LX1662.pdf

Not Recommended For New Design
LX1662 / 62A, LX1663 /63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
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N F I N I T E
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N N O V A T I O N
R O D U C T I O N
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A T A
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H E E T
KEY FEATURES
DESCRIPTION
specification. The device can drive dual
The LX1662/62A and LX1663/63A are
MOSFET’s resulting in typical efficiencies of 85
Monolithic Switching Regulator Controller
- 90% even with loads in excess of 10 amperes.
IC’s designed to provide a low cost, high
For cost sensitive applications, the bottom
performance adjustable power supply for
MOSFET can be replaced with a Schottky diode
advanced microprocessors and other applications
requiring a very fast transient response and a high (non-synchronous operation).
Smallest Package Size. The LX1662 is available
degree of accuracy.
in a narrow body 14-pin surface mount IC
Short-Circuit Current Limiting without
package for space sensitive applications. The
Expensive Current Sense Resistors. CurrentLX1663 provides the additional functions of
sensing mechanism can use PCB trace resistance
Over Voltage Protection (OVP) and Power Good
or the parasitic resistance of the main inductor.
The LX1662A and LX1663A have reduced current (PWRGD) output drives for applications
requiring output voltage monitoring and
sense comparator threshold for optimum
protection functions.
performance using a PCB trace. For applications
requiring a high degree of accuracy, a
Ultra-Fast Transient Response Reduces
System Cost. The modulated offtime architecture
conventional sense resistor can be used to sense
results in the fastest transient response for a given
current.
inductor, reducing output capacitor requirements,
Programmable Synchronous Rectifier Driver
and reducing the total regulator system cost.
for CPU Core. The main output is adjustable
from 1.3V to 3.5V using a 5-bit code. The IC can Over-Voltage Protection and Power Good
Flag. The OVP output in the LX1663 &
read a VID signal set by a DIP switch on the
motherboard, or hardwired into the processor’s
LX1663A can be used to drive an SCR crowbar
circuit to protect the load in the event of a shortpackage (as in the case of Pentium® Pro and
Pentium II processors). The 5-bit code adjusts the circuit of the main MOSFET. The LX1663 &
LX1663A also have a logiclevel Power Good
output voltage between 1.30 and 2.05V in 50mV
Flag to signal when the output voltage is out of
increments and between 2.0 and 3.5V in 100mV
specified limits.
increments, conforming to the Intel Corporation
„ 5-bit Programmable Output For
CPU Core Supply
„ No Sense Resistor Required For
Short-Circuit Current Limiting
„ Designed To Drive Either
„
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„
Synchronous Or NonSynchronous Output Stages
Lowest System Cost Possible
For Price- Sensitive Pentium And
Pentium II Class Applications
Soft-Start Capability
Modulated, Constant Off-Time
Architecture For Fast Transient
Response And Simple System
Design
Available Over-Voltage
Protection (OVP) Crowbar Driver
And Power Good Flag (LX1663
only)
Small, Surface-Mount Packages
„
„
KEY FEATURES
„ Socket 7 Microprocessor
Supplies (including Intel Pentium
Processor, AMDK6TM And
Cyrix® 6x86TM, Gx86TM and
M2TM Processors)
„ Pentium II and Deschutes
Processor & L2-Cache Supplies
„ Voltage Regulator Modules
„ General Purpose DC:DC
Converter Applications
IMPORTANT: For the most current data, consult MICROSEMI’s website: http://www.microsemi.com
PRODUCT HIGHLIGHT
12V
L2
1µH
O
C3
0.1µF
VID0
VID1
VID2
VID3
5V
U1
LX1662
C5
1µF
VC1
14
INV
TDRV
13
3
VCC_CORE
GND
12
4
VID0
BDRV
11
5
VID1
VCC
10
6
VID2
CT
9
7
VID3
VID4
8
1
2
SS
6.3V
1500µF x3
C2
Q1
IRL3102
L1, 2.5µH
C8
680pF
VID4
Q2
IRL3303
R1
2.5m
6.3V, 1500µF x 3**
** Three capacitors for Pentium
Four capacitors for Pentium II
Supply Voltage
for CPU Core
VOUT
C1
14-pin, Narrow Body SOIC
TA (°C)
N
Plastic DIP
14-Pin
PACKAGE ORDER INFO
Plastic DIP
Plastic SOIC
N 16-Pin
D 14-Pin
RoHS Compliant / Pb-free Transition DC:0503
0 to 70
LX1662CN
LX1662ACN
LX1663CN
LX1663ACN
Plastic SOIC
16-Pin
D
RoHS Compliant / Pb-free Transition DC:0440
LX1662CD
LX1662ACD
LX1663CD
LX1663ACD
Note: Available in Tape & Reel. Append the letters ‘TR’ to the part number. (i.e. LX1663CD-TR)
Copyright © 1999
Rev. 1.2a,2005-03-09
LINFINITY MICROELECTRONICS INC.
