UCD3138 datasheet(34/99 Pages) TI2

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9.5.2.3 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.

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

Figure 9-4. 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.

UCD3138

SLUSAP2J – MARCH 2012 – REVISED NOVEMBER 2021

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