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STMicroelectronics E-UC2845BN
- Part No.:
- E-UC2845BN
- Manufacturer:
- STMicroelectronics
- Category:
- DC DC Switching Controllers
- Package:
- 8-DIP (0.300", 7.62mm)
- Datasheet:
-
E-UC2845BN.pdf
- Description:
- IC REG CTRLR BST/FLYBK 8-MINIDIP
- Quantity:
- Payment:
- Shipping:
Inventory:3,395
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Product details
Overview
E-UC2845BN 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 5 V reference, under-voltage lockout with hysteresis (8.4 V turn-on / 7.6 V turn-off), <50% maximum duty cycle via internal toggle flip-flop, oscillator frequency guaranteed at 250 kHz (up to 500 kHz), and ±1 A totem-pole output capable of directly driving N-channel MOSFETs in flyback or forward converters.
For engineers reviewing the E-UC2845BN datasheet, E-UC2845BN pinout, E-UC2845BN application, or E-UC2845BN equivalent, this device is selected for low-input-voltage, current-mode-controlled SMPS where precise duty-cycle limitation, cycle-by-cycle current limiting, and minimal external component count are critical - especially in auxiliary power supplies, AC adapters, and industrial DC-DC modules.
Technical Context
The E-UC2845BN implements current-mode control using a voltage-controlled oscillator synchronized to sensed inductor current, enabling automatic feed-forward compensation and inherent loop stability. Its internal toggle flip-flop blanks the output every other clock cycle, enforcing a hard-limited maximum duty cycle of ≤50% - distinguishing it from UC2842B/3B variants.
It integrates a precision 2.5 V error amplifier input threshold, trimmed 5 V reference (±1% over temperature), latching PWM comparator with 1 V current-sense trip threshold, and UVLO with hysteresis optimized for low-voltage start-up (7.6–8.4 V window). The totem-pole output delivers fast rise/fall times (<150 ns) into 1 nF load while sinking/sourcing up to 200 mA continuously.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | 250 kHz guaranteed at 25°C; supports up to 500 kHz with RT/CT tuning - enables compact magnetics and reduced EMI in mid-power SMPS. |
| Max Duty Cycle | 47–50% (typical 48%) - enforced by internal toggle flip-flop, preventing transformer saturation in forward/flyback topologies. |
| UVLO Threshold | 8.4 V (on), 7.6 V (off) - ensures reliable start-up from low-voltage rails (e.g., 9–12 V DC inputs) with built-in hysteresis. |
| Current Sense Threshold | 1.0 V (±10%) at pin 3 - sets peak inductor current limit; gain of 3.0 V/V enables accurate sensing with low-value shunts. |
| Output Drive | ±1 A peak, 200 mA continuous sink/source - directly drives gate capacitance of medium-power MOSFETs without external buffers. |
| Reference Voltage | 5.00 V ±1% (4.95–5.05 V) at 1 mA load - provides stable bias for RT/CT timing network and feedback divider reference. |
| Start-up Current | <0.5 mA at 6.5 V - minimizes auxiliary winding losses and enables efficient low-power standby operation. |
Pinout & Package
E-UC2845BN is housed in an 8-pin MiniDIP package (body width 7.95–9.75 mm, lead pitch 2.54 mm), suitable for through-hole prototyping and industrial PCB assembly with robust thermal performance (RθJA = 100°C/W).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (COMP) | Error amplifier output | Provides access to EA output for Type II/III compensation network placement - critical for loop stability in current-mode flyback. |
| 2 (VFB) | Inverting input of error amplifier | Receives feedback voltage from output divider; 2.5 V internal reference sets regulation point - enables precise output voltage control. |
| 3 (ISENSE) | Current sense input | Accepts voltage proportional to primary-side current; comparator trips at ~1.0 V to terminate switch conduction - enables cycle-by-cycle limiting. |
| 4 (RT/CT) | Oscillator timing node | Connects external R (to VREF) and C (to GND) to set fOSC and fine-tune max duty cycle - defines switching frequency and slope compensation ramp. |
| 5 (GROUND) | Signal and power ground | Common return for control logic, error amp, and current sense - must be star-connected near pin 5 to minimize noise coupling. |
| 6 (OUTPUT) | PWM output driver | Drives MOSFET gate directly; low-state impedance ensures fast turn-off - eliminates need for external gate driver in ≤60 W designs. |
| 7 (VCC) | Supply input | Accepts 10–30 V DC; powers internal bias circuits - derived from auxiliary winding or bulk rail; UVLO protects during brownout. |
| 8 (VREF) | 5 V reference output | Sources up to 50 mA; powers RT/CT network and optional optocoupler bias - reduces need for external LDO in isolated feedback paths. |
Key Features
| Feature | Design Value |
|---|---|
| Latched PWM with cycle-by-cycle current limiting | Prevents secondary overcurrent events by forcing single-pulse shutdown per fault - essential for transformer-isolated reliability. |
| Internally trimmed 5 V reference (±1%) | Eliminates external reference IC; maintains accuracy across –40°C to +150°C junction range - improves long-term output regulation. |
| Under-voltage lockout with hysteresis (0.8 V) | Guarantees clean start-up and shutdown sequencing; prevents erratic operation during input dips - critical for battery-backed or wide-input systems. |
| High-current totem-pole output (±1 A) | Reduces gate drive loop inductance and enables direct connection to MOSFET gates - lowers EMI and simplifies layout in cost-sensitive designs. |
| Automatic feed-forward compensation | Compensates for line voltage variations in real time - improves transient response and reduces output capacitor stress in offline applications. |
Applications
| AC-DC Adapter | Flyback Auxiliary Supply |
|---|---|
Use Scenario: 12 V/1 A isolated output from universal AC input (85–265 VAC) in wall-mounted chargers. IC Role / Device Role / Timing Role: Primary-side PWM controller implementing current-mode flyback with fixed 250 kHz switching and 48% duty cycle limit. Use Value: Enables compact transformer design and meets IEC 61000-3-2 harmonic limits via controlled switching frequency and soft-start capability. |
