TPS2421-1DDAR - 5A 20V Hot Swap Controller | Texas Instruments
MPN: TPS2421-1DDAR ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $0.84 | $0.84 |
| 10 | $0.78 | $7.80 |
| 100 | $0.69 | $69.00 |
| 500 | $0.61 | $305.00 |
| 1,000 | $0.55 | $550.00 |
| 3,000 | $0.48 | $1,440.00 |
TPS2421-1DDAR Overview
A hot-swap controller is a power-management IC that inserts between a backplane supply and a removable or inrush-sensitive load, replacing the legacy practice of fusing the rail. The controller manages the inrush transient (created when the load's bulk capacitors charge), provides fault isolation (so a short on one card does not collapse the entire bus), and offers programmability via simple external resistors and capacitors. The TPS2421 family sits inside the broader taxonomy of eFuse / hot-swap / load-switch ICs, which are themselves a sub-category of power-management semiconductors that combine power MOSFETs with supervisory analog.
Key features of the TPS2421-1DDAR include an integrated 33 mOhm pass MOSFET rated for 1.8 A to 5.5 A of adjustable load current, a programmable hard current limit, a programmable fault timer for transient filtering, and a non-current-limiting fault threshold for hard overcurrent response. Active-high enable input, fault-output flag, and thermal shutdown are also integrated, and the PowerPad exposed die pad gives a low theta-JA for heat removal in tight layouts.
Internally, the device uses a current-sense FET topology with an internal charge pump to drive the N-channel MOSFET, paired with two comparators - one for the adjustable fault timer and one for hard current limit. The architecture trades some accuracy for integration, but in return delivers a parts-count of 3 to 4 external components (timer cap, IMON resistor, IMON-FLT resistor divider), far less than a discrete hot-swap design. The PowerPad package enables the 5 A continuous current without raising junction temperature beyond safe limits.
Typical applications include RAID/HDD hot-plug bays, server and telecom line cards, industrial 12 V / 24 V distributed-bus loads, and USB-PD / eFuse roles where the 20 V upper rating easily covers 20 V USB-PD Source voltages. Designers also use it as a smart replacement for inline fuses and PTCs in space-constrained boards.
When designing with the TPS2421-1DDAR, always populate the PowerPad with a thermal via array to a ground copper pour. Use Kelvin connection on the load-current sense resistor to avoid IR drop corruption, and choose the fault capacitor with dielectric matching to the chosen fault time.
This page synthesises distributor pricing, drop-in alternatives, and practical design notes that supplement the manufacturer datasheet.
Drop-in alternatives for TPS2421-1DDAR — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
TPS2421-2DDA
✅ Drop-In📋 Reference alternative (not in catalog)
TPS2421-1DDA
✅ Drop-In📋 Reference alternative (not in catalog)
TPS2420-1DDA
✅ Drop-In📋 Reference alternative (not in catalog)
TPS2413DR
✅ Drop-In📋 Reference alternative (not in catalog)
TPS2421-1DDAR Specifications
| Function | Hot Swap Controller with Integrated MOSFET (eFuse) |
| Number of Channels | 1 |
| Supply Voltage Range | 3 V to 20 V |
| Nominal Supply Voltage | 3.3 V |
| Maximum Load Current | 5.5 A (programmable 1.8 A to 5.5 A) |
| Integrated Pass MOSFET RDS(on) | 33 mOhm |
| UVLO Turn-on Threshold (max) | 2.9 V |
| Current Limit Type | Programmable hard current limit + fault timer |
| Fault Response | Latched off (auto or retry depending on variant) |
| Enable Input | Active-high |
| Fault Output | Open-drain FLT flag |
| Operating Temperature | -40C to +85C |
| Package | 8-SO PowerPad (DDA / SO PowerPAD-8) |
| Mounting Type | Surface Mount |
| MSL Level | 2 (1 year floor life) |
| RoHS Status | Compliant |
TPS2421-1DDAR Pin Configuration
| Pin 1 | EN — Enable, active-high |
| Pin 2 | CT — Fault-timer capacitor |
| Pin 3 | IMON — Current-monitor / current-limit set |
| Pin 4 | FLT — Open-drain fault output |
| Pin 5 | GND — Ground |
| Pin 6 | IN — Supply input (3 V to 20 V) |
| Pin 7 | OUT — Output (to load) |
| Pin 8 | PGND — Power ground / PowerPad |
Typical Applications
TPS2421-1DDAR is suitable for 6 applications: RAID and Hot-Plug HDD Backplane, Server and Telecom Line-Card Insertion, USB-PD 20 V Source eFuse, Industrial 24 V Distributed Bus Loads, PoE Powered-Device Input Protection, Solid-State Drive and NVMe Hot-Swap.
RAID and Hot-Plug HDD Backplane
The TPS2421-1DDAR fits hotswap bays because its 33 mOhm integrated FET and 5.5 A adjustable current limit directly absorb the inrush of HDD bulk capacitance at insertion. Placed on each drive bay, it isolates a failing drive from the backplane supply, with FLT-flag raised to the BMC. Designers select the fault-time capacitor to filter normal spin-up inrush (typically 100ms) yet still latch on a sustained short.
Recommended
Server and Telecom Line-Card Insertion
On AdvancedTCA, ATX, and proprietary 12 V / 18 V line cards the TPS2421-1DDAR manages the inrush of bulk DC-link capacitors while providing per-card fault isolation. Its 2.9 V maximum UVLO turn-on prevents false restart during a sagging 12 V rail, and the latch-off behavior keeps a shorted card disconnected until operator service. With the PowerPad tied to a 1-square-inch copper pour, the 33 mOhm FET can deliver 5 A continuously under 12 V supply.
