NSC LM2639MX, LM2639M, LM2639EVAL Datasheet

LM2639
5-Bit Programmable, High Frequency Multi-phase PWM
Controller

General Description

The LM2639 provides an attractive solution for power sup­plies of high power microprocessors (such as Pentium II

™

,

MII

™

,K6™-2, K6™-3, etc.) exhibiting ultra fast load tran­sients. Compared to a conventional single-phase supply, an
LM2639 based multi-phase supply distributes the thermal
and electrical loading amongcomponentsin multiple phases
and greatly reduces the corresponding stress in each com­ponent. The LM2639 can be programmed to control either a
3-phase converter or a 4-phase converter. Phase shift
among the phases is 120˚ in the case of three phase and 90˚
with four-phase. Because the power channels are out of
phase, there can be significant ripple cancellation for both
the input and output current, resulting in reduced input and
output capacitor size. Due to the nominal operating fre­quency of 2 MHz per phase, the size of the output inductors
can be greatly reduced which results in a much faster load
transient response and a dramatically shrunk output capaci­tor bank. Microprocessor power supplies with all surface
mount components can be easily built.

The internal high speed transconductance amplifier guaran­tees good dynamic performance. The output drive voltages
can be adjusted through a resistor divider to control switch­ing loss in the external FETs.

The internal master clock frequency of up to 8 MHz is set by
an external reference resistor. An external clock of 10 MHz
can also be used to drive the chip to achieve frequency con­trol and multi-chip operation.

The LM2639 also provides input under-voltage lock-out with
hysteresis and input over-current protection.

Features

n Ultra fast load transient response
n Enables all surface-mount-design
n Selectable 2, 3, 4 phase operation
n Clock frequency from 40 kHz to 10 MHz
n Precision load current sharing
n 5-bit programmable from 3.5V to 1.3V
n VID code compatible to VRM 8.X specification
n Output voltage is 2.0V for VID code 11111
n Selectable internal or external clock
n Digital 16-step soft start
n Input under-voltage lock-out, over-current protection

Applications

n Servers and workstations
n High current, ultra-fast transient microprocessors

Pin Configuration

MII™is a trademark of Cyrix Corporation a wholly owned subsidiary of National Semiconductor Corporation.
Pentium II

™

is a trademark of Intel Corporation.

K6

™

is a trademark of Advanced Micro Devices, Inc.

24-Pin Plastic SOIC

DS101143-1

Top View

See NS Package Number M24B

February 2000

LM2639 5-Bit Programmable, High Frequency Multi-phase PWM Controller

© 2000 National Semiconductor Corporation DS101143 www.national.com

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

V

CC

5V 7V

V

CC

12V 20V
Junction Temperature 125˚C
Power Dissipation (Note 2) 1.6W

Storage Temperature −65˚C to +150˚C
ESD Susceptibility (Note 8) 2 kV
Soldering Time, Temperature 10 sec., 300˚C

Operating Ratings (Note 1)

V

CC

4.75V to 5.25V

Junction Temperature Range 0˚C to 70˚C

Electrical Characteristics

VCC5V=5V, VCC12V=12V unless otherwise specified. Typicals and limits appearing in plain type apply for T

A

=

T

J

=

+25˚C.

Limits appearing in boldface type apply over the entire operating temperature range.

Symbol Parameter Conditions Min Typ Max Units

Vcc5V V

CC

5V Pin Voltage 4.5 5.0 5.5 V

Vcc12V V

CC

12V Pin Voltage 10.0 12.0 18.0 V

V

DACOUT

5-bit DAC Output Voltage (Note 3)

