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Texas Instruments UC2845DG4
- Part No.:
- UC2845DG4
- Manufacturer:
- Texas Instruments
- Category:
- Power Supply Controllers, Monitors
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
UC2845DG4.pdf
- Description:
- IC REG CTRLR MULT TOP 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:2,726
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Product details
Overview
UC2845DG4 from Texas Instruments is a fixed-frequency current-mode PWM controller IC designed for DC-DC converter applications requiring regulated input voltage operation. It features 8.4 V turn-on / 7.6 V turn-off UVLO thresholds, ≤50% maximum duty cycle, ±1 A peak output drive, and operates across –40°C to 85°C. It directly drives N-channel MOSFETs in buck, flyback, or forward topologies with pulse-by-pulse current limiting.
For engineers reviewing the UC2845DG4 datasheet, UC2845DG4 pinout, UC2845DG4 application, or UC2845DG4 equivalent, key selection criteria include its narrow UVLO hysteresis (0.8 V), 50% max duty cycle architecture, internal toggle flip-flop for frequency halving, and SOIC-8 package compatibility with board space-constrained power supplies.
Technical Context
The UC2845DG4 implements current-mode control using an internal PWM comparator that compares ISENSE voltage against COMP-derived threshold, enabling cycle-by-cycle current limiting. Its oscillator uses RT/CT pin with external R–C network to set fOSC, while OUTPUT switching frequency is exactly half fOSC due to integrated T-type flip-flop-distinct from UC2843's direct fSW = fOSC behavior.
It integrates a trimmed 5-V bandgap reference (±2% over temperature), error amplifier with 1 MHz unity-gain bandwidth and 90 dB PSRR, and undervoltage lockout with hysteresis optimized for stable DC-DC startup. The totem-pole OUTPUT stage sources/sinks up to 1 A peak, with low-state saturation voltage of 0.4 V at 20 mA sink load.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| UVLO Turn-on Threshold | 8.4 V - enables reliable startup from regulated 12 V or 5 V rails without false triggering |
| UVLO Turn-off Threshold | 7.6 V - provides 0.8 V hysteresis to reject supply noise during brownout recovery |
| Max Duty Cycle | 50% - enforced by internal toggle flip-flop; prevents transformer saturation in forward/flyback designs |
| Oscillator Frequency Range | 100–500 kHz - supports compact magnetics and EMI filtering in mid-power DC-DC converters |
| Output Drive Capability | ±1 A peak - directly drives gate capacitance of MOSFETs up to ~2 nF without external buffer |
| Reference Voltage Accuracy | 4.95–5.05 V at 25°C - ensures precise error amplifier biasing and stable feedback loop gain |
| Error Amp Unity-Gain BW | 1 MHz - enables fast transient response in voltage regulation loops with minimal phase lag |
Pinout & Package
UC2845DG4 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. Thermal resistance is RθJA = 117.4°C/W, suitable for natural convection cooling in industrial-grade PCB layouts.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - COMP | Error amplifier output | Open-collector node with internal current limit; sinking COMP to GND forces zero duty cycle |
| 2 - VFB | Inverting input to error amp | Accepts feedback voltage from optocoupler or resistor divider; sets regulation point at 2.5 V |
| 3 - ISENSE | Current sense input | Terminates switch conduction when sensed voltage reaches COMP-derived threshold; supports slope compensation |
| 4 - RT/CT | Oscillator timing node | Connects external R to VREF and C to GROUND; sets fOSC; OUTPUT toggles at fOSC/2 |
| 5 - GROUND | Analog & power return | Serves as common reference for error amp, oscillator, and current sense; requires low-impedance PCB trace |
| 6 - OUTPUT | MOSFET gate driver | Totem-pole output sourcing/sinking up to 1 A; actively held low during UVLO |
| 7 - VCC | Bias supply input | Accepts 12–28 V; includes internal 34 V clamp; bypass capacitor mandatory for stability |
| 8 - VREF | 5-V precision reference | Supplies timing current to RT/CT and powers internal logic; requires ≥0.1 µF ceramic bypass to GROUND |
Key Features
| Feature | Design Value |
|---|---|
| Pulse-by-pulse current limiting | Enables robust short-circuit protection without external sensing circuitry; resets each cycle |
| Internally trimmed 5-V reference | Eliminates need for external voltage reference; maintains ±2% accuracy over full temperature range |
| Automatic feedforward compensation | Improves line regulation by injecting input voltage variation into oscillator timing path |
| Double-pulse suppression | Prevents spurious switching during transients via latch-based PWM control architecture |
| Low start-up current (<1 mA) | Reduces auxiliary supply burden in high-efficiency offline adapters and isolated DC-DC modules |
Applications
| Industrial DC-DC Power Supply | Automotive Body Control Module (BCM) |
|---|---|
Use Scenario: Regulated 12 V input converted to 3.3 V/5 V for microcontroller and sensor rails in factory automation PLCs. IC Role / Device Role / Timing Role: Primary PWM controller implementing current-mode feedback loop with 50% duty cycle constraint for forward topology. Use Value: Narrow UVLO hysteresis (8.4 V / 7.6 V) ensures clean startup/shutdown during battery voltage fluctuations in 12 V systems. | Use Scenario: 12 V automotive battery powering infotainment display backlight and CAN transceiver supply. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller driving external N-MOSFET in buck configuration. Use Value: 1 A peak output drive eliminates gate driver IC, reducing BOM count and layout area in space-constrained BCM PCBs. |
| Telecom Point-of-Load Converter | Medical Diagnostic Equipment Power |
