UCC28521

over operating free-air temperature (unless otherwise noted)†
Supply voltage VCC
Idle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . 20 V
Operating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 V
Gate drive current (GT1, GT2)
Continuous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   . .. . 0.4 A
Pulsed
Sourcing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . −2.5 A
Sinking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  . .. . 3.5 A
Maximum GT1, GT2 voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  . −0.5 V to VCC+0.3 V
Input voltage
VSENSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 V to 11 V
D_MAX, SS2, CAOUT, ISENSE1, MOUT, VFF . . . . . . . . . . . . . . . . .  .−0.5 V to VREF+0.3 V
VAOUT, CT_BUFF, ISENSE2, PKLMT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. −0.5 V to 6 V
Pin Current
RT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   . . .. . −0.5 mA
VFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   . −5 mA
CT_BUFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  . .  1 mA
VAOUT, VERR, ISENSE2, SS2, CAOUT, IAC . . . . . . . . . . . . . . . . . . . . . . . . .  . . . . .. 10 mA
Maximum pin capacitance
ISENSE2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  . . . . . . . . . .  220 pF
Operating junction temperature range, TJ . . . . . . . . . . . . . . . . . . . . . . . −55 to 150
Storage temperature range, Tstg . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. −65 to 150
Lead temperature 1.6mm (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 reliability.

‡ Currents are positive into, negative out of the specified terminal. All voltages are referenced to GND.

The UCC28521 and UCC28528 combination PFC/PWM controllers provide complete control functionality for any off-line power system requiring compliance with the IEC1000−3−2 harmonic reduction requirements. By combining the control and drive signals for the PFC and the PWM stages into a single device, significant performance and cost benefits are gained.

Based on the UCC28511, the new devices employ an average current mode control architecture with input voltage feedforward. The major difference of the UCC28521/28 is the trailing-edge /trailing-edge (TEM/TEM) modulation scheme for the PFC/PWM stages. The UCC28528 differs from the UCC28521 as its PWM stage does not turn off with the falling bulk voltage. The UCC28528 PWM was designed for low power auxiliary supplies.

These devices offer performance advantages over earlier generation combination controllers. A key PWM feature is programmable maximum duty cycle. For the PFC stage, the devices feature an improved multiplier and the use of a transconductance amplifier for enhanced transient response.

The core of the PFC section is in a three-input multiplier that generates the reference signal for the line current. The UCC28521/28 features a highly linearized multiplier circuit capable of producing a low distortion reference for the line current over the full range of line and load
conditions. A low-offset, high-bandwidth current error amplifier ensures that the actual inductor current (sensed through a resistor in the return path) follows the multiplier output command signal. The output voltage error is processed through a transconductance voltage amplifier.