11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841, 714-898-8121, FAX: 714-893-2570
1
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
R O D U C T I O N
D
A T A
S
H E E T
DEVICE SELECTION GUIDE
DEVICE
LX1662
LX1662A
LX1663
LX1663A
Packages
14-pin SOIC
& DIP
16-pin SOIC
& DIP
OVP and
Power Good
Current-Sense
Comp. Thresh. (mV)
No
Yes
100
60
100
60
PACKAGE PIN OUTS
Optimal Load
Pentium-class (<10A)
Pentium II (> 10A)
Pentium-class (<10A)
Pentium II (> 10A)
SS
INV
1
14
2
13
VCC_CORE
VID0
VID1
VID2
VID3
3
12
4
11
5
10
6
9
7
8
VC1
TDRV
GND
BDRV
VCC
CT
VID4
N PACKAGE — 14-Pin
LX1662/1662A (Top View)
(Note 1)
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A B S O L U T E M A X I M U M R AT I N G S
Supply Voltage (VC1) .................................................................................................... 25V
Supply Voltage (VCC) .................................................................................................... 15V
Output Drive Peak Current Source (500ns) ............................................................... 1.5A
Output Drive Peak Current Sink (500ns) ................................................................... 1.5A
Input Voltage (SS, INV, VCC_CORE, CT, VID0-VID4) ........................................... -0.3V to 6V
Operating Junction Temperature
Plastic (N & D Packages) ...................................................................................... 150°C
Storage Temperature Range .................................................................... -65°C to +150°C
Lead Temperature (Soldering, 10 Seconds) ............................................................. 300°C
Peak Package Solder Reflow Temp. (40 second max. exposure)..........................................260°C (+0, -5)
Note 1. Exceeding these ratings could cause damage to the device. All voltages are with respect
to Ground. Currents are positive into, negative out of the specified terminal. Pin
numbers refer to DIL packages only.
T H E R M A L D ATA
N PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
65°C/W
SS
INV
1
16
2
15
VCC_CORE
VID0
VID1
VID2
VID3
VID4
3
14
4
13
5
12
6
11
7
10
8
9
VC1
TDRV
GND
BDRV
VCC
CT
OV
PWRGD
N PACKAGE — 16-Pin
LX1663/1663A (Top View)
SS
INV
VCC_CORE
VID0
VID1
VID2
VID3
1
14
2
13
3
12
4
11
5
10
6
9
7
8
VC1
TDRV
GND
BDRV
VCC
CT
VID4
D PACKAGE — 14-Pin
LX1662/1662A (Top View)
D PACKAGE:
THERMAL RESISTANCE-JUNCTION TO AMBIENT, θJA
120°C/W
O
Junction Temperature Calculation: TJ = TA + (PD x θJA).
The θJA numbers are guidelines for the thermal performance of the device/pc-board system.
All of the above assume no ambient airflow
2
SS
INV
VCC_CORE
VID0
VID1
VID2
VID3
VID4
1
16
2
15
3
14
4
13
5
12
6
11
7
10
8
9
VC1
TDRV
GND
BDRV
VCC
CT
OV
PWRGD
D PACKAGE — 16-Pin
LX1663/1663A (Top View)
RoHS / Pb-free 100% Matte Tin Lead Finish
Copyright © 1999
Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
R O D U C T I O N
D
A T A
S
H E E T
ELECTRICAL CHARACTERISTICS
(Unless otherwise specified, 10.8 < VCC < 13.2, 0°C ≤ TA ≤ 70°C. Test conditions: VCC = 12V, T = 25°C. Use Application Circuit.)
Parameter
Reference & DAC Section
Symbol
Test Conditions
(See Table 1 - Next Page)
(Less 40mV output adaptive positioning), VCC = 12V, ILOAD = 6A
Regulation Accuracy (See Table 1)
Regulation Accuracy
1.8V ≤ VOUT ≤ 2.8V
LX1662/1663 (A)
Min. Typ.
Max.
