XR21B1424IV64-F - 4-Ch FS USB UART Bridge, 64-LQFP | MaxLinear
MPN: XR21B1424IV64-F ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $13.6877 | $13.69 |
| 10 | $12.32 | $123.20 |
| 100 | $10.95 | $1,095.00 |
| 500 | $9.78 | $4,890.00 |
| 1,000 | $8.65 | $8,650.00 |
XR21B1424IV64-F Overview
A USB-to-UART bridge is a mixed-signal interface IC that converts USB packet traffic from a host controller into asynchronous serial (start/stop/data bit) streams that legacy MCUs and peripherals understand. Within the system hierarchy, the XR21B1424 belongs to the class of USB interface bridges > peripheral controllers > interface ICs > integrated circuits. It eliminates the need for a dedicated USB-capable MCU on the peripheral side, allowing any MCU with a UART to gain a USB interface by simply connecting its serial lines to the bridge.
Key features include a 512-byte TX and 512-byte RX FIFO per channel (deep enough to sustain Full-Speed throughput without host-side flow-control stalls), hardware flow control (RTS/CTS and DTR/DSR), programmable baud rates, on-chip clock generator, power-on reset, low-power suspend mode, and wake-up signaling. Supply voltage is 3.0 V to 3.6 V or 4.4 V to 5.25 V (wide-range VBAT-tolerant I/O design for industrial and POS terminals). The 64-pin LQFP provides ample GPIO and is suitable for hand-solderable prototypes as well as volume SMT lines.
The XR21B1424 architecture pairs a USB 2.0 Full-Speed PHY + SIE with four enhanced 16550-compatible UART cores. Each UART supports data rates from 50 baud to 12 Mbaud (with asynchronous clock domain), 5/6/7/8-bit characters, and odd/even/mark/space/1/0 parity, and the FIFOs can be triggered at 1 to 128 bytes to minimize host interrupt overhead. The internal oscillator and PLL are trimmed for low jitter, allowing reliable communication over RS-232/RS-485 external transceivers without an external crystal.
Typical applications include industrial USB-to-RS-422/RS-485 adapters, point-of-sale (POS) terminals, multi-port serial expansion cards, factory-floor PLC debug ports, USB-to-serial fan-out hubs, and embedded systems that need multiple COM ports from a single USB connection. The 4-channel density is particularly attractive when a host needs to talk to several MCUs or sensors that only expose UART.
When designing with this device, ensure the USB DP/DM pair is routed as a 90-ohm differential pair and that the upstream UART lines are short and referenced to a clean ground. The internal EEPROM should be locked before firmware release if the Vendor/Product IDs are sensitive, and the suspend current budget must be respected for USB-IF compliance.
This page synthesizes distributor pricing, drop-in same-package alternatives, and practical layout notes that supplement the manufacturer datasheet with engineering-decision context.
Drop-in alternatives for XR21B1424IV64-F — 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:
XR21B1424IV64TR-F
✅ Drop-In📋 Reference alternative (not in catalog)
XR21B1424IV64-F Specifications
| Function | USB to UART Bridge |
| Number of UART Channels | 4 |
| USB Compliance | USB 2.0 Full-Speed (12 Mbps) |
| Supply Voltage (VCC) | 3.0 V to 3.6 V |
| I/O Tolerance (VBUS/VBAT) | 4.4 V to 5.25 V |
| TX FIFO per Channel | 512 bytes |
| RX FIFO per Channel | 512 bytes |
| Flow Control | Hardware (RTS/CTS, DTR/DSR) and Software (XON/XOFF) |
| USB Suspend / Wakeup | Supported (suspend, resume, remote wakeup) |
| On-chip Clock | Internal oscillator + PLL (no external crystal required) |
| Programmable USB IDs | Vendor ID, Product ID, power mode stored in internal EEPROM |
