XR21B1420IL28-F - 1-Ch USB 2.0 FS UART Bridge, 28-QFN | MaxLinear
MPN: XR21B1420IL28-F ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $3.42 | $3.42 |
| 10 | $3.05 | $30.50 |
| 100 | $2.58 | $258.00 |
| 500 | $2.21 | $1,105.00 |
| 1,000 | $1.94 | $1,940.00 |
XR21B1420IL28-F Overview
A UART (Universal Asynchronous Receiver/Transmitter) is a hardware block that converts parallel data into asynchronous serial frames and vice versa. A USB-to-UART bridge adds a USB device controller on one side so a host MCU or PC can communicate with a legacy UART peripheral using only a USB cable; this eliminates legacy RS-232 transceivers and simplifies cabling in industrial, point-of-sale, and embedded designs.
The XR21B1420 supports the full USB 2.0 Full-Speed data rate of 12 Mbps, suspend/resume/remote-wakeup signaling, and programmable USB Vendor ID, Product ID, and power descriptors. The UART side offers 5, 6, 7, or 8 data bits, configurable baud rates via the MaxLinear configuration utility, hardware and Xon/Xoff flow control, and GPIO pins mapped to modem-control signals. The integrated 512-byte TX/RX FIFO per channel reduces host CPU overhead by allowing burst transfers without byte-level servicing.
Typical applications include industrial USB-to-RS232/RS422/RS485 adapters, point-of-sale terminals, barcode scanners, GPS modules, embedded debug consoles, and any MCU/MPU that requires a USB device port without an on-chip USB controller. The wide industrial temperature range (-40C to +85C) and small 5x5 mm QFN footprint allow placement in compact, thermally-constrained enclosures.
When designing with this part, place the 12 MHz crystal or external clock source within 5 mm of the XI/XO pins and keep the D+/D- traces as a 90-ohm differential pair routed directly to the USB connector. Use the internal LDO for 5V-only supplies, but bypass the internal regulator when a clean external 3.3V rail is available to reduce internal power dissipation.
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes that the manufacturer datasheet does not present in a single view.
Drop-in alternatives for XR21B1420IL28-F — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with XR21B1420IL28-F (same form factor and footprint) — differing in Operating Temperature, Supply Voltage, Package, Protocol.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
XR21B1420IL28TR-F
✅ Drop-In📋 Reference alternative (not in catalog)
XR21B1421IL28-F
✅ Drop-In✓ In Stock
$4.35 / Unit
View Datasheet →XR21B1422IL28-F
✅ Drop-In📋 Reference alternative (not in catalog)
XR21B1420IL28-F Specifications
| Product Type | USB-to-UART Bridge Controller |
| Channels | 1 |
| USB Specification | USB 2.0 Full-Speed (12 Mbps) |
| FIFO Size | 512 byte TX / 512 byte RX |
| UART Data Bits | 5, 6, 7, or 8 bits |
| Supply Voltage | 3.3 V or 5 V single supply (internal 3.3 V LDO) |
| Operating Temperature | -40 C to +85 C (Industrial) |
| Package | 28-QFN (5x5 mm) |
| USB Suspend / Resume / Remote Wakeup | Supported |
| Modem-Control Pins (RTS/CTS/DTR/DSR/DCD/RI) | Yes |
| Flow Control | Hardware (RTS/CTS) and Xon/Xoff |
| Programmable USB VID/PID | Yes |
| Mounting Type | Surface Mount |
| RoHS Status | Compliant |
XR21B1420IL28-F Pin Configuration
| Pin 1 | VDD33 — 3.3V LDO output / 3.3V supply input |
| Pin 2 | GND — Ground |
| Pin 3 | VBUS — USB VBUS detect input |
| Pin 4 | D- — USB D- differential data line |
| Pin 5 | D+ — USB D+ differential data line |
| Pin 6 | XI — 12 MHz crystal input |
| Pin 7 | XO — 12 MHz crystal output |
| Pin 8 | GND — Ground |
| Pin 9 | RST — Active-low reset input |
| Pin 10 | TXD — UART transmit data output |
| Pin 11 | RXD — UART receive data input |
| Pin 12 | RTS — UART request-to-send output |
| Pin 13 | CTS — UART clear-to-send input |
| Pin 14 | DTR — UART data-terminal-ready output |
| Pin 15 | DSR — UART data-set-ready input |
| Pin 16 | DCD — UART data-carrier-detect input |
| Pin 17 | RI — UART ring-indicator input |
| Pin 18 | GPIO0 — General-purpose I/O 0 |
| Pin 19 | GPIO1 — General-purpose I/O 1 |
| Pin 20 | GPIO2 — General-purpose I/O 2 |
| Pin 21 | GPIO3 — General-purpose I/O 3 |
| Pin 22 | SUSPEND — USB suspend state output |
| Pin 23 | WAKEUP — USB remote wakeup input |
| Pin 24 | TEST — Factory test pin (tie low in production) |
| Pin 25 | NC — Not connected (per datasheet) |
| Pin 26 | NC — Not connected (per datasheet) |
| Pin 27 | VCC — Main 3.3V or 5V supply input |
| Pin 28 | EP — Exposed thermal pad - tie to GND |
Typical Applications
XR21B1420IL28-F is suitable for 6 applications: Industrial USB-to-RS232 Adapter, Point-of-Sale (POS) Terminal Connectivity, Barcode Scanner USB Interface, GPS Module USB Debug Console, Embedded Debug Console for MCUs, USB-to-RS422/RS485 Industrial Bridge.
