SLUS352C January   1997  – December 2015 UC1846 , UC2846 , UC3846 , UC3847

PRODUCTION DATA.  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 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. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Current Sense Amplifier
      2. 7.3.2 Oscillator
    4. 7.4 Device Functional Modes
      1. 7.4.1 Current Limit
      2. 7.4.2 Shutdown
  8. 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 Design Switching Frequency
        2. 8.2.2.2 Error Amplifier Output Configuration
        3. 8.2.2.3 Parallel Operation Configuration
        4. 8.2.2.4 Design Pulse by Pulse Current Limit Threshold
        5. 8.2.2.5 Soft-Start and Shutdown, Restart Function Design
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
  11. 11Device and Documentation Support
    1. 11.1 Related Links
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

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6 Specifications

6.1 Absolute Maximum Ratings

over operating free-air temperature range (unless otherwise noted)(1)
MIN MAX UNIT
Supply Voltage (Pin 15) 40 V
Collector Supply Voltage (Pin 13) 40 V
Output Current, Source or Sink (Pins 11, 14) 500 mA
Analog Inputs (Pins 3, 4, 5, 6, 16) –0.3 +VIN V
Reference Output Current (Pin 2) –30 mA
Sync Output Current (Pin 10) –5 mA
Error Amplifier Output Current (Pin 7) –5 mA
Soft Start Sink Current (Pin 1) 50 mA
Oscillator Charging Current (Pin 9) 5 mA
Power Dissipation at TA = 25°C 1000 mW
Power Dissipation at TC = 25°C 2000 mW
Storage temperature, Tstg –65 150 °C
(1) 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.

6.2 ESD Ratings

VALUE UNIT
V(ESD) Electrostatic discharge Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001(1) ±2500 V
Charged-device model (CDM), per JEDEC specification JESD22-C101(2) ±1500
(1) JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
(2) JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.

6.3 Recommended Operating Conditions

over operating free-air temperature range (unless otherwise noted)
MIN NOM MAX UNIT
VREF terminal external capacitance 1 2.2 µF

6.4 Thermal Information

THERMAL METRIC(1) UCx846/7 UNIT
N or DW (PDIP or SOIC) J or DW (CDIP or SOIC)
16 PINS 16 PINS
RθJA Junction-to-ambient thermal resistance 41.8 73.1 °C/W
RθJC(top) Junction-to-case (top) thermal resistance 28.5 34.2 °C/W
RθJB Junction-to-board thermal resistance 21.8 38.0 °C/W
ψJT Junction-to-top characterization parameter 13.0 7.7 °C/W
ψJB Junction-to-board characterization parameter 21.7 37.4 °C/W
RθJC(bot) Junction-to-case (bottom) thermal resistance N/A N/A °C/W
(1) For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report, SPRA953.

