Average Current Mode Synchronous Controller 28-Pin SOIC Tube

The UCC3882 combines high precision reference and voltage monitoring circuitry with average current mode PWM synchronous rectification controller circuitry to power high-end microprocessors with a minimum of external components. The UCC3882 converts 5 V or 12 V to an adjustable output ranging from 1.8VDC to 2.05VDC in 50 mV steps and 2.1VDC to 3.5VDC in 100 mV steps with 1% DC system accuracy. The DAC output voltage is directly compatible with Intel’s 5-bit VID code () which covers 1.3 V to 2.05 V in 50 mV steps and 2.1 V to 3.5 V in 100 mV steps. The accuracy of the DAC/reference combination is better than 1%. Undervoltage lockout circuitry assures the correct logic states at the outputs during power up and power down. The overvoltage and undervoltage comparators monitor the system output voltage and indicate when it rises above or falls below its designed value by more than 9%. A second overvoltage comparator digitally forces GATEHI off and GATELO on when the system output voltage exceeds its designed value by more than 17.5%. For all of the parts, grounding the EN pin disables the GATEHI and GATELO outputs, shutting down the power supply. For the 3882, programming a DAC output voltage below 1.8 V, or programming all of the VID pins high also disables the GATEHI and GATELO outputs. For the –1 option parts, the GATEHI and GATELO outputs are switching, and the power supply output voltage regulates at the programmed DAC output voltage for all VID codes. The voltage and current amplifiers have 2.5 MHz gain-bandwidth product to satisfy high performance system requirements. The internal current sense amplifier permits the use of a low value current sense resistor, minimizing power loss. The oscillator frequency is externally programmed with RT and CT. The foldback circuit reduces the converter short circuit current limit to 50% of its nominal value when the converter is short-circuited, minimizing component stress and dissipation during abnormal conditions. The gate drivers are low impedance totem pole output stages capable of driving large external MOSFETs. Cross conduction is eliminated internally by programming the dead time between turn-off and turn on of the external high side and synchronous MOSFETs. This device is available in a 28-pin wide body surface mount package. The UCC3882 is specified for operation from 0°C to 70°C.

Combined DAC/Voltage Monitor and PWM With Synchronous Rectification Functions

5-Bit Digital-to-Analog (DAC) Converter

1% DAC/Reference Combined Accuracy

Compatible with 5 V and 12 V Systems and 12 V-Only Systems

Low Offset Current Sense Amplifier

Programmable Oscillator Frequency Practical to 700 kHz

Foldback Current Limiting

Overvoltage and Undervoltage Fault Windows

2-O Totem Pole Outputs with Programmable Dead Times to Eliminate Cross-Conduction

Chip Disable Function