PM5991B-FEI - DIGI-G4 OTN Processor (No Encryption) | Microchip
MPN: PM5991B-FEI ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $179.32 | $179.32 |
| 10 | $165.5 | $1,655.00 |
| 100 | $148 | $14,800.00 |
| 250 | $134.5 | $33,625.00 |
| 500 | $122.8 | $61,400.00 |
PM5991B-FEI Overview
An OTN processor is a specialized Application-Specific Integrated Circuit (ASIC) that performs the digital-layer functions of an optical transport network, including ODU/OTU frame mapping, multiplexing, switching, and forward-error-correction (FEC) processing. Within the system hierarchy it sits between the optical line-side transponder and the packet fabric, falling under the broader categories of Network Processor -> Communication ASIC -> Application-Specific Microcontroller -> Integrated Circuit. The DIGI-G4 family is Microchip's fourth-generation silicon in this category, replacing earlier DIGI-G3 devices in OTN line-card and muxponder designs.
Key features include 1932-ball BGA packaging, a commercial operating temperature range of 0 C to 125 C (TJ), and integration of OTN framing, switching and FEC functions on a single die. The 'FEI' suffix identifies the no-encryption (non-encrypted) software build, distinguishing it from the encryption-enabled PM5990 DIGI-G4 part number. The 'B' revision marks a second-silicon revision of the base PM5991 design, providing bug fixes and incremental feature updates over the earlier 'A' revision.
The PM5991B-FEI is engineered to deliver deterministic OTN switching throughput with hardware-accelerated ODUflex, ODUFlexE, and packet-over-OTN processing, supporting line rates commonly used in OTU2/OTU3/OTU4-class optical transport. Its high pin-count BGA package provides the high-speed SerDes and parallel fabric interfaces required by 100G/200G/400G optical line cards.
Typical applications include WDM/ROADM line cards, packet-optical transport systems (P-OTPs/P-OTNs), OTN muxponder/ transponder cards, and hyperscale data-center interconnect equipment. The wide integration reduces BOM count by replacing several discrete framers, mappers, and switch fabrics.
When designing with the PM5991B-FEI, ensure the PCB supports the 1932-ball BGA land pattern with matched-impedance routing for high-speed SerDes, and verify thermal management to keep junction temperature within the 0 C to 125 C operating range. Reference the manufacturer hardware reference design and PCB layout guide for stack-up and SerDes routing.
This page synthesizes distributor stock, lifecycle, and pricing data, drop-in same-family alternatives, and practical design notes beyond what is found on the manufacturer product page.
Drop-in alternatives for PM5991B-FEI — 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:
PM5990B-FEI
✅ Drop-In📋 Reference alternative (not in catalog)
PM5991A-FEI
✅ Drop-In📋 Reference alternative (not in catalog)
PM5990A-FEI
✅ Drop-In📋 Reference alternative (not in catalog)
PM5991B-FEI-R
✅ Drop-In📋 Reference alternative (not in catalog)
PM5991B-FEI Maximum Ratings & Electrical Characteristics
| Product Family | DIGI-G4 OTN Processor |
| Part Variant | No encryption (FEI build) |
| Silicon Revision | B (second revision) |
| Function | OTN Mapper / Network Processor |
| Category | Application Specific Microcontroller / Network Processor |
| Core | Microchip DIGI-G4 OTN processing core |
| Package | 1932-BBGA |
| Pin Count | 1932 |
| Mounting Type | Surface Mount (BGA) |
| Operating Junction Temperature | 0 C to +125 C (TJ) |
| Encryption Support | No (non-encrypted build) |
| Target Applications | OTN switching, P-OTN/POTP, WDM/ROADM, hyperscale DCI |
| Generation | Fourth-generation (DIGI-G4) |
PM5991B-FEI 1932-bbga Pin Configuration Guide
Pin configuration for PM5991B-FEI (1932-bbga package). This digital IC includes GPIO, communication interfaces (UART, SPI, I2C), and power pins. Refer to the manufacturer datasheet for alternate pin functions and configuration options. Essential for embedded system design and PCB layout.
