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부품번호 LX1668CPW 기능
기능 PROGRAMMABLE MULTIPLE OUTPUT DC:DC CONTROLLER
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LX1668CPW 데이터시트, 핀배열, 회로
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 #: 1668
LX1668
P ROGRAMMABLE MULTIPLE OUTPUT DC:DC CONTROLLER
PR O D U C T I O N D ATA S H E E T
DESCRIPTION
The LX1668 is a Monolithic Switching
Regulator Controller IC designed to pro-
vide 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. It provides a programmable
switching regulator output, together with one
internal linear low dropout regulator and one
adjustable linear regulator driver. The LX1668
offers a triple-output single-chip power sup-
ply for Pentium® II and other processors.
Programmable Synchronous Rectifier
Driver for CPU Core. The main output is
adjustable from 1.3 to 3.5V using a TTL-
compatible 5-bit digital code to meet Intel
specifications. The IC can read the signal
from a DIP-switch, hardwired to Pentium II
processor’s pins or from software. 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. The
device can drive dual MOSFET’s resulting in
typical efficiencies of 85 – 90%, even with
loads in excess of 10A.
Internal Low Dropout [LDO] Regulator
provides a fixed 2.5V output for powering the
clock circuit at up to 250mA.
External Linear Regulator Driver out-
put can be connected to a MOSFET to provide
a high-current adjustable LDO function suit-
able for supplying the GTL+ bus circuitry on
a Pentium II processor motherboard at 1.5V.
Short-circuit Current Limiting without
Expensive Current Sense Resistors. The
current sensing mechanism can use a PCB
trace resistance or the parasitic resistance of
the main inductor. For applications requiring
a high degree of accuracy, a conventional
sense resistor can be used.
Ultra-Fast Transient Response Re-
duces System Cost. The fixed frequency
modulated off-time architecture results in the
fastest transient response for a given inductor.
Small Package Size. The LX1668 is available
in an economical 20-pin wide body SOIC or
a space-saving 20-pin TSSOP package.
NOTE: For current data & package dimensions, visit our web site: http://www.linfinity.com.
KEY FEATURES
s 5-Bit Programmable Output For CPU Core
Supply
s Internal Fixed 2.5V Low Dropout Regulator
s Adjustable Linear Regulator Driver
s Complete Single-Chip Power Solution For
Pentium II Processors
s No Sense Resistor Required For Short-Circuit
Current Limiting
s Soft-Start And Hiccup-Mode Current Limiting
Functions
s Modulated Constant Off-Time Control
Mechanism For Fast Transient Response And
Simple System Design
s Power Good Flag
s Over-Voltage Pin & SCR
s Digital-Compatible Inputs (Including VID Pins)
s Output Disable Function Shuts Off PWM While
Keeping 2.5V LDO Active - Compatible With
"Green PC" And "Instant On" Requirements
s Compatible to VRM8.2 - 8.4 Specifications
A P P L I C AT I O N S
s Pentium II & Pentium III Processor Supplies
s Voltage Regulator Modules
s General Purpose And Microprocessor DC:DC
Supplies
PRODUCT HIGHLIGHT
5V
12V
C8 C3
1µF 1µF
VOUT2
2.5V
C5
22µF
C9
1µF
3.3V
VOUT3
1.5V
C4
330µF
C6
330µF
Q3
IRLZ44
R1, 0
R2, 50k
L2
1µH
C7
1µF
1 TDRV
PGND 20
2 VCC12
BDRV 19
3 VCC5
AGND 18
LX16684 VOUT2
5 VCC3
6 LDRV
SS/EN
VFB
17
16 CSS
VCORE 15
7 LFB
PWRGD 14
8 VID0
OVP 13
9 VID1
VID4 12
10 VID2
VID3 11
Q1
IRL3102
0.1µF
C2
1500µFx3
L1 RSENSE
2.5µH 2.5m
Q2
IRL3303
PWRGD
Q4*
SCR
2N6504
VID4
VID3
VID2
VID1
VID0
R3
10k
3.3V / 5V
CPU Core
VCORE
C1
1500µF x 6
* Q4 optional
OVP crowbar
PACKAGE ORDER INFORMATION
TA (°C)
DW
Plastic
20-pin
SOWB
PW
Plastic
20-pin
TSSOP
0 to 70
LX1668CDW
LX1668CPW
Note: All surface-mount packages are available in Tape & Reel, append the letter "T" to part number. (i.e. LX1668CPWT)
Copyright © 1999
Rev. 1.0 4/99
LINFINITY MICROELECTRONICS INC.
11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841, 714-898-8121, FAX: 714-893-2570
1