-30
-1
30
1
Units
mV
%
Timing Section
OT
VCC_CORE = 1.3V, CT = 390pF
VCC_CORE = 3.5V, CT = 390pF
VCC_CORE = 1.3V to 3.5V
VCC_CORE = 1.3V, VCT = 1.5V
2
1
40
210
2
1
0.42
100
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Off Time Initial
Off Time Temp Stability
Discharging Current
Ramp Peak
Ramp Peak-Valley
IDIS
VP
VRPP
Ramp Valley Delay to Output
VCC_CORE = 1.3V
VCC_CORE = 3.5V
10% Overdrive
180
0.9
0.37
240
1.1
0.47
µs
µs
ppm
µA
V
V
V
ns
Error Comparator Section
Input Bias Current
Input Offset Voltage
EC Delay to Output
IB
VIO
1.3V < VSS = VINV < 3.5V
36
0.8
41
200
2
46
µA
mV
ns
85
50
27
100
60
200
35
115
70
µA
mV
mV
ns
10% Overdrive
Current Sense Section
Input Bias Current (VCC_CORE Pin)
Pulse By Pulse CL
LX1662/1663
LX1662A/1663A
CS Delay to Output
IB
VCLP
1.3V < VINV = VCC_CORE < 3.5V
Initial Accuracy
Initial Accuracy
10% Overdrive
Drive Rise Time
Drive Fall Time
Drive High
TR
TF
VDH
Drive Low
VDL
VC1 = VCC = 12V, CL = 3000pF
VC1 = VCC = 12V, CL = 3000pF
VCC = VCC = 12V, ISOURCE = 20mA
VCC = VCC = 12V, ISINK = 200mA
VCC = VCC = 12V, ISOURCE = 20mA
VCC = VCC = 12V, ISINK = 200mA
VCC = VC = 0, IPULL UP = 2mA
Output Drivers Section
Output Pull Down
VPD
70
70
11
10
0.06
0.8
0.8
0.1
1.2
1.4
ns
ns
V
V
V
V
V
UVLO and S.S. Section
O
Start-Up Threshold
Hysteresis
SS Sink Current
SS Sat Voltage
VST
VHYST
ISD
VOL
9.9
VC1 = 10.1V
VC1 = 9V, ISD = 200µA
2
10.1
0.31
5.5
0.15
10.4
0.6
V
V
mA
V
27
mA
92
%
%
V
%
mA
Supply Current Section
Dynamic Operating Current
ICD
VCC = VC1 = 12V, Out Freq = 200kHz, CL = 0
Power Good / Over-Voltage Protection Section (LX1663 Only)
Lower Threshold
Hysteresis
Power Good Voltage Low
Over-Voltage Threshold
OVP Sourcing Current
Copyright © 1999
Rev. 1.2a, 11/04
(VCC_CORE / DACOUT)
88
IPWRGD = 5mA
(VCC_CORE / VDAC)
VOV = 5V
110
30
90
1
0.5
117
45
0.7
125
3
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
R O D U C T I O N
D
S
A T A
H E E T
ELECTRICAL CHARACTERISTICS
Table 1 - Adaptive Transient Voltage Output
Processor Pins
Output Voltage (VCC_CORE)
0 = Ground, 1 = Open (Floating)
VID4
VID3
VID2
VID1
1
1
1
1
1
1
1
1
1
0
1
0
1
0
1
0
0
1
0
1
0
1
0
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
0
1
0
1
0
1
0
0
1
0
1
0
1
0
1
0
0
0
0
0
0
0
0
DAC setpoint voltage
VID0
0.0A
Nominal Output*
1
1
1.34V
1.30V
1
0
1.39V
1.35V
0
1
1.44V
1.40V
0
0
1.49V
1.45V
1
1
1.54V
1.50V
1
0
1.59V
1.55V
0
1
1.64V
1.60V
0
0
1.69V
1.65V
1
1
1.74V
1.70V
1
0
1.79V
1.75V
0
1
1.84V
1.80V
0
0
1.89V
1.85V
1
1
1.94V
1.90V
1
0
1.99V
1.95V
0
1
2.04V
2.00V
0
0
2.09V
2.05V
1
1
2.04V
2.00V
1
0
2.14V
2.10V
0
1
2.24V
2.20V
0
0
2.34V
2.30V
1
1
2.44V
2.40V
1
0
2.54V
2.50V
0
1
2.64V
2.60V
0
0
2.74V
2.70V
1
1
2.84V
2.80V
1
0
2.94V
2.90V
0
1
3.04V
3.00V
0
0
3.14V
3.10V
1
1
3.24V
3.20V
1
0
3.34V
3.30V
0
1
3.44V
3.40V
0
0
3.54V
3.50V
with no adaptive output voltage positioning.
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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
* Nominal =
(Output Voltage Setpoint — Typical)
0 to 14A
Output Voltage
0A
5A/Div.
2.8V
100mV/Div.
O
In order to improve transient response a
40mV offset is built into the Current Sense
comparator. At high currents, the peak
output voltage will be lower than the
nominal set point , as shown in Figure 1.
The actual output voltage will be a function
of the sense resistor, output current and
output ripple.
Output Load
Note:
Adaptive Transient Voltage Output
Time - 100µs/Div.
FIGURE 1 — Output Transient Response
(Using 5mΩ sense resistor and 5µH output inductor)
4
Copyright © 1999
Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
R O D U C T I O N
D
S
A T A
H E E T
CHARACTERISTICS CURVES
95
100
95
EFFICIENCY (%)__
90
85
80
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EFFICIENCY (%)__
90
80
Output Set Point
Output Set Point
EFFICIENCY AT 3.1V
EFFICIENCY AT 2.8V
EFFICIENCY AT 1.8V
75
70
85
EFFICIENCY AT 3.1V
EFFICIENCY AT 2.8V
75
EFFICIENCY AT 1.8V
70
1
2
3
4
5
6
7
8
9
10
11
12
13
14
1
2
3
4
5
6
7
IOUT (A)
8
9
10
11
12
13
14
IOUT (A)
FIGURE 2 — Efficiency Test Results:
Non-Synchronous Operation, VIN = 5V
FIGURE 3 — Efficiency Test Results:
Synchronous Operation, VIN = 5V
90
85
80
O
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, VIN = 12V.
