SN74CBT3245ADWR - Octal FET Bus Switch 5V SOIC-20 | TI
MPN: SN74CBT3245ADWR ✗ پایان تولیدSN74CBT3245ADWR نمای کلی
A FET bus switch is a type of analog switch that uses N-channel MOSFET pass transistors to connect or disconnect signal paths between two ports. Within the signal-routing hierarchy, bus switches sit between logic buffers and analog multiplexers: unlike buffers they add negligible propagation delay, and unlike analog MUXes they are optimized for high-bandwidth digital bus isolation. The SN74CBT3245A belongs to the CBT (CrossBar Technology) family, optimized for low on-state capacitance and high bandwidth.
Key features include a low on-state resistance of typically 5 ohms, propagation delay of less than 250 ps, and near-zero added jitter because signals pass through an analog FET path rather than a buffered logic stage. The switch supports bidirectional data flow and 5-V level handling, suited to signal switching rather than power delivery.
Technically, the device is fabricated in a CMOS process achieving low static power consumption. The internal FET switch presents a low-capacitance, low-resistance path that minimizes signal distortion, and the 245-type pinout matches industry-standard octal transceiver footprints across SOIC, SSOP, TSSOP, and TVSOP package options.
Typical applications include bus isolation in microprocessor systems, hot-swap and power-down isolation on backplanes, memory bus switching, and signal routing in networking and telecommunications equipment where high-speed data buses must be connected or isolated under logic control.
A key design consideration: control the OE pin properly to avoid bus contention, and note this part is EOL per TI.com - plan the drop-in alternatives listed on this page for new designs.
جایگزین‌های drop-in برای SN74CBT3245ADWR — همان پکیج، سازگار پین‌به‌پین. قطعات با پکیج متفاوت که نیاز به تغییر PCB دارند مستثنی هستند.
SN74CBT3245CDWR
✅ جایگزین مستقیم📋 جایگزین مرجع (خارج از کاتالوگ)
SN74CBT3245ADW
✅ جایگزین مستقیم📋 جایگزین مرجع (خارج از کاتالوگ)
74CBT3245AD,112
✅ جایگزین مستقیم ⚠️ مشخصات تأییدنشده📋 جایگزین مرجع (خارج از کاتالوگ)
74FST3245
✅ جایگزین مستقیم ⚠️ مشخصات تأییدنشده📋 جایگزین مرجع (خارج از کاتالوگ)
SN74CBTD3384DW
⚡ پکیج یکسان ⚠️ مشخصات تأییدنشده📋 جایگزین مرجع (خارج از کاتالوگ)
SN74CBT3245ADWR حداکثر مقادیر مجاز و مشخصات الکتریکی
| عملکرد | Octal FET bus switch, 8 x 1:1 (SPST) |
| Configuration | One 8-bit bidirectional switch |
| Supply Voltage Range | 4.5 V to 5.5 V |
| Control Input | OE (active-low output enable) |
| Input Compatibility | TTL-compatible control input |
| Signal Voltage Range | 5 V (switch does not propagate beyond VCC level) |
| Technology Family | CBT (CrossBar Technology), CMOS process |
| بسته‌بندی | SOIC-20 (DW) |
| Pinout | Standard 245-type pinout |
| نوع نصب | Surface Mount |
| Lifecycle | No longer in production (EOL per TI.com) |
پیکربندی پین SN74CBT3245ADWR
| پین 1 | OE — Output enable, active low (switch on when low) |
| پین 2 | A1 — Port A bit 1 |
| پین 3 | A2 — Port A bit 2 |
| پین 4 | A3 — Port A bit 3 |
| پین 5 | A4 — Port A bit 4 |
| پین 6 | A5 — Port A bit 5 |
| پین 7 | A6 — Port A bit 6 |
| پین 8 | A7 — Port A bit 7 |
| پین 9 | A8 — Port A bit 8 |
| پین 10 | GND — Ground |
| پین 11 | B8 — Port B bit 8 |
| پین 12 | B7 — Port B bit 7 |
| پین 13 | B6 — Port B bit 6 |
| پین 14 | B5 — Port B bit 5 |
| پین 15 | B4 — Port B bit 4 |
| پین 16 | B3 — Port B bit 3 |
| پین 17 | B2 — Port B bit 2 |
| پین 18 | B1 — Port B bit 1 |
| پین 19 | OE — Output enable (common control) |
| پین 20 | VCC — 4.5V to 5.5V supply |
کاربردهای معمول
SN74CBT3245ADWR مناسب است برای 6 کاربردs: Microprocessor Bus Isolation, Hot-Swap and Power-Down Isolation, Memory Bus Switching, Networking and Telecommunications Line Cards, Industrial Control Backplanes, Test and Measurement Signal Routing.
Microprocessor Bus Isolation
The SN74CBT3245ADWR isolates a processor memory or peripheral bus from shared backplane resources with sub-nanosecond delay, because the CBT FET path adds no buffered logic delay. Its ~5 ohm on-resistance preserves signal edges on heavily loaded 5V buses, while the single active-low OE gives the CPU simple control over bus connection. Placing the switch between the local bus and the shared bus lets multiple cards share one resource; the trade-off is that the FET does not regenerate signal levels, so bus loading must be budgeted.
