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Analog Devices Inc./Maxim Integrated MAX3268CUB+
- Part No.:
- MAX3268CUB+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Special Purpose Amplifiers
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Datasheet:
-
MAX3268CUB+.pdf
- Description:
- IC LIMITING AMP 10UMAX
- Quantity:
- Payment:
- Shipping:
Inventory:4,065
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Product details
Overview
MAX3268CUB+ from Maxim Integrated is a 1.25Gbps PECL-output limiting amplifier designed for Gigabit Ethernet and Fibre Channel optical receiver front-ends. It features +3.0V to +5.5V supply operation, 11ps deterministic jitter (typ), 300ps max edge speed, programmable loss-of-signal detection via external RTH, and operates in the 0°C to +70°C temperature range. It serves as the final gain stage after transimpedance amplifiers like MAX3266/MAX3267 in SFF optical modules.
For engineers reviewing the MAX3268CUB+ datasheet, MAX3268CUB+ pinout, MAX3268CUB+ application, or MAX3268CUB+ equivalent, key selection criteria include its 10-pin µMAX-EP package, PECL output compatibility with VCC − 2V termination, low-input-referred noise (150µVRMS), and configurable LOS threshold using RTH values from 2.5kΩ to 20kΩ.
Technical Context
The MAX3268CUB+ implements a multistage limiting amplifier architecture with integrated RMS power detection and offset-correction loop (via CAZ1/CAZ2 pins). Its input buffer presents 100Ω differential impedance and accepts signals from TIA outputs, while the PECL output stage drives transmission lines terminated to VCC − 2V with controlled edge rates.
It delivers 55dB total gain with deterministic jitter minimized by lowpass Bessel filtering and DC offset correction. The LOS function uses an internal comparator referenced to RTH-set thresholds, providing hysteresis of 2.5dB to 4.4dB depending on resistor value - critical for stable signal-detect behavior in optical receivers subject to power fluctuations.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Data Rate | 1.25Gbps - supports full-rate Gigabit Ethernet and Fibre Channel 1x operation without oversampling or clock recovery dependency. |
| Deterministic Jitter | 14ps (max) - measured per ANSI X3.230 Annex A using K28.5 pattern; ensures timing margin in high-speed serial links. |
| Input Voltage Range | 10mV to 1200mVpp - accommodates wide dynamic range from TIAs under varying optical input power conditions. |
| LOS Hysteresis | 2.5dB to 4.4dB - set by RTH value; prevents chatter during optical power transitions near detection threshold. |
| Output Interface | PECL - standards-compliant positive-referenced ECL outputs requiring VCC − 2V termination for optimal signal integrity. |
| Supply Voltage | +3.0V to +5.5V - enables direct interface with common 3.3V or 5V system rails without LDO regulation. |
| Package | 10-pin µMAX-EP - 3mm × 3mm exposed-paddle package optimized for thermal dissipation in compact SFF optical modules. |
Pinout & Package
MAX3268CUB+ is housed in a 10-pin µMAX-EP package (3.0mm × 3.0mm, 0.8mm height) with exposed paddle soldered to PCB ground for thermal management.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1, 2 | VCC | Positive supply input - dual VCC pins reduce supply inductance and improve high-frequency PSRR. |
| 3 | TH | Loss-of-signal threshold reference - connects to ground via external resistor (2.5kΩ–20kΩ) to set input voltage detection level. |
| 4, 5 | IN−, IN+ | Differential input - 100Ω matched impedance accepts output from TIAs such as MAX3266/MAX3267. |
| 6 | GND | Ground reference - tied to exposed paddle; must be solidly connected to PCB ground plane. |
| 7, 8 | OUT−, OUT+ | PECL differential data outputs - require 50Ω termination to VCC − 2V for proper logic levels and edge control. |
| 9 | LOS | Inverted loss-of-signal indicator - open-drain TTL-compatible output asserted low when input falls below RTH-set threshold. |
| 10 | CAZ1 | Offset-correction loop capacitor node - used with CAZ2 to stabilize DC offset correction time constant (2MHz default if open). |
Key Features
| Feature | Design Value |
|---|---|
