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STMicroelectronics E-UC3845BD1013TR
- Part No.:
- E-UC3845BD1013TR
- Manufacturer:
- STMicroelectronics
- Category:
- DC DC Switching Controllers
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
E-UC3845BD1013TR.pdf
- Description:
- IC REG CTRLR BOOST/FLYBACK 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,534
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Product details
Overview
E-UC3845BD1013TR from STMicroelectronics is a current-mode PWM controller IC designed for fixed-frequency DC-DC and off-line power supplies. It features 8.4 V turn-on / 7.6 V turn-off UVLO, ≤50% maximum duty cycle (due to internal toggle flip-flop), 250 kHz guaranteed oscillator frequency, and ±1 A totem-pole output capable of directly driving N-channel MOSFET gates. It is used in low-power AC-DC adapters and isolated flyback converters requiring precise cycle-by-cycle current limiting.
For engineers reviewing the E-UC3845BD1013TR datasheet, E-UC3845BD1013TR pinout, E-UC3845BD1013TR application, or E-UC3845BD1013TR equivalent, key selection criteria include UVLO thresholds (8.4 V/7.6 V), 50% max duty cycle limitation, 5 V reference accuracy (±2%), current sense gain (3 V/V), and SO8 package thermal resistance (150 °C/W).
Technical Context
The UC3845B implements current-mode control using an internal error amplifier, PWM latch, and comparator that compares sensed inductor current against the error amp output. Its oscillator uses RT/CT programming with discharge current trimmed to 7.5–8.8 mA, enabling stable 250 kHz operation with <1% tempco drift.
Unlike UC3842B/3B, the UC3845B includes an internal toggle flip-flop that blanks the output every other clock cycle-enforcing a hard 50% maximum duty cycle limit. This architecture prevents transformer saturation in forward and push-pull topologies while maintaining cycle-by-cycle current limiting and automatic feed-forward compensation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | Guaranteed 250 kHz at 25°C; supports up to 500 kHz with external RT/CT tuning |
| UVLO Thresholds | 8.4 V (turn-on), 7.6 V (turn-off); enables reliable start-up in low-input-voltage DC-DC applications |
| Max Duty Cycle | 47–50%; enforced by internal toggle flip-flop for safe operation in forward/push-pull converters |
| Reference Voltage | 5.00 V ±2% (4.90–5.10 V); internally trimmed, supports CT charging and feedback loop stability |
| Output Drive | ±1 A peak sink/source; drives MOSFET gates directly without external buffer in sub-30 W designs |
| Current Sense Gain | 3.0 V/V (2.85–3.15 V/V); converts sense resistor voltage to precise trip point for PWM latch |
| Start-up Current | <0.5 mA at 6.5 V; minimizes auxiliary winding losses in flyback startup circuits |
Pinout & Package
Package: SO8 (Small Outline Integrated Circuit, 150 °C/W junction-to-ambient thermal resistance).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - COMP | Error amplifier output | Provides access to EA output for loop compensation network (e.g., Type II/III RC networks) |
| 2 - VFB | Inverting input of error amplifier | Connects to output voltage divider; sets regulation point via 2.5 V internal reference threshold |
| 3 - ISENSE | Current sense comparator input | Accepts voltage from sense resistor; terminates switch conduction when ≥1.0 V (typ.) |
| 4 - RT/CT | Oscillator timing node | RT connects to VREF (pin 8); CT connects to GND (pin 5); sets fOSC and discharge slope |
| 5 - GROUND | Power and signal common reference | Single-point ground for control logic, oscillator, and current sense to minimize noise coupling |
| 6 - OUTPUT | PWM totem-pole driver output | Sources/sinks up to 1 A; low-state during UVLO or fault latch; drives gate of N-MOSFET directly |
| 7 - VCC | Supply input | Operates from 7.6–30 V; powers internal bias, reference, and logic; self-limiting above 30 V |
| 8 - VREF | 5 V precision reference output | Supplies 50 mA max; charges CT through RT; used for feedback scaling and auxiliary bias |
Key Features
| Feature | Design Value |
|---|---|
| Latching PWM with cycle-by-cycle current limiting | Ensures single-pulse shutdown per overcurrent event; eliminates need for external fault latches in basic SMPS designs |
| Internally trimmed 5 V reference with ±2% tolerance | Eliminates external reference IC; reduces BOM count and improves long-term regulation stability over temperature |
| Automatic feed-forward compensation | Compensates for input line variations in real time without additional sensing circuitry or control loops |
| Low start-up current (<0.5 mA) | Enables high-impedance startup from auxiliary windings, reducing standby losses in flyback adapters |
| High-current totem-pole output (±1 A) | Drives standard 10 nC gate charge MOSFETs at 250 kHz without external drivers, simplifying layout and cost |
Applications
| AC-DC Wall Adapters | Isolated Flyback Converters |
|---|---|
Use Scenario: 5–24 W universal-input (90–264 VAC) offline power supply for consumer electronics. IC Role / Device Role / Timing Role: Primary-side PWM controller implementing current-mode feedback, UVLO, and soft-start via external RC on COMP. Use Value: 50% duty cycle limit prevents transformer core saturation under high-line conditions; 8.4 V/7.6 V UVLO ensures reliable restart after brownout. |
Use Scenario: Regulated 12 V/1 A isolated output for industrial sensors powered from 24 VDC bus. IC Role / Device Role / Timing Role: Secondary-side referenced controller with optocoupler feedback; regulates output via VFB pin with 2.5 V internal EA threshold. Use Value: ±1 A output drives 500 pF gate capacitance at 250 kHz with <150 ns rise/fall; low 0.4 V VOL at 20 mA ensures clean MOSFET turn-off. |
| Forward Converters | Push-Pull DC-DC Modules |