پیشنهادی
Hot-Swap and Power-Down Isolation
On backplane systems, cards being inserted or unpowered must present high impedance to the live bus. The SN74CBT3245ADWR opens the connection path when OE is deasserted or VCC is absent, isolating the card's logic from the backplane with the low capacitance typical of the CBT family. This prevents backplane glitching during card insertion. Note that the switch does not provide current limiting or true hot-swap staging - pair it with proper sequencing control of the OE pin during power ramp.
پیشنهادی
Memory Bus Switching
The device switches 5V memory address/data buses between two controllers, exploiting the standard 245-type pinout so existing 245 footprints accept the part directly. Because the FET path adds less than 250 ps of delay and no jitter-inducing buffers, memory timing margins are preserved even at high clock rates. The on-resistance of roughly 5 ohms adds minimal RC loading with typical bus capacitance. Designers should verify the VCC-threshold limit keeps logic-high levels compatible with the attached 5V memory devices.
پیشنهادی
Networking and Telecommunications Line Cards
Line cards in telecom and networking equipment use the SN74CBT3245ADWR to connect or isolate 5V control and status buses under logic control. The CMOS process draws negligible static current, and the transparent analog path passes signals without the asymmetric edge rates of buffered transceivers. Its EOL status matters here: long-lifetime telecom programs should qualify the NXP 74CBT3245AD cross-brand equivalent or the TI C variant to guarantee supply continuity over the deployment horizon.
پیشنهادی
Industrial Control Backplanes
In PLC and industrial I/O backplanes running 5V logic, the SN74CBT3245ADWR switches shared I/O buses between multiple slot controllers. The 245-type pinout supports legacy boards designed around 74x245 transceivers, enabling drop-in bus-switching upgrades without PCB changes. Robust 5V operation tolerates industrial supply tolerances across the full 4.5V to 5.5V range. Because the part is passive, designers must include pull resistors so buses remain defined when the switch is off.
پیشنهادی
Test and Measurement Signal Routing
Instrumentation designs use the CBT switch to route 5V digital test signals between measurement channels with minimal signal degradation - the FET pass path introduces no deterministic jitter and only the RC delay from ~5 ohms on-resistance against cable and probe capacitance. The high bandwidth of the CBT family keeps edge fidelity for fast digital stimulus. For automated test equipment, the transparent switch also simplifies calibration since it adds no buffer offsets to the path.
پیشنهادی
خلاصه محصولات پیشنهادی
داده‌های مرجع مهندسی برای SN74CBT3245ADWR — مقایسه، راهنمای طراحی و اطلاعات انطباق.
راهنمای انتخاب
مقایسه با جایگزین‌ها
| پارامتر | این محصول | SN74CBT3245CDWR | SN74CBT3245ADW | 74CBT3245AD,112 | 74FST3245 |
|---|---|---|---|---|---|
| Package | SOIC-20 (DW) | SOIC-20 (DW) - same | SOIC-20 (DW) - same | SO-20 - same footprint | SOIC-20 - same footprint |
| Brand | Texas Instruments | Texas Instruments | NXP Semiconductors | Renesas Electronics (IDT) | |
| Configuration | 1 x 8-bit bidirectional | 1 x 8-bit bidirectional | 1 x 8-bit bidirectional | 1 x 8-bit bidirectional | |
| Supply Voltage | 4.5V to 5.5V | 4.5V to 5.5V | 4.5V to 5.5V | 4.5V to 5.5V | |
| Control Input | OE (active low) | OE (active low) | OE (active low) | OE (active low) |
تفاوت‌های کلیدی
- Passive FET path with near-zero delay (در مقابلSN74LVC244A)
- True power-down isolation (در مقابلSN74LVC244A)
- 245-type standard pinout in DW package (در مقابل74FST3245)
یادداشت‌های طراحی
The DW SOIC-20 footprint matches the industry-standard 245 transceiver land pattern, so the SN74CBT3245ADWR drops onto existing layouts. Keep switch traces short and match A/B port trace lengths for high-speed buses; the ~5 ohm on-resistance plus trace and bus capacitance forms the dominant RC in the signal path.
OE is active low and the switch turns on when OE is grounded. Always fit a pull-up on OE so the bus defaults to isolated during power-up, MCU reset, and card insertion - otherwise two drivers can contend on the shared bus. Also remember the CBT switch cannot pass signals above approximately VCC minus a threshold; this part is strictly a 5V-domain switch.
CBT switches draw near-zero static supply current (CMOS), so decoupling needs are modest: one 0.1 uF ceramic at VCC pin 20 plus bulk capacitance per board region is sufficient. The FET path does not consume signal power; budget dissipation by control logic only. The switch itself provides no overcurrent protection - external circuitry must limit fault currents on the bus.
اطلاعات انطباق
Compliance data not present in provided web data; confirm on TI.com product page for SN74CBT3245A.
