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LX1670CD Schematic ( PDF Datasheet ) - Microsemi Corporation

Teilenummer LX1670CD
Beschreibung 5 - BIT PROGRAMMABLE VOTAGE REFERENCE
Hersteller Microsemi Corporation
Logo Microsemi Corporation Logo 




Gesamt 7 Seiten
LX1670CD Datasheet, Funktion
T H E I N F I N I T E P O W E R O F I N N O VAT I O N
L I N D O C #: 1670
LX1670
5-BI T PROGRAMMABLE VOLTAGE REFERENCE
PR O D U C T I O N D ATA S H E E T
DESCRIPTION
The LX1670 is a complete precision
reference and voltage monitor circuit
for the Intel Pentium® Pro Processor
and other high-end microprocessor
supplies. It is designed for use in
conjunction with the LX1660/1661 PWM
controller. The LX1670 reads a 5-bit
voltage identification (VID) code from
the microprocessor and sets the output
voltage reference to be used by the
LX1660/61 controller. Together, they
convert +5 or 12V input power to an
adjustable output ranging from 1.8VDC
to 3.5VDC in 100mV steps (50mV steps
below 2.1V) with 1% DC system
accuracy.
KEY FEATURES
p 1% TOTAL OUTPUT ERROR
p POWER GOOD, UV, 0V COMPARATORS
p 0V COMPARATOR HAS SCR DRIVE
p UNDER-VOLTAGE LOCKOUT CAPABILITY
p 5-BIT INPUT FOR ADVANCED PENTIUM PRO
PROCESSOR APPLICATIONS (5TH BIT IS FOR
AUTOMATIC GAIN AND OFFSET SCALING)
p IMPLEMENTS 1% DC ACCURATE CONTROL
SYSTEM
p 14-PIN NARROW BODY SOIC PACKAGE
PRODUCT HIGHLIGHT
T Y P I C A L A P P L I C AT I O N O F T H E L X 1 6 7 0
VCC
A P P L I C AT I O N S
s PENTIUM II & PENTIUM PRO VOLTAGE
REGULATOR MODULES
s PROGRAMMABLE POWER SUPPLIES
s VOLTAGE REFERENCE
s ADVANCED MICROPROCESSOR SUPPLIES
5-Bit
Digital
Input
Word
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
Enable
Blank Enable
D0
D1
D2
D3
D4
ENABLE
BLKEN
GND
VCC
LX1670
VSENSE
VIDO
OVOUT
PGOOD
System Output
Voltage
To PWM
Error Amplifier
SCR Drive
Power Good
Copyright © 1997
Rev. 1.0 7/97
PA C K A G E O R D E R I N F O
TA (°C)
D
Plastic SOIC
14-pin
0 to 70
LX1670CD
Note: All surface-mount packages are available in Tape & Reel.
Append the letter "T" to part number. (i.e. LX1670CDT)
FOR FURTHER INFORMATION CALL (714) 898-8121
11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841
1






LX1670CD Datasheet, Funktion
LX1670
PRODUCT DATABOOK 1996/1997
5-BI T PROGRAMMABLE VOLTAGE REFERENCE
PRODUCTION DATA SHEET
THEORY OF OPERATION
UNDER-VOLTAGE LOCKOUT
This function keeps order to the IC until the power supply voltage
reaches 85% of its nominal value. The output voltage is pulled low
and PGOOD and OVOUT are pulled low. Once the power supply
voltage crosses 85%, the output voltage, VIDO, is released, and
PGOOD continues to be pulled low. When V SENSE (the
microprocessor's power supply) is within ±7% of VIDO, PGOOD is
released. The comparator has hysteresis to prevent transient
oscillation.
4-BIT DAC and 5th-BIT SCALER
This function generates a precise voltage from a binary, 5-bit
digital word VID [0:4]. It uses a 4-bit, binary weighted current
DAC, driving a precise current to voltage converter. This voltage
is then op-amp buffered and sent out. The scaling is accomplished
by multiplexing the buffer op-amp. The resulting transfer function
is:
VIDO (D0,D1,D2,D3) =
(2.00 + 0.1 * (1*D0 + 2*D1 + 4*D2 + 8*D3))
for D4 = 1
OVER- / UNDER-VOLTAGE COMPARATORS
This function generates an open collector Power Good signal
when VSENSE is within ±7% of VIDO.
OVER-VOLTAGE PROTECTION
This function generates an OVOUT voltage signal when VSENSE is 15%
higher than VIDO. This voltage can be used to drive an external
SCR.
CHIP ENABLE
This function disables the chip when low. VIDO, PGOOD and OVOUT
are all pulled low. When ENABLE is high, the chip's state is then
determined by the other functions.
BLANK ENABLE
This function will disable VIDO for codes with voltages below
1.80V when this pin is high. When pulled low, this function will
allow VIDO to accept codes for voltages of 1.30 to 3.50V.
VIDO (D0,D1,D2,D3) =
(2.00 + 0.6 + 0.1 * (1*D0 + 2*D1 + 4*D2 + 8*D3)) * 0.5
for D4 = 0
for the code VIDO < 1.8V will be blocked and VIDO = 0.
The zero-scale output voltage, full-scale output voltage and the
scale factor are all trimmed on-chip using fusable links.
6 Copyright © 1997
Rev. 1.0 7/97

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