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UCC391
ADVANCE INFORMATION
5-Bit Programmable Output BiCMOS Precision Voltage Reference
FEATURES
* 5 - Bit Digital-to-Analog Converter (DAC) supports Intel Pentium II Microprocessor VID Codes * Compatible with 5V Systems * 1% Output Voltage Accuracy Guaranteed
DESCRIPTION
The UCC391 provides an accurate reference, programmable by a 5-bit DAC, in a tiny 8 pin package. Using few external components, the UCC391 converts 5V to an adjustable output ranging from 3.5VDC to 2.1VDC in 100mV steps and 2.05VDC to 1.3VDC in 50mV steps with 1% DC system accuracy. This device is available in and 8 pin surface mount (150mm SOIC) and TSSOP packages and is specified for operation from 0C to 70C.
BLOCK DIAGRAM
D4 D3 D2 D1 D0
7 8 1 2 3 DAC VREF
4
VCC
5
COMMAND
6
GND
UDG-98200
SLUS437 - NOVEMBER 1998
UCC391
ABSOLUTE MAXIMUM RATINGS
Supply Voltage VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8V Input Voltage, D0, D1, D2, D3, D4 . . . . . . . . . . . . . . . . . . . . 8V
CONNECTION DIAGRAMS
MSOP-8, TSSOP-8 (TOP VIEW) P, PW Packages
D2 1 8 D3
Currents are positive into, negative out of the specified terminal. Consult Packaging Section of Databook for thermal limitations and considerations of packages. All voltages are referenced to GND.
D1
2
7
D4
D0
3
6
GND
VCC
4
5
COMMAND
ELECTRICAL CHARACTERISTICS: Unless otherwise specified these specifications hold for TA = 0C to 70C for the
UCC391, TA = TJ. VCC = 5V. PARAMETER Supply Current Section Supply Current, On DAC Reference Section COMMAND Voltage Accuracy D0 - D4 Voltage High D0 - D4 Voltage Threshold D0 - D4 Input Bias Current Output Current (Maximum Load) V(D4, D3, D2, D1, D0) < 0.5V IOUT (VCOMMAND) 0 4.5V < VIN < 5.5V, measured on COMMAND, 0C < TA < 70C (Note 1) -1.00 4.5 5 2.5 -90 -20 150 1.00 5.5 % V V VCC = 5V 1.8 mA TEST CONDITIONS MIN TYP MAX UNITS
A A
Note 1: Reference and output amplifier offsets are trimmed out before packaging.
PIN DESCRIPTIONS
GND: (Ground) All voltages measured with respect to ground. VCC should be bypassed directly to GND with a 0.1F or larger ceramic capacitor. VCC: (Positive supply voltage) This pin is normally connected to a 5V 10% system voltage. Bypass VCC directly to GND with a 0.1F (minimum) ceramic capacitor. COMMAND: This pin is the output of the IC. It is controlled by the 5-bit input word (D0:D4). This output will have a 1% system accuracy over temperature, process, and input voltage. D0, D1, D2, D3, D4: These are the digital input control codes for the DAC. The DAC is comprised of two ranges set by D4, with D0 representing the least significant bit (LSB) and D3, the most significant bit (MSB). A bit is set low by being connected to GND; a bit is set high by floating the pin. Each control pin is pulled up to approximately 5V by an internal pull-up. If all ones are commanded on the DAC inputs (no CPU command), the output will be disabled.
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UCC391 APPLICATION INFORMATION
D4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 D3 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 D2 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 D1 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 D0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 VOUT 1.3 1.35 1.4 1.45 1.5 1.55 1.6 1.65 1.7 1.75 1.8 1.85 1.9 1.95 2 2.05 NO OUTPUT 2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3 3.1 3.2 3.3 3.4 3.5
Table I. VID Codes and Resulting Regulator Output Voltage
UNITRODE CORPORATION 7 CONTINENTAL BLVD. * MERRIMACK, NH 03054 TEL. (603) 424-2410 * FAX (603) 424-3460
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Copyright (c) 2000, Texas Instruments Incorporated

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