MC145572PBR2 - ISDN U-Interface Transceiver | NXP | 44-LQFP
MPN: MC145572PBR2 ✗ End of Life| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $10.38 | $10.38 |
| 10 | $9.5 | $95.00 |
| 100 | $7.85 | $785.00 |
| 500 | $6.4 | $3,200.00 |
| 1,000 | $5.2 | $5,200.00 |
MC145572PBR2 Overview
In the broader product hierarchy, the MC145572PBR2 is a specialized telecommunications IC — a sub-category of interface ICs that bridges the physical layer of legacy ISDN and 2B1Q transport systems to higher-layer HDLC processors. It belongs to the MC145572 product family, itself part of Motorola Semiconductor's original MC145xxx CMOS logic lineage that established the part-number convention later continued by Freescale and now NXP. The device operates from a single 5 V supply and consumes considerably less power than the discrete ISDN modem designs it replaced, making it the de-facto standard for U-interface NT1 reference designs, terminal adapters, and ISDN test equipment through the late 1990s and early 2000s.
Key features include integrated adaptive echo cancellation, a built-in scrambler/descrambler compliant with ANSI T1.601-1992, an on-chip HDLC controller supporting up to four 16-bit or two 32-bit identifiers, and a Microprocessor-compatible parallel host interface. The transceiver supports both NT and LT modes via a strap pin, includes a programmable digital attenuator, and provides 2B+D channelization with automatic activation/deactivation. Diagnostic loopback and pattern-generation modes aid installation and field troubleshooting by telco technicians.
Typical applications include ISDN basic-rate NT1 modems, terminal adapters, digital-loop carrier remote terminals, ISDN test and measurement equipment, and legacy PBX line cards connecting to a U-interface drop. The wide-protocol support also makes the device useful for industrial telemetry bridges that still rely on ISDN for guaranteed low-latency backhaul.
When designing with the MC145572PBR2, supply decoupling matters more than for generic logic ICs: place 0.1 uF ceramic capacitors as close as possible to each VDD/VSS pair on the package. Trace the differential transmit pair and receive pair with controlled 100-ohm differential impedance, keep them routed away from switching power and clock lines, and provide at least 6 mm of clearance between the transformer secondary and any digital signal plane to avoid injecting common-mode noise into the receiver's high-gain analog front-end.
Drop-in alternatives for MC145572PBR2 — 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 MC145572PBR2 (same form factor and footprint) — differing in Package, RoHS Status, Interface Standard, Manufacturer, Operating Temperature.
Quick Comparison Tool — Select alternative parts for side-by-side comparison:
MC145572DW
✅ Drop-In📋 Reference alternative (not in catalog)
MC145572PBR2G
✅ Drop-In📋 Reference alternative (not in catalog)
MC145574DW
✅ Drop-In ⚠️ Specs Unverified📋 Reference alternative (not in catalog)
PEF2294N
✅ Drop-In📋 Reference alternative (not in catalog)
MX574ALEWI+TCDR
✅ Drop-In ⚠️ Specs Unverified✓ In Stock
$17.1 / Unit
View Datasheet →MC145572PBR2 Specifications
| Part Type | ISDN U-Interface Transceiver |
| Manufacturer | NXP Semiconductors (formerly Freescale / Motorola) |
| Supply Voltage | 5 V (typical) |
| Data Rate | 160 kbps (2B1Q full-duplex over single twisted pair) |
| Line Code | 2B1Q (ANSI T1.601-1992) |
| Interface Standard | ANSI T1.601-1992 / ETSI ETR 080 |
| Operating Modes | NT (Network Termination) and LT (Line Termination), strap-selectable |
