UC1910
UC2910
UC3910
4-Bit DAC and Voltage Monitor
FEATURES
DESCRIPTION
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Precision 5V Reference
The UC3910 is a complete precision reference and voltage monitor cir-
cuit for Intel Pentium® Pro and other high-end microprocessor power
supplies. It is designed for use in conjunction with the UC3886 PWM. The
UC3910 together with the UC3886 converts 5VDC to an adjustable out-
put ranging from 2.0VDC to 3.5VDC in 100mV steps with 1% DC system
accuracy.
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4-Bit Digital-to-Analog (DAC)
Converter
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0.5% DAC/Reference Combined
Error
Programmable Undervoltage and
Overvoltage Fault Windows
The UC3910 utilizes thin film resistors to ensure high accuracy and sta-
bility of its precision circuits. The chip includes a precision 5V voltage ref-
erence which is capable of sourcing 10mA to external circuitry. The
output voltage of the DAC is derived from this reference, and the accu-
racy of the DAC/reference combination is 0.5%. Programmable window
comparators monitor the supply voltage to indicate that it is within ac-
ceptable limits. The window is programmed as a percentage centered
around the DAC output. An overvoltage protection comparator is set at a
percentage 2 times larger than the programmed lower overvoltage level
and drives an external SCR as well as provides an open collector output.
Undervoltage lockout protection assures the correct logic states at the
outputs during power-up and power-down.
Overvoltage Comparator with
Complementary SCR Driver and
Open Collector Outputs
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Undervoltage Lockout
BLOCK DIAGRAM
UDG-95097-3
3/97
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