N

−1

%

NN

+1

%

V

N

−1.5

%

NN

+1.5

%

I

CC

12V Quiescent VCC12V Current Enable=5V, VID=00001,

DRV Outputs Floating

1.3 3 mA

I

CC

5V Operating VCC5V Current V

OUT

=

2.00V 4.3 8 mA

V

REF

Rref Pin Voltage 1.225 V

V

INL

Vid0:4, Clksel, Divsel, and
Enable Pins Logic Threshold

Logic Low (Note 4) 1.8 1.5 V

V

INH

Logic High (Note 5) 3.5 2.8 V

I

INL

Vid0:4 and Enable Pins Internal
Pullup Current

The Corresponding Pin=0V

60 100 140

µA

Clksel, Divsel Pins Internal
Pullup Current

−10 0 10

Gate Driver Resistance When
Sinking Current

I

SINK

=

50 µA, V

CC

12V=14V 12 Ω

V

DRV

DRV0:3 Output Voltage I

DRV

=

10 mA, V

CC

12V=14V,

OutV=12V or 5V

OutV −

0.3V

OutV OutV +

0. 3V

V

t

fall

DRV0:3 Fall Time (Note 6) 7 ns

I

SRC

DRV0:3 Source Current DRV0:3=0V, VCC12V=14V,

OutV=5V

40 60 mA

I

SINK

DRV0:3 Sink Current DRV0:3=5V, VCC12V=14V,

OutV=5V

90 160 250 mA

B

gOUT

Voltage Current Limit Not Activated 4

V

Current Limit Activated 0

I

FB

FB Pin Bias Current FB=2V 30 nA
B

gOUT

Sink Current B

gOUT

=

1V 1.0 2.4 5 mA

F

OSC

Oscillator Frequency 8.02kΩ from Rref Pin to

Ground

7.0 8.0 8.7 MHz

∆

D

DRV0:3 Duty Cycle Match Duty Cycle=50

%

−1 +1

%

∆

ph

DRV0:3 Phase Accuracy Duty Cycle=50%,F

clock

=

8

MHz

−1 +1 Deg

T

off

PWM Off time

Divide by 4 22

%

T

off

Divide by 3 22

OutV Drive Voltage Range Output Freq.=2MHz, V

O

=

2.00V

0 12 Vcc12 V

LM2639

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Electrical Characteristics (Continued)

VCC5V=5V, VCC12V=12V unless otherwise specified. Typicals and limits appearing in plain type apply for T

A

=

T

J

=

+25˚C.

Limits appearing in boldface type apply over the entire operating temperature range.

Symbol Parameter Conditions Min Typ Max Units

V

OCC_CM

Over-current Comparator
Common Mode Range

312V

IB_OC+ OC+ Input Bias Current V

IN

=

5V, OC+=5V, OC−

=

4V

100 145 200 µA

IB_OC− OC− Input Bias Current V

IN

=

5V, OC+=6V, OC−

=

5V

85 125 165 µA

V

OS_OCC

Over-current Comparator Input
Offset Voltage

V

IN

=

5V 2 16 42

mV

V

IN

=

12V 21

D

MAX

Maximun Duty Cycle FB=0V 78

%

gm Error Amplifier

Transconductance

1.36 mmho

V

ramp

Ramp Signal Peak-to-Peak
Amplitude

2V

I

comp

COMP Pin Source Current 250 400 550 µA

I

comp

COMP Pin Sink Current 160 280 400 µA

V

comp_hi

COMP Pin High Clamp 2.9 V

V

comp_lo

COMP Pin Low Clamp 0.19 V

V

POR

Power On Reset Trip Point Vcc5V Pin Voltage Rising 4.0

V

Vcc5V Pin Voltage Falling 3.6

Vcc12V Minimum Working
Voltage

(Note 7) 3.8 V

t

SS

Soft Start Delay F

OSC

=

8MHz 1.6 ms

Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating ratings do not imply guaranteed performance limits.
Note 2: Maximum allowable power dissipation is a function of the maximum junction temperature, T

JMAX

, the junction-to-ambient thermal resistance, θJA, and the

ambient temperature, T

A

. The maximum allowable power dissipation at any ambient temperature is calculated using:

P

MAX

=

(T

JMAX−TA

)/

θ

JA

.

The

junction-to-ambient thermal resistance, θ

JA

, for LM2639 is 78˚C/W. For a T

JMAX

of 150˚C and TAof 25˚C, the maximum allowable power dissipation is 1.6W.

Note 3: The letter

N

stands for the typical output voltages appearing in

italic boldface

type in

Table 1

.

Note 4: Maxvalue of logic low means any voltage below this value is guaranteed to be taken as logic low whereas a voltage higher than this value is not guaranteed
to be taken as a logic low.

Note 5: Minvalueof logic high means any voltage above this value is guaranteed to be taken as logic high whereas a voltage lower than this value is not guaranteed
to be taken as a logic high.

Note 6: When driving bipolar FET drivers in the typical application circuit.
Note 7: When Vcc12V pin goes below this voltage, all DRV pins go to 0V.
Note 8: ESD ratings for pins DRV0, DRV1, DRV2 and DRV3 is 1kV. ESD rating for all other pins is 2kV.

LM2639

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