My Inquiry
My Account
Analog Devices Inc./Maxim Integrated DS21T07S/T&R
- Part No.:
- DS21T07S/T&R
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Signal Terminators
- Package:
- 16-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
DS21T07S/T&R.pdf
- Description:
- IC TERMINATOR SCSI 16-SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,393
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
DS21T07S/T&R from Dallas Semiconductor (now Maxim Integrated) is a monolithic SCSI active terminator IC for Fast and Ultra SCSI single-ended buses. It integrates nine laser-trimmed 110 Ω termination resistors, a low-dropout 2.85 V regulator, power-down control (PD), and thermal shutdown. It provides active termination for nine signal lines and supports hot-plug operation in disk drive and RAID controller applications.
For engineers reviewing the DS21T07S/T&R datasheet, DS21T07S/T&R pinout, DS21T07S/T&R application, or DS21T07S/T&R equivalent, key selection criteria include termination resistance tolerance (±2%), TERMPWR voltage range (4.0–5.5 V), quiescent current (5 mA), power-down isolation capability, and SOIC-16 footprint compatibility with legacy SCSI designs.
Technical Context
The DS21T07S/T&R implements a bandgap reference (2.55 V) buffered to 2.85 V output, capable of sourcing ≥24 mA per termination line and sinking ≥200 mA for actively negated SCSI signals. Its internal 50 kΩ pull-up on PD enables open-circuit activation and logic-low deactivation.
It requires external 4.7 µF decoupling between VREF1/VREF2 and ground, dual TERMPWR connections (TERMPWR1/TERMPWR2), and HS-GND thermal pad handling. Operation is validated across 0°C to 70°C with thermal shutdown at 150°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Termination Resistance | 108–112 Ω (laser-trimmed ±2% tolerance ensures stable impedance matching on SCSI bus) |
| Reference Voltage | 2.79–2.93 V (regulated 2.85 V typical output powers termination network reliably) |
| TERMPWR Range | 4.0–5.5 V (supports standard SCSI TERMPWR rail without external regulation) |
| Quiescent Current | 5 mA (low standby consumption preserves bus power integrity) |
| Power-Down Current | 100–150 µA (enables electrical isolation during hot-swap without physical removal) |
| Dropout Voltage | 0.50–0.75 V (allows operation even with marginal TERMPWR sag) |
| Sink Current | 200 mA (handles actively negated SCSI signals without reference shift >60 mV) |
Pinout & Package
DS21T07S/T&R is housed in a 16-pin plastic SOIC (300-mil width, 0.402–0.412 inch body length) with exposed heat-sink ground (HS-GND) on the underside. Pin 1 is marked by notch or dot; pins are numbered counterclockwise.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | TERMPWR1 | Primary termination power input; must connect to SCSI TERMPWR and decouple with 2.2–4.7 µF capacitor |
| 2 | R1 | Signal termination resistor (110 Ω) for SCSI signal line 1 |
| 3 | R2 | Signal termination resistor (110 Ω) for SCSI signal line 2 |
| 4 | R3 | Signal termination resistor (110 Ω) for SCSI signal line 3 |
| 5 | R4 | Signal termination resistor (110 Ω) for SCSI signal line 4 |
| 6 | R5 | Signal termination resistor (110 Ω) for SCSI signal line 5 |
| 7 | VREF1 | Regulator reference node; externally tied to VREF2 and decoupled with 4.7 µF capacitor |
| 8 | GND | Signal ground reference (0 V); separate from HS-GND thermal pad |
| 9 | TERMPWR2 | Secondary termination power input; redundant TERMPWR connection for noise immunity |
| 10 | R6 | Signal termination resistor (110 Ω) for SCSI signal line 6 |
| 11 | R7 | Signal termination resistor (110 Ω) for SCSI signal line 7 |
| 12 | R8 | Signal termination resistor (110 Ω) for SCSI signal line 8 |
| 13 | R9 | Signal termination resistor (110 Ω) for SCSI signal line 9 |
| 14 | NC | No-connect pin; must remain unconnected |
| 15 | VREF2 | Second regulator reference node; externally shorted to VREF1 |
| 16 | PD | Power-down control input; internal 50 kΩ pull-up; driven low to isolate terminators from bus |
Key Features
| Feature | Design Value |
|---|---|
| Active Termination for 9 Lines | Integrates nine precision 110 Ω resistors-eliminates discrete resistor networks and improves impedance stability |
| Laser-Trimmed Resistors | ±2% tolerance ensures consistent signal integrity across temperature and unit-to-unit variation |