Use Scenario: 48 V input to 5 V/3 A telecom intermediate bus converter operating at 250 kHz. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller with external slope compensation on ISENSE to stabilize duty cycle. Use Value: Internal toggle flip-flop enforces strict 50% max duty cycle, eliminating risk of transformer flux imbalance in forward topology. |
Use Scenario: Dual-switch 24 V to ±15 V isolated module for analog instrumentation requiring symmetrical drive. IC Role / Device Role / Timing Role: Master controller generating complementary gate signals via external logic; OUTPUT drives high-side switch with bootstrap support. Use Value: 250 kHz oscillator accuracy ±3% over –40 to +105°C enables predictable EMI filtering; 5 V reference powers auxiliary comparators and bias rails. |
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 |
|---|---|---|---|
| UC3842BD1013TR | UVLO = 16 V/10 V; 96–100% max duty cycle; no toggle flip-flop | Suitable for boost, buck, and offline flyback where full duty cycle needed | Select when higher input voltage range and >50% duty cycle are required; not drop-in due to UVLO and duty cycle mismatch |
| NCP1014ST100T3G | Integrated 700 V MOSFET; fixed 100 kHz; no external RT/CT; lower IQ (2.5 mA) | Targeted for ultra-low-cost, low-power AC-DC; no current sense gain adjustment | Choose for simplified BOM and smaller footprint in <10 W applications; lacks programmable frequency and flexible compensation |
Compared with UC3842BD1013TR, E-UC3845BD1013TR trades full-duty-cycle capability for inherent transformer safety in forward topologies; versus NCP1014ST100T3G, it offers design flexibility (RT/CT tuning, external compensation, ±1 A drive) at the cost of higher external component count.
Availability
E-UC3845BD1013TR is available at Aetrix Electronics and suitable for AC-DC adapters, isolated flyback converters, and forward-mode DC-DC supplies requiring stable component supply, consistent parametric performance across temperature, and long-lifecycle availability.
Supply support for E-UC3845BD1013TR 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
STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.
E-UC3845BD1013TR belongs to the UC384xB family of current-mode PWM controllers, developed specifically for cost-sensitive, high-reliability fixed-frequency switch-mode power supplies requiring minimal external components and robust fault protection.
FAQ
What is the maximum recommended operating frequency for E-UC3845BD1013TR?
The UC3845B guarantees 250 kHz oscillator frequency at 25°C and supports operation up to 500 kHz with appropriate RT/CT values and layout optimization. At 500 kHz, propagation delays and gate drive strength must be verified; typical designs operate between 200–300 kHz for optimal efficiency and EMI control.
Can E-UC3845BD1013TR drive a P-channel MOSFET directly?
No - the OUTPUT pin is a totem-pole stage optimized for sinking current into an N-channel MOSFET gate. Driving a P-channel device requires level-shifting or an external inverter; the IC's logic is designed for low-side N-MOSFET gate drive with active-low default state during UVLO.
How does the internal toggle flip-flop affect duty cycle in E-UC3845BD1013TR?
The toggle flip-flop forces the OUTPUT to remain low every other clock cycle, limiting maximum duty cycle to ≤50%. This prevents transformer saturation in forward and push-pull topologies and eliminates need for external duty cycle clamping circuits - a key differentiator from UC3842B/3B variants.
What is the purpose of the 1 V threshold on the current sense comparator?
The current sense comparator trips when the voltage at ISENSE (pin 3) reaches ≈1.0 V (typ.), corresponding to peak inductor current Ipk = 1.0 V / Rsense. This precise, temperature-stable threshold enables accurate cycle-by-cycle current limiting without external op-amps or references.
E-UC3845BD1013TR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Output Type:
- Transistor Driver
- Function:
- Step-Up/Step-Down
- Output Configuration:
- Positive, Isolation Capable
- Topology:
- Boost, Flyback
- Number of Outputs:
- 1
- Output Phases:
- 1
- Voltage - Supply (Vcc/Vdd):
- 7.6V ~ 30V
- Frequency - Switching:
- Up to 500kHz
- Duty Cycle (Max):
- 48%
- Synchronous Rectifier:
- No
- Clock Sync:
- No
- Serial Interfaces:
- -
- Control Features:
- Frequency Control
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
E-UC3845BD1013TR FAQ
1.How can I place an order for E-UC3845BD1013TR through Aetrix?
Please submit a Request for Quotation (RFQ) for E-UC3845BD1013TR 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 E-UC3845BD1013TR reliable?
The price and inventory of E-UC3845BD1013TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for E-UC3845BD1013TR is usually 5 days.
3.What payment methods are accepted for E-UC3845BD1013TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for E-UC3845BD1013TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for E-UC3845BD1013TR?
E-UC3845BD1013TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your E-UC3845BD1013TR 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 E-UC3845BD1013TR?
For technical support, including E-UC3845BD1013TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your E-UC3845BD1013TR requirements.
6.How does Aetrix verify that E-UC3845BD1013TR is sourced from the original manufacturer or authorized distributors?
All E-UC3845BD1013TR 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 E-UC3845BD1013TR meets industry standards.
7.What is the process for return or replacement of E-UC3845BD1013TR?
All E-UC3845BD1013TR units undergo pre-shipment inspection (PSI). If there is an issue with E-UC3845BD1013TR, 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 E-UC3845BD1013TR part is unused and in its original packaging.
Return procedure for E-UC3845BD1013TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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