High-Frequency Current- and Voltage-Mode PWM Controllers
19-2830; Rev 0; 4/03
KIT ATION EVALU LE B A IL A AV
Synchronizable, High-Frequency Current- and Voltage-Mode PWM Contr...
Description
19-2830; Rev 0; 4/03
KIT ATION EVALU LE B A IL A AV
Synchronizable, High-Frequency Current- and Voltage-Mode PWM Controllers for Isolated Supplies
General Description
The MAX8540/MAX8541 pulse-width-modulated (PWM) controllers for forward/flyback isolated DC-to-DC converters provide maximum flexibility to power-supply designers and reduce external component count. These controllers allow common PC board layout for currentmode (MAX8540) and voltage-mode (MAX8541) designs. Both controllers feature adjustable switching frequency and external synchronization from 200kHz to 1MHz. Active-high and active-low enable, undervoltage protection (UVP), and overvoltage protection (OVP) reduce external component count. Maximum duty cycle is adjustable, and the feed-forward function scales the maximum duty cycle with input voltage to limit the maximum volt-seconds applied to the transformer primary. The MAX8540 allows the user to select the value of slope compensation to further optimize magnetics design. The MAX8541 features useradjustable ramp magnitude for the PWM comparator. A cycle-by-cycle current-limit function controls the peak primary current during overload and short circuit. Both controllers can be set to latch off or to hiccup when a short circuit is detected. The number of current-limited cycles to initiate the hiccup mode and number of cycles skipped are user selectable to allow startup with high-capacitance loads and protect the converter against sustained short circuits. Th...
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