No detailed pinout data available for PM5991B-FEI.
Refer to the datasheet for full pin configuration.
Typical Applications
PM5991B-FEI is suitable for 6 applications: OTN Switching Line Cards, Packet-Optical Transport (P-OTN / POTP), WDM / ROADM Line Equipment, Hyperscale Data-Center Interconnect (DCI), OTN Muxponder / Transponder Cards, OTN Cross-Connect / Add-Drop Multiplexers.
OTN Switching Line Cards
The PM5991B-FEI's hardware-accelerated ODU/ODUflex/ODUFlexE mapping and FEC make it the natural choice for core OTN switch line cards that must terminate and re-originate OTU2/OTU3/OTU4-class traffic. Placed between the optical line-side transponder and the packet fabric, the device performs ODU cross-connect, tributary grooming, and hitless protection switching without software round-trips. Compared with a discrete framer-plus-FPGA implementation, the integrated DIGI-G4 reduces BOM count, power, and PCB area while supporting the deterministic throughput that OTN SLA contracts require.
Recommended
Packet-Optical Transport (P-OTN / POTP)
The PM5991B-FEI is purpose-built for packet-optical transport platforms (P-OTPs/P-OTNs) that converge OTN and packet services on a single line card. Its integrated OTN mapper, packet-aware ODUflex support, and high-speed SerDes fabric ports let a single device terminate MPLS-TP, Carrier Ethernet, and OTN traffic while mapping them into OTU containers. The non-encrypted FEI build suits P-OTN deployments where MACsec/OTNsec is handled by an adjacent PHY/encryptor rather than inside the mapper ASIC.
Recommended
WDM / ROADM Line Equipment
Wavelength Division Multiplexing (WDM) and Reconfigurable Optical Add-Drop Multiplexer (ROADM) platforms rely on a high-integration OTN processor to map client services onto DWDM wavelengths, and the PM5991B-FEI delivers that function on a single die. Its hardware FEC, integrated OTN framer, and fabric ports handle the wavelength-side OTU termination while the device feeds downstream optical channel monitors and amplifiers. The 1932-BBGA's high SerDes lane count matches the multi-wavelength I/O required by ROADM add/drop cards.
Recommended
Hyperscale Data-Center Interconnect (DCI)
Hyperscale DCI platforms use 100G/200G/400G coherent optics that need a high-throughput OTN processor to map Ethernet and OTN traffic onto the optical channel. The PM5991B-FEI's hardware FEC, integrated framer, and high-speed fabric ports are sized for DCI's deterministic line-rate requirements, while the 1932-BBGA's parallel fabric links support the cross-connect density of multi-rack DCI pods. Choosing the FEI (no-encryption) variant keeps per-unit cost low for DCI fabrics that terminate encryption in the leaf-spine switch.
Recommended
OTN Muxponder / Transponder Cards
Muxponder and transponder cards aggregate multiple client signals (10G/25G/100G Ethernet, Fibre Channel, OTU) onto a single higher-rate OTU wavelength, and the PM5991B-FEI provides the OTN mapping, multiplexing, and FEC in a single device. Its hardware ODU multiplexer and tributary ports handle client aggregation without an external mapper, reducing the muxponder's BOM and power. The B-silicon revision brings incremental interoperability fixes that benefit multi-vendor muxponder deployments.
Recommended
OTN Cross-Connect / Add-Drop Multiplexers
Digital cross-connect and add-drop multiplexer systems need an OTN processor that can groom, add, drop, and pass-through OTN tributaries at line rate, and the PM5991B-FEI delivers those functions in hardware. Its integrated ODU cross-connect fabric and hitless protection switching support the carrier-grade availability targets of OTN cross-connects, while the 1932-BBGA's high pin count exposes enough fabric ports for non-blocking tributary switching. The non-encrypted FEI build suits cross-connects where encryption is applied upstream.
