The MAX17598/MAX17599 low IQ, active clamp current-mode PWM controllers contain all the control circuitry required for the design of wide-input isolated/non-isolated 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 36V 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 ±8% using an external resistor. This allows optimization of the magnetic and filter components, resulting in compact, cost-effective isolated/nonisolated power supplies. For EMI-sensitive applications, the ICs incorporate a programmable frequency-dithering scheme, enabling low-EMI spread-spectrum operation.
An input undervoltage lockout (EN/UVLO) is provided for programming input-supply start voltage, and to ensure proper operation during brownout conditions. 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 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 regulators. Power dissipation under fault conditions is minimized by hiccup overcurrent protection (hiccup mode). 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, negative current limit is provided in the current-sense circuitry, helping limit clamp switch current under dynamic operating conditions.
SYNC feature is provided to synchronize multiple converters to a common external clock in noise-sensitive applications. Overtemperature fault triggers thermal shutdown for reliable protection of the device. The ICs are available in a 16-pin, TQFN package with 0.5 mm lead spacing.
Feature
- Active Clamp, Peak Current-Mode Forward PWM Controller
- 20μA Startup Current in UVLO
- 4.5V to 36V Input-Supply Operating Range (MAX17599)
- Programmable Input Undervoltage Lockout
- Programmable Input Overvoltage Protection
- Programmable 100kHz to 1MHz Switching Frequency
- Switching Frequency Synchronization
- Programmable Frequency Dithering for Low EMI Spread-Spectrum Operation
- Programmable Dead Time
- Adjustable Soft-Start
- Programmable Slope Compensation
- Fast Cycle-by-Cycle Peak-Current-Limit
- 70ns Internal Leading-Edge Current-Sense Blanking
- Hiccup Mode Output Short-Circuit Protection
- Soft-Stop for Well-Controlled Clamp Capacitor Discharge
- Negative Clamp-Switch Current Limit
- 3mm x 3mm, Lead-Free 16-Pin TQFN
- -40°C to +125°C Operating Temperature Range
Applications
- Industrial Power Supplies
- Isolated Battery Chargers
- Servers and Embedded Computing
- Telecom and Datacom Power Supplies
