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Texas Instruments UC3702N
- Part No.:
- UC3702N
- Manufacturer:
- Texas Instruments
- Category:
- Full Half-Bridge (H Bridge) Drivers
- Package:
- 16-DIP (0.300", 7.62mm)
- Datasheet:
-
UC3702N.pdf
- Description:
- IC QUAD PWM RELAY DRIVER 16-DIP
- Quantity:
- Payment:
- Shipping:
Inventory:1,242
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Product details
Overview
UC3702N from Texas Instruments is a quad PWM relay driver IC that regulates constant average voltage across up to four relay coils using the coil inductance as the energy storage element. It operates with unregulated VBUS up to +42.5V, delivers up to 50mA per relay, integrates Schottky flyback diodes, and requires only two external resistors and one capacitor for programming. It is used in industrial control panels where cost-effective relay driving without dedicated relay supplies is required.
For engineers reviewing the UC3702N datasheet, UC3702N pinout, UC3702N application, or UC3702N equivalent, key selection criteria include its 0°C to +70°C operating temperature range, PDIP-16 package, integrated short-circuit protection with periodic retry, and user-selectable 150–200 kHz nominal oscillator frequency via R1/R2/CT.
Technical Context
The UC3702N implements a fixed-frequency, current-regulating PWM architecture where each relay coil serves as the inductive element in a buck-derived converter. The oscillator's ON duty cycle is dynamically adjusted based on VBUS sensing through R1 to maintain programmed average coil voltage independent of supply ripple.
Four independent high-side referenced, open-collector NPN output drivers (OUTA–OUTD) are controlled by logic-level inputs (INA–IND), with global active-low RESET disabling all outputs and halting oscillator operation. Internal Schottky diodes provide flyback path, eliminating need for external diodes.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Operating Temperature | 0°C to +70°C - defines ambient range for guaranteed performance in commercial industrial environments. |
| VBUS Max Rating | +42.5V - supports relay supplies derived from rectified AC or noisy DC rails without regulation. |
| Per-Relay Output Current | 50mA average - sufficient to drive typical 12V/24V industrial relays with 250–500Ω coil resistance. |
| Nominal Oscillator Frequency | 150–200 kHz - set by R1=203kΩ, R2=43.2kΩ, CT=220pF; ensures coil current ripple remains low while minimizing switching losses. |
| VCC Supply | +5V ±5% - serves as precision reference for average voltage regulation; requires ≥1µF local decoupling. |
| Short-Circuit Protection | On-chip with periodic retry - disables output and retries after fault detection, preventing thermal runaway during coil shorts. |
| Input Logic Thresholds | Logic Low ≤0.5V, Logic High ≥3V - compatible with TTL and 5V CMOS microcontroller outputs. |
Pinout & Package
UC3702N is housed in a 16-pin Plastic Dual In-line Package (PDIP-N), with exposed leads suitable for through-hole mounting and manual prototyping. Thermal performance is optimized via low-impedance ground connections at both GND pins.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| INA–IND | Individual digital enable inputs | Active-high logic signals directly control respective relay driver; no external pull-ups required. |
| OUTA–OUTD | Open-collector NPN outputs | Low-side connection points for relay coils; internal Schottky diode provides flyback path to VBUS. |
| R1 | VBUS-sensing input | Connects to VBUS via external resistor; sets average relay voltage via feedback ratio with R2 and VCC. |
| R2 | Oscillator timing input | Grounded via external resistor; together with CT, determines OFF time and thus oscillator frequency. |
| CT | Oscillator timing capacitor | Capacitor from CT to GND sets nominal frequency; ≥220pF recommended for accuracy and stability. |
| RESET | Global active-low reset | Pulls low to halt oscillator and force all outputs into high-impedance state; debouncing recommended. |
| VCC | +5V logic and reference supply | Supplies internal logic, oscillator, and voltage reference; must be regulated and well-decoupled. |
| VBUS | Unregulated relay power rail | High-current input supplying energy to all four relay coils; accepts significant 100/120Hz ripple. |
| GND (Pins 8 & 16) | Signal and power ground | Both pins must connect to low-noise system ground plane to minimize noise coupling and ensure regulation accuracy. |
Key Features
| Feature | Design Value |
|---|---|
| Integrated Schottky flyback diodes | Eliminates need for four discrete 1N400x or similar diodes, reducing BOM count and PCB area. |
| User-programmable relay voltage | Set precisely via R1/R2 ratio and VCC; enables support for 9V, 12V, 24V, or 48V relays with same IC. |
| Constant average coil voltage regulation | Maintains target voltage despite ±20% VBUS variation or 100Hz ripple, ensuring consistent relay pull-in and hold. |
| Short-circuit protection with auto-retry | Detects coil short or wiring fault, disables output, waits, then re-attempts-prevents latch-up and thermal damage. |
| Global reset functionality | Synchronizes all four drivers to safe state during power-up, brown-out, or system fault recovery sequences. |
Applications
| Industrial PLC I/O Modules | Building Automation Control Panels |
|---|---|
Use Scenario: Driving multiple 12V/24V electromechanical relays in DIN-rail mounted programmable logic controller output modules. IC Role / Device Role / Timing Role: Quad relay driver providing isolated, regulated coil drive from shared unregulated 24VDC bus. Use Value: Eliminates need for separate relay supply rails or DC-DC converters, reducing system cost and board space by >30%. | Use Scenario: Controlling HVAC dampers, lighting circuits, and security locks via relay-based outputs in commercial building management systems. IC Role / Device Role / Timing Role: Centralized relay interface IC accepting TTL-level commands from microcontroller and delivering robust coil drive. Use Value: Tolerates field-wiring-induced noise and supply ripple common in long cable runs, improving system reliability. |
| Test Equipment Relay Matrices | Medical Device Isolation Interfaces |
