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STMicroelectronics UC2845BD1013TR
- Part No.:
- UC2845BD1013TR
- Manufacturer:
- STMicroelectronics
- Category:
- DC DC Switching Controllers
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
UC2845BD1013TR.pdf
- Description:
- IC REG CTRLR BOOST/FLYBACK 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:7,427
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Product details
Overview
UC2845BD1013TR from STMicroelectronics is a high-performance current-mode PWM controller IC designed for fixed-frequency DC-DC and off-line power supplies. It features an internally trimmed oscillator (250 kHz guaranteed), 47–50% maximum duty cycle, UVLO thresholds of 8.4 V (on) / 7.6 V (off), and a totem-pole output capable of ±1 A peak drive - enabling direct N-channel MOSFET gate control in flyback and forward converters.
For engineers reviewing the UC2845BD1013TR datasheet, UC2845BD1013TR pinout, UC2845BD1013TR application, or UC2845BD1013TR equivalent, key selection criteria include its low-startup-current (<0.5 mA), precise 5.0 V reference (±1%), current-sense gain of 3.0 V/V, and built-in latch protection for cycle-by-cycle current limiting in regulated SMPS designs.
Technical Context
The UC2845B implements current-mode control using a voltage-controlled oscillator with RT/CT programming, a high-gain error amplifier (90 dB, 1 MHz GBW), and a dedicated current-sense comparator with 1 V threshold and 300 ns delay. Its internal toggle flip-flop limits maximum duty cycle to <50%, distinguishing it from UC2842B/3B variants.
UVLO hysteresis (0.8 V) ensures clean startup/shutdown sequencing, while the 5 V reference provides stable biasing for timing components and feedback networks. The totem-pole output stage delivers fast rise/fall times (≤150 ns into 1 nF) and rail-to-rail swing under load - critical for minimizing MOSFET switching losses in high-efficiency topologies.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | 250 kHz guaranteed at 25°C; supports up to 500 kHz via RT/CT tuning - enables compact magnetics and EMI optimization. |
| Max Duty Cycle | 47–50% - enforced by internal toggle flip-flop; prevents transformer saturation in forward/flyback designs. |
| UVLO Thresholds | 8.4 V (turn-on), 7.6 V (turn-off) - ensures reliable start-up from low-voltage DC rails or auxiliary windings. |
| Reference Voltage | 5.00 V ±1% at 1 mA - provides accurate scaling for feedback dividers and CT charging current. |
| Output Drive | ±1 A peak sink/source - directly drives medium-power MOSFET gates without external buffers. |
| Current Sense Gain | 3.0 V/V (2.85–3.15 V/V) - converts sense resistor voltage to precise PWM termination level. |
| Start-up Current | <0.5 mA at 6.5 V - reduces standby loss and enables high-impedance biasing from HV startup networks. |
Pinout & Package
UC2845BD1013TR is housed in an SO8 (Small Outline 8-pin) package with standard 1.27 mm pitch and JEDEC MS-012AC footprint.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - COMP | Error amplifier output | Provides access to EA output for loop compensation (e.g., Type II/III networks). |
| 2 - VFB | Inverting input of error amplifier | Connects to output voltage divider; sets regulation point via 2.5 V internal reference. |
| 3 - ISENSE | Current-sense comparator input | Terminates switch conduction when sensed voltage reaches ~1 V (gain × Rs × Ipk). |
| 4 - RT/CT | Oscillator timing node | RT to VREF and CT to GND set frequency and max duty cycle; supports 500 kHz operation. |
| 5 - GROUND | Signal and power ground | Single-point return for control circuitry and current-sense path; critical for noise immunity. |
| 6 - OUTPUT | Totem-pole gate driver | Sources/sinks ±1 A; logic-high = MOSFET on; low impedance during off-state minimizes shoot-through risk. |
| 7 - VCC | Supply input | Operates from 7.6–30 V; internal zener clamp (30–36 V) protects against transients. |
| 8 - VREF | 5 V precision reference output | Supplies charging current to CT via RT; stable over temperature and load for accurate timing. |
Key Features
| Feature | Design Value |
|---|---|
| Latched PWM shutdown | Ensures single-cycle fault response and eliminates multiple pulsing during overload or short-circuit events. |
| Internally trimmed 5 V reference | ±1% accuracy at 25°C and ±25 mV over full temperature/load range - eliminates external reference need. |
| Automatic feed-forward compensation | Uses VCC variations to modulate oscillator ramp slope - improves line transient rejection without extra components. |
| Low-startup supply current | <0.5 mA enables direct HV startup from rectified AC via high-value resistor - reduces dissipation in offline adapters. |
| High-speed output stage | Rise/fall ≤150 ns into 1 nF - supports high-frequency operation while maintaining clean gate drive waveforms. |
Applications
| AC-DC Adapter | Flyback SMPS |
|---|---|
|
Use Scenario: 12 V/2 A isolated wall adapter for consumer electronics with universal AC input (85–265 VAC). IC Role / Device Role / Timing Role: Primary-side PWM controller implementing current-mode regulation, fixed 65 kHz switching, and cycle-by-cycle overcurrent protection. Use Value: 47–50% duty cycle limit prevents transformer core saturation during line dips; low start-up current enables efficient HV startup network. |
Use Scenario: 5 V/3 A medical-grade isolated power supply meeting IEC 60601 creepage requirements. IC Role / Device Role / Timing Role: Current-mode flyback controller with optocoupler feedback, 250 kHz operation, and latch-off fault recovery. Use Value: Precise 5.0 V reference ensures tight output regulation; UVLO hysteresis avoids brownout oscillation during unstable mains conditions. |
| Industrial DC-DC Converter | LED Driver (Constant Current) |
|