Note: Non-synchronous operation not recommended for 12V operation, due to power loss in Schottky diode.
Copyright © 1999
Rev. 1.2a, 11/04
5
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
R O D U C T I O N
D
A T A
S
H E E T
BLOCK DIAGRAM
VCC
SS 1
2V Out
UVLO
10.6/10.1
CT 11
S
Q
R
Q
15 TDRV
Internal
VCC
R DOM
14 GND
VREG
Break
Before
Make
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Error Comp
100mV
VCC_CORE 3
2V REF
OV
40mV
INV 2
16 VC1
PWM Latch
Trimmed
13 BDRV
0.7V
Off-Time
Controller
SYNC EN
Comp
12 VCC
**
OV Comp
CS Comp
10 OV*
9 PWRGD*
UV Comp
10k
D OUT
DAC
LX1663/1663A ONLY
4
5
6
7
8
VID0
VID1
VID2
VID3
VID4
Note: Pin numbers are correct for LX1663/1663A, 16-pin package.
* Not connected on the LX1662/1662A.
** 60mV in LX1662A & LX1663A
O
FIGURE 5 — Block Diagram
6
Copyright © 1999
Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
R O D U C T I O N
D
A T A
S
H E E T
FUNCTIONAL PIN DESCRIPTION
Pin
Name
LX1662
Pin #
LX1663
Pin #
SS
1
1
Soft-Start pin, internally connected to the non-inverting input of the error comparator.
INV
2
2
Inverting input of the error comparator.
VCC_CORE
3
3
Output voltage. Connected to non-inverting input of the current-sense comparator.
VID0
4
4
Voltage Identification pin (LSB) input used to set output voltage.
VID1
5
5
Voltage Identification pin (2nd SB) input.
6
6
Voltage Identification pin (3rd SB) input.
7
7
Voltage Identification pin (4th SB) input.
8
8
Voltage Identification pin (MSB) input. This pin is also the range select pin — when low
(CLOSED), output voltage is set to between 1.30 and 2.05V in 0.05V increments. When high
(OPEN), output is adjusted from 2.0 to 3.5V in 0.1V increments.
N.C.
9
Open collector output pulls low when the output voltage is out of limits.
N.C.
10
SCR driver goes high when the processor's supply is over specified voltage limits.
9
11
The off-time is programmed by connecting a timing capacitor to this pin.
10
12
This is the (12V) supply to the IC, as well as gate drive to the bottom FET.
11
13
This is the gate drive to the bottom FET. Leave open in non-synchronous operation (when bottom
FET is replaced by a Schottky diode).
12
14
Both power and signal ground of the device.
13
15
Gate drive for top MOSFET.
14
16
This pin is a separate power supply input for the top drive. Can be connected to a charge pump
when only 12V is available.
VID3
VID4
PWRGD
OV
CT
VCC
BDRV
GND
TDRV
O
VC1
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VID2
Description
Copyright © 1999
Rev. 1.2a, 11/04
7
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
R O D U C T I O N
D
A T A
S
H E E T
T H E O RY O F O P E R AT I O N
IC OPERATION
SYNCHRONOUS CONTROL SECTION
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.
The synchronous control section incorporates a unique breakbefore-make function to ensure that the primary switch and the
synchronous switch are not turned on at the same time. Approximately 100 nanoseconds of deadtime is provided by the breakbefore-make circuitry to protect the MOSFET switches.
PROGRAMMING THE OUTPUT VOLTAGE
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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.
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. Exceeding 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
O
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 different 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.
8
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).
