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Analog Devices Inc./Maxim Integrated DS21S07AE+T&R
- Part No.:
- DS21S07AE+T&R
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Signal Terminators
- Package:
- 20-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
DS21S07AE+T&R.pdf
- Description:
- IC TERMINATOR SCSI 20-TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:2,506
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Product details
Overview
DS21S07AE+T&R from Maxim Integrated is a 20-pin TSSOP SCSI active terminator IC for single-ended Fast and Ultra SCSI bus systems. It integrates a low-dropout 2.85V regulator and nine laser-trimmed 110Ω ±2% termination resistors, delivering 24mA drive per line and 200mA sink capability. It enables hot-plug-compatible, thermally protected active termination in RAID controllers and disk drive backplanes.
For engineers reviewing the DS21S07AE+T&R datasheet, DS21S07AE+T&R pinout, DS21S07AE+T&R application, or DS21S07AE+T&R equivalent, key selection criteria include TERMPWR voltage range (4.0–5.5V), power-down isolation behavior, VREF decoupling requirements (4.7µF), thermal shutdown threshold (150°C), and compatibility with SCSI-1/Fast/Ultra signaling standards.
Technical Context
The DS21S07AE+T&R implements a bandgap-referenced LDO regulator generating a precise 2.85V (±2.5%) reference for nine switched 110Ω termination paths. Each R1–R9 resistor is laser-trimmed to 108–112Ω and supports bidirectional current flow-24mA sourcing when signal lines are low, and 200mA sinking during actively negated SCSI states.
It features an internal 50kΩ pullup on the active-low PD pin; leaving PD open enables operation, while pulling it low disables all terminations and reduces quiescent current to ≤150µA. Thermal shutdown activates at 150°C, and both TERMPWR1/TERMPWR2 must connect to the SCSI bus TERMPWR line with appropriate decoupling.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Termination Resistance | 110Ω ±2% (laser-trimmed); ensures impedance matching within SCSI specification tolerance for signal integrity. |
| VREF Output Voltage | 2.85V (2.79–2.93V); stable reference for active termination biasing across temperature and load. |
| TERMPWR Range | 4.0V to 5.5V; compatible with standard SCSI bus TERMPWR supply without external regulation. |
| Sink Current Capability | 200mA minimum; supports actively negated SCSI signals without reference voltage droop >60mV. |
| Quiescent Current | 2.5–5mA (typical 2.5mA); enables low-power termination in idle bus states. |
| Thermal Shutdown | 150°C; protects device under sustained overload or poor heatsinking conditions. |
| Power-Down Current | ≤150µA; isolates termination resistors from bus while preserving system-level hot-plug safety. |
Pinout & Package
DS21S07AE+T&R uses a 20-pin Thin Shrink Small Outline Package (TSSOP) with exposed thermal pad. Pin 2 and Pin 8 are HS-GND (heat sink ground), internally connected to the mounting pad and intended for grounding or isolation per layout requirements.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | TERMPWR1 | Primary termination power input; must connect to SCSI TERMPWR line and decouple with 2.2µF or 4.7µF capacitor. |
| 2, 8, 12, 18 | HS-GND | Thermal pad connection point; internal tie to exposed copper pad for heat dissipation or isolation. |
| 3–7, 13–16 | R1–R9 | Nine 110Ω termination paths; each connects to one SCSI signal line (e.g., BSY, SEL, ACK, etc.). |
| 9 | VREF1 | Reference voltage output; must be externally tied to VREF2 and decoupled with 4.7µF capacitor. |
| 10 | GND | Signal ground reference for regulator and termination circuitry. |
| 11 | TERMPWR2 | Secondary termination power input; redundant TERMPWR connection for noise immunity and current sharing. |
| 17 | NC | No internal connection; must remain unconnected. |
| 19 | VREF2 | Second reference node; electrically identical to VREF1 and required to be shorted externally. |
| 20 | PD | Active-low power-down control; internal 50kΩ pullup; open-circuit = active, grounded = isolation mode. |
Key Features
| Feature | Design Value |
|---|---|
| SCSI Standard Compliance | Fully compliant with SCSI-1, Fast SCSI, and Ultra SCSI active termination requirements. |
