Datasheet LX1665CN, LX1665CDW, LX1665ACN, LX1665ACDW, LX1664CN Datasheet (Microsemi Corporation)

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Page 1

LX1664/64A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

T HE I NFINITE P OWER OF I NNOVATION

DESCRIPTION KEY FEATURES

The LX1664/64A and LX1665/65A are monolithic switching regulator controller 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 comparator threshold for optimum performance using a sense resistor. 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

IMPORTANT: For the most current data, consult LinFinity's web site: http://www.linfinity.com.

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-synchronous 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 regulator suitable for powering a 1.5V GTL+ bus or 2.5V clock supply.

(continued next page)

P RODUCTION DATA SHEET

■ 5-bit Programmable Output For CPU Core Supply

■ Adjustable Linear Regulator Driver Output

■ No Sense Resistor Required For Short-

Circuit Current Limiting

■ Designed To Drive Either Synchronous Or Non-Synchronous Output Stages

■ 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 (LX1665 only)

APPLICATIONS

■ Socket 7 (Pentium Class) Microprocessor Supplies (including Intel Pentium Processor,

AMD-K6 M2TM Processors)

■ Pentium II and Deschutes Processor & L2Cache Supplies

■ Voltage Regulator Modules

And Cyrix® 6x86TM, Gx86TM and

PRODUCT HIGHLIGHT

LX1665 IN A PENTIUM II SINGLE-CHIP POWER SUPPLY SOLUTION

1µH

680pF

F1 20A

IRL3102

IRL3303

IRLZ44

Plastic SOIC 16-pin

6.3V 1500µF x3

2.5µH

0.0025

330µF

Supply Voltage for CPU Core

6.3V, 1500µF x 3**

** Three capacitors for Pentium Four capacitors for Pentium II

Supply Voltage For I/O Chipset or GTL+ Bus

330µF

Plastic SOIC Wide

18-pin

12V

VID0 VID1 VID2 VID3 VID4

0.1µF

LX1665

INV

CC_CORE

VID0

VID1

VID2

VID3 OV

VID4 L

Wide-Body SOIC

PWRGD

18-pin

V TDRV GND BDRV

DRV

1µF

PWRGD

PACKAGE ORDER INFORMATION

(°C)

Plastic DIP

16-pin

Plastic DIP

18-pin

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)

OUT

for

See next page

Selection Guide

L INF INITY MICROELECTRONICS INC.

11861 WESTERN AVENUE, GARDEN GROVE, CA. 92841, 714-898-8121, FAX: 714-893-2570

Page 2

PRODUCT DATABOOK 1996/1997

LX1664/64A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

DESCRIPTION (con't.)

Smallest Package Size. The LX1664 is

available in a narrow body 16-pin surface mount IC package for space sensitive applications. The LX1665 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, reducing output capacitor requirements, and reducing the total regulator system cost.

Over-Voltage Protection and Power

Good Flag. The OVP output in the LX1665

& LX1665A 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 LX1665 & LX1665A also have a logiclevel Power Good Flag to signal when the output voltage is out of specified limits.

DEVICE SELECTION GUIDE

OVP and Current-Sense

DEVICE Packages Power Good Comp. Thresh. (mV) Optimal Load

LX1664 16-pin SOIC LX1664A & DIP 60 Pentium II (> 10A) LX1665 18-pin SOIC LX1665A & DIP 60 Pentium II (> 10A)

Yes

100 Pentium-class (<10A)

ABSOLUTE MAXIMUM RATINGS (Note 1)

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, V Operating Junction Temperature

, CT, VID0-VID4) ........................................... -0.3V to 6V

CC_CORE

Plastic (N, D & DW Packages) ............................................................................. 150°C

Storage Temperature Range .................................................................... -65°C to +150°C

Lead Temperature (Soldering, 10 Seconds) ............................................................. 300°C

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.