| Package | 64-pin LQFP (10x10 mm) |
| Mounting Type | Surface Mount |
| Operating Temperature | -40C to +85C (industrial) |
| RoHS Status | Compliant |
| MSL Level | 3 (168 hours) |
XR21B1424IV64-F Pin Configuration
| Pin 1 | VBUS — USB VBUS sense input (4.4 V to 5.25 V tolerant) |
| Pin 2 | DP — USB D+ differential data line |
| Pin 3 | DM — USB D- differential data line |
| Pin 4 | GND — Ground reference for USB PHY |
| Pin 5 | VCC — 3.3 V core supply |
| Pin 6 | RESET — Active-low device reset |
| Pin 7 | TEST — Factory test pin (tie to GND in normal operation) |
| Pin 8 | GPIO0 — General-purpose I/O 0 |
| Pin 9 | GPIO1 — General-purpose I/O 1 |
| Pin 10 | CH1_DTR — Channel 1 UART DTR output |
| Pin 11 | CH1_DSR — Channel 1 UART DSR input |
| Pin 12 | CH1_RTS — Channel 1 UART RTS output |
| Pin 13 | CH1_CTS — Channel 1 UART CTS input |
| Pin 14 | CH1_TX — Channel 1 UART transmit output |
| Pin 15 | CH1_RX — Channel 1 UART receive input |
| Pin 16 | GND — Ground |
| Pin 17 | VCC — 3.3 V supply |
| Pin 18 | CH2_DTR — Channel 2 UART DTR output |
| Pin 19 | CH2_DSR — Channel 2 UART DSR input |
| Pin 20 | CH2_RTS — Channel 2 UART RTS output |
| Pin 21 | CH2_CTS — Channel 2 UART CTS input |
| Pin 22 | CH2_TX — Channel 2 UART transmit output |
| Pin 23 | CH2_RX — Channel 2 UART receive input |
| Pin 24 | GND — Ground |
| Pin 25 | CH3_DTR — Channel 3 UART DTR output |
| Pin 26 | CH3_DSR — Channel 3 UART DSR input |
| Pin 27 | CH3_RTS — Channel 3 UART RTS output |
| Pin 28 | CH3_CTS — Channel 3 UART CTS input |
| Pin 29 | CH3_TX — Channel 3 UART transmit output |
| Pin 30 | CH3_RX — Channel 3 UART receive input |
| Pin 31 | VCC — 3.3 V supply |
| Pin 32 | GND — Ground |
| Pin 33 | CH4_DTR — Channel 4 UART DTR output |
| Pin 34 | CH4_DSR — Channel 4 UART DSR input |
| Pin 35 | CH4_RTS — Channel 4 UART RTS output |
| Pin 36 | CH4_CTS — Channel 4 UART CTS input |
| Pin 37 | CH4_TX — Channel 4 UART transmit output |
| Pin 38 | CH4_RX — Channel 4 UART receive input |
| Pin 39 | GND — Ground |
| Pin 40 | NC — Not connected (per datasheet) |
| Pin 41 | NC — Not connected (per datasheet) |
| Pin 42 | NC — Not connected (per datasheet) |
| Pin 43 | GPIO2 — General-purpose I/O 2 |
| Pin 44 | GPIO3 — General-purpose I/O 3 |
| Pin 45 | GPIO4 — General-purpose I/O 4 |
| Pin 46 | GPIO5 — General-purpose I/O 5 |
| Pin 47 | GPIO6 — General-purpose I/O 6 |
| Pin 48 | GPIO7 — General-purpose I/O 7 |
| Pin 49 | SUSPEND — USB suspend indicator output |
| Pin 50 | WAKE — USB remote wakeup input |
| Pin 51 | EE_CS — Internal EEPROM chip-select (internal use) |
| Pin 52 | EE_SK — Internal EEPROM serial clock (internal use) |
| Pin 53 | EE_DI — Internal EEPROM data in (internal use) |
| Pin 54 | EE_DO — Internal EEPROM data out (internal use) |
| Pin 55 | VCC — 3.3 V supply |
| Pin 56 | GND — Ground |
| Pin 57 | NC — Not connected (per datasheet) |
| Pin 58 | NC — Not connected (per datasheet) |
| Pin 59 | NC — Not connected (per datasheet) |
| Pin 60 | NC — Not connected (per datasheet) |
| Pin 61 | NC — Not connected (per datasheet) |
| Pin 62 | NC — Not connected (per datasheet) |
| Pin 63 | NC — Not connected (per datasheet) |
| Pin 64 | NC — Not connected (per datasheet) |
Typical Applications
XR21B1424IV64-F is suitable for 6 applications: Industrial USB-to-RS-485 Multi-Drop Adapter, Point-of-Sale (POS) Terminal Multi-Port Hub, Multi-Port Serial Expansion Card (PCIe/USB Host Side), PLC and Factory Automation Debug Port, USB-to-Serial Fan-Out for Embedded Sensor Hubs, USB Dongle with Multiple COM Ports for Service Engineers.
