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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > DC DC Switching Controllers

STMicroelectronics UC3845BD1013TR

Name: UC3845BD1013TR
Brand: STMicroelectronics
SKU: UC3845BD1013TR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: UC3845BD1013TR

Manufacturer:: STMicroelectronics

Category:: DC DC Switching Controllers

Package:: 8-SOIC (0.154", 3.90mm Width)

Datasheet:: UC3845BD1013TR.pdf

Description:: IC REG CTRLR BOOST/FLYBACK 8SOIC

Quantity:: RFQ Add To RFQ list

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Inventory:5,698

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Product details

Overview

UC3845BD1013TR 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 (UVLO) with 8.4 V turn-on/7.6 V turn-off thresholds, <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 MOSFET gates in flyback or forward converters.

For engineers reviewing the UC3845BD1013TR datasheet, UC3845BD1013TR pinout, UC3845BD1013TR application, or UC3845BD1013TR equivalent, key selection criteria include UVLO threshold compatibility with low-input-voltage systems, 47–50% duty cycle limitation for transformer reset safety, current-sense gain of 3 V/V, 2.5 V error amplifier reference, and SO8 package thermal performance (R_{th j-amb} = 150 °C/W).

Technical Context

The UC3845BD1013TR implements current-mode control using a single-ended PWM architecture with cycle-by-cycle current limiting via a latched comparator. Its oscillator uses RT/CT timing with internal discharge current of 7.5–8.8 mA, enabling precise frequency setting and automatic feed-forward compensation through the current-sense path.

It integrates a 2.5 V precision error amplifier with 65–90 dB open-loop gain and 0.7–1 MHz unity-gain bandwidth, referenced to the 5 V VREF pin. The UVLO circuit includes hysteresis and disables all internal logic until VCC exceeds 8.4 V, then maintains operation down to 7.6 V - optimized for low-voltage DC-DC applications such as telecom bricks and industrial 12 V input supplies.

Key Specifications

Parameter	Value and Actual Design Meaning
Oscillator Frequency	Guaranteed 250 kHz at T_J = 25°C; supports up to 500 kHz with external RT/CT tuning for high-efficiency SMPS designs.
Max Duty Cycle	47–50% due to internal toggle flip-flop - enforces safe transformer reset in forward/flyback topologies.
UVLO Thresholds	8.4 V (turn-on), 7.6 V (turn-off) - enables reliable start-up from low-input rails like 9–12 V systems.
Current Sense Gain	3 V/V (2.85–3.15 V/V) - converts sensed resistor voltage to precise PWM trip point for accurate peak-current control.
VREF Output	5.00 V ±100 mV (0–70°C) - provides stable bias for RT/CT network and feedback divider reference.
Output Drive	±1 A peak sink/source - directly drives gate capacitance of medium-power MOSFETs without buffer stage.
Error Amp Input Ref	2.50 V ±8 mV - sets regulation setpoint for feedback loop; used with resistive divider on VFB pin.

Pinout & Package

UC3845BD1013TR is housed in a standard SO8 (Small Outline 8-pin) package with 1.27 mm pitch, 5.0 mm × 6.2 mm body, and R_{th j-amb} = 150 °C/W - suitable for convection-cooled industrial PCB layouts.

Pin/Terminal	Circuit Role	Design Meaning
1 - COMP	Error amplifier output	Provides access to EA output for Type II/III compensation network placement near pin.
2 - VFB	Inverting input of error amplifier	Connected to output voltage divider; regulates output by comparing against 2.5 V internal reference.
3 - ISENSE	Current sense comparator input	Accepts voltage from sense resistor; terminates switch conduction when ≥1.0 V (typical trip).
4 - RT/CT	Oscillator timing node	RT to VREF and CT to GND set frequency and max duty cycle; discharge current 7.5–8.8 mA.
5 - GROUND	Power and signal common	Single-point ground for control logic, oscillator, and current-sense circuits - critical for noise immunity.
6 - OUTPUT	Totem-pole gate driver	Sources/sinks ±1 A; low-state voltage ≤0.4 V @ 20 mA ensures MOSFET turn-off even under load.
7 - VCC	Supply input	Operates from 7.6–30 V; draws ≤0.5 mA start-up current and 12–17 mA operating current.
8 - VREF	5 V reference output	Supplies 5 V ±2% at up to 20 mA; powers RT resistor and can bias auxiliary circuitry.

Key Features

Feature	Design Value
Latched PWM with cycle-by-cycle current limit	Prevents multiple switching events during overcurrent - ensures single-pulse shutdown per fault event.
Internally trimmed 5 V reference	±2% accuracy over temperature eliminates external reference IC in cost-sensitive designs.
Under-voltage lockout with hysteresis	8.4 V / 7.6 V window prevents erratic operation during brown-out or soft-start conditions.
High-current totem-pole output	±1 A drive capability reduces need for external gate drivers in sub-100 W applications.
Automatic feed-forward compensation	Uses sensed input voltage variation to adjust PWM timing - improves line transient response.

Applications

AC-DC Adapter

Industrial DC-DC Converter

Use Scenario: 12 V input, 5 V/3 A isolated flyback supply for embedded controllers.