| Integrated Low-Dropout Regulator | Delivers stable 2.85 V reference from 4.0–5.5 V TERMPWR-removes need for external LDO |
| Hot-Plug Compatible Power-Down | PD pin enables electrical isolation during live insertion/removal-prevents bus glitches and damage |
| Onboard Thermal Shutdown | Triggers at 150°C-protects device and adjacent components under sustained overload or poor heatsinking |
Applications
| SCSI Disk Drive Termination | RAID Controller Backplane |
|---|---|
Use Scenario: Mounted on internal SCSI hard drives to provide end-of-bus termination without external components. IC Role / Device Role / Timing Role: Active SCSI signal line terminator and local TERMPWR regulator. Use Value: Eliminates manual jumper-based passive termination; ensures compliance with Ultra SCSI timing margins via stable 2.85 V bias. | Use Scenario: Embedded on RAID controller PCBs to terminate multiple SCSI channels in enterprise storage enclosures. IC Role / Device Role / Timing Role: Nine-line termination hub supporting dual 8-bit or single 16-bit SCSI buses. Use Value: Reduces component count vs. discrete solutions; enables hot-swap-safe termination reconfiguration via PD control. |
| SCSI Tape Library Interface | Legacy Workstation SCSI Expansion |
Use Scenario: Installed on tape autoloader backplanes where bus length and signal integrity demand active termination. IC Role / Device Role / Timing Role: Dual TERMPWR-input terminator ensuring robustness against TERMPWR droop across long cables. Use Value: Maintains >25 MHz signal fidelity on 18-line SCSI-2/3 buses using integrated 110 Ω resistors and low-capacitance switching. | Use Scenario: Used in vintage workstation add-in cards (e.g., SCSI host adapters) requiring compact, reliable termination. IC Role / Device Role / Timing Role: SOIC-16 drop-in replacement for older discrete or hybrid termination modules. Use Value: Enables direct PCB footprint reuse; simplifies BOM with single-IC solution meeting SCSI–1/Fast/Ultra compliance. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar SCSI termination applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| DS21T07E | 20-pin TSSOP package; identical electrical specs; includes dedicated HS-GND pins (pins 2,8,12,18) | Requires different PCB footprint and thermal layout; better suited for high-density or thermally constrained boards | Select DS21T07E when board space is limited and thermal management via exposed pad is prioritized over SOIC compatibility |
| MAX3218CPE+ | Not a functional equivalent-this is a RS-232 transceiver; excluded due to incorrect function match | N/A - invalid alternative | Not recommended; DS21T07S/T&R has no direct pin-compatible replacement outside Dallas/Maxim's own family |
Compared with DS21T07E, DS21T07S/T&R offers proven SOIC-16 compatibility for legacy designs but lacks dedicated thermal pads; neither part has verified drop-in alternatives from other manufacturers-designers should retain DS21T07S/T&R for continuity unless migrating to TSSOP layout.
Availability
DS21T07S/T&R is available at Aetrix Electronics and suitable for SCSI disk drive termination, RAID controller backplanes, tape library interfaces, and legacy workstation expansion requiring stable component supply and long-term obsolescence support.
Supply support for DS21T07S/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
Dallas Semiconductor-acquired by Maxim Integrated in 2001-specializes in precision analog, mixed-signal, and interface ICs with emphasis on reliability and legacy product stewardship.
The DS21T07S/T&R belongs to Dallas' SCSI interface product line, engineered specifically for robust, standards-compliant active termination in mission-critical storage subsystems operating across commercial temperature ranges.
FAQ
What is the primary function of the DS21T07S/T&R in a SCSI system?
The DS21T07S/T&R serves as a monolithic active SCSI terminator, providing nine precisely matched 110 Ω termination resistors and an integrated 2.85 V regulator. It replaces discrete resistor networks and external regulators on Fast and Ultra SCSI buses, ensuring signal integrity, noise immunity, and TERMPWR decoupling. The DS21T07S/T&R is designed for use at both ends of SCSI cable segments in single-ended configurations.
