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PDF ( 数据手册 , 数据表 ) LX1663A

零件编号 LX1663A
描述 SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
制造商 Microsemi Corporation
LOGO Microsemi Corporation LOGO 


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LX1663A 数据手册, 描述, 功能
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 # : 1662
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
PRODUCTION DATA SHEET
DESCRIPTION
The LX1662/62A and LX1663/63A are
Monolithic Switching Regulator Con-
troller IC’s designed to provide a low cost,
high performance adjustable power supply
for advanced microprocessors and other
applications requiring a very fast transient
response and a high degree of accuracy.
Short-Circuit Current Limiting with-
out Expensive Current Sense Resistors.
Current-sensing mechanism can use PCB
trace resistance or the parasitic resistance of
the main inductor. The LX1662A and
LX1663A have reduced current sense com-
parator threshold for optimum perfor-
mance using a PCB trace. For applications
requiring a high degree of accuracy, a
conventional sense resistor can be used to
sense current.
Programmable Synchronous Recti-
fier Driver for CPU Core. The main
output is adjustable from 1.3V to 3.5V using
a 5-bit code. The IC can read a VID signal
set by a DIP switch on the motherboard, or
hardwired into the processor’s package (as
in the case of Pentium® Pro and Pentium II
processors). The 5-bit code adjusts the
output voltage between 1.30 and 2.05V in
50mV increments and between 2.0 and 3.5V
in 100mV increments, conforming to the
Intel Corporation specification. The device
can drive dual MOSFET’s resulting in typical
efficiencies of 85 - 90% even with loads in
excess of 10 amperes. For cost sensitive
applications, the bottom MOSFET can be
replaced with a Schottky diode (non-syn-
chronous operation).
Smallest Package Size. The LX1662 is
available in a narrow body 14-pin surface
mount IC package for space sensitive appli-
cations. The LX1663 provides the additional
functions of Over Voltage Protection (OVP)
and Power Good (PWRGD) output drives
for applications requiring output voltage
monitoring and protection functions.
Ultra-Fast Transient Response Re-
duces System Cost. The modulated off-
time architecture results in the fastest tran-
sient response for a given inductor, reduc-
ing output capacitor requirements, and re-
ducing the total regulator system cost.
Over-Voltage Protection and Power
Good Flag. The OVP output in the LX1663
& LX1663A can be used to drive an SCR
crowbar circuit to protect the load in the
event of a short-circuit of the main MOSFET.
The LX1663 & LX1663A also have a logic-
level Power Good Flag to signal when the
output voltage is out of specified limits.
IMPORTANT: For the most current data, consult LinFinity's web site: http://www.linfinity.com.
PRODUCT HIGHLIGHT
KEY FEATURES
I 5-bit Programmable Output For CPU Core
Supply
I No Sense Resistor Required For Short-
Circuit Current Limiting
I Designed To Drive Either Synchronous Or
Non-Synchronous Output Stages
I Lowest System Cost Possible For Price-
Sensitive Pentium And Pentium II Class
Applications
I Soft-Start Capability
I Modulated, Constant Off-Time Architecture
For Fast Transient Response And Simple
System Design
I Available Over-Voltage Protection (OVP)
Crowbar Driver And Power Good Flag
(LX1663 only)
I Small, Surface-Mount Packages
A P P L I C AT I O N S
I Socket 7 Microprocessor Supplies
(including Intel Pentium Processor, AMD-
K6TM And Cyrix® 6x86TM, Gx86TM and M2TM
Processors)
I Pentium II and Deschutes Processor & L2-
Cache Supplies
I Voltage Regulator Modules
I General Purpose DC:DC Converter
Applications
LX1662
IN A PENTIUM/PENTIUM II
SINGLE-CHIP POWER
SUPPLY SOLUTION
C3
0.1µF
VID0
VID1
VID2
VID3
VID4
12V 5V
U1
LX1662
1 SS
2 INV
V3
CC_CORE
4 VID0
5 VID1
6 VID2
7 VID3
VC1 14
TDRV 13
GND 12
BDRV 11
VCC 10
CT 9
VID4 8
14-pin, Narrow Body SOIC
L2
1µH
C5
1µF
Q1
IRL3102
6.3V
1500µF x3
C2
C8
680pF
L1, 2.5µH
R1
Q2
IRL3303
2.5m9
6.3V, 1500µF x 3**
** Three capacitors for Pentium
Four capacitors for Pentium II
Supply Voltage VOUT
for CPU Core
C1
TA (°C)
PACKAGE ORDER INFORMATION
N
Plastic DIP
14-pin
N
Plastic DIP
16-pin
D
Plastic SOIC
14-pin
D
Plastic SOIC
16-pin
0 to 70
LX1662CN
LX1662ACN
LX1663CN
LX1663ACN
LX1662CD
LX1662ACD
LX1663CD
LX1663ACD
Note: All surface-mount packages are available in Tape & Reel. Append the letter "T" to part number. (i.e. LX1662CDT)
Copyright © 1999
Rev. 1.1 11/99
LINFINITY MICROELECTRONICS INC.
11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841, 714-898-8121, FAX: 714-893-2570
1







