SLUS224F September   1994  – October 2017 UC1842A , UC1843A , UC1844A , UC1845A , UC2842A , UC2843A , UC2844A , UC2845A , UC3842A , UC3843A , UC3844A , UC3845A

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Pulse-by-Pulse Current Limiting
      2. 7.3.2 Current Sense Circuit
      3. 7.3.3 Error Amplifier Configuration
      4. 7.3.4 Undervoltage Lockout
      5. 7.3.5 Oscillator
    4. 7.4 Device Functional Modes
      1. 7.4.1 Normal Operation
      2. 7.4.2 Undervoltage Lockout (UVLO) Start-Up
      3. 7.4.3 UVLO Turnoff Mode
  8. Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Custom Design With WEBENCH® Tools
        2. 8.2.2.2 UC2842A Design Procedure
      3. 8.2.3 Application Curves
  9. Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Device Support
      1. 11.1.1 Development Support
        1. 11.1.1.1 Custom Design With WEBENCH® Tools
      2. 11.1.2 Device Nomenclature
    2. 11.2 Documentation Support
      1. 11.2.1 Related Documentation
    3. 11.3 Related Links
    4. 11.4 Receiving Notification of Documentation Updates
    5. 11.5 Community Resources
    6. 11.6 Trademarks
    7. 11.7 Electrostatic Discharge Caution
    8. 11.8 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Specifications

Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted)(1)
MIN MAX UNIT
Supply voltage (low impedance source) VCC pin 30 V
Output current, IOUT ±1 A
Output energy (capacitive load) 5 µJ
Analog inputs –0.3 6.3 V
Maximum negative voltage All pins –0.3 V
Differential voltage between VC and VCC VC pin –0.3 V
Error amplifier output sink current, ICOMP 10 mA
Power dissipation at TA ≤ 25°C 1 W
Lead temperature (soldering, 10 s) 300 °C
Junction temperature, TJ –55 150 °C
Storage temperature, Tstg –65 150 °C
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

ESD Ratings

VALUE UNIT
V(ESD) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) ±2000 V
Charged-device model (CDM), per JEDEC specification JESD22-C101(2) ±1500
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.

Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)
MIN NOM MAX UNIT
VCC Bias supply voltage VCC pin 11 V
VFB, VRC, VVFB Voltage on analog pins FB, ISENSE, and RT/CT pins –0.1 5 V
VOUT Gate driver output voltage –0.1 VCC V
IVCC Supply bias current 25 mA
IVREF Output current VREF pin 10 mA
fOSC Oscillator frequency 500 kHz
TA Operating free-air temperature UC184xA –55 125 °C
UC284xA –40 85
UC384xA 0 70

Thermal Information

THERMAL METRIC(1) UC184xA UC2843A UC284xA, UC384xA UNIT
JG (CDIP) FK (LCCC) FN (PLCC) P (PDIP) D (SOIC) D (SOIC) DW (SOIC)
8 PINS 20 PINS 20 PINS 8 PINS 8 PINS 14 PINS 16 PINS
RθJA Junction-to-ambient thermal resistance 56.7 53.4 104.3 77.9 73.6 °C/W
RθJC(top) Junction-to-case (top) thermal resistance 64 36.2 34.6 46.4 46.8 35.8 35 °C/W
RθJB Junction-to-board thermal resistance 92.5 35.4 21.8 30.7 45.3 32.5 38.4 °C/W
ψJT Junction-to-top characterization parameter 10.4 16.8 6 6.6 9.7 °C/W
ψJB Junction-to-board characterization parameter 21.5 30.6 44.6 32.2 37.8 °C/W
RθJC(bot) Junction-to-case (bottom) thermal resistance 15.1 4.1 °C/W
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report.