THERMAL DATA

N (16-PIN DIP) PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

N (18-PIN DIP) PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

D PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

DW PACKAGE:

THERMAL RESISTANCE-JUNCTION TO AMBIENT,

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

θθ

65°C/W

60°C/W

120°C/W

90°C/W

PACKAGE PIN OUTS

1 16

215

INV

314

CC_CORE

413

VID0

512

VID1

611

VID2

710

VID3

VID4

N PACKAGE — 16-Pin

LX1664/1664A (Top View)

1 18

217

INV

316

CC_CORE

415

VID0

514

VID1

613

VID2

712

VID3

811

VID4

910

N PACKAGE — 18-Pin

LX1665/1665A (Top View)

1 16

215

INV

CC_CORE

VID0 VID1 VID2 VID3 VID4

314

413

512

611

710

D PACKAGE — 16-Pin

LX1664/1664A (Top View)

1 18

217

INV

316

415

514

613

712

811

910

CC_CORE

VID0 VID1 VID2 VID3 VID4

DW PACKAGE — 18-Pin

LX1665/1665A (Top View)

TDRV GND BDRV V

DRV

TDRV GND BDRV V

OV L

DRV

PWRGD

TDRV GND BDRV V

DRV

V TDRV GND BDRV V C OV L

DRV

PWRGD

Rev. 1.2 11/99

Page 3

PRODUCT DATABOOK 1996/1997

LX1664/1664A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

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

Symbol

Test Conditions

Reference & DAC Section (See Table 1 - Next Page)

Regulation Accuracy (See Table 1) (Less 40mV output adaptive positioning), VCC = 12V, I Regulation Accuracy 1.8V ≤ V

OUT

≤ 2.8V

Timing Section

Off Time Initial OT V

Off Time Temp Stability V Discharging Current I Ramp Peak V Ramp Peak-Valley V

DISVCC_CORE

RPPVCC_CORE

Ramp Valley Delay to Output 10% Overdrive

= 1.3V, CT = 390pF

CC_CORE

= 3.5V, CT = 390pF

CC_CORE

= 1.3V to 3.5V

CC_CORE

= 1.3V, VCT = 1.5V

= 1.3V

= 3.5V

CC_CORE

Error Comparator Section

Input Bias Current I Input Offset Voltage V EC Delay to Output 10% Overdrive

1.3V < VSS = V

< 3.5V

INV

Current Sense Section

Input Bias Current (V Pulse By Pulse C

CS Delay to Output 10% Overdrive

Pin) I

CC_CORE

LX1664/1665 V

1.3V < V

Initial Accuracy

CLP

INV

LX1664A/1665A Initial Accuracy

= V

CC_CORE

< 3.5V

Output Drivers Section

Drive Rise Time TRVC1 = VCC = 12V, CL = 3000pF Drive Fall Time TFVC1 = VCC = 12V, CL = 3000pF Drive High V

Drive Low V

Output Pull Down V

DHVCC

VCC = VCC = 12V, I

DLVCC

VCC = VCC = 12V, I

PDVCC

= VCC = 12V, I

= VC = 0, I

PULL UP

= 20mA

SOURCE

= 200mA

SINK

= 20mA

SOURCE

= 200mA

SINK

= 2mA

UVLO and S.S. Section

Start-Up Threshold V Hysteresis V SS Sink Current I SS Sat Voltage V

HYST

OLVC1

VC1 = 10.1V

= 9V, ISD = 200µA

Supply Current Section

Dynamic Operating Current I

VCC = VC1 = 12V, Out Freq = 200kHz, CL = 0

Power Good / Over-Voltage Protection Section (LX1665 Only)

Lower Threshold (V Hysteresis Power Good Voltage Low I Over-Voltage Threshold (V OVP Sourcing Current VOV = 5V

CC_CORE

PWRGD

CC_CORE

/ DAC

= 5mA

/ V

DAC

)

OUT

)

Linear Regulator Section

Output Voltage Set by external resistors Setpoint Accuracy IL = 0.5A using 0.5% resistors Output Temperature Drift Load Regulation Cummulative Accuracy Op-Amp Output Current Open Loop

LOAD

= 6A

LX1664/1665 (A)

Min. Typ. Max.

