BCM84758AKFSBLG - 40G Ethernet Transceiver | Broadcom
MPN: BCM84758AKFSBLG ✓ Active| Qty | Unit Price | Extended |
|---|---|---|
| 1 | $32.5 | $32.50 |
| 10 | $30.1 | $301.00 |
| 100 | $27.85 | $2,785.00 |
| 500 | $25.4 | $12,700.00 |
| 1,000 | $23.1 | $23,100.00 |
BCM84758AKFSBLG Overview
An Ethernet transceiver is a mixed-signal integrated circuit that combines a physical coding sublayer (PCS), physical medium attachment (PMA), and analog front-end to serialize, deserialize, and condition multi-gigabit data streams between a Media Access Controller (MAC) and an optical or copper physical medium. The BCM84758AKFSBLG sits within the hierarchy: ethernet transceiver -> PHY -> network interface IC -> wired communication semiconductor. The category exists because modern switches and routers require dense multi-lane I/O that scales to data-center and carrier-grade line rates.
Key features of the BCM84758AKFSBLG include 40G Ethernet data-rate capability, low power consumption suitable for high-density port-count line cards, integrated SERDES with adaptive equalization, and compliance with industry-standard high-speed networking interfaces. The device supports hot-pluggable module integration and is intended for use behind QSFP modules or with on-board optical engines.
Architecturally, the part leverages a high-performance CMOS mixed-signal process that combines a multi-gigabit analog front end with digital PCS logic. Adaptive equalization, pre-emphasis, and receive-signal-conditioning circuitry compensate for channel loss at 10+ GHz fundamental frequencies, enabling robust BER performance over typical FR4 backplane channels and direct-attach copper assemblies.
Typical applications include 40G Ethernet line cards in top-of-rack switches, QSFP module interfacing in aggregation switches, datacenter fabric interconnects, and telecom OTN/PTN platforms. Low power is essential because line cards may host 24 to 48 such transceivers, and thermal density quickly becomes a board-level constraint.
When designing with this part, PCB layout must follow strict high-speed signal-integrity practices: controlled-impedance differential traces, length matching within Skew budget, and a contiguous reference plane on layer 2 directly beneath the SERDES lanes to suppress return-path discontinuities. .
This page synthesizes distributor pricing, drop-in alternatives, and practical design notes not found in the manufacturer datasheet to help sourcing engineers and PCB hardware designers quickly evaluate the BCM84758AKFSBLG for their 40G networking builds.
Drop-in alternatives for BCM84758AKFSBLG — 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:
BCM84758AKFSBG
✅ Drop-In📋 Reference alternative (not in catalog)
BCM84758AKFSBLG
✅ Drop-In✓ In Stock
$23.1 / Unit
View Datasheet →BCM84758AKFSBLG Specifications (manufacturer-published)
| Manufacturer | Broadcom |
| Part Number | BCM84758AKFSBLG |
| Product Type | Ethernet Transceiver |
| Application Category | Telecom / Networking |
| Series | BCM84758 |
| Description | Ethernet Transceiver IC for line-card access switches |
| Interface | Telecom / Ethernet PHY |
| Mounting Type | Surface Mount |
| Power Consumption | Low power (per Broadcom BCM84758 family description) |
BCM84758AKFSBLG Interfaces & Connectors
No manufacturer-published interface list is available for BCM84758AKFSBLG. Refer to the manufacturer documentation for connector and header details.
Refer to the manufacturer documentation for the full expansion header pinout and connector pin numbering.
Power & Thermal Characteristics
| Power Consumption | Low power (per Broadcom BCM84758 family description) |
Power input and thermal parameters for BCM84758AKFSBLG as published by the manufacturer.
Typical Applications
BCM84758AKFSBLG is suitable for 6 applications: 40G Ethernet Top-of-Rack Switch Line Card, Carrier-Grade OTN/PTN Platform, Datacenter Fabric Interconnect Leaf-Spine, Enterprise Aggregation Switch, 40G Direct-Attach Copper Cable Assembly, White-Box Network Switch Design.
40G Ethernet Top-of-Rack Switch Line Card
The BCM84758AKFSBLG is purpose-built for 40G Ethernet aggregation in top-of-rack (ToR) switches used in hyperscale datacenters. The part's integrated SERDES lane architecture directly drives QSFP+ optical modules or direct-attach copper assemblies, providing four lanes of 10G or one lane of 40G connectivity per port. Its low power dissipation makes it well-suited for high port-density line cards hosting 32 to 48 such transceivers, where total board thermal budget is constrained. Engineers typically pair the BCM84758AKFSBLG with a Broadcom Tomahawk or Trident switch ASIC for full switching-fabric integration, leveraging the shared SerDes lane map to simplify MAC-to-PHY bring-up.
Recommended
Carrier-Grade OTN/PTN Platform
The BCM84758AKFSBLG is specified for telecom carrier-grade OTN and PTN platforms where 40G interfaces replace legacy 10G uplinks in metro aggregation nodes. The transceiver supports the standard 40G Ethernet rate and integrates the PHY layer required to map packet data onto optical transport networks. Low power and high SERDES density suit the constrained thermal envelopes of carrier shelf equipment, and Broadcom's long-term support lifecycle fits telecom-grade 10-year deployment expectations. The part interfaces with OTN framer ASICs to deliver full transport-layer termination at the line card.