LX1663A pdf, 数据表
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
PRODUCTION DATA SHEET
THEORY OF OPERATION
IC OPERATION
Referring to the block diagram and typical application circuit, the
output turns ON the top MOSFET, allowing the inductor current
to increase. At the error comparator threshold, the PWM latch is
reset, the top MOSFET turns OFF and the synchronous MOSFET
turns ON. The OFF-time capacitor CT is now allowed to discharge.
At the valley voltage, the synchronous MOSFET turns OFF and the
top MOSFET turns on. A special break-before-make circuit
prevents simultaneous conduction of the two MOSFETs.
The VCC_CORE pin is offset by +40mV to enhance transient
response. The INV pin is connected to the positive side of the
current sense resistor, so the controller regulates the positive side
of the sense resistor. At light loads, the output voltage will be
regulated above the nominal setpoint voltage. At heavy loads, the
output voltage will drop below the nominal setpoint voltage. To
minimize frequency variation with varying output voltage, the
OFF-time is modulated as a function of the voltage at the VCC_CORE
pin.
ERROR VOLTAGE COMPARATOR
The error voltage comparator compares the voltage at the positive
side of the sense resistor to the set voltage plus 40mV. An external
filter is recommended for high-frequency noise.
CURRENT LIMIT
Current limiting is done by sensing the inductor current. Exceed-
ing the current sense threshold turns the output drive OFF and
latches it OFF until the PWM latch Set input goes high again. See
Current Limit Section in "Using The LX1662/63 Devices" later in
this data sheet.
OFF-TIME CONTROL TIMING SECTION
The timing capacitor CT allows programming of the OFF-time. The
timing capacitor is quickly charged during the ON time of the top
MOSFET and allowed to discharge when the top MOSFET is OFF.
In order to minimize frequency variations while providing differ-
ent supply voltages, the discharge current is modulated by the
voltage at the VCC_CORE pin. The OFF-time is inversely proportional
to the VCC_CORE voltage.
UNDER VOLTAGE LOCKOUT SECTION
The purpose of the UVLO is to keep the output drive off until the
input voltage reaches the start-up threshold. At voltages below
the start-up voltage, the UVLO comparator disables the internal
biasing, and turns off the output drives, and the SS (Soft-Start) pin
is pulled low.
SYNCHRONOUS CONTROL SECTION
The synchronous control section incorporates a unique break-
before-make function to ensure that the primary switch and the
synchronous switch are not turned on at the same time. Approxi-
mately 100 nanoseconds of deadtime is provided by the break-
before-make circuitry to protect the MOSFET switches.
PROGRAMMING THE OUTPUT VOLTAGE
The output voltage is set by means of a 5-bit digital Voltage
Identification (VID) word (See Table 1). The VID code may be
incorporated into the package of the processor or the output
voltage can be set by means of a DIP switch or jumpers. For a low
or '0' signal, connect the VID pin to ground (DIP switch ON/
CLOSED); for a high or '1' signal, leave the VID pin open (DIP
switch OFF/OPEN).
The five VID pins on the LX166x series are designed to
interface directly with a Pentium Pro or Pentium II processor.
Therefore, all inputs are expected to be either ground or floating.
Any floating input will be pulled high by internal connections. If
using a Socket 7 processor, or other load, the VID code can be set
directly by connecting jumpers or DIP switches to the VID[0:4]
pins.
The VID pins are not designed to take TTL inputs, and
should not be connected high. Unpredictable output voltages
may result. If the LX166x devices are to be connected to a logic
circuit, such as BIOS, for programming of output voltage, they
should be buffered using a CMOS gate with open-drain, such as
a 74HC125 or 74C906.
POWER GOOD SIGNAL (LX1663 only)
An open collector output is provided which presents high
impedance when the output voltage is between 90% and 117% of
the programmed VID voltage, measured at the SS pin. Outside this
window the output presents a low impedance path to ground.
The Power Good function also toggles low during OVP operation.
OVER-VOLTAGE PROTECTION
The controller is inherently protected from an over-voltage
condition due to its constant OFF-time architecture. However,
should a failure occur at the power switch, an over-voltage drive
pin is provided (on the LX1663 only) which can drive an external
SCR crowbar (Q3), and so blow a fuse (F1). The fault condition
must be removed and power recycled for the LX1663 to resume
normal operation (See Figure 9).
8 Copyright © 1999
Rev. 1.1 11/99














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