My Inquiry
My Account
STMicroelectronics E-UC3843BD1
- Part No.:
- E-UC3843BD1
- Manufacturer:
- STMicroelectronics
- Category:
- DC DC Switching Controllers
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
E-UC3843BD1.pdf
- Description:
- IC REG CTRLR BOOST/FLYBACK 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,025
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
E-UC3843BD1 from STMicroelectronics is a high-performance current-mode PWM controller IC designed for fixed-frequency DC-DC and off-line power supplies. It features a trimmed oscillator (250 kHz guaranteed), 8.5 V turn-on / 7.9 V turn-off UVLO, up to 100% duty cycle capability, ±1 A totem-pole output, and internal 5 V reference with <0.2 mV/°C drift - deployed in AC-DC adapters and industrial SMPS.
For engineers reviewing the E-UC3843BD1 datasheet, E-UC3843BD1 pinout, E-UC3843BD1 application, or E-UC3843BD1 equivalent, key selection criteria include UVLO threshold compatibility, current-sense gain (3.0 V/V), oscillator timing flexibility (RT/CT programmable up to 500 kHz), and SO8 package thermal resistance (150 °C/W).
Technical Context
The E-UC3843BD1 implements peak-current-mode control with automatic feed-forward compensation and latched PWM for cycle-by-cycle current limiting. Its error amplifier provides 90 dB open-loop gain and 1 MHz unity-gain bandwidth, enabling stable loop compensation in flyback and forward converters.
Oscillator frequency is set via external RT/CT network with discharge current of 7.8–8.8 mA at 2 V; the internal toggle flip-flop is absent (distinguishing it from UC3844B/45B), enabling full-range duty cycle operation without inherent 50% limitation.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator Frequency | Guaranteed 250 kHz at 25°C; supports 50–500 kHz via RT/CT tuning for flexible switching node design. |
| UVLO Threshold | 8.5 V (on) / 7.9 V (off) hysteresis - optimized for low-voltage DC-DC start-up and brownout resilience. |
| Current Sense Gain | 3.0 V/V (±5%) - enables precise 1 V current-limit threshold setting with minimal RS resistor tolerance impact. |
| Output Drive | ±1 A peak source/sink - directly drives N-channel MOSFET gates without external buffer in ≤100 W designs. |
| Reference Voltage | 5.00 V ±10 mV at 1 mA load - stable bias for RT/CT charging and feedback divider reference. |
| Error Amp GBW | 1 MHz unity-gain bandwidth - supports robust phase margin in current-mode loops with typical Type II compensation. |
| Start-up Current | <0.5 mA at 6.5 V - reduces auxiliary winding losses and enables high-impedance VCC startup networks. |
Pinout & Package
Package: SO8 (Small Outline Integrated Circuit, 150 °C/W junction-to-ambient thermal resistance). Pin functions validated per STMicroelectronics UC384xB datasheet (D95IN332 top view).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - COMP | Error amplifier output | Provides access to EA output for external Type II/III compensation network placement. |
| 2 - VFB | Inverting input of error amplifier | Connects to output voltage divider; sets regulation point via 2.5 V internal reference comparison. |
| 3 - ISENSE | Current sense input | Accepts voltage from shunt/resistor; triggers PWM termination when ≥1.0 V (trip point). |
| 4 - RT/CT | Oscillator timing interface | RT connects to VREF (pin 8); CT grounds - sets fOSC and max duty cycle via RC time constant. |
| 5 - GROUND | Signal and power return | Single-point ground for control logic, oscillator, and current sense - critical for noise immunity. |
| 6 - OUTPUT | Gate drive output | Totem-pole stage sinks/sources up to 1 A; low-state voltage ≤0.4 V at 20 mA ensures MOSFET turn-off margin. |
| 7 - VCC | Supply input | Operates 7.9–30 V; internal zener clamp at 36 V protects against transient overvoltage. |
| 8 - VREF | 5 V reference output | Supplies 5 V ±10 mV; sources up to 50 mA - powers RT resistor and optional auxiliary circuitry. |
Key Features
| Feature | Design Value |
|---|---|
| Latched PWM comparator | Ensures single-pulse-per-cycle current limiting - prevents subharmonic oscillation in continuous conduction mode. |
| Internally trimmed 5 V reference | 0.2 mV/°C temperature coefficient enables stable feedback across –40°C to +150°C ambient. |
| Automatic feed-forward compensation | Compensates for line voltage variation in real time - improves transient response without extra components. |
| Low-startup current (<0.5 mA) | Reduces dissipation in high-impedance startup circuits - enables use of >1 MΩ startup resistors. |
| High-current totem-pole output | Drives 1000 pF gate capacitance with <150 ns rise/fall - supports MOSFETs up to 200 kHz switching. |
Applications
| AC-DC Adapter | Industrial DC-DC Converter |
|---|---|
Use Scenario: 12 V/2 A wall adapter for IoT gateway powering. IC Role / Device Role / Timing Role: Primary-side PWM controller regulating flyback transformer output via optocoupler feedback. Use Value: 8.5 V UVLO ensures reliable start-up from 9 V input during brownout; 100% duty cycle supports wide input range (90–264 VAC rectified). |
Use Scenario: 24 V input to 5 V/10 A isolated supply in PLC backplane. IC Role / Device Role / Timing Role: Fixed-frequency current-mode controller driving synchronous rectifier MOSFETs in forward topology. Use Value: ±1 A output drive eliminates gate driver IC; 3.0 V/V current sense gain enables accurate 10 A limit with 10 mΩ shunt. |
| LED Driver Supply | Telecom Power Module |
Use Scenario: Constant-current LED driver for street lighting (36 V/1.5 A output). IC Role / Device Role / Timing Role: Peak-current-mode controller with primary-side sensing and analog dimming via VFB pin. Use Value: 1 MHz error amp bandwidth supports fast dimming response; 250 kHz base frequency minimizes EMI filter size. |
