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I have some questions about TI's TPS92641. Please see below:

1.) Does anybody know the principle of Chopper OTA? there are no too much information in the datasheet. enter image description here

2.) What's Quasi-hysteretic control? I google it but I couldn't find paper told this control theory.

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  • \$\begingroup\$ Do you know what hysteretic control is? Do you know what quasi means? \$\endgroup\$
    – Andy aka
    Jan 9 at 14:03
  • \$\begingroup\$ @Andyaka I know hysteretic control. but I don't know quasi \$\endgroup\$
    – EEC
    Jan 9 at 14:40
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    \$\begingroup\$ Hysteretic control implies a simple on/off techniques for activating the upper-side switch in a buck converter based on the output ripple. Add a constant-on- or constant-off-time generator and it becomes a quasi-hysteretic mode of operation. This is a quasi-comment : ) \$\endgroup\$ Jan 9 at 16:19
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    \$\begingroup\$ It's proprietary PWM that allows 20k levels of PWM but sync'd choppers allow offset free sampling and restoring DC levels by switching the complementary differential voltage and thus is AC coupled gain \$\endgroup\$ Jan 9 at 16:58
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    \$\begingroup\$ My book describes constant on- and off-time hysteretic converters small-signal models, yes. \$\endgroup\$ Jan 16 at 19:57

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For the offset compensation, Ccomp is integrating the current out of the gm amp. There's a clock and switches on the input and output of the amplifier that switch the polarity of BOTH the input and output, presumably with a 50% duty cycle.

Therefore, any offset in the amplifier increases the voltage on Ccomp during 1/2 clock cycle and decreases it during the other, averaging to zero.

The buck is a constant on-time converter where the on time is set based on Vin and Vout. At the start of each switching cycle the buck switch turns on for a fixed period of time. If the output voltage rises above the regulation point the switch stays off until it falls below the setpoint. Then the cycle repeats. This has the advantage that during transients the switching frequency can increase for very good transient response. In steady-state with fixed input voltage the switching frequency will be close to constant.

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  • \$\begingroup\$ Hi John, Do you have related figure could share with me, it is hard to understand for me. \$\endgroup\$
    – EEC
    Jan 15 at 6:24

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