| PECL Output Compatibility | Meets industry-standard PECL voltage levels (−0.88V to −1.81V w.r.t. VCC) and drive strength for direct interface with FPGA/CPLD clock/data inputs. |
| Programmable LOS Threshold | Configurable over 3 sensitivity ranges (low/medium/high) using single external RTH, enabling adaptation to diverse optical link budgets. |
| Low Input-Referred Noise | 150µVRMS - preserves signal-to-noise ratio from TIA output, minimizing bit error rate degradation in weak-signal conditions. |
| Stable Offset Correction | Internal feedback loop reduces input offset to <100µV; CAZ1/CAZ2 allow time-constant tuning to match data encoding (e.g., 8B/10B vs. scrambled NRZ). |
| High-Speed Edge Control | 300ps max edge speed - optimized for 1.25Gbps eye opening while suppressing harmonic content that could radiate or cause crosstalk. |
Applications
| Gigabit Ethernet Optical Receiver | Fibre Channel 1x Receiver |
|---|---|
|
Use Scenario: Front-end signal conditioning in SFP/SFF pluggable optical transceivers receiving 1.25Gbps serial data over multimode fiber. IC Role / Device Role / Timing Role: Final limiting amplifier stage that converts variable-amplitude TIA output into clean, constant-level PECL data stream for clock-data recovery (CDR) ICs. Use Value: Enables robust signal detect (LOS) with 4.4dB hysteresis and maintains <14ps deterministic jitter - meeting IEEE 802.3 and FC-PI-2 eye mask requirements. |
Use Scenario: Signal amplification in Fibre Channel storage area network (SAN) optical modules operating at 1062.5MBd. IC Role / Device Role / Timing Role: High-gain (55dB), low-jitter limiting amplifier driving PECL-compatible SERDES inputs in host bus adapters and switch line cards. Use Value: Supports wide input dynamic range (10–1200mVpp) and delivers consistent edge speed (≤300ps), ensuring reliable link training and low BER across temperature. |
| Small-Form-Factor (SFF) Transceiver | GBIC Module Receiver |
|
Use Scenario: Space-constrained optical receiver in legacy SFF modules where board area is limited to ~12mm × 13mm. IC Role / Device Role / Timing Role: Compact 10-pin µMAX-EP limiting amplifier replacing larger TSSOP solutions while maintaining PECL output compatibility and thermal performance. Use Value: Exposed paddle enables efficient heat dissipation at 76mA typical supply current - critical for reliability in sealed, convection-limited modules. |
Use Scenario: Signal conditioning in Gigabit Interface Converter (GBIC) modules compliant with INF-8074i specification. IC Role / Device Role / Timing Role: Provides TTL-compatible inverted LOS output and PECL data outputs meeting GBIC electrical interface requirements for host controller handshaking. Use Value: Internal 16kΩ pull-up on LOS pin eliminates need for external biasing, simplifying GBIC design and reducing component count. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar limiting amplifier applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX3268CUB | Identical electrical specs and pinout; differs only in lead-free finish (CUB+ = RoHS-compliant, CUB = non-RoHS). | No functional difference; both rated for 0°C to +70°C and 10-pin µMAX-EP package. | Select MAX3268CUB+ for new designs requiring lead-free compliance per JEDEC J-STD-609. |
| MAX3768CUB+ | Same package and pinout, but rated for extended temperature range (−40°C to +85°C); otherwise identical AC/DC specs. | Suitable for industrial or outdoor optical equipment where ambient temperature exceeds +70°C. | Choose MAX3768CUB+ when operating in extended temperature environments; otherwise MAX3268CUB+ is optimal for commercial-grade SFF modules. |
Compared with MAX3268CUB and MAX3768CUB+, the MAX3268CUB+ offers the same 1.25Gbps PECL performance and µMAX footprint but targets standard commercial temperature operation with guaranteed RoHS compliance - making it the preferred choice for cost-sensitive, volume SFP/SFF deployments.
Availability
MAX3268CUB+ is available at Aetrix Electronics and suitable for Gigabit Ethernet optical receivers, Fibre Channel 1x receivers, and small-form-factor (SFF) transceivers requiring stable component supply, lead-free compliance, and proven interoperability with TIAs like MAX3266/MAX3267.