Recommended
Datacenter Fabric Interconnect Leaf-Spine
The BCM84758AKFSBLG enables leaf-spine datacenter fabric interconnects at 40G, providing the PHY layer on each leaf and spine port. With port densities of 32 to 64 transceivers per chassis, the part's low power consumption and integrated SERDES are essential to meet datacenter PUE targets. The 40G rate on each port supports aggregate bandwidth of 6.4 Tbps on a 64-port leaf switch, well-suited to modern east-west traffic patterns. The BCM84758AKFSBLG interoperates with optical AOCs and copper DAC cables for flexible cabling topologies in white-box and OEM switch designs.
Recommended
Enterprise Aggregation Switch
The BCM84758AKFSBLG enables 40G uplinks in enterprise aggregation switches that aggregate traffic from multiple access-layer switches at 10G. The 40G rate provides oversubscription headroom for bursty traffic patterns typical in campus networks and provides 4:1 oversubscription ratios when aggregating 48 ports of 10G. The integrated PHY eliminates the need for an external retimer, simplifying PCB layout. For enterprise switching products, the BCM84758AKFSBLG often pairs with a Broadcom StrataConnect or StrataXGS switch ASIC to deliver a cost-effective and power-efficient aggregation solution.
Recommended
40G Direct-Attach Copper Cable Assembly
The BCM84758AKFSBLG drives the host-side of 40G direct-attach copper (DAC) cable assemblies used for short-reach in-rack and inter-rack connections. The integrated SERDES with adaptive equalization compensates for the loss and skew of typical 3 to 7 meter DAC cables, enabling error-free link operation without external retimers. Compared to active optical cables (AOCs), DAC assemblies are more cost-effective and lower-power for short reaches. The BCM84758AKFSBLG supports the IEEE 802.3ba 40GBASE-CR4 standard needed to interoperate with compliant DAC assemblies from third-party cable vendors.
Recommended
White-Box Network Switch Design
The BCM84758AKFSBLG is a key component in white-box disaggregated network switch designs where the line card is decoupled from a specific brand of software NOS (such as ONLP or SONiC). The part interoperates with Broadcom-based reference designs from ODMs such as Edgecore and Delta, enabling fast time-to-market for new white-box platforms. 40G port densities of up to 48 ports on a single line card make the BCM84758AKFSBLG the PHY of choice for both 1U and 2U white-box ToR switches. Designers should validate the Broadcom SDK and reference hardware bring-up guide against the specific ODM chosen for the platform.
Recommended
Recommended Products Summary
Engineering reference data for BCM84758AKFSBLG — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | BCM84758AKFSBG |
|---|---|---|
| Brand | Broadcom | Broadcom |
| Package | Broadcom proprietary SMD | Broadcom proprietary SMD - same |
| Product Type | Ethernet Transceiver | Ethernet Transceiver |
| Series | BCM84758 | BCM84758 |
| Mounting Type | Surface Mount | Surface Mount |
| Power Profile | Low power (family spec) | Low power (family spec, identical die) |
| Lifecycle Status | Active | Active |
Key Differentiators
- BCM84758 family long-term supply continuity for telecom deployments (vs BCM84758AKFSBG)
- Low power consumption per port (vs Marvell Alaska 88X4340)
- Integrated SERDES lanes without external retimer (vs PHY + external retimer two-chip solution)
Design Notes
Estimated: for the BCM84758AKFSBLG's high-speed SERDES lanes, maintain 100-ohm differential impedance for each transmit and receive pair, and length-match within a 0.15 mm (6 mil) intra-pair and 6 mm inter-pair skew budget over the full breakout region. Place a continuous ground reference plane on layer 2 directly beneath the SERDES routing to suppress return-path discontinuities; any gap in the reference plane induces resonance and degrades eye margin at 10+ GHz fundamental frequencies.
The BCM84758AKFSBLG requires low-noise, low-impedance power supply rails; place 0.1 uF MLCC bypass capacitors within 1 mm of each supply pin and a 4.7 uF / 10 uF bulk capacitor near the device. For the analog supply pins, use a ferrite bead or pi-filter to isolate noise from the digital core rail, which otherwise couples into the SERDES analog front end and degrades TX jitter and RX sensitivity.
Estimated: at full 40G operation across all lanes, the BCM84758AKFSBLG dissipates moderate power per the BCM84758 family datasheet. Designers should evaluate the board-level thermal budget by simulating at least 1 ounce copper pour on top and bottom layers under the device footprint and ensuring adequate airflow (200 LFM minimum) for line-card applications. For 48-port line cards, thermal simulation must consider the aggregate heat dissipation of all populated transceivers on the same card.
Use a clean reference clock source for the BCM84758AKFSBLG with phase noise below -110 dBc/Hz at 100 kHz offset; spread-spectrum clocking is generally not recommended for 40G SERDES as it can degrade jitter margin. The reference clock distribution network must use controlled-impedance traces with a continuous reference plane. For compliance with IEEE 802.3ba jitter templates, use a high-performance differential crystal oscillator or a jitter-cleaner PLLU to drive the device's REFCLK input.
Compliance Information
RoHS/REACH/lead-free/Halogen-free compliance not explicitly stated in the verified distributor data; consult Broadcom datasheet or contact Broadcom directly for compliance declarations. AEC-Q100 is not applicable for non-automotive networking transceivers.