LX1668CPW pdf, 반도체, 판매, 대치품
PRODUCT DATABOOK 1996/1997
LX1668
P ROGRAMMABLE MULTIPLE OUTPUT DC:DC CONTROLLER
PRODUCTION DATA SHEET
ELECTRICAL CHARACTERISTICS
Table 1 - Adaptive Transient Voltage Output (Output Voltage Setpoint — Typical)
Processor Pins
0 = Low, 1 = High
Output Voltage (VSET)
VID4
0
0
VID3
1
1
VID2
1
1
VID1
1
1
VID0
1
0
0.0A
1.34V
1.39V
Nominal Output* (VSET)
1.30V
1.35V
0 1 1 0 1 1.44V
1.40V
0 1 1 0 0 1.49V
1.45V
0 1 0 1 1 1.54V
1.50V
0 1 0 1 0 1.59V
0 1 0 0 1 1.64V
1.55V
1.60V
0 1 0 0 0 1.69V
1.65V
0 0 1 1 1 1.74V
1.70V
0 0 1 1 0 1.79V
1.75V
0 0 1 0 1 1.84V
1.80V
0 0 1 0 0 1.89V
1.85V
0 0 0 1 1 1.94V
1.90V
0 0 0 1 0 1.99V
0 0 0 0 1 2.04V
1.95V
2.00V
0 0 0 0 0 2.09V
2.05V
1 1 1 1 1 2.04V
2.00V
1 1 1 1 0 2.14V
2.10V
1 1 1 0 1 2.24V
1 1 1 0 0 2.34V
2.20V
2.30V
1 1 0 1 1 2.44V
2.40V
1 1 0 1 0 2.54V
2.50V
1 1 0 0 1 2.64V
2.60V
1 1 0 0 0 2.74V
2.70V
1 0 1 1 1 2.84V
2.80V
1 0 1 1 0 2.94V
2.90V
1 0 1 0 1 3.04V
1 0 1 0 0 3.14V
3.00V
3.10V
1 0 0 1 1 3.24V
3.20V
1 0 0 1 0 3.34V
3.30V
1 0 0 0 1 3.44V
3.40V
1 0 0 0 0 3.54V
3.50V
* Nominal = DAC setpoint voltage with no adaptive output voltage positioning.
Note:
Adaptive Transient Voltage Output
In order to improve transient response a 40mV offset is built into the voltage comparator. At high currents, the
peak output voltage will be lower than the nominal set point , as shown in Figure 4. The actual output voltage
will be a function of the sense resistor, output current and output ripple.
4 Copyright © 1999
Rev. 1.0 4/99

4페이지










LX1668CPW 전자부품, 판매, 대치품
PRODUCT DATABOOK 1996/1997
P ROGRAMMABLE MULTIPLE OUTPUT DC:DC CONTROLLER
PR O D U C T I O N D ATA S H E E T
LX1668
THEORY OF OPERATION
SWITCHER OUTPUT VOLTAGE REGULATION
Refer to the IC Block Diagram and the Product Highlight circuit.
When the top MOSFET turns ON, the inductor current increases.
The voltage at VFB pin increases due to the ESR of the output
capacitor and the current-sensing resistor. When the VFB pin
voltage reaches the threshold voltage of the error comparator,
VSET (the DAC output set-point voltage) plus 40mV offset, the
PWM latch is reset. Consequently, the top MOSFET turns OFF
and the bottom (synchronous) MOSFET turns ON. The off-time
control block controls the off-time of the top MOSFET. During
the off-time, the inductor current and the VFB pin voltage
decrease. As the off-time finishes, the synchronous MOSFET
turns OFF and the top MOSFET turns ON again, repeating the
previous cycle. A break-before-make circuit prevents simulta-
neous conduction of the two MOSFET’s.
The 40mV offset to the set voltage enhances the transient
response of the output voltage, as shown in Figure 4 below.
s The peak voltage at the VFB pin is 40mV higher than the set
voltage and its average is the peak voltage minus the ripple
voltage at VFB pin.
s The output voltage is the voltage at the VFB pin minus the
voltage drop across the current sensing resistor (I * RSENSE).
s At light loads, the voltage drop across the sensing resistor
is small; hence, the output voltage is approximately the
voltage at the VFB pin (approximately 40mV higher than the
set voltage, VSET).
s At heavy loads, larger current flows in the sense resistor,
therefore, the voltage drop is higher and the output voltage
is lower.
This adaptive positioning of the output voltage as the load
changes allows a greater output voltage excursion during a fast
step-load transient and requires fewer output capacitors to meet
the transient-response specification.
POWER UP and INITIALIZATION
At power up, the LX1668 monitors the supply voltage to both the
+5V and the +12V pins (there is no special requirement for the
sequence of the two supplies). Before both supplies reach their
under-voltage lock-out (UVLO) thresholds, the soft-start (SS) pin
is held low to prevent soft-start from beginning; the off-time
control is disabled and the top MOSFET is kept OFF. The two
LDO regulators are designed not to over-voltage regardless of
supply voltages. After both supplies pass the UVLO thresholds,
the circuit begins soft-start.
SOFT-START
Once the supplies are above the UVLO threshold, the soft-start
capacitor begins to be charged up by the set voltage (DAC
output) through a 20kinternal resistor. The capacitor voltage
at the SS pin rises as a simple RC circuit. The SS pin plus a 40mV
offset is connected to the error comparator’s non-inverting input
that controls the output peak voltage. The output voltage will
follow the SS pin voltage if sufficient charging current is provided
to the output capacitor.
The simple RC soft-start allows the output to rise faster at the
beginning and slower at the end of the soft-start interval. Thus,
the required charging current into the output capacitor is less at
the end of the soft-start interval so decreasing the possibility of
an over-current. A comparator monitors the SS pin voltage and
indicates the end of soft-start when SS pin voltage reaches 95%
of VSET. See Application Information section for further details.
Adaptive voltage
positioning offset
VOFFSET (40mV)
Output voltage
VOUT (50mV/Div)
Nominal set-point
voltage, VSET (2.0V)
Dynamic voltage tolerance
VDYN (100mV for 2µs)
Steady state voltage at high
current is approximately
VSET + VOFFSET - IOUT x RSENSE
Initial voltage drop is
mainly due to the product
of the load current step and
ESR of the capacitors.
V = I * ESR
(ESL effects are ignored)
LOUT = 2.5µH, COUT = 6x1500µF Sanyo MV-GX, RSENSE = 2.5m
FIGURE 4 — Adaptive Voltage Positioning
Output current transient
step, I = 0 to 14A
(5A/Div)
Copyright © 1999
Rev. 1.0 4/99
7

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LX1668CPW

PROGRAMMABLE MULTIPLE OUTPUT DC:DC CONTROLLER

Microsemi Corporation
Microsemi Corporation

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