Industrial USB-to-RS232 Adapter
The XR21B1420IL28-F is a strong match for industrial USB-to-RS232 adapters because it integrates a USB 2.0 Full-Speed PHY, full modem-control signals (RTS/CTS/DTR/DSR/DCD/RI), and a 512-byte FIFO per direction that offloads the host MCU. The -40C to +85C industrial temperature rating enables deployment in factory cabinets and outdoor enclosures. A typical design powers the chip from 5V through its internal regulator, eliminating the need for an external 3.3V LDO and reducing BOM cost by roughly $0.10-$0.20 per adapter.
Recommended
Point-of-Sale (POS) Terminal Connectivity
POS terminals require reliable USB connectivity to cash drawers, barcode scanners, and customer displays, and the XR21B1420IL28-F provides a single-chip bridge between a USB host port and any legacy UART peripheral. The 12 Mbps USB Full-Speed data rate is more than sufficient for barcode data streams, magnetic-stripe readers, and printer handshakes, while the integrated 3.3V LDO simplifies the power tree in slim POS enclosures. The small 5x5 mm QFN footprint leaves room for additional USB ports on the same PCB.
Recommended
Barcode Scanner USB Interface
Handheld and fixed-mount barcode scanners typically expose a TTL UART to their host PCB and require USB device connectivity, which is exactly the role the XR21B1420IL28-F is designed for. The 512-byte TX/RX FIFOs absorb burst scans of up to several KB without dropping characters, while hardware RTS/CTS flow control prevents overruns when the scanner reads 1D/2D codes at high scan rates. The industrial temperature range supports freezer-cooler and outdoor scanning environments.
Recommended
GPS Module USB Debug Console
GPS receiver modules and telematics hardware commonly expose an NMEA-0183 stream over a 3.3V TTL UART, and the XR21B1420IL28-F bridges that stream to a host computer over USB without an external transceiver. The internal 3.3V LDO can power the GPS module directly when the system runs on 5V, eliminating a separate regulator. NMEA streams at 115200 baud with periodic bursts require only a few bytes of FIFO, but the deeper FIFOs prevent loss during host CPU interrupts.
Recommended
Embedded Debug Console for MCUs
Many ARM Cortex-M and RISC-V development boards expose a debug console through a UART, and the XR21B1420IL28-F provides a USB-to-UART bridge with industrial temperature support for evaluation and production boards. The VBUS-present detection pin allows the host MCU to detect USB connection state without additional glue logic. The QFN-28 footprint is small enough to fit alongside QFP-48 and QFP-64 MCU targets on a 4-layer debug board.
Recommended
USB-to-RS422/RS485 Industrial Bridge
When paired with an external RS-422/RS-485 line transceiver, the XR21B1420IL28-F becomes a USB-to-industrial-bus bridge suitable for factory automation, building-automation, and BMS networks. The modem-control signals drive driver-enable lines for half-duplex RS-485 with direction turnaround in microseconds, and the industrial temperature rating allows deployment in unheated control cabinets. The 12 Mbps USB Full-Speed rate is the bottleneck for multi-drop RS-485 baud rates above 1 Mbps.
Recommended
Recommended Products Summary
Engineering reference data for XR21B1420IL28-F — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | XR21B1420IL28TR-F | XR21B1421IL28-F | XR21B1422IL28-F |
|---|---|---|---|---|
| Brand | MaxLinear | MaxLinear | MaxLinear | MaxLinear |
| Package | 28-QFN (5x5 mm) | 28-QFN (5x5 mm) - same | 28-QFN (5x5 mm) - same | 28-QFN (5x5 mm) - same |
| USB Specification | USB 2.0 Full-Speed (12 Mbps) | USB 2.0 Full-Speed (12 Mbps) | USB 2.0 Full-Speed (12 Mbps) | USB 2.0 Full-Speed (12 Mbps) |
| FIFO Size (TX/RX) | 512 B / 512 B | 512 B / 512 B | 512 B / 512 B | 512 B / 512 B |
| UART Data Bits | 5, 6, 7, or 8 bits | 5, 6, 7, or 8 bits | 5, 6, 7, or 8 bits | 5, 6, 7, or 8 bits |
| Operating Temperature | -40C to +85C | -40C to +85C | -40C to +85C | -40C to +85C |
| USB Charger Detection | No | No | Yes | Yes |
| GPIO Count | 4 | 4 | 8 | 8 |
Key Differentiators
- Larger 512-byte TX/RX FIFOs compared to legacy FT232RL-class bridges (vs FT232RL)
- Integrated 3.3V LDO enables single 5V supply operation (vs CP2102N)
- Industrial -40C to +85C operating temperature (vs CP2102N)
Design Notes
Route the USB D+ and D- traces as a 90-ohm differential pair with continuous ground reference directly to the USB connector. Keep the pair length matched to within 2 mm and avoid routing near switching power or RF traces to preserve USB 2.0 Full-Speed signal integrity. Place the 12 MHz crystal or external clock source within 5 mm of the XI and XO pins, and guard the traces with a ground pour to minimize EMI pickup.
When powering from a single 5V rail, the integrated 3.3V LDO automatically generates the USB PHY rail; no external 3.3V regulator is required. Add a 1 uF X7R bypass capacitor on VDD33 close to the IC and a 10 uF bulk capacitor on VCC for USB inrush transients. When a clean external 3.3V rail is available, route it directly to VDD33 to bypass the internal regulator and reduce on-chip power dissipation at high VBUS current draw.
Do not leave the TEST pin floating; tie TEST low in production to disable the factory test mode. Verify that USB D+/D- traces do not cross over plane splits, which can cause impedance discontinuities and fail USB compliance. Ensure the host-side driver stack supports the programmable VID/PID configuration, since custom VID/PID values may not match default OS drivers without an INF file or driver package.
Compliance Information
RoHS compliance confirmed via MaxLinear product page; AEC-Q100 not applicable for non-automotive commercial/industrial interface ICs. Halogen-free status not explicitly stated in the verified data.
