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Analog Devices Inc./Maxim Integrated DS2118MB+
- Part No.:
- DS2118MB+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Signal Terminators
- Package:
- 36-BSOP (0.295", 7.50mm Width)
- Datasheet:
-
DS2118MB+.pdf
- Description:
- IC TERM SCSI LVD/SE ULT-3 36SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:3,514
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Product details
Overview
DS2118MB+ from Maxim Integrated is an Ultra3 multimode SCSI terminator supporting both low-voltage differential (LVD) and single-ended (SE) bus configurations, with auto-sensing of bus mode via DIFFSENSE voltage detection, 110Ω SE termination resistance, 105Ω differential impedance in LVD mode, and thermal shutdown protection. It enables backward-compatible SCSI-3/4 bus termination in server backplanes and storage enclosures.
For engineers reviewing the DS2118MB+ datasheet, DS2118MB+ pinout, DS2118MB+ application, or DS2118MB+ equivalent, key selection considerations include multimode autoselection logic, 36-pin SSOP package compatibility, SCSI SPI-2–SPI-4 compliance, and precise 5% tolerance on termination resistors under varying TERMPWR conditions.
Technical Context
The DS2118MB+ integrates dual-reference regulation (1.25V for LVD, 2.85V for SE), precision laser-trimmed resistor strings, and trinary DIFFSENS decoding to distinguish HVD/SE/LVD bus states. Its control logic dynamically switches termination topology and biasing based on real-time DIFFCAP monitoring.
It provides fail-safe 112mV common-mode bias in LVD idle state, supports active negation in SE mode with 22mA sink capability per line, and isolates termination pins when ISO is asserted or thermal shutdown activates at 150°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Termination Modes | LVD and SE auto-selected via DIFFSENS voltage; HVD isolation supported |
| SE Termination Resistance | 110Ω ±5% - ensures compliant 110Ω bus termination for legacy SCSI devices |
| LVD Differential Impedance | 105Ω - matches Ultra160/Ultra320 differential signaling requirements |
| Reference Voltages | 1.25V (LVD), 2.85V (SE) - stable bias references for termination current sources |
| Thermal Shutdown Threshold | 150°C - disables termination and isolates pins to prevent bus fault propagation |
| Power-Down Capacitance | 3pF - minimizes signal reflection and timing skew on high-speed SCSI lines |
| Operating Temperature | 0°C to +70°C - validated for commercial-grade storage subsystem environments |
Pinout & Package
DS2118MB+ is housed in a 36-pin SSOP (0.300") lead-free/RoHS-compliant package with exposed heat-sink ground pads (pins 8, 9, 10, 26, 27, 28) for thermal management.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VREF (Pin 1) | Reference Voltage Output | Supplies 2.85V (SE) or 1.25V (LVD); requires 4.7µF decoupling for regulation stability |
| RxP/RxN (Pins 4–7, 11–16, 22–25, 29–32) | Signal Termination Terminals | Connect directly to SCSI differential or single-ended signal pairs; nine line pairs supported |
| DIFFSENSE (Pin 20) | Bus Mode Driver Output | Drives SCSI DIFFSENS line when MSTR/SLV = 1; asserts 1.2–1.4V for bus negotiation |
| DIFF_CAP (Pin 21) | Differential Mode Sense Input | Monitors DIFFSENS voltage via 0.1µF capacitor; enables trinary (HVD/SE/LVD) detection |
| ISO (Pin 17) | Termination Isolation Control | Pull high to disconnect RxP/RxN from bus while preserving VREF and mode indicators |
| TPWR (Pin 36) | Termination Power Input | Accepts 4.0–5.5V (SE) or 2.7–5.5V (LVD) from SCSI TERMPWR; bypass with 2.2µF + 0.01µF |
Key Features
| Feature | Design Value |
|---|---|
| Autoselecting LVD/SE Termination | Eliminates manual configuration; detects bus mode via DIFFSENS voltage thresholds (0.6V/2.15V boundaries) |
| Fail-Safe LVD Bias | Maintains 112mV common-mode offset during bus idle - prevents false triggering in absence of drivers |
| Active SE Negation Support | Sinks 22mA per line while regulating 2.85V reference - compatible with active-negation SCSI drivers |
| Thermal Shutdown Protection | Isolates termination pins and disables DIFFSENSE driver at 150°C - preserves bus integrity during overtemperature events |
| HVD Bus Isolation | Detects >2.4V on DIFFSENS and disconnects termination to prevent damage from incompatible high-voltage devices |
Applications
| RAID Controller Backplane | SCSI Tape Library Interface |
|---|---|
Use Scenario: Termination of wide SCSI bus connecting multiple drives in a hot-swappable RAID enclosure. IC Role / Device Role / Timing Role: Multimode bus terminator that auto-selects LVD or SE mode depending on attached drive types. Use Value: Enables mixed LVD/SE device deployment without manual jumpering or firmware reconfiguration. | Use Scenario: SCSI termination at the host interface of an enterprise tape autoloader supporting legacy and modern drives. IC Role / Device Role / Timing Role: Active terminator providing precise 110Ω SE and 105Ω LVD impedance matching. Use Value: Ensures signal integrity across 320MB/s Ultra320 transfers while maintaining compatibility with older SE tape drives. |
| Server Storage Expansion Card | Industrial SCSI Data Acquisition System |
Use Scenario: Termination on PCIe-to-SCSI bridge add-in card used in rack-mount servers. IC Role / Device Role / Timing Role: Hot-plug–compatible terminator with thermal shutdown and ISO-controlled isolation. Use Value: Prevents bus corruption during field-replaceable module insertion/removal under live operation. | Use Scenario: SCSI termination in ruggedized data acquisition chassis operating in extended temperature environments. IC Role / Device Role / Timing Role: Commercial-grade (0°C to +70°C) terminator with robust 5% resistor tolerance and low 3pF capacitance. Use Value: Maintains timing margin and signal fidelity in noise-sensitive measurement applications with long cable runs. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar SCSI termination applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| DS2118M | No "+" suffix; leaded (non-RoHS) SSOP package; identical electrical specs and pinout | Not suitable for RoHS-compliant production; requires separate Pb-free sourcing approval | Select DS2118MB+ for new designs requiring lead-free compliance and tape-and-reel delivery. |
| MAX3243ESE+ | RS-232 transceiver, not a SCSI terminator; no DIFFSENSE, no multimode termination | Designed for serial communication, not parallel SCSI bus termination | Not functionally comparable; only considered if misidentified as SCSI component. |
Compared with DS2118M, DS2118MB+ offers identical performance with RoHS compliance and tape-and-reel packaging; MAX3243ESE+ serves a completely different interface standard and cannot substitute for SCSI termination functionality.
