UCC3960

Input voltage, V_I(VDD) . . . . . . . . . . . . . . .. . . . . . . . . .. . . .. . . .. . . . . . . . . . . . 19 V
Input current, I_I(VDD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 25 V
Output current, I_O  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  . 1.5 A / 2 A
Reference current, IREF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7.5 mA
Output voltage: REF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.3 V to VDD+0.3 V
Input voltage: SS, RT, CS . . . . . . . . . . . . . . . . . . . . . . . . . . .. 0.3 V to VDD+0.3 V
FB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 7.0 V to VDD+0.3 V
Operating junction temperature range, T_J . . . . . . . . . . . . . . . . . . . 55 to 150

Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . 65 to 150
Lead temperature soldering 1,6 mm (1/16 inch) from case for 10 seconds . . 300

† Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
‡ Unless otherwise indicated, voltages are reference to ground and currents are positive into and negative out of the specified terminals. Pulsed is defined as a less than 10% duty cycle with a maximum duration of 500 ms.
4 nF load with 4-W series resistor.

The UCC3960 primary-side startup controller is a unique solution that provides all the primary-side functions required for a single-ended, isolated offline, switch-mode power converter that uses secondary-side PWM control. It is usable with a wide range of secondary circuits and is especially well suitable for systems where sophisticated handling of overload conditions is required.

Secondary-side control assumes that output voltage and current measurements are interfaced directly to an output ground-referenced PWM stage that develops the power switch command for the supply. This digital PWM command can then be transmitted to the primary-side power switch through a simple and low-cost isolating pulse transformer. With secondary-side control, it is much easier to monitor and control the system load with tightly coupled analog control loops. Load-oriented features such as output current sharing and synchronous rectification are implemented more easily.

The UCC3960 provides all the circuitry required on the primary side of a secondaryside controlled power supply. It features a free running 60-kHz to 360-kHz oscillator that is synchronizable to the secondary-side PWM signal and also has the ability to accept start/stop PWM commands from the isolating pulse edge transformer. The use of an extremely small and low-cost pulse transformer allows for higher converter bandwidth. This also eliminates the loop-gain variations due to initial accuracy and aging of an opto-coupler feedback element or the size penalty of a gate transformer. It also includes an undervoltage lockout circuit with 2-V hysteresis, a low current startup with active low during UVLO, a soft-start capability, a 5-V reference and a high current power output.

In a non-typical use, the UCC3960 can accommodate an analog feedback signal through an opto-isolator where it can operate in voltage-mode control mode with primary-side peak current limiting.

The UCC3960 and the UCC2960 are available in the 8-pin SOIC (D) and PDIP (P) packages. A 14-pin package version is available as UCC2961 and UCC3961 that includes additional protection features such as multimode overcurrent protection, volt-second clamp, programmable overvoltage and undervoltage sense lines, and the self-bias regulator.