SLUU070A December   2001  – June 2021

 

  1.   Trademarks
  2. 1Features
  3. 2Description
  4. 3Feedback Considerations
    1. 3.1 Error Amplifier
    2. 3.2 Open-Loop Small Signal AC Model
      1. 3.2.1 Open-Loop Small Signal AC Model
  5. 4Operating Instructions
    1. 4.1 Connect a DC Power Supply to Terminal TB1
    2. 4.2 Connect the Load to TB2
    3. 4.3 Place a Jumper on CB2
      1. 4.3.1 Placing a Jumper on CB1 is Optional
    4. 4.4 Turn on the Electronic Load
    5. 4.5 Turn on the Input Power Supply
    6. 4.6 Shut Down the Converter
  6. 5Evaluation Module Layouts
  7. 6Evalulation Module Components
  8. 7References
  9. 8Revision History

3.2.1 Open-Loop Small Signal AC Model

M1 is the lumped gain corresponding to the input voltage and the PWM gain. Since the ramp height in the chip is about 1V the PWM gain is 100%/V or just 1 in the free running case. The 8x factor comes from the input voltage of 8 V. The PWM gain increases with synchronization. For instance, syncronizing a 1-MHz nominal free run oscillator to 1.2 MHz increases the PWM gain to:

Equation 1. GSYNC= FSYNCFFREE × GFREE

where

  • GFREE is the free running PWM gain (one here)
  • GSYNC is the synchronized PWM gain
  • FFREE is the free running oscillator frequency
  • FSYNC is the synchronized frequency
GUID-20210615-CA0I-QQRZ-RDZB-TXLCQWSCS8X8-low.gif Figure 3-2 Open-Loop Small Signal Alternating Current (AC) Model
GUID-20210615-CA0I-HJZW-6HDJ-CGVVZ1HHSMWF-low.gif Figure 3-3 Connection Diagram