Use Scenario: 5 V/0.5 A auxiliary supply powering main controller and gate drivers in industrial motor drives. IC Role / Device Role / Timing Role: Off-line flyback controller with UVLO tailored for 9–15 V DC bus start-up and regulated 5 V output. Use Value: Low start-up current (<0.5 mA) minimizes auxiliary winding losses; 5 V reference powers optocoupler and TL431 without extra regulator. |
| Industrial DC-DC Module | LED Driver Power Stage |
Use Scenario: 24 V input to 5 V/2 A isolated output for PLC I/O modules requiring reinforced insulation. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller with latch protection and precise 5 V reference for feedback path. Use Value: Internal 50% duty cycle clamp prevents transformer core saturation during overload, enhancing safety compliance (IEC 62368-1). |
Use Scenario: Constant-current LED driver for signage lighting using flyback topology with analog dimming interface. IC Role / Device Role / Timing Role: PWM controller regulating average LED current via primary-side sensing and error amplifier feedback. Use Value: High-accuracy current sense threshold (1.0 V ±10%) enables tight LED current regulation (±3%) without secondary sensing. |
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 |
|---|---|---|---|
| UC3845BN | Same pinout and electrical specs, but rated for 0–70°C ambient (vs. –40–105°C for UC2845BN); higher operating supply current (17 mA vs. 12 mA typ.) | Targeted at commercial-grade equipment; not qualified for extended industrial temperature range | Select UC3845BN only if ambient temperature stays below 70°C and qualification to AEC-Q100 or industrial temp grade is unnecessary. |
| NCP1200DR2G | Fixed-frequency current-mode controller with integrated HV startup, lower start-up current (50 µA), no internal VREF; requires external timing components | Optimized for ultra-low standby power; lacks 5 V reference and latch protection - needs external fault handling | Choose NCP1200DR2G when energy efficiency (ERP Tier 2) is mandatory and board space allows added external components. |
Compared with UC3845BN, E-UC2845BN offers wider temperature qualification and lower operating current; versus NCP1200DR2G, it provides integrated reference and latch protection at the cost of higher standby draw - making it optimal for ruggedized, medium-power industrial SMPS where reliability trumps ultra-low-no-load consumption.
Availability
E-UC2845BN is available at Aetrix Electronics and suitable for AC-DC adapters, industrial DC-DC modules, and flyback auxiliary supplies requiring stable component supply, long-term lifecycle support, and consistent parametric performance across manufacturing lots.
Supply support for E-UC2845BN 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, microcontroller, power, and sensor solutions for automotive, industrial, and consumer markets.
E-UC2845BN belongs to the UCx84xB family of current-mode PWM controllers, developed specifically for cost-sensitive, high-reliability off-line and DC-DC power conversion - emphasizing minimal external parts, robust fault protection, and production-ready stability.
FAQ
What is the maximum recommended operating junction temperature for E-UC2845BN?
The absolute maximum junction temperature is 150°C, and the device is characterized for continuous operation from –40°C to +105°C ambient. Thermal derating begins above 25°C ambient at 100°C/W junction-to-ambient resistance; sustained operation above 125°C junction requires heatsinking or airflow per the Minidip thermal data sheet.
Can E-UC2845BN drive a P-channel MOSFET directly?
No - the OUTPUT pin is a totem-pole stage configured for source/sink operation referenced to ground, optimized for N-channel MOSFET gate drive with low-side switching. Driving a P-channel high-side switch would require level-shifting circuitry or an external driver, as the IC lacks high-side floating output capability.
How does the internal toggle flip-flop affect dead time in E-UC2845BN?
The toggle flip-flop enforces strict 50% maximum duty cycle by blanking the OUTPUT pin every other oscillator cycle - it does not introduce programmable dead time. This architecture prevents transformer saturation but eliminates synchronous rectification support; dead time must be managed externally if used in half-bridge configurations.
Is the 5 V reference on pin 8 internally current-limited?
Yes - the VREF pin is specified to source up to 50 mA while maintaining regulation within ±1%. Beyond that, output voltage drops linearly; typical short-circuit current is –180 mA. For loads exceeding 20 mA, a series resistor or local decoupling is recommended to maintain stability and avoid reference droop affecting RT/CT timing.
E-UC2845BN Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-DIP (0.300", 7.62mm)
- Packaging:
- Tube
- 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:
- -25°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- 8-Mini DIP
E-UC2845BN FAQ
1.How can I place an order for E-UC2845BN through Aetrix?
Please submit a Request for Quotation (RFQ) for E-UC2845BN 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-UC2845BN reliable?
The price and inventory of E-UC2845BN are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for E-UC2845BN is usually 5 days.
3.What payment methods are accepted for E-UC2845BN?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for E-UC2845BN transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for E-UC2845BN?
E-UC2845BN orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your E-UC2845BN 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-UC2845BN?
For technical support, including E-UC2845BN datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your E-UC2845BN requirements.
6.How does Aetrix verify that E-UC2845BN is sourced from the original manufacturer or authorized distributors?
All E-UC2845BN 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-UC2845BN meets industry standards.
7.What is the process for return or replacement of E-UC2845BN?
All E-UC2845BN units undergo pre-shipment inspection (PSI). If there is an issue with E-UC2845BN, 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-UC2845BN part is unused and in its original packaging.
Return procedure for E-UC2845BN:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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