| Laser-Trimmed Resistors | 110Ω ±2% tolerance ensures consistent bus termination across temperature and unit-to-unit variation. |
| Hot-Plug Compatibility | Power-down mode and bus isolation allow safe insertion/removal without disrupting SCSI bus operation. |
| Integrated Thermal Protection | On-die thermal shutdown at 150°C prevents latch-up or damage during overcurrent or high-ambient conditions. |
| Low-Dropout Regulation | 0.75V max dropout enables stable 2.85V VREF even at 5.0V TERMPWR minimum. |
Applications
| RAID Controller Backplane Termination | Disk Drive Internal Termination |
|---|---|
Use Scenario: Termination of 16-bit-wide "P" cable SCSI buses in enterprise RAID enclosures requiring three DS21S07AE+T&R per end. IC Role / Device Role / Timing Role: Active SCSI signal line terminator providing regulated 2.85V bias and 110Ω impedance match for all 27 signal lines. Use Value: Eliminates need for discrete resistor networks and external regulators, reducing BOM count and PCB area by >60% versus passive solutions. | Use Scenario: Embedded termination inside SCSI hard disk drives where space and thermal constraints limit discrete component use. IC Role / Device Role / Timing Role: Monolithic active terminator enabling hot-plug-safe bus isolation via PD pin control during drive insertion/removal. Use Value: Prevents bus glitches during hot-swap events and maintains signal integrity under varying TERMPWR loading from multiple drives. |
| SCSI Tape Library Interface | Legacy Workstation SCSI Expansion |
Use Scenario: Termination of differential SCSI buses in automated tape libraries with long cable runs and mixed-device topologies. IC Role / Device Role / Timing Role: Provides intrinsic TERMPWR decoupling and high-level noise immunity to suppress crosstalk-induced false asserts on busy lines like MSG or C/D. Use Value: Reduces bit error rate by maintaining stable 2.85V reference despite TERMPWR sag up to 1.5V, unlike passive terminators. | Use Scenario: Retrofitting active termination into aging SCSI workstations supporting legacy peripherals (scanners, CD-ROMs, ZIP drives). IC Role / Device Role / Timing Role: Replaces obsolete DS2107A-based termination modules with pin-compatible upgrade offering tighter resistor tolerance and lower quiescent current. Use Value: Extends system uptime by eliminating voltage-drop-related termination failures observed with aging 110Ω ±5% discrete networks. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar SCSI active termination applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| DS21S07AS+T&R | 16-pin SO package; same electrical specs but larger footprint and higher thermal resistance (θJA ≈ 120°C/W vs. 75°C/W for TSSOP). | Preferred for through-hole or legacy SO-reflow assembly; unsuitable for high-density TSSOP layouts. | Select DS21S07AS+T&R only if board space allows SO footprint and thermal margin exceeds 25°C above ambient. |
| MAX3243ESE+ | RS-232 transceiver with integrated charge-pump LDO; no termination resistors or SCSI-specific logic; not a functional replacement. | Not applicable - serves serial interface, not SCSI termination. | Not a valid alternative; included only due to Maxim part number similarity - verify function before substitution. |
Compared with DS21S07AS+T&R, DS21S07AE+T&R offers superior thermal performance and smaller PCB area, while MAX3243ESE+ lacks termination functionality entirely and must be excluded from SCSI termination designs.
Availability
DS21S07AE+T&R is available at Aetrix Electronics and suitable for RAID controller backplanes, disk drive internal termination, SCSI tape library interfaces, and legacy workstation SCSI expansion requiring stable component supply and long-term industrial availability.
Supply support for DS21S07AE+T&R 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, mixed-signal, and power management ICs for industrial, communications, and computing applications.
The DS21S07AE+T&R belongs to Maxim's legacy SCSI interface product line, engineered specifically to replace discrete active termination networks in single-ended SCSI-1/Fast/Ultra systems with monolithic reliability and reduced board space.
FAQ
What is the operating temperature range for DS21S07AE+T&R?
