESISTOR 7.5mΩ
VDD 25mΩ MOSFET OUT
+– GATE
IMON INTVCC
DN466 F01 CURRENT AMP
Figure 1. Tiny Integrated Controller
Package Results in a Small Footprint
OV MOSFET CONTROL
AND LOGIC
UV FLT
GND TIMER
DN466 F02
Figure 2. Simplifi ed Block Diagram of the LTC4217
Page Summary Contents For LINEAR Hot Swap Controller with Integrated MOSFETs and Sensing Resistors - 5mm x 3mm DFN for Accurate Current Limiting and Load Current Monitoring in Tight Spaces - Design Note 466
Manual Details
| Brand | Current |
|---|---|
| Pages | 2 |
| File Size | 88.11 KB |
| Published | May 28, 2026 |
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Frequently Asked Questions
What is the primary function of the LTC4217 Hot Swap controller?
It limits potentially destructive inrush current and acts as a circuit breaker with an accurate current limit.
Does the LTC4217 allow for external adjustment of its functions?
Yes, the active current limit voltage, load current monitoring, and soft-start time can be adjusted using external resistors or capacitors.
How does the device monitor the load current to an ADC?
A dedicated sense resistor produces a voltage signal that is proportional to the load current, which can be monitored by an ADC.
What happens if the MOSFET die temperature gets too high?
If the die temperature exceeds 145°C, the MOSFET is turned off and will attempt to re-engage when the temperature drops below 125°C.