Availability
DS2118MB+ is available at Aetrix Electronics and suitable for RAID controller backplanes, SCSI tape library interfaces, and server storage expansion cards requiring stable component supply and full SPI-2–SPI-4 compliance.
Supply support for DS2118MB+ 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) designs precision analog and mixed-signal ICs for industrial, communications, and computing applications.
The DS2118MB+ belongs to Maxim's Ultra3 SCSI terminator product line, engineered specifically for multimode, hot-plug–capable parallel SCSI bus termination in enterprise storage systems.
FAQ
What is the primary function of the DS2118MB+ in a SCSI system?
The DS2118MB+ serves as an auto-sensing multimode SCSI terminator, providing compliant LVD or SE termination based on real-time DIFFSENS voltage detection. It ensures signal integrity across Ultra160 and Ultra320 buses by delivering precise 105Ω differential or 110Ω single-ended impedance. The DS2118MB+ also incorporates thermal shutdown and HVD isolation to protect the bus during fault conditions.
How does the DS2118MB+ determine whether to use LVD or SE termination?
The DS2118MB+ monitors the SCSI DIFFSENS line through its DIFF_CAP pin using internal comparators. When the sensed voltage falls between 0.7V and 1.9V, it selects LVD mode; below 0.6V triggers SE mode; above 2.4V indicates HVD presence and initiates isolation. This trinary detection is implemented entirely within the DS2118MB+ without external logic.
What are the required external components for stable operation of the DS2118MB+?
The DS2118MB+ requires a 4.7µF capacitor between VREF and GND for reference regulation, a 0.1µF capacitor on DIFF_CAP for noise filtering, and dual bypassing on TPWR (2.2µF + 0.01µF). All capacitors must be placed adjacent to the DS2118MB+ package. Additionally, TPWR must connect directly to the SCSI TERMPWR line.
Does the DS2118MB+ support hot-plug operation on a live SCSI bus?
Yes, the DS2118MB+ is explicitly designed for SCSI bus hot-plug compatibility. Its ISO pin allows controlled termination isolation, and thermal shutdown automatically disconnects pins at 150°C. The DS2118MB+ maintains SE/LVD/HVD status outputs during isolation events, enabling host firmware to monitor bus mode without interruption.
What is the significance of the '+' suffix in DS2118MB+?
The '+' suffix in DS2118MB+ denotes a lead-free, RoHS-compliant version in the same 36-pin SSOP package. It shares identical electrical specifications, pinout, and thermal characteristics with the non-RoHS DS2118M, but uses matte-tin lead finish and complies with EU RoHS Directive 2011/65/EU. The DS2118MB+ is supplied in tape-and-reel format (DS2118MB+T&R).
DS2118MB+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 36-BSOP (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Type:
- SCSI, LVD, SE
- Number of Terminations:
- 9
- Voltage - Supply:
- 4V ~ 5.5V
- Operating Temperature:
- 0°C ~ 70°C
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 36-SSOP
DS2118MB+ FAQ
1.How can I place an order for DS2118MB+ through Aetrix?
Please submit a Request for Quotation (RFQ) for DS2118MB+ 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 DS2118MB+ reliable?
The price and inventory of DS2118MB+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for DS2118MB+ is usually 5 days.
3.What payment methods are accepted for DS2118MB+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DS2118MB+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DS2118MB+?
DS2118MB+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DS2118MB+ 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 DS2118MB+?
For technical support, including DS2118MB+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DS2118MB+ requirements.
6.How does Aetrix verify that DS2118MB+ is sourced from the original manufacturer or authorized distributors?
All DS2118MB+ 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 DS2118MB+ meets industry standards.
7.What is the process for return or replacement of DS2118MB+?
All DS2118MB+ units undergo pre-shipment inspection (PSI). If there is an issue with DS2118MB+, 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 DS2118MB+ part is unused and in its original packaging.
Return procedure for DS2118MB+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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