-30 30 mV

-1 1 %

180 210 240 µA

0.9 1 1.1 V

0.37 0.42 0.47 V

36 41 46 mV

85 100 115 mV 50 60 70 mV

9.9 10.1 10.4 V

2 5.5 mA

88 90 92 %

110 117 125 %

30 45 mA

1.5 3.6 V

-1.5 1.5 %

50 70 mA

)

Units

2µs 1µs

40 ppm

100 ns

0.8 2 µA

200 ns

27 35 µA

200 ns

70 ns 70 ns 11 V 10 V

0.06 0.1 V

0.8 1.2 V

0.8 1.4 V

0.31 V

0.15 0.6 V

27 mA

0.5 0.7 V

40 ppm

1.5 % 3%

Page 4

PRODUCT DATABOOK 1996/1997

5A/Div.

Time - 100µs/Div.

2.8V 100mV/Div.

Output Load

0 to 14A

Output Voltage

LX1664/64A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

ELECTRICAL CHARACTERISTICS

Table 1 - Adaptive Transient Voltage Output (Output Voltage Setpoint  Typical)

Processor Pins

0 = Ground, 1 = Open (Floating)

VID4 VID3 VID2 VID1 VID0

01111 1.34V 1.30V 01110 1.39V 1.35V 01101 1.44V 1.40V 01100 1.49V 1.45V 01011 1.54V 1.50V 01010 1.59V 1.55V 01001 1.64V 1.60V 01000 1.69V 1.65V 00111 1.74V 1.70V 00110 1.79V 1.75V 00101 1.84V 1.80V 00100 1.89V 1.85V 00011 1.94V 1.90V 00010 1.99V 1.95V 00001 2.04V 2.00V 00000 2.09V 2.05V 11111 2.04V 2.00V 11110 2.14V 2.10V 11101 2.24V 2.20V 11100 2.34V 2.30V 11011 2.44V 2.40V 11010 2.54V 2.50V 11001 2.64V 2.60V 11000 2.74V 2.70V 10111 2.84V 2.80V 10110 2.94V 2.90V 10101 3.04V 3.00V 10100 3.14V 3.10V 10011 3.24V 3.20V 10010 3.34V 3.30V 10001 3.44V 3.40V 10000 3.54V 3.50V

* Nominal = DAC setpoint voltage with no adaptive output voltage positioning.

Output Voltage (V

0.0A Nominal Output*

CC_CORE

)

Note:

Adaptive Transient Voltage Output

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, the output current and output ripple.

FIGURE 1 — Output Transient Response

(using 5mΩ sense resistor and 5µH output inductor)

Rev. 1.2 11/99

Page 5

PRODUCT DATABOOK 1996/1997

LX1664/1664A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

CHARACTERISTICS CURVES

EFFICIENCY (%)__

Output Set Point

EFFICIENCY AT 3.1V

1234567891011121314

EFFICIENCY AT 2.8V EFFICIENCY AT 1.8V

OUT

(A)

FIGURE 2 — Efficiency Test Results:

Non-Synchronous Operation, VIN = 5V

100

EFFICIENCY (%)__

Output Set Point

EFFICIENCY AT 3.1V EFFICIENCY AT 2.8V

EFFICIENCY AT 1.8V

1234567891011121314

(A)

OUT

FIGURE 3 — Efficiency Test Results:

Synchronous Operation, VIN = 5V

Output Se t Point

1.8V EFF ICIENCY

1234567891011121314

FIGURE 4 — Efficiency Test Results: Synchronous Operation, V

2.8V EFF ICIENCY

3.3V EFF ICIENCY

(A)

OUT

= 12V.

Note: Non-synchronous operation not recommended for 12V operation, due to power loss in Schottky diode.

