UCD3138RJAT datasheet(33/89 Pages) TI1

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Filter Duty

Low – Lower Threshold

High – Lower Threshold

Control

Auto Config High

Auto Config Mid

High – Upper Threshold

Low – Upper Threshold

Full Range

Automatic Mode Switching

With Hysteresis

UCD3138

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SLUSAP2G – MARCH 2012 – REVISED SEPTEMBER 2016

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Detailed Description

6.5.2.3

Mechanism for Automatic Mode Switching

The UCD3138 allows the customer to enable up to two distinct levels of automatic mode switching. These

different modes are used to enhance light load operation, short circuit operation and soft start. Many of the

configuration parameters for the DPWM are in DPWM Control Register 1. For automatic mode switching,

some of these parameters are duplicated in the Auto Config Mid and Auto Config High registers.

If automatic mode switching is enabled, the filter duty signal is used to select which of these three

registers is used. There are 4 registers which are used to select the points at which the mode switching

takes place. They are used as shown below.

Figure 6-4. Automatic Mode Switching

As shown, the registers are used in pairs for hysteresis. The transition from Control Register 1 to Auto

Config Mid only takes place when the Filter Duty goes above the Low Upper threshold. It does not go

back to Auto Config Mid until the Low Lower Threshold is passed. This prevents oscillation between

modes if the filter duty is close to a mode switching point.

UCD3138RJAT 数据表(PDF) 33 Page - Texas Instruments