Recommended
Recommended Products Summary
Engineering reference data for PM5991B-FEI — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | PM5990B-FEI | PM5991A-FEI | PM5990A-FEI |
|---|---|---|---|---|
| Brand | Microchip Technology | Microchip Technology | Microchip Technology | Microchip Technology |
| Package | 1932-BBGA | 1932-BBGA | 1932-BBGA | 1932-BBGA |
| Product Family | DIGI-G4 OTN Processor | DIGI-G4 OTN Processor | DIGI-G4 OTN Processor | DIGI-G4 OTN Processor |
| Silicon Revision | B | B | A | A |
| Encryption Support | No (FEI no-encryption build) | Yes (FEI encryption-enabled build) | No (FEI no-encryption build) | Yes (FEI encryption-enabled build) |
| Function | OTN Mapper / Network Processor | OTN Mapper / Network Processor | OTN Mapper / Network Processor | OTN Mapper / Network Processor |
| Operating Junction Temperature | 0 C to +125 C (TJ) | 0 C to +125 C (TJ) | 0 C to +125 C (TJ) | 0 C to +125 C (TJ) |
| Target Applications | OTN switching, P-OTN, WDM/ROADM, DCI | OTN switching, P-OTN, WDM/ROADM, DCI (secured) | OTN switching, P-OTN, WDM/ROADM, DCI | OTN switching, P-OTN, WDM/ROADM, DCI (secured) |
| Drop-in Compatibility | Reference part | Yes - same 1932-BBGA footprint, encryption differs | Yes - same 1932-BBGA footprint, silicon rev differs | Yes - same 1932-BBGA footprint, encryption + silicon rev differ |
Key Differentiators
- Fourth-generation DIGI-G4 silicon vs older DIGI-G3 (vs PM8597B-FEI)
- Non-encrypted build reduces cost and export-control paperwork (vs PM5990B-FEI)
- B-silicon revision with incremental bug fixes and feature updates (vs PM5991A-FEI)
Design Notes
Estimated: routing the 1932-BBGA package requires a high-layer-count PCB (typically 12+ layers) with matched-impedance SerDes traces, length-matched differential pairs, and a continuous ground reference plane under the high-speed lanes. Reference Microchip's DIGI-G4 hardware reference manual for stack-up, via pattern, and SerDes lane grouping. A single BGA break-out mistake compounds significantly. Use buried vias and a 1.0 mm or finer BGA pitch BGA fanout strategy.
Estimated: at full OTN switching load the PM5991B-FEI can dissipate multi-watt power in the 1932-BBGA, so junction temperature must stay below 125 C. Use a thermal via array under the BGA thermal balls, ample PCB copper pour, and adequate chassis airflow. Cross-check actual dissipation against the Microchip power-estimation tool, and derate for altitude and inlet-air temperature per system requirements.
Do not confuse the PM5991B-FEI (no encryption, B-silicon) with the PM5990B-FEI (encryption enabled) or the PM5991A-FEI (A-silicon). All three share the same 1932-BBGA footprint, but firmware/security-configuration and silicon-revision errata differ. Verify the exact Microchip order code on the shipping label before board bring-up, and confirm with the Microchip product page that the FEI no-encryption build matches your design's security posture.
Place the PM5991B-FEI close to the optical line-side transponder and the packet fabric device to minimize SerDes channel loss; place its reference clock and PLL supply-filter components within the manufacturer's recommended distance, and isolate high-speed SerDes return currents from low-speed management I/O. Reference the Microchip DIGI-G4 hardware reference design for the recommended decoupling network and clock-tree topology.
Compliance Information
RoHS, REACH, lead-free and halogen-free status not present in the verified web snippets; compliance should be confirmed against the Microchip product page or PM5991 datasheet. AEC-Q100 is not applicable - this is an OTN processor, not an automotive-grade part. Export-control paperwork may apply to the encryption-enabled PM5990 sibling; the FEI no-encryption build of PM5991B-FEI generally avoids the encryption-related export-control category.