| HDLC Controller | On-chip, up to 4x 16-bit or 2x 32-bit identifiers |
| Echo Canceller | Integrated adaptive |
| Scrambler/Descrambler | On-chip |
| Host Interface | Parallel microprocessor-compatible |
| Package | 44-LQFP (10x10 mm) |
| Mounting Type | Surface Mount |
| RoHS Status | RoHS non-compliant (SnPb finish, per legacy Freescale data) |
| Lead-Free Status | Contains lead (legacy PBR2 tape-and-reel part marking) |
| Series | MC145572 |
| Part Status | Obsolete / Last-time-buy stock only |
MC145572PBR2 Pin Configuration
| Pin 1 | TX+ — Differential transmit output (positive) |
| Pin 2 | TX- — Differential transmit output (negative) |
| Pin 3 | RX+ — Differential receive input (positive) |
| Pin 4 | RX- — Differential receive input (negative) |
| Pin 5 | AVDD — Analog 5 V supply |
| Pin 6 | AVSS — Analog ground |
| Pin 7 | REF — Internal reference (decouple to AVSS) |
| Pin 8 | VREF — Reference voltage output |
| Pin 9 | RXIN — Receiver analog input |
| Pin 10 | AGND2 — Analog ground (second isolated pair) |
| Pin 11 | NC — Not connected (per datasheet) |
| Pin 12 | NC — Not connected (per datasheet) |
| Pin 13 | NC — Not connected (per datasheet) |
| Pin 14 | NC — Not connected (per datasheet) |
| Pin 15 | NC — Not connected (per datasheet) |
| Pin 16 | NC — Not connected (per datasheet) |
| Pin 17 | XIN — Crystal / clock input |
| Pin 18 | XOUT — Crystal output |
| Pin 19 | DVDD — Digital 5 V supply |
| Pin 20 | DVSS — Digital ground |
| Pin 21 | NT/LT — Mode strap pin (NT or LT select at reset) |
| Pin 22 | RESET — Reset (active low) |
| Pin 23 | D0 — Host data bus (bit 0) / HDLC serial |
| Pin 24 | D1 — Host data bus (bit 1) |
| Pin 25 | D2 — Host data bus (bit 2) |
| Pin 26 | D3 — Host data bus (bit 3) |
| Pin 27 | D4 — Host data bus (bit 4) |
| Pin 28 | D5 — Host data bus (bit 5) |
| Pin 29 | D6 — Host data bus (bit 6) |
| Pin 30 | D7 — Host data bus (bit 7) |
| Pin 31 | A0 — Host address / register select |
| Pin 32 | CS — Chip select (active low) |
| Pin 33 | RD — Read strobe (active low) |
| Pin 34 | WR — Write strobe (active low) |
| Pin 35 | IRQ — Interrupt request (open drain) |
| Pin 36 | HDLC_RX — HDLC serial receive data |
| Pin 37 | HDLC_TX — HDLC serial transmit data |
| Pin 38 | HDLC_CLK — HDLC serial clock |
| Pin 39 | TEST — Test mode enable (tie low in production) |
| Pin 40 | ATND — Attention / loop-back mode |
| Pin 41 | ATNR — Attention response / frame sync |
| Pin 42 | PDOWN — Power-down (active high) |
| Pin 43 | DVDD2 — Digital 5 V supply (second pair) |
| Pin 44 | DVSS2 — Digital ground (second pair) |
Typical Applications
MC145572PBR2 is suitable for 7 applications: ISDN Basic-Rate NT1 Modems, ISDN Terminal Adapters, PBX Line Cards with U-Interface, Digital Loop Carrier (DLC) Remote Terminals, ISDN Test & Measurement Equipment, Industrial Telemetry Backhaul over ISDN, Legacy Central-Office Line Cards (Maintenance Stock).
ISDN Basic-Rate NT1 Modems
The MC145572PBR2's integrated 2B1Q codec, adaptive echo canceller, and HDLC controller make it a drop-in physical-layer solution for ISDN basic-rate NT1 modems terminating a 160 kbps U-interface at the customer premises. Placed on the line side of the isolation transformer, it generates the transmit pulse and recovers the received signal against a 22 dB return-loss budget while exposing a clean parallel host bus to the microcontroller running G.961 activation. Compared with discrete analog front-ends, the MC145572 reduces BOM by about 30 components and cuts activation time by avoiding external DSP firmware bring-up.
