UCC2880-4_08 Datasheet, PDF (1/9 Pages) Texas Instruments – Pentium Pro Controller

Pentium® Pro Controller
UCC2880-4/-5/-6
UCC3880-4/-5/-6
PRELIMINARY
FEATURES
• Combined DAC/Voltage
Monitor and PWM Functions
• 4-Bit Digital-to-Analog
Converter (DAC)
• 1.0% DAC/Reference
• Low Offset X20 Current Sense
Amplifier
• 100kHz, 200kHz, 400kHz
Oscillator Frequency Options
• Foldback Current Limiting
• Overvoltage and Undervoltage
Fault Windows
• Undervoltage Lockout
• 2Ω Totem Pole Output
• Chip Disable Function
DESCRIPTION
The UCC3880-4/-5/-6 combines high precision reference and voltage monitor-
ing circuitry with average current mode PWM controller circuitry to power Intel
Pentium Pro and other high-end microprocessors with a minimum of external
components. The UCC3880-x converts 5VDC to an adjustable output, ranging
from 2.0VDC to 3.5VDC in 100mV steps with 1% DC system accuracy.
The chip includes a precision 5V reference which is capable of sourcing cur-
rent to an external load. The output voltage of the DAC is derived from this
reference, and is programmed directly by Intel’s VID pins (Table 1).
The accuracy of the DAC/reference combination is 1.0%. The overvoltage and
undervoltage comparators monitor the system output voltage and indicate
when it rises above or falls below its programmed value by more than 7.5%. A
second overvoltage protection comparator pulls the current amplifier output
voltage low to force zero duty cycle when the system output voltage exceeds
its designed value by more than 15%. This comparator also terminates the cy-
cle. Undervoltage lockout circuitry assures the correct logic states at the out-
puts during powerup and powerdown. Grounding the ENABLE pin forces the
GATE output low.
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BLOCK DIAGRAM
10/96
UDG-96106-1