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PDF LX1664CN Data sheet ( Hoja de datos )
| Número de pieza | LX1664CN | |
| Descripción | DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC | |
| Fabricantes | Microsemi Corporation | |
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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
LX1664/64A, LX1665/65A
DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC
PRODUCTION DATA SHEET
DESCRIPTION
The LX1664/64A and LX1665/65A 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 LX1664A and
LX1665A have reduced current sense com-
parator threshold for optimum perfor-
mance using a sense resistor. For applica-
tions 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).
Linear Regulator Driver. The LX1664/
65 family of devices have a secondary
regulator output. This can drive a MOSFET
or bipolar transistor as a pass element to
construct a low-cost adjustable linear regu-
lator suitable for powering a 1.5V GTL+ bus
or 2.5V clock supply.
(continued next page)
IMPORTANT: For the most current data, consult LinFinity's web site: http://www.linfinity.com.
KEY FEATURES
I 5-bit Programmable Output For CPU Core
Supply
I Adjustable Linear Regulator Driver Output
I No Sense Resistor Required For Short-
Circuit Current Limiting
I Designed To Drive Either Synchronous Or
Non-Synchronous Output Stages
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
(LX1665 only)
A P P L I C AT I O N S
I Socket 7 (Pentium Class) 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
PRODUCT HIGHLIGHT
LX1665 IN A PENTIUM II SINGLE-CHIP POWER SUPPLY SOLUTION
C3
0.1µF
VID0
VID1
VID2
VID3
VID4
12V
U1
LX1665
1 SS
2 INV
V3
CC_CORE
4 VID0
5 VID1
6 VID2
7 VID3
8 VID4
9 LFB
VC1 18
TDRV 17
GND 16
BDRV 15
VCC 14
CT 13
OV 12
LDRV 11
PWRGD 10
18-pin
Wide-Body SOIC
F1 20A
5V
L2
1µH
C5
1µF
Q1
IRL3102
Q2
IRL3303
6.3V
1500µF x3
C2
L1
2.5µH
R1
0.0025
Supply Voltage
for CPU Core
VOUT
C1
6.3V, 1500µF x 3**
C8
680pF
Q4
IRLZ44
C9
330µF
** Three capacitors for Pentium
Four capacitors for Pentium II
Supply Voltage
For I/O Chipset or GTL+ Bus
R5 C7
OV 330µF
PWRGD
R6
TA (°C)
PACKAGE ORDER INFORMATION
N
Plastic DIP
16-pin
N
Plastic DIP
18-pin
D
Plastic SOIC
16-pin
DW
Plastic
18-pin
SOIC
Wide
0 to 70
LX1664CN
LX1665CN
LX1664CD
LX1665CDW
LX1664ACN
LX1665ACN
LX1664ACD
LX1665ACDW
Note: All surface-mount packages are available in Tape & Reel. Append the letter "T" to part number. (e.g. LX1664CDT)
Copyright © 1999
Rev. 1.2 11/99
LINFINITY MICROELECTRONICS INC.
11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841, 714-898-8121, FAX: 714-893-2570
1
1 page  
PRODUCT DATABOOK 1996/1997
LX1664/1664A, LX1665/65A
DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC
PRODUCTION DATA SHEET
CHARACTERISTICS CURVES
95
90
85
80
Output Set Point
EFFICIENCY AT 3.1V
75 EFFICIENCY AT 2.8V
EFFICIENCY AT 1.8V
70
1 2 3 4 5 6 7 8 9 10 11 12 13 14
IOUT (A)
FIGURE 2 — Efficiency Test Results:
Non-Synchronous Operation, VIN = 5V
100
95
90
85
80
Output Set Point
EFFICIENCY AT 3.1V
75 EFFICIENCY AT 2.8V
EFFICIENCY AT 1.8V
70
1 2 3 4 5 6 7 8 9 10 11 12 13 14
IOUT (A)
FIGURE 3 — Efficiency Test Results:
Synchronous Operation, VIN = 5V
90
85
80
75
70
Output Set Point
1.8V EFFICIENCY
65 2.8V EFFICIENCY
3.3V EFFICIENCY
60
1 2 3 4 5 6 7 8 9 10 11 12 13 14
IOUT (A)
FIGURE 4 — Efficiency Test Results: Synchronous Operation, V = 12V.