IC Role / Device Role / Timing Role: Primary-side PWM controller managing MOSFET switching, current sensing, and feedback regulation via optocoupler.

Use Value: 47–50% duty cycle prevents core saturation; 8.4 V UVLO ensures reliable start-up from 12 V rail with margin.

Use Scenario: 24 V input, 15 V/2 A forward converter powering PLC I/O modules.

IC Role / Device Role / Timing Role: Current-mode controller providing cycle-by-cycle current limiting and precise 250 kHz switching.

Use Value: ±1 A output drives 500 V MOSFET gate directly; 3 V/V current-sense gain enables accurate 0.1 Ω shunt use.

Telecom Power Module

LED Driver Supply

Use Scenario: -48 V input (with DC-DC pre-regulator), 3.3 V/10 A intermediate bus converter.

IC Role / Device Role / Timing Role: Secondary-side controller regulating intermediate bus voltage with fast transient response.

Use Value: 0.7–1 MHz error amp bandwidth supports tight regulation; 2.5 V VFB reference enables precise 3.3 V setpoint.

Use Scenario: Constant-current 36 V LED string driver with analog dimming interface.

IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller modulating MOSFET duty cycle based on LED current feedback.

Use Value: Latched PWM prevents current overshoot during dimming transients; 5 V VREF powers dimming DAC reference.

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
UC3845N	Same electrical specs but in PDIP-8 package; R_{th j-amb} = 100 °C/W vs. SO8's 150 °C/W.	Better thermal performance in low-airflow environments; requires through-hole PCB layout.	Select for prototyping or legacy through-hole designs where thermal headroom is constrained.
TL494CN	Fixed-frequency voltage-mode controller; dual-output, adjustable dead time, no integrated UVLO hysteresis.	Supports push-pull and full-bridge topologies; lacks cycle-by-cycle current limiting.	Choose for multi-rail supplies or when dual complementary outputs are required - not drop-in for UC3845B current-mode designs.

Compared with UC3845N, the UC3845BD1013TR offers superior board-level integration and reflow compatibility; versus TL494CN, it delivers inherent current-mode stability and simpler loop compensation but lacks dual-output flexibility.

Availability

UC3845BD1013TR is available at Aetrix Electronics and suitable for AC-DC adapters, industrial DC-DC converters, telecom power modules, and LED driver supplies requiring stable component supply, long-lifecycle support, and consistent parametric performance across production batches.

Supply support for 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, specializing in power management, analog, microcontrollers, and automotive ICs.

The UC384xB series was developed specifically for cost-effective, high-reliability current-mode switching power supplies - targeting off-line and DC-DC applications where minimal external components and robust fault protection are essential.

FAQ

What is the maximum recommended operating temperature for UC3845BD1013TR?

The UC3845BD1013TR has a specified junction operating temperature range of –40°C to +150°C. For continuous operation in SO8 packaging, ambient temperature must be limited to ensure junction temperature stays within this range - typically ≤85°C with 150 °C/W thermal resistance and ≤300 mW dissipation at full load.

Can UC3845BD1013TR replace UC3842BD1013TR in an existing design?

No - UC3845BD1013TR has 8.4 V/7.6 V UVLO thresholds and 47–50% max duty cycle, while UC3842BD1013TR uses 16 V/10 V UVLO and supports up to 100% duty cycle. Swapping them risks failure to start or improper transformer reset; redesign of UVLO biasing and timing components is required.

What is the typical current-sense threshold voltage for UC3845BD1013TR?

The current-sense comparator trips when the voltage at pin 3 (ISENSE) reaches approximately 1.0 V, with a tolerance of ±0.1 V over temperature and supply. This corresponds to a peak primary current of I_pk ≈ 1.0 V / R_sense, enabling precise overcurrent protection in flyback and forward converters.

Does UC3845BD1013TR support external clock synchronization?

Yes - pin 4 (RT/CT) can accept an external clock signal via a diode clamp configuration (as shown in Figure 22 of the datasheet), allowing synchronization to system master clock or noise reduction in multi-converter systems. The internal oscillator is disabled when external sync amplitude exceeds ~300 mV below ground.

UC3845BD1013TR 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

UC3845BD1013TR FAQ

1.How can I place an order for UC3845BD1013TR through Aetrix?

Please submit a Request for Quotation (RFQ) for 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 UC3845BD1013TR reliable?

The price and inventory of UC3845BD1013TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for UC3845BD1013TR is usually 5 days.

3.What payment methods are accepted for UC3845BD1013TR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for UC3845BD1013TR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for UC3845BD1013TR?

UC3845BD1013TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 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 UC3845BD1013TR?

For technical support, including UC3845BD1013TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your UC3845BD1013TR requirements.

6.How does Aetrix verify that UC3845BD1013TR is sourced from the original manufacturer or authorized distributors?

All 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 UC3845BD1013TR meets industry standards.

7.What is the process for return or replacement of UC3845BD1013TR?

All UC3845BD1013TR units undergo pre-shipment inspection (PSI). If there is an issue with 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 UC3845BD1013TR part is unused and in its original packaging.

Return procedure for UC3845BD1013TR:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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