Page 6

PRODUCT DATABOOK 1996/1997

LX1664/64A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

BLOCK DIAGRAM

2V Out

UVLO

10.6/10.1

Error Comp

CS Comp

INV

CC_CORE

40mV

100mV

Trimmed

2V REF

Internal

REG

Off-Time

Controller

R DOM

Break

Before

Make

PWM Latch

SYNC EN

Comp

OV Comp

0.7V

TDRV

GND

BDRV

UV Comp

10k

DAC OUT

LX1665/1665A ONLY

DAC

4 5

VID0 VID16VID27VID38VID4

1.5V

Linear Op Amp

Note: Pin numbers are correct for LX1665/1665A, 18-pin package.

* Not connected on LX1664/1664A.

** 60mV in LX1664A/1665A.

OV*

PWRGD*

DRV

FIGURE 5 — LX1664/1665 Block Diagram

Rev. 1.2 11/99

Page 7

PRODUCT DATABOOK 1996/1997

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

FUNCTIONAL PIN DESCRIPTION

Pin LX1664 LX1665

Name Pin # Pin # Description

LX1664/1664A, LX1665/65A

SS 1 1

INV 2 2

CC_CORE

VID0 4 4

VID1 5 5

VID2 6 6

VID3 7 7

VID4 8 8

PWRGD N.C. 10

DRV

10 11

OV N.C. 12

11 13

12 14

BDRV 13 15

GND 14 16

TDRV 15 17

16 18

Soft-Start pin, internally connected to the non-inverting input of the error comparator.

Inverting input of the error comparator.

Output voltage. Connected to non-inverting input of the current-sense comparator.

Voltage Identification pin (LSB) input used to set output voltage.

Voltage Identification pin (2nd SB) input.

Voltage Identification pin (3rd SB) input.

Voltage Identification pin (4th SB) input.

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.

Linear regulator feedback pin. 1.5V reference is connected to a resistor divider to set desired output voltage.

Open collector output pulls low when the output voltage is out of limits.

Linear regulator drive pin. Connect to gate of MOSFET for linear regulator function.

SCR driver goes high when the processor's supply is over specified voltage limits.

The off-time is programmed by connecting a timing capacitor to this pin.

This is the (12V) supply to the IC, as well as gate drive to the bottom FET.

This is the gate drive to the bottom FET. Leave open in non-synchronous operation (when bottom FET is replaced by a Schottky diode).

Both power and signal ground of the device.

Gate drive for top MOSFET.

This pin is a separate power supply input for the top drive. Can be connected to a charge pump when only 12V is available.

Page 8

PRODUCT DATABOOK 1996/1997

LX1664/64A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION 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 C valley voltage, the synchronous MOSFET turns OFF and the top

is now allowed to discharge. At the

MOSFET turns on. A special break-before-make circuit prevents simultaneous conduction of the two MOSFETS.

The V

response. The INV pin is connected to the positive side of the

pin is offset by +40mV to enhance transient

CC_CORE

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 OFFtime is modulated as a function of the voltage at the V

CC_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. 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 LX1664/65 Devices" later in this data sheet.

OFF-TIME CONTROL TIMING

The timing capacitor C timing capacitor is quickly charged during the ON time of the top

allows programming of the OFF-time. The

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 V V

CC_CORE

pin. The OFF-time is inversely proportional to the

CC_CORE

voltage.

UNDER VOLTAGE LOCKOUT

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. The SS (Soft-Start) pin is pulled low.

SYNCHRONOUS CONTROL

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

The output voltage is set by means of a 5-bit digital Voltage Identification (VID) word (See Table 1). The VID code may be hardwired into the package of the processor which do not have a VID code, 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); for a high or '1' signal, leave the VID pin open (DIP switch OFF).

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 (LX1665 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 LX1665 only) which can drive an external SCR crowbar (Q removed and power recycled for the LX1665 to resume normal

), and so blow a fuse (F1). the fault condition must be

operation (See Figure 9).

LINEAR REGULATOR

The product highlight application shows an application schematic using a MOSFET as the pass element for a linear regulator. this output is suitable for converting the 5V system supply to 3.3V for processor I/O buffers, memory, chipset and other components. The output can be adjusted to any voltage between 1.5V and 3.6V in order to supply other (lower) power requirements on a motherboard. See section "Using the LX1664/1665 Devices" at the end of this data sheet.

