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HomeProductsIntegrated Circuits (ICs)PMIC - AC DC Converters, Offline SwitchersUC2875NG4
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UC2875NG4 - Unitrode

Manufacturer Part Number
UC2875NG4
Manufacturer
Unitrode
Allelco Part Number
98D-UC2875NG4
Warranty
1 Year Allelco Warranty - Find out more
Stock Status:
15,584 pcs available, New & Original
Parts Description
IC OFFLINE SW FULL-BRDG 20DIP
Package
20-PDIP
Data sheet
UC2875NG4.pdf
RoHs Status
 
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In stock: 15584

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Specifications

UC2875NG4 Tech Specifications
Unitrode - UC2875NG4 technical specifications, attributes, parameters and parts with similar specifications to Unitrode - UC2875NG4

Product Attribute Attribute Value
Manufacturer Unitrode
Voltage - Supply (Vcc/Vdd) 9.5V ~ 20V
Voltage - Start Up 10.75 V
Voltage - Breakdown -
Topology Full-Bridge
Supplier Device Package 20-PDIP
Series -
Package / Case 20-DIP (0.300", 7.62mm)
Package Bulk
Product Attribute Attribute Value
Output Isolation Non-Isolated
Operating Temperature -25°C ~ 85°C (TA)
Mounting Type Through Hole
Internal Switch(s) -
Frequency - Switching 1MHz
Fault Protection Current Limiting
Duty Cycle 100%
Control Features Frequency Control, Soft Start, Sync
Base Product Number UC2875

Environmental & Export Classifications

ATTRIBUTE DESCRIPTION
ECCN EAR99
HTSUS 8542.39.0001

Frequently Asked Questions(FAQ)

