UC3842D vs UC2844D: Component Comparison for Power Electronics Design

Quick verdict

For standard off-line fixed-frequency PWM power supplies operating in a narrow commercial temperature range (0°C to 70°C), the UC3842D is a solid, cost-effective choice with straightforward implementation. For designs requiring extended temperature range, higher reliability under harsh environments, or adjustable duty cycle operation up to 100%, the UC2844D offers superior flexibility and robustness.

Spec comparison table

SpecUC3842DUC2844DNotes
ManufacturerTexas Instrumentsonsemi (Rochester Electronics)
Device TypeRegulator Output DC-DC ControllerRegulator Output DC-DC ControllerEquivalent function
Package14-SOIC14-SOICIdentical package type and size (0.154” / 3.90mm width)
Mounting TypeSurface MountSurface MountIdentical
Operating Temperature Range (TA)0°C to 70°C-40°C to 85°CUC2844D supports extended commercial to industrial range, better for harsh environments
Storage Temperature Range-65°C to 150°CNot explicitly statedUC3842D datasheet specifies storage range
Junction Temperature Max150°CNot explicitly statedUC3842D data available; UC2844D typical max junction temp usually similar but check datasheet
Supply Voltage Min12 V8.4 VUC2844D can start at lower voltage, enabling use in lower voltage rails
Supply Voltage Typ28 V16 VUC3842D accommodates higher typical supply voltage
Supply Voltage MaxNot explicitly stated28 VUC2844D max supply voltage specified; UC3842D max likely similar
Max Operating Frequency500 kHz500 kHzEqual maximum switching frequency
Oscillator Frequency Typ52 kHzNot explicitly statedUC3842D typical oscillator frequency given; UC2844D adjustable
Max Duty CycleApproaching 100% (typ)50% (typ)UC3842D supports duty cycles near 100%, UC2844D limited to ~50% typical
Output Current Peak1 A peak2 A maxUC2844D supports higher peak output current, useful for driving larger MOSFET gates
Output Drive Current Typ±1 ANot explicitly statedUC3842D specified typical ±1 A peak output drive current
Start-up Current Typ<1 mA<1 mAComparable low start-up currents
UVLO Threshold On Typ16 V8.4 VUC3842D requires higher voltage to start; UC2844D suits lower-voltage start-up
UVLO Threshold Off Typ10 V7.6 VUC2844D turns off at lower voltage, better for low-voltage systems
Reference Voltage5 V (typical)5 V (typical)Equal voltage reference levels
Reference Voltage Stability±2% (typ)Not explicitly statedUC3842D provides typical stability specs
Output Short Circuit Current-30 mA to -180 mA30 mAUC3842D sink current range specified; UC2844D less detailed
Line Regulation Typ20 mVNot explicitly statedUC3842D line regulation specified
Load Regulation Typ25 mVNot explicitly statedUC3842D load regulation specified
ESD Rating (Human Body Model)3000 V2000 VUC3842D has higher HBM ESD rating, better for static discharge robustness
ESD Rating (Charged Device Model)2000 V2000 VEqual CDM ratings
Operating Free Air Temperature0°C to 70°C-40°C to 85°CUC2844D supports wider operating temp range, suitable for industrial and automotive environments
Thermal Resistance (Junction-to-Ambient)117.4 °C/W (typ)Not explicitly statedUC3842D data available for thermal design considerations
Power Dissipation Max350 mWNot explicitly statedUC3842D max power dissipation specified
Internal Oscillator Discharge Current-50 µA (typ)Not explicitly statedUC3842D oscillator current specs aid timing design
Timing Resistor Range5 kΩ to 100 kΩ5 kΩ (min)Both allow similar timing resistor values
Timing Capacitor Range1 nF to 100 nF1 nF (min)Both allow similar timing capacitor values
Dead Time Typ10 µsNot explicitly statedUC3842D specifies dead time typical
Output Rise/Fall Time25 ns min, 150 ns typNot explicitly statedUC3842D output switching times specified
Supply Current Typ11–17 mA25 mA (typ)UC3842D typically draws less supply current, aiding efficiency
Output Diode Average Current4 ANot explicitly statedUC3842D diode rating specified
Input Voltage Range (VCC)Not explicitly stated8.4 V to 28 VUC2844D specifies precise input voltage limits
Recommended Operating Temp Min0°C-40°CUC2844D better for cold start or extended temp use
Recommended Operating Temp Max70°C125°CUC2844D better for high-temp applications
Package QuantityNot specifiedNot specified
RoHS ComplianceYesNot explicitly statedUC3842D confirmed RoHS compliant

Design trade-offs

The most significant difference between the UC3842D and UC2844D is the operating temperature range and start-up voltage thresholds. The UC3842D targets commercial applications with a limited 0°C to 70°C range and a UVLO turn-on threshold around 16 V, making it suitable for standard off-line power supplies running from typical 12 V or higher rails. This means it is less suited for low-voltage or cold-start applications. The UC2844D, with a wider -40°C to 85°C range and lower UVLO thresholds (8.4 V turn-on, 7.6 V turn-off), is better for industrial environments and systems needing robust cold-start performance.

Duty cycle capability is a critical architectural difference. The UC3842D can approach near 100% duty cycle, which simplifies designs requiring extended on-time and allows for higher power transfer in certain topologies. The UC2844D is typically limited to 50% duty cycle, aligning it more with push-pull or half-bridge topologies where symmetrical duty cycles are standard. This difference impacts transformer design and switching waveforms, and firmware or analog control loops must respect these constraints.

Output drive strength and peak current handling differ. The UC2844D supports up to 2 A output current, which can directly drive larger MOSFET gates without additional buffers, reducing BOM and complexity. The UC3842D’s ±1 A typical output current is sufficient for most smaller MOSFETs but may require external gate drivers in higher power designs.

Thermal dissipation and efficiency also differ. The UC3842D typically consumes less quiescent current (11–17 mA typ) versus the UC2844D’s 25 mA, which may translate to slightly better efficiency in low-load or standby conditions. Designers targeting high-efficiency or low-power standby modes should consider this difference. The UC3842D’s published thermal resistances provide a clearer basis for thermal management planning.

ESD robustness favors the UC3842D with a 3000 V HBM rating compared to 2000 V for the UC2844D. This is an important consideration in manufacturing and field reliability, especially in static-prone environments.

Layout concerns are similar due to identical 14-SOIC packages and pin counts, but the UC2844D’s wider operating temperature and higher output current capability may require more careful PCB thermal design and possibly gate drive impedance matching.

Cost at volume is not specified here but historically, the UC3842D tends to be more widely available and less expensive due to mature production and broader adoption, while the UC2844D’s industrial rating and higher drive capabilities can command a premium.

Use-case fit

Choose UC3842D when…