The DS21S07AE+T&R is specified for operation from 0°C to +70°C. This commercial-grade range aligns with standard SCSI peripheral environments such as disk drives and RAID controllers housed in temperature-controlled enclosures. The device includes on-die thermal shutdown that activates at 150°C to prevent damage during transient overloads, but continuous operation outside the 0°C to +70°C range is not guaranteed or tested. DS21S07AE+T&R must be used within this range to ensure compliance with SCSI timing and termination specifications.
How does DS21S07AE+T&R achieve hot-plug compatibility?
DS21S07AE+T&R achieves hot-plug compatibility through its active-low PD (power-down) pin and internal isolation circuitry. When PD is pulled low, all nine termination resistors disconnect from the SCSI signal lines, electrically isolating the DS21S07AE+T&R from the bus without physical removal. Its internal 50kΩ pullup ensures default activation when PD is left open. This behavior prevents bus contention or signal corruption during insertion or removal - a critical requirement for modular SCSI storage systems. DS21S07AE+T&R maintains this capability across its full 4.0–5.5V TERMPWR range.
What capacitor values are required for DS21S07AE+T&R VREF and TERMPWR pins?
DS21S07AE+T&R requires a 4.7µF tantalum capacitor between the VREF1 and VREF2 pins and ground to stabilize the 2.85V reference under dynamic load. For TERMPWR1 and TERMPWR2, either a 2.2µF or 4.7µF capacitor is acceptable per pin, as specified in the functional description and Figure 2. A 0.1µF high-frequency bypass capacitor may be added in parallel with the 4.7µF VREF capacitor for systems using fast rise/fall time drivers. These values are mandatory for stable DS21S07AE+T&R operation and are validated in Maxim's reference designs.
Is DS21S07AE+T&R pin-compatible with DS2107A?
No, DS21S07AE+T&R is not pin-compatible with DS2107A. While DS21S07AE+T&R is backward compatible in function and electrical behavior per the datasheet, it uses a 20-pin TSSOP package versus the DS2107A's 16-pin SO package. Pin counts, spacing, and terminal assignments differ - for example, DS21S07AE+T&R has dedicated HS-GND pins (2, 8, 12, 18) and dual TERMPWR/VREF inputs absent in DS2107A. Migration requires PCB layout revision. DS21S07AE+T&R replaces DS2107A functionally but not mechanically.
What is the maximum sink current supported by DS21S07AE+T&R on each termination line?
DS21S07AE+T&R supports a minimum sink current of 200mA per termination line (R1–R9), as specified in the DC Characteristics table. This capability ensures stable VREF regulation (<60mV droop) during actively negated SCSI signal states, where multiple lines may be simultaneously pulled low. The 200mA rating applies under recommended operating conditions (TA = 0°C to +70°C, TERMPWR = 4.0–5.5V) and is guaranteed by design. DS21S07AE+T&R maintains this sink strength across all nine channels without cross-talk or thermal derating in typical SCSI bus configurations.
DS21S07AE+T&R Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 20-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tape & Reel (TR)
- 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:
- 20-TSSOP
DS21S07AE+T&R FAQ
1.How can I place an order for DS21S07AE+T&R through Aetrix?
Please submit a Request for Quotation (RFQ) for DS21S07AE+T&R 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 DS21S07AE+T&R reliable?
The price and inventory of DS21S07AE+T&R are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for DS21S07AE+T&R is usually 5 days.
3.What payment methods are accepted for DS21S07AE+T&R?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DS21S07AE+T&R transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DS21S07AE+T&R?
DS21S07AE+T&R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DS21S07AE+T&R 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 DS21S07AE+T&R?
For technical support, including DS21S07AE+T&R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DS21S07AE+T&R requirements.
6.How does Aetrix verify that DS21S07AE+T&R is sourced from the original manufacturer or authorized distributors?
All DS21S07AE+T&R 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 DS21S07AE+T&R meets industry standards.
7.What is the process for return or replacement of DS21S07AE+T&R?
All DS21S07AE+T&R units undergo pre-shipment inspection (PSI). If there is an issue with DS21S07AE+T&R, 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 DS21S07AE+T&R part is unused and in its original packaging.
Return procedure for DS21S07AE+T&R:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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