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MAX17598][
MAX17599]
The MAX17598/MAX17599 low I
Q, active clamp current-mode PWM controllers contain all the control circuitry required for the design of wide-input isolated/nonisolated forward-converter industrial power supplies. The MAX17598 is well-suited for universal input (rectified 85V AC to 265V AC) or telecom (-36V DC to -72V DC) power supplies. The MAX17599 is optimized for low-voltage industrial supplies (4.5V DC to 30V DC).
The devices include an AUX driver that drives an auxiliary MOSFET (clamp switch) that helps implement the active-clamp transformer reset topology for forward converters. Such a reset topology has several advantages including reduced voltage stress on the switches, transformer size reduction due to larger allowable flux swing, and improved efficiency due to elimination of dissipative snubber circuitry. Programmable dead time between the AUX and main driver allows for zero voltage switching (ZVS).
The switching frequency is programmable from 100kHz to 1MHz for the devices with an accuracy of ±5% using an external resistor. This allows the optimization of the magnetic and filter components, resulting in compact, cost-effective isolated/nonisolated power supplies. For EMI-sensitive design, the ICs incorporate a programmable frequency dithering feature and enables low EMI spread-spectrum operation.
An input undervoltage lockout (EN/UVLO) is provided for programming the input-supply start voltage, and to ensure proper operation during brownout conditions. The EN/UVLO input is also used to turn on/off the ICs. Input overvoltage (OVI) protection scheme is provided to make sure that the regulator shuts down when the input supply exceeds its maximum allowed value.
To control inrush current, the devices incorporate an SS pin to set the soft-start time for the regulator. Power dissipation under fault conditions is minimized by a hiccup overcurrent protection (hiccup mode). A soft-stop feature provides safe discharging of the clamp capacitor when the device is turned off, and allows the controller to restart in a well-controlled manner. Additionally, a negative current limit is provided in the current-sense circuitry, helping limit the clamp switch current under dynamic operating conditions.
A SYNC feature is provided to synchronize multiple converters to a common external clock in noise-sensitive applications. Overtemperature faults trigger a thermal shutdown for reliable protection of the device. The ICs are available in a 16-pin, TQFN package with 0.5 mm lead spacing.
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