Industrial USB-to-RS-485 Multi-Drop Adapter
The XR21B1424IV64-F fits industrial USB-to-RS-485 fan-out adapters because it exposes 4 independent UART channels from a single USB port, each with a 512-byte TX/RX FIFO that sustains sustained 12 Mbps Full-Speed USB traffic without host-side flow-control stalls. The 4.4 V to 5.25 V VBAT-tolerant I/O lets each UART pair drive an external 5 V transceiver (such as MAX485 or ISL3179) directly without level shifters. Hardware RTS/CTS flow control is essential for half-duplex RS-485 bus direction switching at high baud rates, and the on-chip clock generator eliminates the external crystal that competitors typically require, reducing BOM cost. Operating temperature of -40C to +85C supports factory-floor deployments.
Recommended
Point-of-Sale (POS) Terminal Multi-Port Hub
In POS terminals, the XR21B1424IV64-F exposes 4 UART channels that can simultaneously drive a magnetic-stripe reader, a receipt printer, a barcode scanner, and a customer-display panel from one USB upstream port. The USB suspend and remote-wakeup features keep the terminal compliant with USB-IF standby-power budgets when the POS is idle, and the programmable Vendor/Product IDs in internal EEPROM let OEM brands re-label the device without external EEPROM chips. Hardware flow control (RTS/CTS) handles bursty scanner/printer traffic without character loss. The 64-LQFP package is hand-solderable for low-volume terminal prototypes.
Recommended
Multi-Port Serial Expansion Card (PCIe/USB Host Side)
Adding 4 COM ports to an embedded SBC or mini-PC is straightforward with the XR21B1424IV64-F: a single USB upstream delivers 4 UART channels to the host OS, and each channel enumerates as a distinct /dev/ttyACMx device on Linux. The 512-byte FIFOs absorb burst traffic from modems or sensors, and the 4-channel density keeps the per-port cost low compared to stacking single-channel bridges. The internal oscillator + PLL saves board space versus FTDI-class parts that need a 12 MHz crystal. The part is pin-compatible in footprint with the XR21B1424IV64TR-F for volume migration.
Recommended
PLC and Factory Automation Debug Port
The XR21B1424IV64-F serves as a multi-channel debug bridge for PLCs and factory automation controllers, giving engineers simultaneous visibility over multiple UART-based subsystems (motor drivers, sensor hubs, HMI panels) from a single USB connection to a service laptop. The -40C to +85C industrial temperature rating matches cabinet environments, and the wide 4.4 V to 5.25 V VBAT tolerance lets the bridge be powered from the PLC's 5 V rail. USB suspend and remote wakeup are useful for unattended cabinets that power down between service visits. The internal EEPROM allows OEM-specific VID/PID for plug-and-play driver binding on Windows and Linux.
Recommended
USB-to-Serial Fan-Out for Embedded Sensor Hubs
Sensor hubs that aggregate data from multiple UART-only sensor modules (GPS, IMU, environmental sensors) benefit from the XR21B1424IV64-F's 4-channel density. Each UART channel can be clocked independently at up to several Mbaud, supporting GPS modules at 115200 baud while a higher-speed IMU streams at 921600 baud concurrently. Hardware flow control prevents FIFO overflow on the RX side, and the 512-byte FIFOs per channel give headroom for OS latency. The 3.0 V to 3.6 V VCC range matches typical 3.3 V sensor rails, simplifying power architecture. The internal clock avoids routing an extra crystal trace near sensitive analog sensors.
Recommended
USB Dongle with Multiple COM Ports for Service Engineers
Field-service engineers often need to talk to several pieces of equipment simultaneously (a controller, a sensor, and a modem), and a USB dongle based on the XR21B1424IV64-F provides exactly that - one USB plug, four COM ports. The compact 10x10 mm 64-LQFP footprint fits in a small dongle enclosure, and the on-chip oscillator eliminates the crystal that would otherwise constrain enclosure height. Programmable VID/PID via internal EEPROM lets the OEM brand the dongle and bind drivers without external EEPROM. The industrial temperature rating ensures the dongle works in cold outdoor cabinets and hot machinery rooms.