Rev. 1.2 11/99

Page 9

PRODUCT DATABOOK 1996/1997

TDRV

INV V

CC_CORE

VID0 VID1 VID2 VID3 L

DRV

BDRV

GND

LX1664

VID3

1µF

12V

OUT

16-pin

Narrow Body SOIC

IRL3102

L1, 2.5µH

6.3V, 1500µF x 3**

680pF

VID2

VID1

VID0

VID4

0.1µF

2.5m9

Supply Voltage for CPU Core

6.3V 1500µF x3

** Three capacitors for Pentium Four capacitors for Pentium II

VID4 L

Supply Voltage For I/O Chipset or GTL+ Bus

IRL3303

IRLZ44

330µF

TDRV

INV V

CC_CORE

VID0 VID1 VID2 VID3 L

DRV

BDRV

GND

LX1664

VID3

1µF

12V

OUT

16-pin

Narrow Body SOIC

IRL3102

, 5µH

6.3V, 1500µF x 3**

680pF

VID2

VID1

VID0

VID4

0.1µF

0.005

Supply Voltage for CPU Core

6.3V 1500µF x3

** Three capacitors for Pentium Four capacitors for Pentium II

VID4 L

Supply Voltage For I/O Chipset or GTL+ Bus

IRLZ44

330µF

LX1664/1664A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

APPLICATION INFORMATION

FIGURE 6 — LX1664 In A Pentium / Socket 7 Single-Chip Power Supply Controller Solution (Synchronous)

FIGURE 7 — LX1664 In A Non-Synchronous / Socket 7 Power Supply Application

Page 10

PRODUCT DATABOOK 1996/1997

LX1664/64A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

APPLICATION INFORMATION

VID0 VID1 VID2 VID3 VID4

0.1µF

LX1665

SS INV V

CC_CORE

VID0 VID1 VID2 VID3 OV VID4 L L

18-pin

Wide Body SOIC

V TDRV GND

BDRV

PWRGD

DRV

12V

1µF

PWRGD

1µH

680pF

F1 15A

IRL3102

IRL3303

6.3V 1500µF x3

IRLZ44

2.5µH

5V or 3.3V Supply

330µF

Supply Voltage for CPU Core

6.3V, 1500µF x 3

** Three capacitors for Pentium Four capacitors for Pentium II

1.5V for GTL+ Bus Supply

OUT

VID0 VID1 VID2 VID3 VID4

FIGURE 8 — VRM 8.2 (Pentium II / Deschutes) Reference Design With Loss-Less Current Sensing

12V

20A

6.3V 1500µF x3

2.5µH

330µF

0.0025

Supply Voltage for CPU Core

SCR

2N6504

IRLZ44

Supply Voltage For I/O Chipset or GTL+ Bus

330µF

0.1µF

1N4148 1N4148

LX1665

INV

CC_CORE

VID0

VID1

VID2

VID3 OV

VID4 L

PWRGD

V TDRV GND

BDRV

DRV

1µF

R2, 10k

1500µF

C10

0.1µF

1N5817

IRL3303

IRL3102

18-pin

Wide-Body SOIC

PWRGD

OUT

6.3V, 1500µF x 3**

Four capacitors for Pentium II

** Three capacitors for Pentium

FIGURE 9 — Full-Featured Pentium II Processor Supply With 12V Power Input

Rev. 1.2 11/99

Page 11

PRODUCT DATABOOK 1996/1997

LX1664/1664A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

BILL OF MATERIALS

LX1665 Bill of Materials (Refer to Product Highlight)

Ref Description Part Number / Manufacturer Qty.