Use Scenario: 24 V input to ±15 V dual-output converter for PLC I/O modules operating in -40°C to +85°C ambient. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller managing synchronous forward topology with auxiliary winding sensing. Use Value: Guaranteed 250 kHz oscillator tolerance allows predictable EMI filter design; wide junction temp range (-40°C to +150°C) ensures reliability. |
Use Scenario: 36 V input constant-current LED driver for street lighting with analog dimming interface. IC Role / Device Role / Timing Role: Buck-derived current-mode controller regulating LED string current via sense-resistor feedback and PWM dimming sync. Use Value: High-gain current-sense path (3.0 V/V) enables accurate low-side sensing with mΩ-level resistors; totem-pole output drives logic-level MOSFETs directly. |
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 |
|---|---|---|---|
| UC3845BD1 | Same pinout and electrical specs, but rated for 0°C to +70°C industrial temp range (vs. UC2845B's -40°C to +100°C extended range). | Not qualified for extended temperature environments such as automotive under-hood or outdoor industrial enclosures. | Select UC3845BD1 only for cost-sensitive commercial applications where ambient stays within 0–70°C. |
| NCP1200DR2G | Voltage-mode controller with 65 kHz fixed frequency, no internal reference, requires external Vref; lower start-up current (100 µA). | Lacks current-mode advantages (inherent slope compensation, better line rejection); suited for simpler, lower-cost flyback designs. | Choose only if system prioritizes ultra-low standby power over dynamic line/load regulation performance. |
Compared with UC3845BD1, the UC2845BD1013TR offers extended temperature qualification and tighter reference tolerance; versus NCP1200DR2G, it delivers superior transient response and integrated current sensing - making it preferable for demanding regulated SMPS where reliability and precision matter.
Availability
UC2845BD1013TR is available at Aetrix Electronics and suitable for AC-DC adapters, industrial DC-DC converters, and LED drivers requiring stable component supply across extended temperature ranges and long production lifecycles.
Supply support for UC2845BD1013TR 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, specializing in power management, analog, microcontrollers, and automotive ICs.
The UC284xB family was developed for cost-effective, high-reliability current-mode PWM control in offline and DC-DC power conversion - targeting applications where minimal external components, precise frequency control, and robust fault handling are essential.
FAQ
What is the maximum recommended oscillator frequency for UC2845BD1013TR?
The UC2845BD1013TR supports oscillator frequencies up to 500 kHz when configured with appropriate RT/CT values and layout practices. However, the device guarantees 250 kHz operation across temperature and supply voltage; higher frequencies require careful attention to PCB grounding, decoupling, and propagation delays to maintain stability and latch integrity.
Can UC2845BD1013TR drive a P-channel MOSFET directly?
No - UC2845BD1013TR's OUTPUT pin is a totem-pole stage optimized for driving N-channel MOSFET gates with logic-high = ON. Driving a P-channel device would require level-shifting circuitry or an external driver, as the IC lacks high-side gate drive capability or bootstrap support.
How does the internal toggle flip-flop affect duty cycle in UC2845BD1013TR?
The internal toggle flip-flop forces alternating clock cycles to be blanked, limiting maximum duty cycle to approximately 47–50%. This prevents transformer saturation in forward and push-pull topologies and eliminates need for external duty-cycle clamping circuits - a key differentiator from UC2842B/3B variants.
Is external slope compensation required when using UC2845BD1013TR in continuous conduction mode (CCM)?
Yes - unlike some newer controllers, UC2845BD1013TR does not include automatic slope compensation. In CCM flyback or boost converters, an external ramp signal must be injected at the ISENSE pin to prevent subharmonic oscillation when duty cycle exceeds 50%; typical implementation uses a resistor from VREF to ISENSE with RC filtering.
UC2845BD1013TR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Type:
- Transistor Driver
- Function:
- Step-Up, 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:
- -40°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
UC2845BD1013TR FAQ
1.How can I place an order for UC2845BD1013TR through Aetrix?
Please submit a Request for Quotation (RFQ) for UC2845BD1013TR 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 UC2845BD1013TR reliable?
The price and inventory of UC2845BD1013TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC2845BD1013TR is usually 5 days.
3.What payment methods are accepted for UC2845BD1013TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC2845BD1013TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for UC2845BD1013TR?
UC2845BD1013TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your UC2845BD1013TR 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 UC2845BD1013TR?
For technical support, including UC2845BD1013TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC2845BD1013TR requirements.
6.How does Aetrix verify that UC2845BD1013TR is sourced from the original manufacturer or authorized distributors?
All UC2845BD1013TR 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 UC2845BD1013TR meets industry standards.
7.What is the process for return or replacement of UC2845BD1013TR?
All UC2845BD1013TR units undergo pre-shipment inspection (PSI). If there is an issue with UC2845BD1013TR, 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 UC2845BD1013TR part is unused and in its original packaging.
Return procedure for UC2845BD1013TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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