Electrical Characteristics

Unless otherwise stated, these specifications apply for TA = –55°C to 125°C (UC184xA), TA = –40°C to 125°C (UC284xAQ), TA = –40°C to 85°C (UC284xA), TA = 0°C to 70°C (UC384xA); TA = TJ; VCC = 15 V(4); RT = 10 kΩ; CT = 3.3 nF.
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
REFERENCE
Output voltage TJ = 25°C, IO = 1 mA UC184xA, UC284xA 4.95 5 5.05 V
UC384xA 4.9 5 5.1
Line regulation 12 ≤ VIN ≤ 25 V 6 20 mV
Load regulation 1 ≤ IO ≤ 20 mA 6 25 mV
Temperature stability See (1)(6) 0.2 0.4 mV/°C
Total output variation Line, Load, Temperature UC184xA, UC284xA 4.9 5.1 V
UC384xA 4.82 5.18
Output noise voltage 10 Hz ≤ f ≤ 10 kHz; TJ = 25°C(1) 50 µV
Long-term stability TA = 125°C, 1000 hrs(1) 5 25 mV
Output short circuit –30 –100 –180 mA
OSCILLATOR
Initial accuracy TJ = 25°C(5) 47 52 57 kHz
Voltage stability 12 ≤ VCC ≤ 25 V 0.2% 1%
Temperature stability TMIN ≤ TA ≤ TMAX(1) 5%
Amplitude VRT/CT peak to peak(1) 1.7 V
Discharge current TJ = 25°C, VRT/CT = 2 V(7) 7.8 8.3 8.8 mA
VRT/CT = 2 V(7) UC184xA, UC284xA 7.5 8.8
UC384xA 7.6 8.8
ERROR AMPLIFIER
Input voltage VCOMP = 2.5 V UC184xA, UC284xA 2.45 2.5 2.55 V
UC384xA 2.42 2.5 2.58
Input bias current –0.3 –1 µA
–0.3 –2
AVOL Open-loop gain 2 ≤ VO ≤ 4 V 65 90 dB
Unity gain bandwidth TJ = 25°C(1) 0.7 1 MHz
CMRR Common mode rejection ratio 12 ≤ VCC ≤ 25 V 60 70 dB
Output sink current VFB = 2.7 V, VCOMP = 1.1 V 2 6 mA
Output source current VFB = 2.3 V, VCOMP = 5 V –0.5 –0.8 mA
VOUT high VFB = 2.3 V, RL = 15 kΩ to ground 5 6 V
VOUT low VFB = 2.7 V, RL = 15 kΩ to VREF 0.7 1.1 V
CURRENT SENSE
Gain See (2)(3) 2.85 3 3.15 V/V
Maximum input signal VCOMP = 5 V(2) 0.9 1 1.1 V
PSRR Power supply rejection ratio 12 ≤ VCC 25 V(2) 70 dB
Input bias current –2 –10 µA
Delay to output VISENSE = 0 to 2 V(1) 150 300 ns
OUTPUT
Output low level ISINK = 20 mA 0.1 0.4 V
ISINK = 200 mA 15 2.2
Output high level ISOURCE = 20 mA 13 13.5 V
ISOURCE = 200 mA 12 13.5
Rise time TJ = 25°C, CL = 1 nF(1) 50 150 ns
Fall time TJ = 25°C, CL = 1 nF(1) 50 150 ns
UVLO saturation VCC = 5 V, ISINK = 10 mA 0.7 1.2 V
UNDERVOLTAGE LOCKOUT
Start threshold UC1842A, UC1844A, UC2842A, and UC2844A 15 16 17 V
UC3842A and UC3844A 14.5 16 17.5
UCx843A and UCx845A 7.8 8.4 9
Minimum operation voltage after turnon UC1842A, UC1844A, UC2842A, and UC2844A 9 10 11 V
UC3842A and UC3844A 8.5 10 11.5
UCx843A and UCx845A 7 7.6 8.2
PWM
Maximum duty cycle UCx842A, UCx843A 94% 96% 100%
UCx844A, UCx845A 47% 48% 50%
Minimum duty cycle 0%
TOTAL STANDBY CURRENT
Start-up current 0.3 0.5 mA
Operating supply current VFB = VISENSE = 0 V 11 17 mA
VCC Zener voltage ICC = 25 mA 30 34 V
Ensured by design, but not 100% production tested.
Parameter measured at trip point of latch with VFB = 0.
Gain defined as: A = ΔVCOMP / ΔVISENSE; 0 ≤ VISENSE ≤ 0.8 V.
Adjust VCC above the start threshold before setting at 15 V.
Output frequency equals oscillator frequency for the UC1842A and UC1843A. Output frequency is one half oscillator frequency for the UC1844A and UC1845A.
Temperature stability, sometimes referred to as average temperature coefficient, is described by: Temperature stability = ( VREF(max) – VREF(min)) / (TJ(max) – TJ(min) ). VREF(max) and VREF(min) are the maximum and minimum reference voltage measured over the appropriate temperature range. Note that the extremes in voltage do not necessarily occur at the extremes in temperature.
This parameter is measured with RT = 10 kΩ to VREF. This contributes approximately 300 µA of current to the measurement. The total current flowing into the RT/CT pin is approximately 300 µA higher than the measured value.

Typical Characteristics

UC1842A UC1843A UC1844A UC1845A UC2842A UC2843A UC2844A UC2845A UC3842A UC3843A UC3844A UC3845A slus224_typchar_1.gif Figure 1. Output Saturation Characteristics
UC1842A UC1843A UC1844A UC1845A UC2842A UC2843A UC2844A UC2845A UC3842A UC3843A UC3844A UC3845A slus224_typchar_2.gif Figure 2. Error Amplifier Open-Loop Frequency Response