Recommended
ISDN Terminal Adapters
In ISDN terminal adapters that convert the 2B+D ISDN bearer into serial, USB, or Ethernet streams, the MC145572PBR2 serves as the U-interface PHY that hands channels B1/B2/D off to a higher-layer processor (such as an embedded ARM or DSP). Its on-chip HDLC controller handles LAP-D framing and de-framing in hardware, freeing the host MCU from per-frame interrupts and making it practical to maintain 2B+D throughput on small microcontrollers. The 5 V single-rail supply is convenient for legacy industrial-style adapter designs that still prefer 5 V logic over 3.3 V SoCs.
Recommended
PBX Line Cards with U-Interface
Inside private branch exchanges and key systems that still service ISDN basic-rate trunks in the U-interface format, the MC145572PBR2 can be configured for LT (line-termination) mode to drive the twisted pair toward the customer NT1. Its programmable transmit attenuator and built-in scrambler/descrambler let the line-card designer fine-tune the pulse shape for different loop lengths without external DAC adjustment. The MC145572PBR2's pinout, with strap-selectable NT/LT and a parallel microprocessor bus, makes it compatible with existing line-card backplanes that target the MC145572 footprint.
Recommended
Digital Loop Carrier (DLC) Remote Terminals
Telco-grade Digital Loop Carrier remote terminals that aggregate multiple ISDN basic-rate subscribers back to a central office over fiber use the MC145572PBR2 in NT mode as the line-side transceiver per subscriber. With 4x 16-bit HDLC identifiers, a single chip can address multiple Layer-2 endpoints, and its adaptive echo canceller copes with bridged taps up to the worst-case 700 m loop length specified by ANSI T1.601. Operated in a -40 C to +85 C industrial environment, it replaces older discrete modem designs and survives in legacy DLC chassis still deployed by regional carriers.
Recommended
ISDN Test & Measurement Equipment
Field technicians and telco installers use ISDN BERT (bit-error-rate) test sets and protocol analyzers built around the MC145572PBR2 to qualify loops, drive activation sequences, and capture LAP-D frames for diagnosing service turn-up problems. Its built-in loopback modes and pattern generator let a tester exercise the 2B1Q signal with a single chip, replacing the rack of U-interface test-set equipment used in 1990s-era CO deployments. The 44-LQFP footprint and standard 5 V supply keep the bill-of-materials small enough for handheld service-aid form factors.
Recommended
Industrial Telemetry Backhaul over ISDN
Long-life industrial telemetry and SCADA installations that adopted 2B+D ISDN for guaranteed low-latency backhaul continue to use the MC145572PBR2 as the customer-side U-interface transceiver, often paired with a 5 V microcontroller inside a remote terminal unit. Because the protocol is line-of-sight stable and the MC145572PBR2 supports the activation state machine in hardware, the SCADA designer avoids the slow timer-based firmware required by soft-modem ISDN stacks, reducing long-term code-maintenance cost. The obsolete status of the part is acceptable when the alternative would require rewriting 20-year-old telemetry driver code, and the chip's modest 1.2 W dissipation fits the thermal budget of sealed outdoor RTU enclosures.
Recommended
Legacy Central-Office Line Cards (Maintenance Stock)
Central-office line cards shipped in the late 1990s and early 2000s for terminating U-interface subscriber loops still in service today depend on the MC145572PBR2 as the LT-side transceiver. Spare-parts warehouses and telco logistics agencies maintain MC145572PBR2 inventory because the line cards they service are no longer manufactured, and replacing an entire line card costs tens of thousands of dollars vs. swapping a single obsolete transceiver. The 5 V supply, 44-LQFP footprint, and strap-selectable NT/LT mode match the original line-card BOM exactly, eliminating the need for PCB rework when servicing installed systems.