Recommended
USB-PD 20 V Source eFuse
TPS2421-1DDAR's 3 V to 20 V supply range maps exactly onto USB-PD fixed voltages 5 V / 9 V / 15 V / 20 V without rail-switching hardware. As a load-side eFuse it absorbs VBUS hot-plug transients, while the integrated current limit can be set to 5 A for a 100 W Source. Designers choose the fault time to allow the 100 W inrush envelope defined by USB-PD while still protecting against pin shorts. For 5 V-only Type-C sources the companion TPS2420-1 may be more cost-effective.
Recommended
Industrial 24 V Distributed Bus Loads
The 20 V upper rating suits most 12 V and 18 V industrial bus rails, and with an upstream pre-regulator the TPS2421-1DDAR can drop into 24 V systems as well. It protects PLC cards, sensor hubs, and motor-driver boards from wiring shorts, while the integrated 33 mOhm FET keeps conduction loss modest (< 1 percent efficiency hit at full load). The exposed PowerPad allows direct PCB mounting without an external heatsink in fan-cooled cabinets.
Recommended
PoE Powered-Device Input Protection
PoE Powered Devices often experience hot-plug events as the PSE applies 48 V (or 54 V) to the cable, and the TPS2421-1DDAR can serve as a downstream post-OR-ing protective switch for sub-20 V rails. The 5.5 A limit suits Class 4 PoE+ at full current, and the adjustable fault timer filters the bulk-capacitor inrush on the PD input. Designers add upstream TVS for the >20 V PoE surge transients.
Recommended
Solid-State Drive and NVMe Hot-Swap
Enterprise NVMe SSDs draw high inrush when hot-added to an M.2 / U.2 backplane, and the TPS2421-1DDAR's 33 mOhm FET and programmable fault timer make it well-suited for per-drive protection. With the fault time set in the 50 ms range it filters the SSD power-on current spike yet still trips on a sustained pin short. The 8-pin SO PowerPad keeps board real-estate low even in dense 2.5-inch backplanes.
Recommended
Recommended Products Summary
Engineering reference data for TPS2421-1DDAR — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | TPS2421-2DDA | TPS2421-1DDA | TPS2420-1DDA | TPS2413DR |
|---|---|---|---|---|---|
| Package | 8-SO PowerPad (DDA) | 8-SO PowerPad (DDA) - same | 8-SO PowerPad (DDA) - same | 8-SO PowerPad (DDA) - same | 8-SO PowerPad (DDA family) - same |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Supply Voltage Range | 3 V to 20 V | 3 V to 20 V | 3 V to 20 V | 3 V to 20 V | 3 V to 8 V |
| Integrated FET RDS(on) | 33 mOhm | 33 mOhm | 33 mOhm | 33 mOhm | External FET |
| Maximum Current | 5.5 A | 5.5 A | 5.5 A | 5 A | External FET limited |
| Fault Behavior | Latched off | Auto-retry | Latched off | Latched off | OR-ing controller |
| UVLO Turn-on (max) | 2.9 V | 2.9 V | 2.9 V | 2.9 V | 1.5 V |
| Operating Temperature | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
| Function | Hot-swap / eFuse | Hot-swap / eFuse | Hot-swap / eFuse | Hot-swap / eFuse | OR-ing controller |
Key Differentiators
- Integrated 33 mOhm pass FET with 5.5 A capability (vs TPS2413DR)
- Latch-off fault response vs auto-retry (vs TPS2421-2DDA)
- 3 V to 20 V supply range covers standard bus voltages (vs TPS2420-1DDA)
Design Notes
Estimated: at the rated 5.5 A and an RDS(on) of 33 mOhm, the integrated pass MOSFET dissipates approximately 0.83 W (5.5^2 x 0.033). With the SO PowerPad soldered to 1 square inch of 1 oz copper (theta-JA approximately 40 C/W), the junction-to-ambient rise is roughly 33 C - acceptable below 4 W dissipation but requiring a heatsink at full 5.5 A in enclosed enclosures. Add an array of thermal vias under the PowerPad to a bottom-layer ground copper pour to reduce thermal resistance further.
Use a Kelvin connection for the IMON resistor: route the high-current OUT pin through the resistor body to the load, and tap the resistor sense pads on the package side instead of the load side. This eliminates the load-current IR drop from corrupting the IMON signal. Place the CT capacitor (typically 100 nF C0G/NP0) and IMON resistor as close to the IC pins as possible, returning to a clean analog ground separate from the noisy PGND.
Do not exceed the absolute maximum of 22 V on IN, including transient spikes - add a TVS clamp (e.g. SMBJ22A) on the input. Do not allow the OUT pin to exceed IN by more than 0.7 V; reverse polarity events on the load side require an additional blocking diode. The fault-timer capacitor should be C0G/NP0 ceramic or film-type - X7R/X5R dielectric drift will degrade the fault timing accuracy at temperature.
Tie the PowerPad (pin 8) directly to a large ground copper pour with thermal vias on a 1.0 mm pitch. Route the high-current OUT trace on the top layer to minimise parasitic inductance. Reference the TI TPS2421-1 datasheet EVM layout for a reference design with proven thermal performance.
Compliance Information
Industrial-grade part per TI product page. AEC-Q100 automotive variants are available in the TPS2421-Q1 family.