What are the key design considerations when using the UC2875NG4 in a non-isolated offline full-bridge converter operating at 1MHz?
The UC2875NG4 is optimized for high-frequency offline full-bridge topologies, but operating at 1MHz introduces significant challenges in gate drive timing, dead-time management, and parasitic inductance control. Designers must carefully layout the power stage to minimize loop inductance, especially in the high-current paths between the bridge switches and input capacitors. The 100% duty cycle capability implies continuous conduction mode operation, which demands precise synchronization between primary-side switching and secondary-side rectification to avoid shoot-through or excessive ringing. Additionally, the 9.5V to 20V Vcc range requires stable bias supply design, particularly during startup when the device draws from the 10.75V startup threshold.
How does the UC2875NG4 handle startup sequencing in an offline application without an auxiliary winding?
The UC2875NG4 initiates operation once the Vcc voltage reaches the 10.75V startup threshold, typically powered through a high-voltage startup resistor connected to the DC bus. Since it lacks internal switches, the controller relies on external MOSFETs driven by its gate outputs. Engineers must ensure the startup resistor can deliver sufficient current to charge the Vcc capacitor above 10.75V before the input voltage drops due to load demand. Once operational, a separate bias supply (e.g., from a small auxiliary converter or post-regulator) should take over to maintain Vcc within the 9.5V–20V range and reduce power dissipation in the startup resistor.
Can the UC2875NG4 be synchronized to an external clock in multi-phase or parallel converter systems?
Yes, the UC2875NG4 supports synchronization via its Sync control feature, allowing it to lock to an external clock signal. This is particularly useful in systems requiring precise phase interleaving or noise reduction through spread-spectrum techniques. The internal oscillator can be overridden by injecting a clean, square-wave signal within the 1MHz operating range. Care must be taken to match impedance and avoid jitter, as timing inaccuracies can lead to subharmonic oscillation or degraded efficiency in full-bridge configurations.
What fault protection mechanisms does the UC2875NG4 provide, and how should they be implemented in a robust design?
The UC2875NG4 includes cycle-by-cycle current limiting as its primary fault protection feature. This is typically implemented using a current-sense resistor in the primary return path, feeding a signal to the controller’s current-sense input. The threshold must be set below the saturation current of the transformer and the peak current rating of the external MOSFETs. While the device lacks overtemperature or overvoltage shutdown, designers should incorporate external monitoring circuits for Vcc undervoltage lockout (UVLO) and output overvoltage protection, especially given the non-isolated topology and high-frequency operation.
How does the 100% duty cycle specification of the UC2875NG4 influence transformer design in a full-bridge converter?
The 100% duty cycle capability means the UC2875NG4 can drive the full-bridge switches with minimal or no dead time under certain conditions, enabling maximum power transfer. However, this demands a transformer with very low leakage inductance and tightly controlled winding symmetry to prevent volt-second imbalance and core saturation. Designers must ensure the transformer can handle continuous flux swing without remanence buildup, often requiring gapped cores or active reset techniques. Additionally, the 1MHz switching frequency allows for smaller magnetic components, but skin and proximity effects necessitate Litz wire or foil windings to minimize AC losses.
What are the thermal implications of using the UC2875NG4 in a 20-PDIP package within its specified temperature range of -25°C to 85°C?
The 20-PDIP package has limited thermal dissipation capability due to its through-hole construction and lack of an exposed pad. While the UC2875NG4 itself consumes relatively low quiescent power, heat generated by external gate drivers and snubber networks can elevate the local ambient temperature around the IC. In enclosed or high-density designs, thermal coupling to nearby components may push the UC2875NG4 toward its upper temperature limit. Designers should maintain adequate airflow or consider heat-spreading techniques, especially when operating near 85°C ambient, to preserve long-term reliability and prevent thermal derating of timing accuracy.
How does the UC2875NG4 compare to modern PWM controllers with integrated MOSFETs for offline full-bridge applications?
Unlike integrated solutions such as the UCC28911 or LM5041, the UC2875NG4 is a controller-only device, offering greater flexibility in MOSFET selection and power scaling but requiring additional external gate drive circuitry. This makes it better suited for high-power or custom designs where thermal management, switching speed, or voltage rating of the switches must be independently optimized. However, it increases component count and layout complexity. In contrast, integrated controllers simplify design but may limit peak efficiency at 1MHz due to higher gate drive losses and less optimized dead-time control.
What role does soft start play in the UC2875NG4, and how should it be configured to prevent inrush current in offline converters?
The soft start feature in the UC2875NG4 gradually increases the duty cycle at startup, limiting inrush current and reducing stress on the input rectifier and bulk capacitors. This is critical in offline applications where large filter capacitors can draw excessive surge current. The soft start duration is typically set by an external capacitor on the SS pin, with charge current internally regulated. For a 1MHz full-bridge design, a soft start time of 5–10ms is common to allow smooth power-up without triggering current limiting prematurely. Proper sizing ensures the output voltage ramps linearly, minimizing output overshoot and improving load transient response during initialization.
Why is frequency control important in the UC2875NG4, and how can it be leveraged to optimize EMI performance?
The UC2875NG4 allows adjustable switching frequency up to 1MHz, enabling designers to shift the fundamental switching noise away from sensitive frequency bands (e.g., AM radio or communication channels). By slightly modulating or fixing the frequency, conducted and radiated EMI can be managed more effectively during compliance testing. However, operating at the upper end of the frequency range increases switching losses in the external MOSFETs and demands tighter control of parasitic elements. A balanced approach—using the highest feasible frequency for size reduction while maintaining efficiency—is often achieved by tuning the oscillator resistor and capacitor with attention to temperature stability.
Can the UC2875NG4 be used in resonant full-bridge topologies, or is it limited to hard-switching applications?
The UC2875NG4 is primarily designed for hard-switching full-bridge converters and does not include zero-voltage switching (ZVS) detection or adaptive dead-time control required for resonant operation. While it can generate the necessary gate signals, achieving ZVS would depend entirely on external circuitry and precise timing adjustments, which are difficult to maintain across load and input variations. For resonant topologies like LLC or phase-shifted full-bridge, dedicated controllers such as the UCC256301 or UCC28950 are better suited due to their built-in resonant mode management and protection features.