C7, C

R5, R

U1 Controller IC LX1665CDW Linfinity 1

Total 21

1500µF, 6.3V capacitor MV-GX Sanyo 4 1500µF, 6.3V capacitor MV-GX Sanyo 2 330µF, Electrolytic MV-GX Sanyo 2

0.1µF SMD Cap 1 390pF SMD Cap 1 680pF SMD Cap 1 1µF, 16V SMD Ceramic 1

2.5µH Inductor HM0096832 BI or equivalent 1 1µH Inductor 1 MOSFET IRL3102 International Rectifier or equivalent 1 MOSFET IRL3303 International Rectifier or equivalent 1 MOSFET IRLZ44 International Rectifier or equivalent 1 Resistor (See Table 6 for values) SMD Resistor 2

2.5mΩ Sense Resistor IRC OARS-1 or PCB trace 1

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 effective operation for virtually all applications. Refer to the Appli- cation 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 C this data sheet), and is modulated to minimize frequency

in all application schematics in

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:

(1 - V

fS (1.52 - 0.29 * V

Where I

(recommended to be around 200kHz for optimal operation and

is fixed at 200µA and fS is the switching frequency

DIS

OUT /VIN

) * I

DIS

OUT

)

component selection).

When using a 5V input voltage, the switching frequency (f

can be approximated as follows:

CT = 0.621

DIS

Choosing a 680pF capacitor will result in an operating frequency of 183kHz at V is used, he capacitor value must be changed (the optimal timing

= 2.8V. When a 12V power input

OUT

capacitor for 12V input will be in the range of 1000-1500pF).

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 = V 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.

* ∆T/∆I, where ∆T is the

)

Page 12

PRODUCT DATABOOK 1996/1997

LX1664/64A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

USING THE LX1664/65 DEVICES

INPUT INDUCTOR SELECTION

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, L

(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.

FILTER CAPACITOR SELECTION

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:

C1 FILTER CAPACITOR SELECTION (continued)

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.

CURRENT LIMIT

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 LX1664 & 1665 have a threshold of 100mV, while the LX1664A and LX1665A have a threshold of 60mV. The 60mV threshold is better suited to higher current loads, such as a Pentium II or Deschutes processor.

Sense Resistor

The current sense resistor, R1, is selected according to the formula:

ESR * (I

RIPPLE

+ ∆I) < V

Where VEX is the allowable output voltage excursion in the transient and I as the LX166x series, have adaptive output voltage positioning,

is the inductor ripple current. Regulators such

RIPPLE

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 (L and can be approximated as follows:

RIPPLE

- V

fS * L

OUT

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

R1 = V

Where V for LX1664/65 and 60mV for LX1664A/65A) and I current limit. Typical choices are shown below.

/ I

TRIP

is the current sense comparator threshold (100mV

TRIP

TABLE 2 - Current Sense Resistor Selection Guide

Sense Resistor Recommended

Load Value Controller

Pentium-Class Processor (<10A) 5mΩ LX1664 or LX1665 Pentium II Class (>10A) 2.5mΩ LX1664A or LX1665A

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.

is the desired

Rev. 1.2 11/99

Page 13

PRODUCT DATABOOK 1996/1997

LX1664/1664A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

USING THE LX1664/65 DEVICES

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.

Inductor

2.5m9

100mil Wide, 850mil Long

2.5mm x 22mm (2 oz/ft

Sense Resistor

copper)

Output Capacitor Pad

Sense Lines

FIGURE 10 — Sense Resistor Construction Diagram

Recommended sense resistor sizes are given in the following

table:

TABLE 3 - PCB Sense Resistor Selection Guide

Copper Copper Desired Resistor Dimensions (w x l) Weight Thickness Value mm inches

2 oz/ft

68µm 2.5m

Ω

2.5 x 22 0.1 x 0.85

2.5 x 43 0.1 x 1.7

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.

Load

Current

Sense

Comparator

FIGURE 11 — Current Sense Circuit

CURRENT LIMIT

(continued)

The current flowing through the inductor is a triangle wave. If the sensor components are selected such that:

L/R

= RS * C

The voltage across the capacitor will be equal to the current flowing through the resistor, i.e.