6.5 Electrical Characteristics

TA=–55°C to +125°C for UC1846/7; –40°C to +85°C for the UC2846/7; and 0°C to +70°C for the UC3846/7; VIN=15 V, RT=10k, CT=4.7 nF, TA=TJ (unless otherwise noted)
PARAMETER TEST CONDITIONS UC1846/7
UC2846/7		 UC3846/7 UNIT
MIN TYP MAX MIN TYP MAX
REFERENCE
Output Voltage TJ = 25°C, IO = 1 mA 5.05 5.10 5.15 5.00 5.10 5.20 V
Line Regulation VIN = 8 V to 40 V 5 20 5 20 mV
Load Regulation IL = 1 mA to 10 mA 3 15 3 15 mV
Temperature Stability Over Operating Range, (1) 0.4 0.4 mV/°C
Total Output Variation Line, Load, and Temperature (1) 5.00 5.20 4.95 5.25 V
Output Noise Voltage 10 Hz ≤ f ≤10 kHz, TJ = 25°C(1) 100 100 µV
Long Term Stability TJ = 125°C, 1000 Hrs(1) 5 5 mV
Short Circuit Output Current VREF = 0 V –10 –45 –10 –45 mA
OSCILLATOR
Initial Accuracy TJ = 25°C 39 43 47 39 43 47 kHz
Voltage Stability VIN =8 V to 40 V –1% 2% –1% 2%
Temperature Stability Over Operating Range (1) –1% –1%
Sync Output High Level 3.9 4.35 3.9 4.35 V
Sync Output Low Level 2.3 2.5 2.3 2.5 V
Sync Input High Level Pin 8 = 0 V 3.9 3.9 V
Sync Input Low Level Pin 8 = 0 V 2.5 2.5 V
Sync Input Current Sync Voltage = 3.9 V, Pin 8 = 0 V 1.3 1.5 1.3 1.5 mA
ERROR AMPLIFIER
Input Offset Voltage 0.5 5 0.5 10 mV
Input Bias Current –0.6 –1 –0.6 –2 µA
Input Offset Current 40 250 40 250 nA
Common Mode Range VIN = 8 V to 40 V 0 VIN - 2 V 0 VIN - 2 V V
Open Loop Voltage Gain ΔVO = 1.2 to 3 V, VCM = 2 V 80 105 80 105 dB
Unity Gain Bandwidth TJ = 25°C(1) 0.7 1.0 0.7 1.0 MHz
CMRR VCM = 0 V to 38 V, VIN = 40 V 75 100 75 100 dB
PSRR VIN = 8 V to 40 V 80 105 80 105 dB
Output Sink Current VID = –15 mV to -5 V, VPIN7 = 1.2 V 2 6 2 6 mA
Output Source Current VID = 15 mV to -5 V, VPIN7 = 2.5 V –0.4 –0.5 –0.4 –0.5 mA
High Level Output Voltage RL = (Pin 7) 15 kΩ 4.3 4.6 4.3 4.6 V
Low Level Output Voltage RL = (Pin 7) 15 kΩ 0.7 1 0.7 1 V
CURRENT SENSE AMPLIFIER
Amplifier Gain VPIN 3 = 0 V, Pin 1 Open(2), (3) 2.5 2.75 3.0 2.5 2.75 3.0 V
Maximum Differential Input Signal (VPIN 4-VPIN 3) Pin 1 Open (2); RL (Pin 7) = 15 kW 1.1 1.2 1.1 1.2 V
Input Offset Voltage VPIN 1 = 0.5 V, Pin 7 Open(2) 5 25 5 25 mV
CMRR VCM = 1 V to 12 V 60 83 60 83 dB
PSRR VIN = 8 V to 40 V 60 84 60 84 dB
Input Bias Current VPIN 1 = 0.5 V, Pin 7 Open(2) –2.5 –10 –2.5 –10 µA
Input Offset Current VPIN 1 = 0.5 V, Pin 7 Open(2) 0.08 1 0.08 1 µA
Input Common Mode Range 0 VIN-3 0 VIN-3 V
Delay to Outputs TJ = 25°C (1) 200 500 200 500 ns
CURRENT LIMIT ADJUST
Current Limit Offset VPIN 3 = 0 V, VPIN 4 = 0 V, Pin 7 Open (2) 0.45 0.5 0.55 0.45 0.5 0.55 V
Input Bias Current VPIN 5 = VREF, VPIN 6 = 0 V –10 –30 –10 –30 µA
SHUTDOWN TERMINAL
Threshold Voltage 250 350 400 250 350 400 mV
Input Voltage Range 0 VIN 0 VIN V
Minimum Latching Current (IPIN1) (5) 3.0 1.5 3.0 1.5 mA
Maximum Latching Current (IPIN1) (6) 1.5 0.8 1.5 0.8 mA
Delay to Outputs TJ = 25°C (1) 300 600 300 600 ns
OUTPUT
Collector-Emitter Voltage 40 40 V
Collector Leakage Current VC = 40 V (4) 200 200 µA
Output Low Level ISINK = 20 mA 0.1 0.4 0.1 0.4 V
ISINK = 100 mA 0.4 2.1 0.4 2.1
Output High Level ISOURCE = 20 mA 13 13.5 13 13.5 V
ISOURCE = 100 mA 12 13.5 12 13.5
Rise Time CL = 1 nF, TJ = 25°C (1) 50 300 50 300 ns
Fall Time CL = 1 nF, TJ = 25°C (1) 50 300 50 300 ns
UNDERVOLTAGE LOCKOUT
Start-Up Threshold 7.7 8.0 7.7 8.0 V
Threshold Hysteresis 0.75 0.75 V
TOTAL STANDBY CURRENT
Supply Current 17 21 17 21 mA
(1) These parameters, although ensured over the recommended operating conditions, are not 100% tested in production.
(2) Parameter measured at trip point of latch with VPIN 5 = VREF, VPIN 6 = 0 V.
(3) Amplifier gain defined as: G = ΔVPIN7 / ΔVPIN4; VPIN4 = 0 to 1.0 V
(4) Applies to UC1846/UC2846/UC3846 only due to polarity of outputs.
(5) Current into Pin 1 ensured to latch circuit in shutdown state.
(6) Current into Pin 1 ensured not to latch circuit in shutdown state.

6.6 Typical Characteristics

UC1846 UC1847 UC2846 UC2847 UC3846 UC3847 slus352_typchar_1.gif
Figure 1. Error Amplifier Gain and Phase vs Frequency
UC1846 UC1847 UC2846 UC2847 UC3846 UC3847 slus352_typchar_2.gif
Figure 2. Error amplifier Open-Logic DC Gain vs Load Resistance