Supply support for MAX3268CUB+ includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Maxim Integrated (now part of Analog Devices) is a semiconductor company specializing in high-performance analog, mixed-signal, and RF ICs for communications, computing, and industrial systems.
The MAX3268CUB+ belongs to Maxim's optical receiver limiting amplifier product line, engineered specifically for high-speed fiber-optic data links requiring low jitter, programmable signal detection, and compact PECL-compatible interfaces in SFF form factors.
FAQ
What is the maximum data rate supported by the MAX3268CUB+?
The MAX3268CUB+ is specified for operation up to 1.25Gbps, matching the line rate of Gigabit Ethernet and Fibre Channel 1x standards. Its electrical characteristics-including 14ps deterministic jitter and 300ps edge speed-are guaranteed at this rate under +3.0V to +5.5V supply and 0°C to +70°C ambient conditions. It is not rated for 2.5Gbps operation; for that, the MAX3265CUB+ or MAX3765CUB+ should be selected.
How is loss-of-signal (LOS) detection configured on the MAX3268CUB+?
LOS detection on the MAX3268CUB+ is configured using an external resistor RTH connected between pin 3 (TH) and ground. Values from 2.5kΩ to 20kΩ select low/medium/high sensitivity ranges, setting assert/deassert thresholds from 2.2mV to 41.5mV differential input. The internal comparator provides 2.5dB to 4.4dB hysteresis, preventing false triggering during optical power fluctuations. No additional components are required beyond RTH.
What is the correct termination for the PECL outputs of the MAX3268CUB+?
The MAX3268CUB+ PECL outputs (pins 7 and 8) must be terminated to VCC − 2V using two 50Ω resistors-one from OUT+ to VCC − 2V and one from OUT− to VCC − 2V-as shown in Figure 1(c) of the datasheet. This ensures proper logic levels (−0.88V to −1.81V w.r.t. VCC), minimizes reflections, and maintains the specified 300ps edge speed. Termination to ground or VCC will result in invalid output voltages and degraded jitter performance.
Does the MAX3268CUB+ support squelch functionality?
No, the MAX3268CUB+ does not support squelch functionality. Per the datasheet Pin Description table, the SQUELCH pin is labeled "N.C." (No Connection) in the 10-pin µMAX package variant. Unlike the TSSOP versions (e.g., MAX3264CUE+), the MAX3268CUB+ lacks internal squelch circuitry and has no dedicated pin for enabling output muting. Signal muting must be implemented externally if required.
What is the purpose of the CAZ1 and CAZ2 pins on the MAX3268CUB+?
The CAZ1 (pin 10) and CAZ2 (pin 9 is N.C. in MAX3268; CAZ2 is unused) pins configure the offset-correction loop time constant. In the MAX3268CUB+, only CAZ1 is active; CAZ2 is internally unconnected. A capacitor from CAZ1 to ground sets the loop bandwidth: open = 2MHz cutoff (for 8B/10B coding), ≥0.1µF = ~2kHz (for scrambled NRZ). This loop suppresses input DC offsets (<100µV), preserving deterministic jitter performance and RMS power detection accuracy.
MAX3268CUB+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
- Packaging:
- Tube
- Product Status:
- Obsolete
- Type:
- Limiting Amplifier
- Applications:
- Optical Networks
- Mounting Type:
- Surface Mount
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 10-uMAX-EP
MAX3268CUB+ FAQ
1.How can I place an order for MAX3268CUB+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX3268CUB+ on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for MAX3268CUB+ reliable?
The price and inventory of MAX3268CUB+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX3268CUB+ is usually 5 days.
3.What payment methods are accepted for MAX3268CUB+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX3268CUB+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX3268CUB+?
MAX3268CUB+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX3268CUB+ order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for MAX3268CUB+?
For technical support, including MAX3268CUB+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX3268CUB+ requirements.
6.How does Aetrix verify that MAX3268CUB+ is sourced from the original manufacturer or authorized distributors?
All MAX3268CUB+ products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MAX3268CUB+ meets industry standards.
7.What is the process for return or replacement of MAX3268CUB+?
All MAX3268CUB+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX3268CUB+, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The MAX3268CUB+ part is unused and in its original packaging.
Return procedure for MAX3268CUB+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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