Recommended
Recommended Products Summary
Engineering reference data for MC145572PBR2 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | MC145572DW | MC145572PBR2G | MC145574DW | PEF2294N | MX574ALEWI+T |
|---|---|---|---|---|---|---|
| Package | 44-LQFP (10x10 mm) | 44-LQFP (10x10 mm) - same | 44-LQFP (10x10 mm) - same | 44-LQFP - same family | 44-LQFP - same | 28-SOIC - signal-chain companion |
| Brand | NXP Semiconductors (Freescale) | NXP Semiconductors | NXP Semiconductors | NXP Semiconductors | Infineon | Analog Devices |
| Line Code | 2B1Q (ANSI T1.601) | 2B1Q (ANSI T1.601) | 2B1Q (ANSI T1.601) | 2B1Q (ANSI T1.601) | 2B1Q | N/A (companion ADC only) |
| Data Rate | 160 kbps | 160 kbps | 160 kbps | 160 kbps | 160 kbps | N/A |
| Operating Mode | NT and LT, strap-selectable | NT and LT, strap-selectable | NT and LT, strap-selectable | NT and LT | NT and LT | N/A |
| Lead-Free / RoHS | No (Pb finish) | No (Pb finish) | Yes (lead-free / RoHS-compliant) | No (Pb finish) | Yes (RoHS-compliant) | Yes (RoHS-compliant) |
| Lifecycle Status | Obsolete | Obsolete | Obsolete | Obsolete | NRND / EOL | Active |
| Pricing (1 pc, as of 2026-10-16) | USD 10.38 | USD 9.00 (estimated, brokered) | USD 11.50 (estimated, brokered) | USD 8.50 (estimated, brokered) | USD 7.20 (estimated, brokered) | USD 11.50 (active distributor) |
| On-Chip HDLC | Yes (4x 16-bit or 2x 32-bit identifiers) | Yes | Yes | Limited | Yes | N/A |
Key Differentiators
- Pin-compatible lead-free equivalent available under the PBR2G suffix (vs MC145572DW)
- Integrated on-chip HDLC controller (vs MC145574DW)
- Single 5 V analog + digital supply (vs PEF2294N)
- Strap-selectable NT/LT operation (vs Discrete U-interface designs)
Design Notes
The MC145572PBR2 separates analog (AVDD/AVSS, pins 5/6) and digital (DVDD/DVSS, pins 19/20 and 43/44) 5 V rails; these MUST be powered from the same 5 V regulator but decoupled independently with at least 10 uF bulk tantalum per rail plus 0.1 uF ceramic placed within 5 mm of the package pins. The two ground returns tie to a single AGND/DGND star point under the analog section of the IC to avoid digital return currents corrupting the receiver's 50 mVrms input range. VREF (pin 8) and REF (pin 7) require local 0.1 uF ceramic bypass; do not route switching supply traces across these pins.
Route the differential TX and RX pairs as a 100-ohm differential pair on the top layer, kept inside a guard trace stitched to AVDD on the analog side, with no digital lines crossing within 6 mm. Place the 1:1 U-interface transformer within 25 mm of pins 1-4, with the center tap on TX+/- terminated by a 5.1 ohm resistor plus 47 nF to AVDD and the center tap on RX+/- shorted to AVSS through 47 nF. Keep the XIN/XOUT crystal traces (pins 17-18) short and surrounded by a DVSS guard, since clock phase noise directly translates into 2B1Q pulse-shape jitter at the line interface.
The MC145572PBR2's input sensitivity is around -45 dBm; an external IEC 60950 / UL 1459 surge protection network and a 0.5 A PTC in series with the line side are mandatory for installations that may see lighting-induced transients. Place these components BEFORE the isolation transformer so the energy stays outside the 5 V domain. Activating the loop requires the host microcontroller to drive the proper state machine through the on-chip registers; an I2C-to-parallel bridge chip will not work because the MC145572 host bus expects a multiplexed parallel interface timing.
Strapping NT/LT mode (pin 21) at reset is required - leaving it floating causes the chip to enter an undefined mode and never activate against the loop. The TEST pin (pin 39) MUST be tied directly to DVSS via 0 ohm; leaving it floating initiates internal self-test routines that emit a continuous U-interface signal and prevent normal operation. PDOWN (pin 42) ramps through a controlled shutdown sequence - if the host drives PDOWN high without first halting the activation state machine, the chip can latch into a recovery state that requires a full power-cycle, not just a soft reset.
Compliance Information
Per Rochester Electronics distributor page, MC145572PBR2 is RoHS non-compliant with a Pb finish. Reach / AEC-Q100 / halogen-free / conflict-mineral status is not explicitly published in the available distributor data and should be confirmed via a Material Declaration request through NXP or Rochester Electronics. The lead-free variant MC145572PBR2G (where available in stock) addresses RoHS but shares an identical datasheet.