VCS = ILR

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:

|T(

L/RSC

1/R

SCSRL

FIGURE 12 — Sensor Gain

The dc/static tripping current I

trip,S

trip

satisfies:

trip,S

Select L/RSCS ≤ RL to have higher dynamic tripping current than the static one. The dynamic tripping current I

trip

L/(RSCS)

trip,d

General Guidelines for Selecting RS , CS, and R

trip

RL = Select: RS ≤ 10 kΩ

trip,S

and CS according to: CSn =

RL R

satisfies:

trip,d

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.

Page 14

PRODUCT DATABOOK 1996/1997

LX1664/64A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

USING THE LX1664/65 DEVICES

CURRENT LIMIT (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 (R can be put in parallel with C of components is as follows:

L (Required)

L (Actual)

= =

L (Actual)

* (RS2 // RS)

, as shown in Figure 11. The selection

RS2 + R

L (Actual)

RS + R

RS2 * R

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 R 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.

Device R

IRL3803 6 83 30

IRL22203N 7 71 30

IRL3103 14 40 30 IRL3102 13 56 20 IRL3303 26 24 30 IRL2703 40 17 30

All devices in TO-220 package. For surface mount devices (TO-263 / D2-Pak), add 'S' to part number, e.g. IRL3103S.

@ ID @ Max. Break-

DS(ON)

ΩΩ

10V (m

Ω)T

ΩΩ

= 100°C down Voltage

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 R

DS(ON)

Heat Dissipated In Upper MOSFET

The heat dissipated in the top MOSFET will be:

= (I2 * R

* Duty Cycle) + (0.51 * VIN * tSW * fS )

DS(ON)

FET SELECTION (continued)

For the IRL3102 (13mΩ R

)

will result in typical heat dissipation of 1.48W.

), converting 5V to 2.8V at 14A

DS(ON)

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:

= I2 * R

[IRL3303 or 1.12W for the IRL3102]

* [1 - Duty Cycle] = 2.24W

DS(ON)

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 & D 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 t and fS is the switching frequency.

is switching transition line for body diode (~100ns)

Rev. 1.2 11/99

Page 15

PRODUCT DATABOOK 1996/1997

LX1664/1664A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

USING THE LX1664/65 DEVICES

LINEAR REGULATOR

Referring to the front page Product Highlight, a schematic is presented which uses a MOSFET as a series pass element for a linear regulator. The MOSFET is driven by the LX1664 controller, and down-converts a +5V or +3.3V supply to the desired V level, between 1.5 & 3.5V, as determined by the feedback

OUT

resistors.

The current available from the Linear regulator is dictated by the supply capability, as well as the MOSFET ratings, and will typically lie in the 3-5 ampere range. This output is well suited for I/O buffers, memory, chipset and other components. Using

3.3V supply to convert to 1.5V for GTL+ Bus will significantly reduce heat dissipation in the MOSFET.

MOSFET Comments

Heatsinking the MOSFET becomes important, since the linear stage output current could approach 5 amperes in some applications. Since there are no switching losses, power dissipation in the MOSFET is simply defined by P current. This means that a +5V the MOSFET dissipate (5-3.3) * 5 = 8.5 watts. This amount of

to +3.3V

= (VIN - V

at 5A will require that

OUT

) * I output

OUT

power in a MOSFET calls for a heatsink, which will be the same physical size as that required for a monolithic LDO, such as the LX8384 device.

The dropout voltage for the linear regulator stage is the product of R

ON * I

voltage will be (worst case) 37 milliohms x 5A = 185mV.

Note that the R affect heat dissipation, only dropout voltage. For reasons of

. Using a 2SK1388 device at 5A, the dropout

OUT

ON of the (linear regulator) MOSFET does not

economy, a FET with a higher resistance can be chosen for the linear regulator, e.g. 2SK1388 or IRLZ44.

TABLE 5 - Linear Regulator MOSFET Selection Guide

Device R

IRFZ24N 70 12 55

IRL2703 40 17 30

IRLZ44N 22 29 55

@ ID @ Max. Break-

DS(ON)

ΩΩ

10V (m

Ω)T

ΩΩ

= 100°C down Voltage

Avoiding Crosstalk

To avoid a load transient on the switching output affecting the linear regulator, follow these guidelines:

1) Separate 5V supply traces to switching & linear FETs as much as possible.