IN
Note: Non-synchronous operation not recommended for 12V operation, due to power loss in Schottky diode.
Copyright © 1999
Rev. 1.2 11/99
5
5 Page 
Ref
C1
C2
C7, C9
C3
C4
C8
C5
L1
L2
Q1
Q2
Q3
R5, R6
R1
U1
Total
PRODUCT DATABOOK 1996/1997
LX1664/1664A, LX1665/65A
DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC
PRODUCTION DATA SHEET
BILL OF MATERIALS
LX1665 Bill of Materials (Refer to Product Highlight)
Description
Part Number / Manufacturer
1500µF, 6.3V capacitor
1500µF, 6.3V capacitor
330µF, Electrolytic
0.1µF
390pF
680pF
1µF, 16V
2.5µH Inductor
1µH Inductor
MOSFET
MOSFET
MOSFET
Resistor (See Table 6 for values)
2.5mΩ Sense Resistor
Controller IC
MV-GX Sanyo
MV-GX Sanyo
MV-GX Sanyo
SMD Cap
SMD Cap
SMD Cap
SMD Ceramic
HM0096832 BI or equivalent
IRL3102 International Rectifier or equivalent
IRL3303 International Rectifier or equivalent
IRLZ44 International Rectifier or equivalent
SMD Resistor
IRC OARS-1 or PCB trace
LX1665CDW Linfinity
Qty.
4
2
2
1
1
1
1
1
1
1
1
1
2
1
1
21
USING THE LX1664/65 DEVICES
The LX1664/65 devices are very easy to design with, requiring
only a few simple calculations to implement a given design. The
following procedures and considerations should provide effec-
tive operation for virtually all applications. Refer to the Appli-
cation Information section for component reference designa-
tors.
TIMING CAPACITOR SELECTION
The frequency of operation of the LX166x is a function of duty
cycle and OFF-time. The OFF-time is proportional to the timing
capacitor (which is shown as C8 in all application schematics in
this data sheet), and is modulated to minimize frequency
variations with duty cycle. The frequency is constant, during
steady-state operation, due to the modulation of the OFF-time.
The timing capacitor (CT) should be selected using the
following equation:
CT =
(1 - VOUT /VIN ) * IDIS
fS (1.52 - 0.29 * VOUT )
Where IDIS is fixed at 200µA and fS is the switching frequency
(recommended to be around 200kHz for optimal operation and
component selection).
When using a 5V input voltage, the switching frequency (fS)
can be approximated as follows:
CT = 0.621 *
IDIS
fS
Choosing a 680pF capacitor will result in an operating
frequency of 183kHz at VOUT = 2.8V. When a 12V power input
is used, he capacitor value must be changed (the optimal timing
capacitor for 12V input will be in the range of 1000-1500pF).
L OUTPUT INDUCTOR SELECTION
1
The inductance value chosen determines the ripple current
present at the output of the power supply. Size the inductance
to allow a nominal ±10% swing above and below the nominal DC
load current, using the equation L = VL * ∆T/∆I, where ∆T is the
OFF-time, VL is the voltage across the inductor during the OFF-
time, and ∆I is peak-to-peak ripple current in the inductor. Be
sure to select a high-frequency core material which can handle
the DC current, such as 3C8, which is sized for the correct power
level. Typical inductance values can range from 2 to 10µH.
Note that ripple current will increase with a smaller inductor.
Exceeding the ripple current rating of the capacitors could cause
reliability problems.
Copyright © 1999
Rev. 1.2 11/99
11
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