Use Scenario: Intermediate 48 V bus stepped down to 1.2 V/1.8 V for FPGA core logic in base station radios. IC Role / Device Role / Timing Role: High-frequency (300 kHz) PWM controller with external RC timing for tight EMI compliance. Use Value: 1 MHz error amplifier bandwidth enables fast load transient response required for burst-mode digital loads. | Use Scenario: Isolated 24 V input converted to 5 V/±15 V for analog front-end amplifiers and ADC references. IC Role / Device Role / Timing Role: Current-sense based controller in flyback topology with optocoupler feedback. Use Value: Internal 5-V reference provides stable bias for optocoupler LED drive, improving regulation accuracy over temperature. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PWM controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UC2844DG4 | Same SOIC-8 package and pinout; higher UVLO (16 V ON / 10 V OFF); same 50% max duty cycle | Designed for unregulated AC-DC inputs (e.g., rectified 100–240 VAC); not suitable for 12 V DC-DC | Select UC2844DG4 only when operating from high-voltage bulk DC with wide input variation |
| TL494CN | Dual-output, adjustable dead time, fixed 2.5 V reference; no integrated UVLO hysteresis; 16-pin DIP/SOIC | Supports push-pull and full-bridge topologies; lacks current-mode architecture and automatic feedforward | Choose TL494CN for dual-ended topologies or when independent control of two switches is required |
Compared with UC2844DG4 and TL494CN, UC2845DG4 offers tighter UVLO hysteresis and current-mode control optimized for single-switch DC-DC regulators, delivering superior line/load regulation and simplified loop compensation-but requires external slope compensation for >50% duty cycle operation (not applicable here).
Availability
UC2845DG4 is available at Aetrix Electronics and suitable for industrial DC-DC power supplies, automotive body control modules, and telecom point-of-load converters requiring stable component supply with guaranteed long-term manufacturability.
Supply support for UC2845DG4 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 leader specializing in analog, embedded processing, and power management technologies, with decades of expertise in power conversion IC design.
The UC284x product line delivers cost-effective, highly integrated current-mode PWM controllers for off-line and DC-DC applications, emphasizing minimal external components, robust protection, and thermal reliability across industrial temperature ranges.
FAQ
What is the maximum switching frequency supported by UC2845DG4?
The UC2845DG4 supports oscillator frequencies up to 500 kHz. Because its OUTPUT toggles at half the oscillator frequency due to the internal toggle flip-flop, the effective PWM switching frequency is up to 250 kHz. This is confirmed in Section 6.5 Electrical Characteristics and Figure 7-2 block diagram of the UCx844/UCx845 family, which includes UC2845DG4.
Does UC2845DG4 require external slope compensation?
No, UC2845DG4 does not require external slope compensation because its maximum duty cycle is limited to 50% by the internal toggle flip-flop. Slope compensation is only necessary for current-mode controllers operating above 50% duty cycle to prevent subharmonic oscillation-making it unnecessary for UC2845DG4 in typical applications.
What is the purpose of the VC pin on UC2845DG4?
The UC2845DG4 does not have a VC pin. That pin exists only on 14-pin and 20-pin variants (e.g., UC2845D in SOIC-14). The UC2845DG4 is the 8-pin SOIC version, which uses VCC to bias both control circuitry and the output stage-confirmed in Table 5-1 Pin Functions and Figure 5-1 pinout diagram.
Can UC2845DG4 drive a P-channel MOSFET directly?
No, UC2845DG4 is designed to drive N-channel MOSFETs with source grounded. Its OUTPUT stage is a totem-pole that actively pulls low and sources current to turn on the N-MOSFET gate. Driving a P-channel device would require level-shifting or inverting logic, which is not supported by the UC2845DG4 architecture or pin configuration.
How does the UVLO hysteresis of UC2845DG4 differ from UC2842DG4?
UC2845DG4 has UVLO thresholds of 8.4 V (turn-on) and 7.6 V (turn-off), yielding 0.8 V hysteresis-optimized for regulated DC inputs like 12 V batteries. UC2842DG4 uses 16 V / 10 V thresholds (6 V hysteresis) for unregulated AC-DC supplies. This difference is explicitly defined in Table 4 Device Comparison and Section 7.1 Overview of the UCx84x datasheet.
UC2845DG4 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- UCx84x
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- 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
UC2845DG4 FAQ
1.How can I place an order for UC2845DG4 through Aetrix?
Please submit a Request for Quotation (RFQ) for UC2845DG4 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 UC2845DG4 reliable?
The price and inventory of UC2845DG4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC2845DG4 is usually 5 days.
3.What payment methods are accepted for UC2845DG4?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC2845DG4 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC2845DG4?
UC2845DG4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC2845DG4 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 UC2845DG4?
For technical support, including UC2845DG4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC2845DG4 requirements.
6.How does Aetrix verify that UC2845DG4 is sourced from the original manufacturer or authorized distributors?
All UC2845DG4 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 UC2845DG4 meets industry standards.
7.What is the process for return or replacement of UC2845DG4?
All UC2845DG4 units undergo pre-shipment inspection (PSI). If there is an issue with UC2845DG4, 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 UC2845DG4 part is unused and in its original packaging.
Return procedure for UC2845DG4:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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