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Texas Instruments UC2845DTRG4
- Part No.:
- UC2845DTRG4
- Manufacturer:
- Texas Instruments
- Category:
- Power Supply Controllers, Monitors
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
UC2845DTRG4.pdf
- Description:
- IC REG CTRLR MULT TOP 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,364
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Product details
Overview
UC2845DTRG4 from Texas Instruments is a current-mode PWM controller IC designed for regulated-input DC-DC converters, featuring 8.4 V turn-on/7.6 V turn-off UVLO hysteresis, ≤1 mA start-up current, 50% maximum duty cycle, 5 V internal reference (±2%), and up to 500 kHz oscillator frequency. It drives N-channel MOSFETs via a 1 A peak totem-pole output stage and supports fixed-frequency operation with external RT/CT timing.
For engineers reviewing the UC2845DTRG4 datasheet, UC2845DTRG4 pinout, UC2845DTRG4 application, or UC2845DTRG4 equivalent, key selection criteria include its narrow UVLO hysteresis optimized for stable DC-DC regulation, 50% duty-cycle limit due to internal toggle flip-flop, and SOIC-8 package compatibility with board space-constrained power supplies.
Technical Context
The UC2845DTRG4 implements current-mode control using an internal PWM comparator that terminates switch conduction based on ISENSE voltage, with gain of 3 V/V and 1 V threshold at COMP = 5 V. Its oscillator uses RT/CT pin with 1.72/(RRT × CCT) frequency calculation and supports up to 500 kHz operation.
Unlike UC2842/UC2843 variants, UC2845DTRG4 incorporates an internal toggle flip-flop that halves the OUTPUT switching frequency relative to fOSC, enforcing ≤50% maximum duty cycle. Its UVLO thresholds (8.4 V ON / 7.6 V OFF) are specifically calibrated for regulated DC input rails, not off-line AC-DC applications.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| UVLO Threshold | 8.4 V turn-on / 7.6 V turn-off - enables reliable startup and hold-off on stable DC bus voltages like 12 V or 24 V systems |
| Max Duty Cycle | 50% - enforced by internal toggle flip-flop; limits conduction time per cycle for safe transformer-coupled or forward converter topologies |
| Oscillator Freq | Up to 500 kHz - sets maximum switching rate; actual fSW = fOSC/2 due to toggle logic |
| VREF Accuracy | 4.95–5.05 V at 25°C - provides precise 5 V reference for error amplifier bias and RT/CT charging current |
| ISENSE Gain | 3 V/V - converts sensed current into proportional voltage for PWM comparator trip point |
| OUTPUT Drive | ±1 A peak - directly drives N-MOSFET gates without external buffer; low-state saturation < 0.4 V @ 200 mA sink |
| Start-up Current | < 1 mA - minimizes auxiliary supply loading during initial power-up in low-power DC-DC designs |
Pinout & Package
UC2845DTRG4 is housed in an 8-pin SOIC (D) package measuring 4.90 mm × 6.00 mm, with gull-wing leads and standard JEDEC MS-012AC footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - COMP | Error amplifier output | Open-collector node with internal current limiting; forces zero duty cycle when pulled to GROUND |
| 2 - VFB | Inverting input to error amplifier | Accepts feedback voltage from output divider; 2.5 V nominal setpoint for regulation loop stability |
| 3 - ISENSE | Current sense input | Terminates PWM pulse when voltage reaches ~1 V; supports slope compensation via external ramp injection |
| 4 - RT/CT | Oscillator timing interface | Connects external R to VREF and C to GROUND; sets fOSC = 1.72/(R × C); fSW = fOSC/2 |
| 5 - GROUND | Analog and power return | Serves as common reference for all analog circuits and output stage; requires low-impedance PCB trace |
| 6 - OUTPUT | MOSFET gate driver output | Totem-pole stage sourcing/sinking up to 1 A peak; actively held low during UVLO |
| 7 - VCC | Supply input | Bias rail (12–28 V); includes 34 V internal clamp; bypass capacitor required for noise immunity |
| 8 - VREF | 5 V reference output | Stable 5 V source for timing resistor and external circuitry; requires ≥0.1 µF ceramic bypass to GROUND |