Copyright © 1999
Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
R O D U C T I O N
D
A T A
S
H E E T
A P P L I C AT I O N I N F O R M AT I O N
12V
L2
1µH
C3
0.1µF
U1
LX1662
2
3
VID1
VID2
VID3
VID4
CS
6.3V
1500µF x3
C5
1µF
bs
ol
et
e
1
VID0
5V
4
5
VC1
14
INV
TDRV
13
VCC_CORE
GND
12
BDRV
11
10
SS
VID0
VID1
VCC
6
VID2
CT
9
7
VID3
VID4
8
C2
RS
Q1
IRL3102
C8
680pF
14-pin, Narrow Body SOIC
L1, 2.5µH
Supply Voltage
for CPU Core
Q2
IRL3303
6.3V, 1500µF x 3**
VOUT
C1
** Three capacitors for Pentium
Four capacitors for Pentium II
FIGURE 6 — LX1662 In A Pentium / Pentium II Processor Single Chip Power Supply Controller
Solution With Loss-Less Current Sensing (Synchronous)
12V
5V
C3
0.1µF
6.3V
1500µF x3
U1
LX1662
1
O
2
3
VID0
VID1
VID2
VID3
VID4
4
5
6
7
SS
INV
VC1
TDRV
VCC_CORE
GND
VID0
BDRV
VID1
VCC
VID2
CT
VID3
VID4
14
C5
1µF
C2
Q1
IRL3102
13
12
11
10
9
8
14-pin, Narrow Body SOIC
D1
MBR2535
C8
680pF
L1, 5µH
R1
0.005
6.3V, 1500µF x 3**
** Three capacitors for Pentium
Four capacitors for Pentium II
VOUT
Supply Voltage
for CPU Core
C1
FIGURE 7 — LX1662 In A Non-Synchronous Pentium / Socket 7 Power Supply Application
Copyright © 1999
Rev. 1.2a, 11/04
9
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
D
R O D U C T I O N
S
A T A
H E E T
A P P L I C AT I O N I N F O R M AT I O N
F1
20A
12V
5V
C3
0.1µF
6.3V
1500µF x3
CS
bs
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et
e
C5
1µF
U1
LX1663
VC1
16
INV
TDRV
15
3
VCC_CORE
GND
14
4
VID0
BDRV
13
1
2
VID0
VID1
VID2
VID3
5
VID1
VCC
12
6
VID2
CT
11
7
VID3
OV
10
8
VID4
SS
VID4
PWRGD
C2
Q1
IRL3102
RS
L1, 2.5µH
Q2
IRL3303
C8
680pF
9
16-pin
Narrow Body SOIC
Supply Voltage
for CPU Core
6.3V, 1500µF x 3**
VOUT
C1
** Three capacitors for Pentium
Four capacitors for Pentium II
OV
PWRGD
FIGURE 8 — Pentium II Processor Application With OVP, Power Good And Loss-Less Current Sensing (Synchronous)
D3
1N4148
C9
1µF
C3
0.1µF
O
U1
LX1663
1
VID0
VID1
VID2
VID3
VID4
SS
VC1
16
INV
TDRV
15
3
VCC_CORE
GND
14
4
VID0
BDRV
13
5
VID1
VCC
12
6
VID2
CT
11
10
2
7
VID3
OV
8
VID4
PWRGD
16-pin
Narrow Body SOIC
9
F1 20A
D2
1N4148
C10
0.1µF
12V
16V
1500µF x3
Q1
IRL3102
R7
10
C2
R1
L1, 2.5µH
D4
C8, 1200pF
C10, 1µF
Q2
IRL3303
1N5817
R2
10k
2.5m9
Supply Voltage
for CPU Core
VOUT
C1
Q3
6.3V, 1500µF x 3**
SCR
** Three capacitors for Pentium
2N6504 Four capacitors for Pentium II
PWRGD
FIGURE 9 — Full-Featured Pentium II Processor Supply With 12V Power Input
10
Copyright © 1999
Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
R O D U C T I O N
D
A T A
S
H E E T
B I L L O F M AT E R I A L S
LX1662 Bill of Materials (Refer to Product Highlight)
Ref
Description
Part Number / Manufacturer
1500µF, 6.3V capacitor
MV-GX Sanyo
2
1500µF, 6.3V capacitor
MV-GX Sanyo
4
C8
680pF
SMD Cap
1
C3
0.1µF
SMD Cap
1
C5
1µF, 16V
SMD Ceramic
1
L1
5µF Inductor
HM0096832 BI
1
bs
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e
C2
C1
L2
1µF Inductor
1
Q1
MOSFET
IRL3102 International Rectifier or equivalent
Q2
MOSFET
IRL3303 International Rectifier or equivalent
R1
2.5mΩ Sense Resistor (PCB trace)
U1
Controller IC
LX1662CD Linfinity
The LX1662/63 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 effective operation for virtually all applications. Refer to the Application Information section for component reference designators.
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:
O
1
1
15
USING THE LX1662/63
CT =
1
1
Total
(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).
Copyright © 1999
Rev. 1.2a, 11/04
Qty.
DEVICES
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).
L1 OUTPUT INDUCTOR SELECTION
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 OFFtime, 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.
11
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
R O D U C T I O N
D
A T A
S
H E E T
USING THE LX1662/63 DEVICES
C1 FILTER CAPACITOR SELECTION (continued)
In order to cope with faster transient load changes, a smaller
output inductor is needed. However, reducing the size of the
output inductor will result in a higher ripple voltage on the input
supply. This noise on the 5V rail can affect other loads, such as
graphics cards. It is recommended that a smaller input inductor,
L2 (1 - 1.5µH), is used on the 5V rail to filter out the ripple. Ensure
that this inductor has the same current rating as the output
inductor.
aluminum electrolytic, and have demonstrated reliability. The
Oscon series from Sanyo generally provides the very best
performance in terms of long term ESR stability and general
reliability, but at a substantial cost penalty. The MV-GX series
provides excellent ESR performance, meeting all Intel transient
specifications, at a reasonable cost. Beware of off-brand, very-low
cost filter capacitors, which have been shown to degrade in both
ESR and general electrolyte characteristics over time.