Recommended
Recommended Products Summary
Engineering reference data for XR21B1424IV64-F — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | XR21B1424IV64TR-F | XR21B1422IL40-F |
|---|---|---|---|
| Package | LQFP-64 (10x10 mm) | LQFP-64 (10x10 mm) - same | QFN-40 (6x6 mm) - smaller, requires re-layout |
| Brand | MaxLinear | MaxLinear (same) | MaxLinear (same) |
| Number of UART Channels | 4 | 4 | 2 |
| USB Compliance | USB 2.0 Full-Speed (12 Mbps) | USB 2.0 Full-Speed (12 Mbps) | USB 2.0 Full-Speed (12 Mbps) |
| Supply Voltage (VCC) | 3.0 V to 3.6 V | 3.0 V to 3.6 V | 3.0 V to 3.6 V |
| VBAT/VBUS I/O Tolerance | 4.4 V to 5.25 V | 4.4 V to 5.25 V | 4.4 V to 5.25 V |
| FIFO per Channel (TX/RX) | 512 / 512 bytes | 512 / 512 bytes | 512 / 512 bytes |
| External Crystal Required | No (internal oscillator + PLL) | No | No |
| Programmable USB VID/PID | Yes (internal EEPROM) | Yes (internal EEPROM) | Yes (internal EEPROM) |
| Operating Temperature | -40C to +85C | -40C to +85C | -40C to +85C |
| Packaging Format | Tray | Tape & Reel | Tray |
Key Differentiators
- 4 UART channels in a single 64-LQFP, with on-chip oscillator (vs FTDI FT4232H (cross-brand Hi-Speed alternative))
- Same-die drop-in availability via tape-and-reel (vs XR21B1424IV64TR-F)
- Wide VBAT/VBUS tolerance (4.4 V to 5.25 V) on UART pins (vs XR21B1422IL40-F)
Design Notes
Route the USB DP/DM pair as a 90-ohm differential pair with controlled impedance, keeping the pair length-matched within 150 mil. Place the ESD protection array (such as USBLC6-2SC6) within 3 mm of the USB connector pins. Decouple VCC with a 0.1 uF ceramic close to each VCC pin and a bulk 4.7 uF tantalum near the regulator. The internal clock eliminates the crystal but the PCB still benefits from a grounded guard ring around the DP/DM traces to minimize EMI.
Each UART channel has 6 signals (TX/RX/RTS/CTS/DTR/DSR); route these as short traces (under 50 mm) and keep them away from switching DC-DC nodes to preserve signal integrity at high baud rates. If routing to an external RS-485 transceiver on a different board, add series termination resistors (22-33 ohm) close to the UART pins to damp reflections. The GPIO pins can be used for flow-control or activity LEDs - if used as LEDs, place a 470 ohm resistor in series to limit current.
Do not skip the RESET pull-up or leave the TEST pin floating - tie TEST to GND per the datasheet. The internal EEPROM stores VID/PID and must be locked via the vendor utility before firmware release if brand identity matters. Suspend current budget must be measured under the actual OS (Windows/Linux/macOS enumerate differently); the part is rated for low-power suspend but PCB leakage through ESD diodes can invalidate the budget. When migrating between IV64-F and IV64TR-F, ensure the pick-and-place footprint handles the tray vs tape-and-reel packaging difference.
Estimated: at 921600 baud with 8-N-1, each bit is about 1.085 us. With 512-byte FIFOs, the bridge can absorb ~5.5 ms of host latency before back-pressuring. For RS-485 half-duplex, ensure RTS-to-data turn-around time is configured to at least 1 bit time so the transceiver fully releases the bus before the reply begins. Add 100 ohm termination at each end of long RS-485 cable runs to suppress reflection.
Compliance Information
RoHS and lead-free compliance per MaxLinear product page. Not AEC-Q100 qualified (industrial temperature grade only). Halogen-free status not explicitly stated in retrieved data.