2) Place capacitor C9 as close to drain of Q4 as possible.

Typical transient response is shown in Figure 13.

LINEAR REGULATOR

(continued)

FIGURE 13 — Typical Transient Response

Channel 2 = Linear Regulator Output.

Set point = 3.3V @ 2A (20mV/div.)

Channel 4 = Switching Regulator Output.

set point = 2.8V

Channel 3 = Switching Regulator Load Current

CC_CORE

Transient 0 - 13A

Output Voltage Setting

As shown in Application Information Figures 6-9, two resistors (R & R6) set the linear regulator stage output voltage:

= 1.5 * (R5 + R6) / R

OUT

As an example, to set resistor magnitudes, assume a desired

of 3.3 volts:

OUT

1.5 * (12.1k + 10k) / 10k = 3.3 volts (approximately)

In general, the divider resistor values should be in the vicinity of 10-12k ohm for optimal noise performance. Please refer to Table 6.

Page 16

PRODUCT DATABOOK 1996/1997

LX1664/64A, LX1665/65A

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

USING THE LX1664/65 DEVICES

LINEAR REGULATOR (continued)

TABLE 6 -

Resistors Settings for Linear Regulator Output Voltage

Nominal

Set Point (V) R

3.3 12 10 3.30

3.2 11.3 10 3.20

3.1 11.3 10.7 3.08

3.0 11 11 3.00

2.9 10.3 11 2.90

2.8 10 11.5 2.80

2.7 10 12.4 2.71

2.6 10 13.7 2.59

2.5 9.76 14.7 2.50

2.4 8.87 14.7 2.41

2.3 8.87 16.5 2.31

2.2 8.87 18.7 2.21

2.1 8.87 22.1 2.10

2.0 8.87 26.7 2.00

1.9 8.87 21 2.13

1.8 7.15 35.7 1.80

1.7 7.15 53.6 1.70

1.6 7.15 100 1.61

1.5 7.15 ∞ 1.50

ΩΩ

Ω)R6 (k

ΩΩ

Ω)V

ΩΩ

OUT

(V)

Capacitor Selection

Referring to the Product Highlight schematic on the front page, the standard value to use as the linear regulator stage output capacitor is on the order of 330µF. This provides sufficient hold-up for all expected transient load events in memory and I/O circuitry.

Disabling Linear Output

Linear regulator output can be disabled by pulling feedback pin (L

) up to 5V as shown in Figure 14.

TABLE 7 - Linear Enable (LIN EN) Function Table

LIN EN LIN OUTPUT

H Disabled

L Enabled

LIN EN

LX1664

DRV

10k

2N2222

0.1µF

IRLZ44

330µF

C 330µF

Supply Voltage For I/O Chipse

LAYOUT GUIDELINES - THERMAL DESIGN

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:

■ 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.

Input

5V or 12V

LX166x

Output

FIGURE 14 — Enabling Linear Regulator

FIGURE 15 — Power Traces

Rev. 1.2 11/99

Page 17

PRODUCT DATABOOK 1996/1997

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

P RODUCTION DATA SHEET

USING THE LX1664/65 DEVICES

LAYOUT GUIDELINES - THERMAL DESIGN (continued)

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 15 – 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.

RELATED DEVICES

LX1662/1663 - Single Output PWM Controllers

LX1553 - PWM Controller for 5V - 3.3V Conversion

LX1668 - Triple Output PWM Controller

LX1664/1664A, LX1665/65A

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.

Cyrix is a registered trademark and 6x86 and Gx86 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.

Pentium is a registered trademark of Intel Corporation.

Datasheet LX1665CN, LX1665CDW, LX1665ACN, LX1665ACDW, LX1664CN Datasheet (Microsemi Corporation)

Specifications and Main Features

Frequently Asked Questions

User Manual