C1 FILTER CAPACITOR SELECTION
CURRENT LIMIT
The capacitors on the output of the PWM section are used to filter
the output current ripple, as well as help during transient load
conditions, and the capacitor bank should be sized to meet ripple
and transient performance specifications.
When a transient (step) load current change occurs, the output
voltage will have a step which equals the product of the Effective
Series Resistance (ESR) of the capacitor and the current step (∆I).
when current increases from low (in sleep mode) to high, the
output voltage will drop below its steady state value. In the
advanced microprocessor power supply, the capacitor should
usually be selected on the basis of its ESR value, rather than the
capacitance or RMS current capability. Capacitors that satisfy the
ESR requirement usually have a larger capacitance and current
capability than needed for the application. The allowable ESR can
be found by:
Current limiting occurs when a sensed voltage, proportional to
load current, exceeds the current-sense comparator threshold
value. The current can be sensed either by using a fixed sense
resistor in series with the inductor to cause a voltage drop
proportional to current, or by using a resistor and capacitor in
parallel with the inductor to sense the voltage drop across the
parasitic resistance of the inductor.
The LX166x family offers two different comparator thresholds.
The LX1662 & 1663 have a threshold of 100mV, while the LX1662A
and LX1663A have a threshold of 60mV. The 60mV threshold is
better suited to higher current loads, such as a Pentium II or
Deschutes processor.
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INPUT INDUCTOR SELECTION
Sense Resistor
The current sense resistor, R1, is selected according to the formula:
ESR * (IRIPPLE + ∆I) < VEX
O
Where VEX is the allowable output voltage excursion in the
transient and IRIPPLE is the inductor ripple current. Regulators such
as the LX166x series, have adaptive output voltage positioning,
which adds 40mV to the DC set-point voltage — VEX is therefore
the difference between the low load voltage and the minimum
dynamic voltage allowed for the microprocessor.
Ripple current is a function of the output inductor value (LOUT),
and can be approximated as follows:
IRIPPLE =
VIN - VOUT
VOUT
*
fS * LOUT
VIN
Where fS is the switching frequency.
Electrolytic capacitors can be used for the output filter capacitor bank, but are less stable with age than tantalum capacitors. As
they age, their ESR degrades, reducing the system performance
and increasing the risk of failure. It is recommended that multiple
parallel capacitors are used so that, as ESR increases with age,
overall performance will still meet the processor's requirements.
There is frequently strong pressure to use the least expensive
components possible, however, this could lead to degraded longterm reliability, especially in the case of filter capacitors. Linfinity's
demo boards use Sanyo MV-GX filter capacitors, which are
12
R1 = VTRIP / ITRIP
Where VTRIP is the current sense comparator threshold (100mV
for LX1662/63 and 60mV for LX1662A/63A) and ITRIP is the desired
current limit. Typical choices are shown below.
TABLE 2 - Current Sense Resistor Selection Guide
Load
Pentium-Class Processor (<10A)
Pentium II Class (>10A)
Sense Resistor
Value
Recommended
Controller
5mΩ
2.5mΩ
LX1662 or LX1663
LX1662A or LX1663A
A smaller sense resistor will result in lower heat dissipation (I²R)
and also a smaller output voltage droop at higher currents.
There are several alternative types of sense resistor. The
surface-mount metal “staple” form of resistor has the advantage of
exposure to free air to dissipate heat and its value can be
controlled very tightly. Its main drawback, however, is cost. An
alternative is to construct the sense resistor using a copper PCB
trace. Although the resistance cannot be controlled as tightly, the
PCB trace is very low cost.
Copyright © 1999
Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
R O D U C T I O N
D
A T A
S
H E E T
USING THE LX1662/63 DEVICES
CURRENT LIMIT (continued)
CURRENT LIMIT (continued)
PCB Sense Resistor
A PCB sense resistor should be constructed as shown in Figure
10. By attaching directly to the large pads for the capacitor and
inductor, heat is dissipated efficiently by the larger copper masses.
Connect the current sense lines as shown to avoid any errors.
The current flowing through the inductor is a triangle wave. If the
sensor components are selected such that:
2.5m9
Sense Resistor
The voltage across the capacitor will be equal to the current
flowing through the resistor, i.e.
VCS = ILRL
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100mil Wide, 850mil Long
2.5mm x 22mm (2 oz/ft2 copper)
L/RL = RS * CS
Inductor
Since VCS reflects the inductor current, by selecting the
appropriate RS and CS, VCS can be made to reach the comparator
voltage (60mV for LX166xA or 100mV for the LX166x) at the
desired trip current.