Use Scenario: Configuring signal routing paths in automated test equipment using banks of SPST/SPDT reed and mechanical relays. IC Role / Device Role / Timing Role: Precision current-regulated driver ensuring consistent relay actuation timing and contact life across channels. Use Value: Programmable frequency and voltage reduce coil heating during extended closed states, extending relay MTBF. | Use Scenario: Providing galvanically isolated relay control in diagnostic imaging or patient monitoring devices requiring safety-rated switching. IC Role / Device Role / Timing Role: Safety-critical interface IC enabling microcontroller to safely energize medical-grade relays without auxiliary supplies. Use Value: Integrated protection features prevent single-point failures from causing unintended relay activation or latch-up. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar quad relay driver applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ULN2803A | Fixed 500mA Darlington sink drivers; no voltage regulation, no oscillator, no short-circuit retry. | Requires external flyback diodes and regulated relay supply; suited for simple on/off, not precision voltage control. | Select ULN2803A when relay load current exceeds 50mA or when VBUS is already well-regulated and cost is primary concern. |
| TPL7407L | 7-channel NMOS sink driver with integrated diodes; no regulation, no oscillator, no RESET pin; max 600mA per channel. | Lacks average voltage control and short-circuit protection; designed for higher-current loads with simpler drive requirements. | Select TPL7407L when driving higher-current solenoids or when multi-channel count (7 vs 4) outweighs regulation needs. |
Compared with ULN2803A and TPL7407L, the UC3702N uniquely delivers regulated average coil voltage from unregulated rails, making it the only option among the three capable of stable relay operation under 100Hz ripple or wide VBUS variation-critical for cost-sensitive industrial designs avoiding dedicated DC-DC stages.
Availability
UC3702N is available at Aetrix Electronics and suitable for industrial PLC I/O modules, building automation control panels, and test equipment relay matrices requiring stable component supply and long-term obsolescence management.
Supply support for UC3702N 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
Texas Instruments is a global semiconductor company headquartered in Dallas, Texas, designing and manufacturing analog, embedded processing, and logic products for industrial, automotive, and communications markets.
The UC3702N belongs to TI's legacy power interface product line, engineered specifically to simplify relay-based control in cost-sensitive industrial systems by replacing discrete transistor/diode/flyback regulator combinations with a single integrated solution.
FAQ
What is the maximum VBUS voltage the UC3702N can handle?
The UC3702N has an absolute maximum VBUS rating of +50V, but its specified operational limit is +42.5V. Exceeding +42.5V may cause premature device failure or regulation inaccuracy. For reliable long-term operation, VBUS should remain ≤42.5V with appropriate derating margin, especially under high-temperature conditions. The UC3702N datasheet confirms this value in the Absolute Maximum Ratings table.
Does the UC3702N require external flyback diodes for relay coils?
No, the UC3702N does not require external flyback diodes. It integrates Schottky diodes internally, connected from each OUTx pin to VBUS, providing a low-loss path for inductive kickback energy. This eliminates the need for four discrete diodes in typical implementations, reducing component count, PCB area, and assembly cost. The UC3702N datasheet explicitly lists "Integrated Schottky Flyback Diodes" as a key feature.
Can the UC3702N drive relays with different rated voltages simultaneously?
No, the UC3702N cannot drive relays with different rated voltages simultaneously. All four relays must share the same programmed average coil voltage because the R1/R2 network sets a single reference for all outputs. The UC3702N datasheet states: "The rated relay coil voltage of all relays to be driven by a single UC3702 must be the same." Mixed-voltage operation would result in under- or over-driving some coils.
What is the purpose of the RESET pin on the UC3702N?
The RESET pin on the UC3702N is an active-low global control that halts the internal oscillator and forces all four output drivers (OUTA–OUTD) into high-impedance open-collector state. This provides synchronized safe shutdown during power-up sequencing, brown-out events, or system fault recovery. The UC3702N datasheet specifies RESET delay of 2µs and recommends debouncing for noise immunity.
How is the nominal oscillator frequency set for the UC3702N?
The nominal oscillator frequency of the UC3702N is set by external components: resistor R2 (to GND), resistor R1 (to VBUS), and capacitor CT (to GND). With R1 = 203kΩ, R2 = 43.2kΩ, and CT = 220pF, the frequency is 150–200 kHz. The UC3702N datasheet provides the exact formula and tolerance ranges in the Electrical Characteristics table under "NOMINAL Operating Frequency."
UC3702N Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 16-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Output Configuration:
- -
- Applications:
- -
- Interface:
- -
- Load Type:
- -
- Technology:
- -
- Rds On (Typ):
- -
- Current - Output / Channel:
- 50mA
- Current - Peak Output:
- 175mA
- Voltage - Supply:
- 4.5V ~ 8V
- Voltage - Load:
- -
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Features:
- -
- Fault Protection:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 16-PDIP
UC3702N FAQ
1.How can I place an order for UC3702N through Aetrix?
Please submit a Request for Quotation (RFQ) for UC3702N 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 UC3702N reliable?
The price and inventory of UC3702N are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3702N is usually 5 days.
3.What payment methods are accepted for UC3702N?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3702N transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC3702N?
UC3702N orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC3702N 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 UC3702N?
For technical support, including UC3702N datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3702N requirements.
6.How does Aetrix verify that UC3702N is sourced from the original manufacturer or authorized distributors?
All UC3702N 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 UC3702N meets industry standards.
7.What is the process for return or replacement of UC3702N?
All UC3702N units undergo pre-shipment inspection (PSI). If there is an issue with UC3702N, 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 UC3702N part is unused and in its original packaging.
Return procedure for UC3702N:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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