UC3845BD1 STMicroelectronics Integrated Circuit (Small Outline Packages) In Stock
The UC3845BD1 is a current-mode PWM controller IC supporting boost and flyback topologies with up to 500 kHz switching frequency, 1 A gate drive output, and an 8V to 30V input range in an 8-pin SOIC package. It integrates cycle-by-cycle current limiting and undervoltage lockout for robust power supply designs.
- Manufacturer
- STMicroelectronics
- Package
- Small Outline Packages
- Pin Count
- 8
- Lifecycle
- ACTIVE
- Datasheet
- UC3845BD1 Datasheet PDF
- Category
- Integrated Circuit
- Price
- From $0.4547(MOQ 100)
- Temp Range
- ?°C to 70.0°C
- RoHS
- Compliant
- Lead Time
- 3–7 business days
- Shipping
- DHL Express · Worldwide
What are the key features of UC3845BD1?
- Current-mode PWM control up to 500 kHz with cycle-by-cycle peak current limiting for inherent short-circuit protection in boost and flyback power stages
- 1 A gate drive output with 8.2V to 30V operating input range, enabling direct drive of power MOSFETs in off-line and DC-DC converter designs without external gate drivers
- Integrated UVLO (undervoltage lockout) and soft-start in an 8-pin SOIC-8 package, minimizing external component count for compact isolated and non-isolated power supplies
What is UC3845BD1 used for?
The UC3845BD1 is designed for off-line and DC-DC power converter applications including flyback SMPS, boost converters, and forward converters operating from 8.2V to 30V input rails. Its 500 kHz maximum switching frequency allows transformer miniaturization and reduces output filter size in space-constrained industrial and consumer power supply designs. Battery chargers, auxiliary power modules in motor drives, and HVAC control board supplies commonly employ this controller for its robust current-mode regulation and protection features.
What are the specifications of UC3845BD1?
| Reach Compliance Code | Compliant |
| Factory Lead Time | 14Weeks |
| YTEOL | 7 |
| Analog IC - Other Type | SWITCHING CONTROLLER |
| Control Mode | CURRENT-MODE |
| Control Technique | PULSE WIDTH MODULATION |
| Input Voltage-Max | 30V |
| Input Voltage-Min | 8.2V |
| Input Voltage-Nom | 15V |
| JESD-30 Code | R-PDSO-G8 |
| JESD-609 Code | e4 |
| Number of Functions | 1 |
| Output Current-Max | 1A |
| Package Body Material | PLASTIC/EPOXY |
| Package Equivalence Code | SOP8,.25 |
| Package Shape | RECTANGULAR |
| Package Style | SMALL OUTLINE |
| Peak Reflow Temperature (Cel) | 260 |
| Qualification Status | Not Qualified |
| Surface Mount | YES |
| Switcher Configuration | SINGLE |
| Switching Frequency-Max | 500kHz |
| Technology | BIPOLAR |
| Temperature Grade | COMMERCIAL |
| Terminal Finish | Nickel/Palladium/Gold (Ni/Pd/Au) |
| Terminal Form | GULL WING |
| Terminal Pitch | 1.27mm |
| Terminal Position | DUAL |
| Time@Peak Reflow Temperature-Max (s) | 30 |
| Package | Small Outline Packages |
Compliance & Regulatory
| RoHS Status | Compliant |
| Lead-Free | Yes (Pb-Free) |
| Moisture Sensitivity Level | MSL 1 |
| ECCN | EAR99 |
| HTS Code | 8542.39.00.60 |
| Country of Origin | Morocco |
Where can I find the UC3845BD1 datasheet?
UC3845BD1 Datasheet DownloadOfficial datasheet from STMicroelectronics
What are equivalent replacements for UC3845BD1?
Compatible alternatives and drop-in replacements for UC3845BD1:
Switching Controller, Current-mode, 1A, 500kHz Switching Freq-Max, BIPolar, PDSO8
Frequently Asked Questions
What switching frequency range does the UC3845BD1 support, and how does this affect transformer size in a flyback converter?
The UC3845BD1 supports switching frequencies up to 500 kHz set by an external RC timing network. Operating near 500 kHz reduces the required transformer core size by approximately 4x compared to a 50 kHz design for the same power level, enabling significantly more compact flyback transformer construction and smaller output filter capacitors in space-constrained 8V to 30V input power supplies.
How does the UC3845BD1 protect a power supply from output overload or short-circuit conditions?
The UC3845BD1 implements cycle-by-cycle peak current limiting using the current sense input pin. Each PWM cycle is terminated immediately when the sensed MOSFET current exceeds the reference threshold set by the error amplifier output, limiting peak current to approximately 1 A per cycle and preventing transformer saturation or MOSFET failure during sustained output short-circuit conditions without requiring separate protection ICs.
Can the UC3845BD1 directly drive a power MOSFET gate, or does it require an external gate driver stage?
The UC3845BD1 provides a 1 A peak gate drive output capable of directly driving the gate of most power MOSFETs with gate charge up to approximately 50 nC at 500 kHz, achieving acceptable switching transition times without an external buffer. For high-capacitance MOSFETs above this charge level or parallel MOSFET configurations, an external gate driver such as a totem-pole buffer may be needed to maintain switching efficiency at the full 500 kHz operating frequency.
What input voltage range does the UC3845BD1 require, and does it include undervoltage lockout protection?
The UC3845BD1 operates from an input voltage of 8.2V minimum to 30V maximum, with a nominal bias of 15V. It includes an integrated UVLO circuit that holds the output off until the supply exceeds the 8.2V start threshold and resumes shutdown if the supply drops below approximately 7.6V, preventing erratic low-voltage switching that could cause power stage damage or output voltage instability during input transients.
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Why Buy from FindMyChip
About STMicroelectronics
STMicroelectronics is a global semiconductor leader serving customers across the spectrum of electronics applications. ST's products are found in a wide range of applications including automotive, industrial, personal electronics, and communications.
| Qty. | Unit Price | Ext. Price |
|---|---|---|
| 100+ | $0.9100 | $91.00 |
| 250+ | $0.8400 | $210.00 |
| 391+ | $0.7700 | $301.07 |
| 1000+ | $0.5100 | $510.00 |
| 2500+ | $0.5080 | $1270.00 |
| 10000+ | $0.4547 | $4547.00 |
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