Design Example
(Pentium II circuit, with a maximum static current of 14.2A)
The gain of the sensor can be characterized as:
Output
Capacitor Pad
|T(j M )|
Sense Lines
FIGURE 10 — Sense Resistor Construction Diagram
Recommended sense resistor sizes are given in the following
table:
RL
L/RSCS
TABLE 3 - PCB Sense Resistor Selection Guide
Copper
Weight
2 oz/ft2
Copper Desired Resistor
Thickness
Value
68µm
Dimensions (w x l)
mm
inches
2.5mΩ
2.5 x 22
0.1 x 0.85
5mΩ
2.5 x 43
0.1 x 1.7
O
Loss-Less Current Sensing Using Resistance of Inductor
Any inductor has a parasitic resistance, RL, which causes a DC
voltage drop when current flows through the inductor. Figure 11
shows a sensor circuit comprising of a surface mount resistor, RS,
and capacitor, CS, in parallel with the inductor, eliminating the
current sense resistor.
L
RS
Current
Sense
Comparator
VCS
RL
Load
CS
RS2
FIGURE 11 — Current Sense Circuit
Copyright © 1999
Rev. 1.2a, 11/04
1/RSCS
RL/L
M
FIGURE 12 — Sensor Gain
The dc/static tripping current Itrip,S satisfies:
Vtrip
Itrip,S =
RL
Select L/RSCS ≤ RL to have higher dynamic tripping current
than the static one. The dynamic tripping current Itrip,d satisfies:
Vtrip
Itrip,d =
L/(RSCS)
General Guidelines for Selecting RS , CS , and RL
Vtrip
RL = I
Select: RS ≤ 10 kΩ
trip,S
Ln
and CS according to:
CS n = R R
L S
The above equation has taken into account the current-dependency of the inductance.
The test circuit (Figure 6) used the following parameters:
RL = 3mΩ, RS = 9kΩ, CS = 0.1µF, and L is 2.5µH at 0A current.
13
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
R O D U C T I O N
D
A T A
S
H E E T
USING THE LX1662/63 DEVICES
CURRENT LIMIT (continued)
FET SELECTION (continued)
In cases where RL is so large that the trip point current would
be lower than the desired short-circuit current limit, a resistor (RS2)
can be put in parallel with CS, as shown in Figure 11. The selection
of components is as follows:
For the IRL3102 (13mΩ RDS(ON)), converting 5V to 2.8V at 14A
will result in typical heat dissipation of 1.48W.
RL (Required)
RS2
=
RL (Actual)
RS2 + RS
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L
L
RS + RS2
=
*
RL (Actual) * (RS2 // RS)
RL (Actual)
RS2 * RS
Synchronous Rectification – Lower MOSFET
The lower pass element can be either a MOSFET or a Schottky
diode. The use of a MOSFET (synchronous rectification) will result
in higher efficiency, but at higher cost than using a Schottky diode
(non-synchronous).
Power dissipated in the bottom MOSFET will be:
CS =
PD = I2 * RDS(ON) * [1 - Duty Cycle] = 2.24W
[IRL3303 or 1.12W for the IRL3102]
Again, select (RS2//RS) < 10kΩ.
FET SELECTION
To insure reliable operation, the operating junction temperature
of the FET switches must be kept below certain limits. The Intel
specification states that 115°C maximum junction temperature
should be maintained with an ambient of 50°C. This is achieved
by properly derating the part, and by adequate heat sinking. One
of the most critical parameters for FET selection is the RDS ON
resistance. This parameter directly contributes to the power
dissipation of the FET devices, and thus impacts heat sink design,
mechanical layout, and reliability. In general, the larger the
current handling capability of the FET, the lower the RDS ON will
be, since more die area is available.
TABLE 4 - FET Selection Guide
This table gives selection of suitable FETs from International Rectifier.
RDS(ON) @
Ω)
10V (mΩ
ID @
TC = 100°C
Max. Breakdown Voltage
IRL3803
IRL22203N
IRL3103
IRL3102
IRL3303
IRL2703
6
7
14
13
26
40
83
71
40
56
24
17
30
30
30
20
30
30
O
Device
All devices in TO-220 package. For surface mount devices (TO-263 /
D2-Pak), add 'S' to part number, e.g. IRL3103S.
The recommended solution is to use IRL3102 for the high side
and IRL3303 for the low side FET, for the best combination of cost
and performance. Alternative FET’s from any manufacturer could
be used, provided they meet the same criteria for RDS(ON).
Heat Dissipated In Upper MOSFET
The heat dissipated in the top MOSFET will be:
PD = (I2 * RDS(ON) * Duty Cycle) + (0.51 * VIN * tSW * fS )
Catch Diode – Lower MOSFET
A low-power Schottky diode, such as a 1N5817, is recommended
to be connected between the gate and source of the lower
MOSFET when operating from a 12V-power supply (see Figure 9).