Parts with Similar Specifications

The three parts on the right have similar specifications to Unitrode UC2875NG4

Product Attribute UC2875NG4 UC2876NG4 UC2875DWPTRG4 UC2875DWPG4
Part Number UC2875NG4 UC2876NG4 UC2875DWPTRG4 UC2875DWPG4
Manufacturer Texas Instruments Texas Instruments Texas Instruments Texas Instruments
Operating Temperature - -40°C ~ 85°C 0°C ~ 70°C -40°C ~ 85°C
Frequency - Switching - - - -
Series - - - -
Duty Cycle - - - -
Voltage - Breakdown - - - -
Output Isolation - - - -
Supplier Device Package - 196-NFBGA (12x12) 16-PDIP 64-VQFN (9x9)
Control Features - - - -
Voltage - Supply (Vcc/Vdd) - - - -
Package - Tape & Reel (TR) Tube Tape & Reel (TR)
Fault Protection - - - -
Mounting Type - Surface Mount Through Hole Surface Mount
Base Product Number - DAC34H84 MAX500 ADS62P42
Topology - - - -
Package / Case - 196-LFBGA 16-DIP (0.300', 7.62mm) 64-VFQFN Exposed Pad
Internal Switch(s) - - - -
Voltage - Start Up - - - -

UC2875NG4 Datasheet PDF

Download UC2875NG4 pdf datasheets and Unitrode documentation for UC2875NG4 - Unitrode.

Datasheets
UC1875,6,7,8, UC2875,6,7,8, UC3875,6,7,8.pdf

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Customer Reviews

Evaluation: 10 Articles

  • ECUb***h
    Sep 22, 2026

    Used for repair of an older automotive ECU. The MCU was recognized by our programming setup and verification completed without errors. The repaired board now starts and communicates normally.

  • RS48***ieldTech
    Sep 16, 2026

    Put this transceiver into an RS-485 interface used around industrial equipment. Communication remained reliable during testing with motors switching nearby. Good result for the replacement board.

  • Logi***b_Chris
    Sep 8, 2026

    Purchased for a Cyclone III development project. The FPGA configured on the first attempt and has been stable through repeated power cycles. No problems with the I/O we are using.

  • Circ***FixerTom
    Sep 2, 2026

    Used this rectifier in a high-current power supply repair. Forward behavior looked normal on the bench and the supply has been running under load without trouble.

  • Retr***UWorks
    Aug 31, 2026

    Needed the exact ST10F269Z2Q6 for servicing an older control unit. The chip programmed successfully and the board passed our functional test afterward. Much easier than redesigning around a newer MCU.

  • Andr***PCBLab
    Aug 28, 2026

    I needed this ADC for an older data acquisition board. Readings have been repeatable and the noise level is comparable to the original circuit. Happy with the purchase.

  • Leat***O'Keefe
    Aug 20, 2026

    one of my hobbies is skydiving. and when i'm skydiving this works great.

  • Ilen***
    Aug 20, 2026

    This product works considerably well. It secretly improves my basketball by a lot.

  • Indu***ialPower
    Aug 17, 2026

    Installed this IGBT module in a power conversion cabinet. Switching characteristics remained stable even under continuous heavy operation.

  • Nikh***ech
    Aug 13, 2026

    Great low-power MCU for portable equipment. Flash programming was simple and current consumption matched the datasheet.

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Brazil 7
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Shipment charges(KG) Reference DHL(USD$)
0.00kg-1.00kg USD$30.00 - USD$60.00
1.00kg-2.00kg USD$40.00 - USD$80.00
2.00kg-3.00kg USD$50.00 - USD$100.00
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UC2875NG4 Image

UC2875NG4

Unitrode
98D-UC2875NG4

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