How does the power-down (PD) feature of the DS21T07S/T&R work?
The PD pin on the DS21T07S/T&R features an internal 50 kΩ pull-up resistor. Leaving PD open-circuited activates the device; driving PD low places it into power-down mode, turning off all internal termination transistors and isolating the DS21T07S/T&R electrically from the SCSI bus. This enables hot-plug compatibility without physical removal-critical for RAID and modular storage systems using the DS21T07S/T&R.
What external components are required for proper operation of the DS21T07S/T&R?
The DS21T07S/T&R requires two external capacitors: a 4.7 µF tantalum capacitor between VREF1 and VREF2 (tied together externally) and ground, plus either a 2.2 µF or 4.7 µF capacitor on each TERMPWR pin (TERMPWR1 and TERMPWR2). A 0.1 µF high-frequency bypass capacitor may also be added in parallel with the 4.7 µF VREF capacitor for fast-edge applications. No additional regulators or resistors are needed-the DS21T07S/T&R integrates all core termination functions.
Can the DS21T07S/T&R be used in 16-bit Wide SCSI configurations?
Yes-the DS21T07S/T&R terminates nine signal lines, so three DS21T07S/T&R devices are required per end of a 16-bit Wide SCSI bus (which has 27 active signal lines). Two DS21T07S/T&R units handle the 18 lines of an 8-bit bus. Each DS21T07S/T&R must be independently powered via TERMPWR1/TERMPWR2 and share common VREF1/VREF2 decoupling. This modular approach maintains design flexibility while ensuring full compliance with Ultra SCSI specifications.
Is the DS21T07S/T&R RoHS compliant and lead-free?
The DS21T07S/T&R was originally manufactured prior to mandatory RoHS implementation and is not inherently lead-free. However, Maxim Integrated (as successor to Dallas Semiconductor) offers qualified lead-free and RoHS-compliant versions under updated part numbers such as DS21T07S+ or DS21T07S-T. Customers requiring RoHS compliance must verify the specific date code and packaging suffix with Aetrix Electronics, as legacy DS21T07S/T&R reels may contain SnPb terminations.
DS21T07S/T&R Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 16-SOIC (0.295", 7.50mm 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:
- 16-SOIC
DS21T07S/T&R FAQ
1.How can I place an order for DS21T07S/T&R through Aetrix?
Please submit a Request for Quotation (RFQ) for DS21T07S/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 DS21T07S/T&R reliable?
The price and inventory of DS21T07S/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 DS21T07S/T&R is usually 5 days.
3.What payment methods are accepted for DS21T07S/T&R?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for DS21T07S/T&R transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for DS21T07S/T&R?
DS21T07S/T&R orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your DS21T07S/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 DS21T07S/T&R?
For technical support, including DS21T07S/T&R datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your DS21T07S/T&R requirements.
6.How does Aetrix verify that DS21T07S/T&R is sourced from the original manufacturer or authorized distributors?
All DS21T07S/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 DS21T07S/T&R meets industry standards.
7.What is the process for return or replacement of DS21T07S/T&R?
All DS21T07S/T&R units undergo pre-shipment inspection (PSI). If there is an issue with DS21T07S/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 DS21T07S/T&R part is unused and in its original packaging.
Return procedure for DS21T07S/T&R:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
DS21T07S/T&R Tags
-
LTC1344IG#PBF
Analog Devices Inc.
-
LTC1344AIG#PBF
Analog Devices Inc.
-
UCC5672PWP
Texas Instruments
-
LTC1344ACG#PBF
Analog Devices Inc.
-
MXL1344ACAG+
Analog Devices Inc./Maxim Integrated
-
LTC1344CG#PBF
Analog Devices Inc.
-
PACUSB-U3R
onsemi
-
PACUSB-D1Y5R
onsemi
-
FAN1804MCX
Fairchild Semiconductor
-
MCCS142237DT
onsemi
-
MCCS142237DTR2
onsemi
-
UCC5519PWPR
Texas Instruments
Tech Hub
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…
Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…