This will help protect the controller IC against latch-up due to the
inductor voltage going negative. Although latch-up is unlikely, the
use of such a catch diode will improve reliability and is highly
recommended.
Non-Synchronous Operation - Schottky Diode
A typical Schottky diode, with a forward drop of 0.6V will dissipate
0.6 * 14 * [1 – 2.8/5] = 3.7W (compared to the 1.1 to 2.2W dissipated
by a MOSFET under the same conditions). This power loss
becomes much more significant at lower duty cycles – synchronous rectification is recommended especially when a 12V-power
input is used. The use of a dual Schottky diode in a single TO-220
package (e.g. the MBR2535) helps improve thermal dissipation.
MOSFET GATE BIAS
The power MOSFETs can be biased by one of two methods:
charge pump or 12V supply connected to VC1.
1) Charge Pump (Bootstrap)
When 12V is supplied to the drain of the MOSFET, as in
Figure 9, the gate drive needs to be higher than 12V in order
to turn the MOSFET on. Capacitor C10 and diodes D2 & D3
are used as a charge pump voltage doubling circuit to raise
the voltage of VC1 so that the TDRV pin always provides a
high enough voltage to turn on Q1. The 12V supply must
always be connected to VCC to provide power for the IC
itself, as well as gate drive for the bottom MOSFET.
2) 12V Supply
When 5V is supplied to the drain of Q1, a 12V supply should
be connected to both VCC and VC1.
Where tSW is switching transition line for body diode (~100ns)
and fS is the switching frequency.
14
Copyright © 1999
Rev. 1.2a, 11/04
PRODUCT DATABOOK 1996/1997
LX1662/62A, LX1663/63A
SINGLE-CHIP PROGRAMMABLE PWM CONTROLLERS WITH 5-BIT DAC
P
R O D U C T I O N
D
A T A
S
H E E T
USING THE LX1662/63 DEVICES
LAYOUT GUIDELINES - THERMAL DESIGN
Input
5V or 12V
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A great deal of time and effort were spent optimizing the thermal
design of the demo boards. Any user who intends to implement
an embedded motherboard would be well advised to carefully
read and follow these guidelines. If the FET switches have been
carefully selected, external heatsinking is generally not required.
However, this means that copper trace on the PC board must now
be used. This is a potential trouble spot; as much copper area as
possible must be dedicated to heatsinking the FET switches, and
the diode as well if a non-synchronous solution is used.
In our VRM module, heatsink area was taken from internal
ground and VCC planes which were actually split and connected
with VIAS to the power device tabs. The TO-220 and TO-263
cases are well suited for this application, and are the preferred
packages. Remember to remove any conformal coating from all
exposed PC traces which are involved in heatsinking.
General Notes
As always, be sure to provide local capacitive decoupling close to
the chip. Be sure use ground plane construction for all highfrequency work. Use low ESR capacitors where justified, but be
alert for damping and ringing problems. High-frequency designs
demand careful routing and layout, and may require several
iterations to achieve desired performance levels.
Power Traces
To reduce power losses due to ohmic resistance, careful consideration should be given to the layout of traces that carry high
currents. The main paths to consider are:
O
■ Input power from 5V supply to drain of top MOSFET.
■ Trace between top MOSFET and lower MOSFET or Schottky
diode.
■ Trace between lower MOSFET or Schottky diode and
ground.
■ Trace between source of top MOSFET and inductor, sense
resistor and load.
LX166x
Output
FIGURE 13 — Power Traces
All of these traces should be made as wide and thick as
possible, in order to minimize resistance and hence power losses.
It is also recommended that, whenever possible, the ground, input
and output power signals should be on separate planes (PCB
layers). See Figure 13 – bold traces are power traces.
C5 Input Decoupling (VCC) Capacitor
Ensure that this 1µF capacitor is placed as close to the IC as
possible to minimize the effects of noise on the device.
Layout Assistance
Please contact Linfinity’s Applications Engineers for assistance
with any layout or component selection issues. A Gerber file
with layout for the most popular devices is available upon request.
Evaluation boards are also available upon request. Please
check Linfinity's web site for further application notes.
R E L AT E D D E V I C E S
LX1664/1665 - Dual Output PWM for µProcessor Applications
LX1668 - Triple Output PWM for µProcessor Applications
LX1553 - PWM for 5V - 3.3V Conversion
Pentium is a registered trademark of Intel Corporation.
Cyrix is a registered trademark and 6x86, Gx86 and M2 are trademarks of Cyrix Corporation. K6 is a trademark of AMD.
Power PC is a trademark of International Business Machines Corporation. Alpha is a trademark of Digital Equipment Corporation.
PRODUCTION DATA - Information contained in this document is proprietary to LinFinity, and is current as of publication date. This document
may not be modified in any way without the express written consent of LinFinity. Product processing does not necessarily include testing of
all parameters. Linfinity reserves the right to change the configuration and performance of the product and to discontinue product at any time.
Copyright © 1999
Rev. 1.2a, 11/04
15