LX1664A MICROSEMI [Microsemi Corporation], LX1664A Datasheet

LX1664A

Manufacturer Part Number

LX1664A

Description

DUAL OUTPUT PWM CONTROLLERS WITH 5-BIT DAC

Manufacturer

MICROSEMI [Microsemi Corporation]

Datasheet

1.LX1664A.pdf (17 pages)

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H E

The LX1664/64A and LX1665/65A are

monolithic switching regulator con-

troller IC’s designed to provide a low cost,

high performance adjustable power supply

for advanced microprocessors and other

applications requiring a very fast transient

response and a high degree of accuracy.

out Expensive Current Sense Resistors.

Current-sensing mechanism can use PCB

trace resistance or the parasitic resistance of

the main inductor. The LX1664A and

LX1665A have reduced current sense com-

parator threshold for optimum perfor-

mance using a sense resistor. For applica-

tions requiring a high degree of accuracy, a

conventional sense resistor can be used to

sense current.

fier Driver for CPU Core.

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.

Short-circuit Current Limiting with-

Programmable Synchronous Recti-

N F I N I T E

VID0

VID1

VID2

VID3

VID4

Note: All surface-mount packages are available in Tape & Reel. Append the letter "T" to part number. (e.g. LX1664CDT)

0.1µF

11861 W

O W E R

ESTERN

Plastic DIP

16-pin

The main

O F

INV

VID0

VID1

VID2

VID3

VID4

CC_CORE

I N

Wide-Body SOIC

VENUE

LX1665

N N O V A T I O N

18-pin

I N I T Y

, G

PWRGD

set by a DIP switch on the motherboard, or

hardwired into the processor’s package (as

in the case of Pentium

processors). The 5-bit code adjusts the

output voltage between 1.30 and 2.05V in

50mV increments and between 2.0 and 3.5V

in 100mV increments, conforming to the

Intel Corporation specification. The device

can drive dual MOSFET’s resulting in typical

efficiencies of 85 - 90% even with loads in

excess of 10 amperes. For cost sensitive

applications, the bottom MOSFET can be

replaced with a Schottky diode (non-syn-

chronous operation).

65 family of devices have a secondary

regulator output. This can drive a MOSFET

or bipolar transistor as a pass element to

construct a low-cost adjustable linear regu-

lator suitable for powering a 1.5V GTL+ bus

or 2.5V clock supply.

ARDEN

BDRV

TDRV

GND

Linear Regulator Driver. The LX1664/

DRV

12V

Plastic DIP

18-pin

ROVE

I C R O E L E C T R O N I C S

, CA. 92841, 714-898-8121, F

PWRGD

1µF

(continued next page)

680pF

1µH

Pro and Pentium II

LX1664/64A, LX1665/65A

IRL3102

IRL3303

20A

Plastic SOIC

16-pin

IRLZ44

6.3V

1500µF x3

2.5µH

N C

I 5-bit Programmable Output For CPU Core

I Adjustable Linear Regulator Driver Output

I No Sense Resistor Required For Short-

I Designed To Drive Either Synchronous Or

I Soft-Start Capability

I Modulated, Constant Off-Time Architecture

I Available Over-Voltage Protection (OVP)

I Socket 7 (Pentium Class) Microprocessor

I Pentium II and Deschutes Processor & L2-

I Voltage Regulator Modules

330µF

: 714-893-2570

330µF

0.0025

Supply

Circuit Current Limiting

Non-Synchronous Output Stages

For Fast Transient Response And Simple

System Design

Crowbar Driver And Power Good Flag

(LX1665 only)

Supplies (including Intel Pentium Processor,

AMD-K6

Cache Supplies

Supply Voltage

For I/O Chipset or GTL+ Bus

Processors)

Plastic SOIC Wide

18-pin

And Cyrix

Supply Voltage

for CPU Core

6.3V, 1500µF x 3**

** Three capacitors for Pentium

Four capacitors for Pentium II

6x86

OUT

, Gx86

and

Related parts for LX1664A

LX1664A Summary of contents

Page 1

... Short-circuit Current Limiting with- out Expensive Current Sense Resistors. Current-sensing mechanism can use PCB trace resistance or the parasitic resistance of the main inductor. The LX1664A and LX1665A have reduced current sense com- parator threshold for optimum perfor- mance using a sense resistor. For applica- ...

Page 2

LX1664/64A, LX1665/65A Smallest Package Size. The LX1664 is available in a narrow body 16-pin surface mount IC package for space sensitive appli- cations. The LX1665 provides the additional functions of Over Voltage Protection (OVP) and Power Good (PWRGD) output drives ...

Page 3

... Input Offset Voltage Delay to Output C Current Sense Section Input Bias Current (V Pin) I CC_CORE B Pulse By Pulse C LX1664/1665 V L CLP LX1664A/1665A C Delay to Output S Output Drivers Section Drive Rise Time T R Drive Fall Time T F Drive High V DH Drive Low V DL Output Pull Down ...

Page 4

LX1664/64A, LX1665/65A * 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 Current Sense comparator. At high currents, the peak ...

Page 5

Output Set Point EFFICIENCY AT 3.1V EFFICIENCY AT 2.8V 75 EFFICIENCY AT 1. (A) OUT FIGURE 2 — Efficiency Test Results: Non-Synchronous Operation, V ...

Page 6

... Note: Pin numbers are correct for LX1665/1665A, 18-pin package. VID2 VID3 VID4 FIGURE 5 — LX1664/1665 Block Diagram PWM Latch DOM R Q Break Before Make 0.7V SYNC EN Comp OV Comp UV Comp LX1665/1665A ONLY Linear Op Amp * Not connected on LX1664/1664A. ** 60mV in LX1664A/1665A TDRV 17 GND 16 BDRV OV* 12 PWRGD DRV L 9 ...

Page 7

Pin LX1664 LX1665 Name Pin # Pin # Description 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 ...

Page 8

LX1664/64A, LX1665/65A 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 ...

Page 9

C 3 0.1µF U1 LX1664 INV 3 V CC_CORE 4 VID0 VID0 5 VID1 VID1 6 VID2 VID2 7 VID3 VID3 8 VID4 VID4 16-pin Narrow Body SOIC FIGURE 6 — LX1664 In A Pentium / Socket ...

Page 10

LX1664/64A, LX1665/65A C 3 0.1µ VID0 5 VID1 6 VID2 7 VID3 8 VID4 9 FIGURE 8 — VRM 8.2 (Pentium II / Deschutes) Reference Design With Loss-Less Current Sensing C 3 0.1µ ...

Page 11

Ref Description Ω The LX1664/65 devices are very easy to design with, requiring only a few simple calculations to implement a given design. The following procedures and considerations should provide effec- tive operation for virtually all applications. Refer to the ...

Page 12

... 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 ...

Page 13

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 ...

Page 14

LX1664/64A, LX1665/65A CURRENT LIMIT (continued) In cases where large that the trip point current would L be lower than the desired short-circuit current limit, a resistor (R can be put in parallel with shown ...

Page 15

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 ...

Page 16

LX1664/64A, LX1665/65A LINEAR REGULATOR (continued) TABLE 6 - Resistors Settings for Linear Regulator Output Voltage Ω Ω Ω Ω Ω Capacitor Selection Referring to the Product Highlight schematic on the front page, the standard value to use as the linear ...

Page 17

LAYOUT GUIDELINES - THERMAL DESIGN All of these traces should be made as wide and thick as possible, in order to minimize resistance and hence power losses also recommended that, whenever possible, the ground, input and output power ...

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