Key Features
| Feature | Design Value |
|---|---|
| Pulse-by-pulse current limiting | Real-time overcurrent protection per switching cycle using ISENSE voltage threshold, preventing MOSFET failure during fault conditions |
| Automatic feedforward compensation | Direct coupling of input voltage variations into oscillator timing, improving line transient response without external components |
| Double-pulse suppression | Internal logic prevents consecutive switching pulses during recovery from overcurrent or UVLO events, ensuring clean restart behavior |
| Enhanced load-response characteristics | High-gain error amplifier (65–90 dB) with 0.7–1 MHz unity-gain bandwidth enables fast correction of output voltage deviations |
| Internally trimmed bandgap reference | 5 V reference trimmed to ±2% accuracy across temperature, eliminating need for external calibration in precision DC-DC designs |
Applications
| Industrial DC-DC Power Supply | Telecom Point-of-Load Regulator |
|---|---|
Use Scenario: 24 V input to 5 V/3.3 V isolated or non-isolated conversion in programmable logic controllers and sensor interfaces. IC Role / Device Role / Timing Role: Primary PWM controller implementing current-mode feedback loop with fixed 250 kHz switching frequency. Use Value: Narrow UVLO hysteresis ensures stable operation under tightly regulated 24 V bus; 50% duty cycle prevents transformer saturation in forward converters. | Use Scenario: Compact 48 V to 12 V intermediate bus conversion feeding multiple downstream buck regulators in base station equipment. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller driving external N-MOSFET in active-clamp forward topology. Use Value: 1 A peak OUTPUT drive eliminates gate driver IC; integrated 5 V reference simplifies feedback network design. |
| Automotive Body Control Module | Medical Instrument DC Power |
Use Scenario: 12 V battery input to 3.3 V/5 V regulated outputs powering microcontrollers and CAN transceivers in vehicle ECUs. IC Role / Device Role / Timing Role: Core PWM controller managing synchronous rectification and current sensing in buck-derived topology. Use Value: −40°C to 85°C operating range meets automotive ambient requirements; low 1 mA start-up current reduces quiescent drain on battery. | Use Scenario: Isolated 24 V to ±15 V dual-output supply for op-amp signal conditioning stages in diagnostic imaging equipment. IC Role / Device Role / Timing Role: Current-mode controller regulating forward converter with optocoupler feedback and primary-side current sensing. Use Value: Pulse-by-pulse current limiting protects against short-circuit faults in safety-critical medical systems; double-pulse suppression ensures predictable fault recovery. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar current-mode PWM controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UC2844DTRG4 | Same SOIC-8 package and pinout; 16 V/10 V UVLO, 50% max duty cycle, same oscillator architecture | Designed for off-line AC-DC inputs (e.g., 100–240 VAC rectified), not regulated DC buses | Select UC2844DTRG4 only when input is unregulated high-voltage DC derived from rectified AC |
| UC3845N | PDIP-8 package; 0°C to 70°C temp range; identical UVLO (8.4 V/7.6 V) and 50% duty cycle | Lower temperature rating limits use to commercial-grade applications; through-hole mounting only | Choose UC3845N for prototyping or low-volume through-hole assembly where industrial temp range is not required |
Compared with UC2844DTRG4 and UC3845N, UC2845DTRG4 uniquely combines industrial temperature range (−40°C to 85°C), narrow UVLO hysteresis for DC-DC stability, and SOIC-8 surface-mount compatibility-making it optimal for volume-manufactured embedded power supplies requiring reliability and board-area efficiency.
Availability
UC2845DTRG4 is available at Aetrix Electronics and suitable for industrial DC-DC power supplies, telecom point-of-load regulators, and automotive body control modules requiring stable component supply, long-term lifecycle support, and consistent parametric performance.