Use Scenario: -48 V telecom rectifier module supplying 3.3 V/20 A to server blades. IC Role / Device Role / Timing Role: Secondary-side synchronous buck controller using isolated current sense and VREF-referenced feedback. Use Value: 5 V reference accuracy (±10 mV) ensures tight 3.3 V output regulation; low 12 mA operating current improves light-load efficiency. |
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 |
|---|---|---|---|
| UCC3803D | TI part with 7.7 V / 6.9 V UVLO, 100% duty cycle, but no internal 5 V reference - requires external VREF. | Requires external 5 V reference and bias supply; less suitable for space-constrained adapters. | Select when existing design uses external reference and higher UVLO hysteresis is acceptable. |
| NCP1200DR2G | ON Semiconductor part with 16.5 V / 10.5 V UVLO, 70% max duty cycle, and built-in soft-start - no latch protection. | Optimized for universal-input offline SMPS; lacks cycle-by-cycle current limiting latch. | Prefer for cost-sensitive universal-input designs where latch is not required and soft-start is needed. |
Compared with UCC3803D and NCP1200DR2G, E-UC3843BD1 uniquely combines low-threshold UVLO, full-duty-cycle operation, integrated 5 V reference, and latched PWM - making it optimal for low-input-voltage DC-DC and regulated adapter applications requiring robust current limiting.
Availability
E-UC3843BD1 is available at Aetrix Electronics and suitable for AC-DC adapters, industrial DC-DC converters, and LED driver supplies requiring stable component supply, long-lifecycle support, and consistent SO8 packaging.
Supply support for E-UC3843BD1 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, delivering silicon solutions for automotive, industrial, and power applications since 1987.
The UC384xB family was engineered specifically for cost-effective, high-reliability current-mode switch-mode power supplies - emphasizing minimal external components, precise oscillator control, and rugged gate drive capability.
FAQ
What is the maximum recommended oscillator frequency for E-UC3843BD1?
The datasheet guarantees operation up to 500 kHz with appropriate RT/CT selection and layout. At 500 kHz, propagation delays and gate drive slew rates remain within specification, but thermal dissipation must be managed - SO8 package limits practical continuous operation to ~350 kHz in unforced-air environments due to 800 mW power dissipation limit.
Can E-UC3843BD1 drive a P-channel MOSFET directly?
No - the OUTPUT pin is a totem-pole stage referenced to GROUND (pin 5), sourcing current when high and sinking when low. Driving a P-channel high-side switch requires level-shifting or an external driver; the IC is optimized for N-channel MOSFETs configured in low-side or active-clamp topologies.
How does the current sense threshold vary with temperature?
The current sense comparator trip point is fixed at 1.0 V (±100 mV) across –40°C to +150°C, as confirmed by Figure 7 in the datasheet. This stability is achieved through matched internal resistor ratios and PTAT biasing - no external temperature compensation is needed for standard shunt-based sensing.
Is external slope compensation required for E-UC3843BD1 in DCM flyback designs?
No - slope compensation is only necessary in continuous conduction mode (CCM) flyback or boost converters to prevent subharmonic oscillation when duty cycle exceeds 50%. In discontinuous conduction mode (DCM), the natural current ramp reset eliminates this instability, so external ramp injection is not required.
E-UC3843BD1 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- 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):
- 96%
- 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-UC3843BD1 FAQ
1.How can I place an order for E-UC3843BD1 through Aetrix?
Please submit a Request for Quotation (RFQ) for E-UC3843BD1 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-UC3843BD1 reliable?
The price and inventory of E-UC3843BD1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for E-UC3843BD1 is usually 5 days.
3.What payment methods are accepted for E-UC3843BD1?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for E-UC3843BD1 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for E-UC3843BD1?
E-UC3843BD1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your E-UC3843BD1 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-UC3843BD1?
For technical support, including E-UC3843BD1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your E-UC3843BD1 requirements.
6.How does Aetrix verify that E-UC3843BD1 is sourced from the original manufacturer or authorized distributors?
All E-UC3843BD1 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-UC3843BD1 meets industry standards.
7.What is the process for return or replacement of E-UC3843BD1?
All E-UC3843BD1 units undergo pre-shipment inspection (PSI). If there is an issue with E-UC3843BD1, 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-UC3843BD1 part is unused and in its original packaging.
Return procedure for E-UC3843BD1:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
E-UC3843BD1 Tags
-
UCC28C45DR
Texas Instruments
-
UCC28C40DR
Texas Instruments
-
UCC28C43DR
Texas Instruments
-
ZXSC410E6TA
Diodes Incorporated
-
LM3524DMX/NOPB
Texas Instruments
-
LM3489MMX/NOPB
Texas Instruments
-
MIC2102YML-TR
Microchip Technology
-
LM5148RGYR
Texas Instruments
-
TL598CDR
Texas Instruments
-
LM5155DSSR
Texas Instruments
-
LM25085MYX/NOPB
Texas Instruments
-
UCC2813DTR-0
Texas Instruments
Tech Hub
A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.
TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