Supply support for UC2845DTRG4 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 specializing in analog and embedded processing technologies, with leadership in power management ICs and industrial-grade control solutions.
The UC284x product line delivers cost-effective, highly integrated current-mode PWM controllers for fixed-frequency DC-DC and off-line power conversion, emphasizing minimal external component count and robust protection features.
FAQ
What is the maximum switching frequency supported by UC2845DTRG4?
The UC2845DTRG4 oscillator operates up to 500 kHz, but its OUTPUT switching frequency is half the oscillator frequency due to the internal toggle flip-flop. Therefore, UC2845DTRG4 supports a maximum switching frequency of 250 kHz. This 50% duty-cycle limitation is inherent to the UC2844/UC2845 family and is confirmed in the Electrical Characteristics table and Functional Block Diagram section of the datasheet.
Does UC2845DTRG4 require an external gate driver for typical MOSFETs?
No, UC2845DTRG4 does not require an external gate driver for most medium-power N-channel MOSFETs. Its totem-pole OUTPUT stage sources and sinks up to 1 A peak current, enabling direct gate drive. The datasheet specifies 200 mA average output current capability and low saturation voltages (< 0.4 V sink, >12 V source at 200 mA), making UC2845DTRG4 suitable for driving MOSFETs with gate charges up to ~200 nC at 250 kHz.
How does the UVLO behavior of UC2845DTRG4 differ from UC2842DTRG4?
UC2845DTRG4 has a turn-on threshold of 8.4 V and turn-off threshold of 7.6 V, providing narrow hysteresis optimized for regulated DC inputs like 12 V or 24 V buses. In contrast, UC2842DTRG4 uses 16 V turn-on / 10 V turn-off thresholds suited for unregulated off-line applications. This difference is explicitly defined in the Device Comparison Table and prevents interchangeability without circuit redesign.
Can UC2845DTRG4 be used in voltage-mode control configurations?
Yes, UC2845DTRG4 supports voltage-mode control by injecting a sawtooth ramp signal onto the ISENSE pin, overriding the current-sense function. The datasheet confirms this capability in Section 7.3.1.3, stating "A voltage ramp can be applied to this pin to run the device with a voltage-mode control configuration or to add slope compensation." This allows reuse of the UC2845DTRG4 in designs where current-mode is not required.
What is the purpose of the VC pin, and is it present on UC2845DTRG4?
The VC pin provides a dedicated bias supply for the output gate driver stage and appears only on 14-pin and 20-pin UCx84x packages (e.g., SOIC-14, LCCC-20). UC2845DTRG4 is an 8-pin SOIC device and does not include the VC pin; its output stage is biased directly from VCC. This is confirmed in Pin Configuration Figures 5-1 and Table 5-1, where VC is marked "-" for the 8-pin SOIC (D) package.
UC2845DTRG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- UCx84x
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Discontinued at Digi-Key
- Programmable:
- -
- Applications:
- PWM Controller
- Voltage - Input:
- -0.3V ~ 6.3V
- Voltage - Supply:
- 12V ~ 28V
- Current - Supply:
- 11 mA
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-SOIC
UC2845DTRG4 FAQ
1.How can I place an order for UC2845DTRG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for UC2845DTRG4 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 UC2845DTRG4 reliable?
The price and inventory of UC2845DTRG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC2845DTRG4 is usually 5 days.
3.What payment methods are accepted for UC2845DTRG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC2845DTRG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC2845DTRG4?
UC2845DTRG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC2845DTRG4 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 UC2845DTRG4?
For technical support, including UC2845DTRG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC2845DTRG4 requirements.
6.How does Aetrix verify that UC2845DTRG4 is sourced from the original manufacturer or authorized distributors?
All UC2845DTRG4 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 UC2845DTRG4 meets industry standards.
7.What is the process for return or replacement of UC2845DTRG4?
All UC2845DTRG4 units undergo pre-shipment inspection (PSI). If there is an issue with UC2845DTRG4, 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 UC2845DTRG4 part is unused and in its original packaging.
Return procedure for UC2845DTRG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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