Datasheet nx2511ds Datasheets

Evaluation board available.

NEXSEM

2-4 PHASE SELECTABLE VRD10.X CONTROLLER

DESCRIPTION

The NX2511 is a multiphase PWM controller with the
ability to operate in 2,3 or 4 phase control operation.
This device with external FET drivers such as NX3202 ,
NX3203 or NX3212 is designed to provide a high perfor­mance high current multiphase converter that meets
the VRD10.0 specification.The NX2511 uses differential
remote sensing using either current sense resistor or
inductor DCR sensing to achieve accurate current match­ing between the three channels. Differential sensing elimi­nates the error caused by PCB board trace resistance
that is otherwise present when using a single ended volt­age sensing. In addition, the NX2511 offers complete
VRD10 signal interface using 6 bit DAC with on the fly
DAC change, Differential Output Voltage Sensing, ac­curate programmable droop allowing to reduce number
of output capacitors, accurate enable circuit provides
programmable start up point for Bus voltage, PGOOD
output, programmable switching frequency and hiccup
current limiting circuitry.

NX2511

PRELIMINARY DATA SHEET

Pb Free Product

FEATURES

n VRM9/VRM10 compatible 6 bit VID
n 2 to 4 Phase selectable interleaved PWM stages.
n Differential current sensing allows accurate current

share using Inductor ESR or current sense resistor

n Programmable output voltage droop & offset control
n Programmable UVLO for both BUS voltage and

Driver Supply Voltage

n Differential Remote Voltage Sensing
n Over Voltage Protection (OVP)
n Hiccup Current current Limit (OCP)
n Power Good signal for Power Sequencing
n Internal Soft start operation
n Programmable switching frequency from 100kHz to

600kHz per phase
n Pb-free and RoHS compliant

APPLICATIONS

n Desktop mother board VRD10.X
n Low voltage high current applications

+5V

+12V

+5V

CS2

48

EN

39

ENDRV

47

ENBUS

12

DROOP

4

RT

37

OVP

40

PGOOD

5

OFS

16

CS2COMP

19 18

CS3COMP

CS3

22

CS4

CS4COMP

6

VP

8

VCOMP

7

FB

9

DIFF

45

VID0

44

VID1

43

VID2

42

VID3

41

VID4

46

VID12.5

N X 2 5 1 1

AGND

1,36

Figure1 - Typical application of 2511

VCC

2,35

PWM1

PWM2

PWM3

PWM4

VSEN

RGND

STRT

CS+1

CS-1

CS+2

CS-2

CS+3

CS-3

CS+4

CS-4

TYPICAL APPLICATION

PHASE1

BST

VCC

HDRV

EN

IN1

SW

LDRV

PGND

PHASE2

PHASE3

PHASE4

34

33

14

15

32
17

31
20
21

30
23
24

10
11

+12V

VOUT

Rev. 1.0
01/24/05

ORDERING INFORMATION

Device Temperature Package Pb-Free
NX2511CMTR 0 to 70oC MLPQ-48 L Yes

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1

NEXSEM

C/W

PARAMETER

SYM

Test Condition

Min

TYP

MAX

Units

VID2, VID1,VID0, VID12.5)

DAC initial accuracy

0.5

%

DAC Voltage line regulation

Vcc=4.75 to 5.25V

0.1

%

VID Pull up Current

355065

uA

VID Input Low Level

0.4

V

VID Input HI Level

0.8VSupply Voltage(Vcc)

NX2511

ABSOLUTE MAXIMUM RATINGS

Vcc to PGND & BST to SW voltage .................... -0.3V to 6.5V

All other pins .................................................... -0.3V to 6.5V

Storage Temperature Range ............................... -65oC to 150oC

Operating Junction Temperature Range ............... -40oC to 125oC

CAUTION: Stresses above those listed in "ABSOLUTE MAXIMUM RATINGS", may cause permanent
damage to the device. This is a stress only rating and operation of the device at these or any other condi­tions above those indicated in the operational sections of this specification is not implied.

PACKAGE INFORMATION

48-LEAD PLASTIC MLPQ

VID1

ENBUS

VID0

VID12.5

NX2511

VID2

VID3

VID4

ENDRV

PGOOD

4142434445464748

3940

OVP

PHS

3738

AGND

36

VCC35
STRT

34

PWM1

33

PWM2

32

PWM3

31

PWM4

30

NC

29

NC

28

NC

27

NC

26

NC

25

23

24

θ≈29

ο

JA

AGND

VCC

VREF

RT

OFS

VP

FB

VCOMP

DIFF

VSEN

RGND

DROOP

EN

1
2
3
4
5
6
7
8
9

10
11
12

13 14 15 16 17 181920 21 22

OCP

CS-1

CS+1

CS+2

CS2COMP

CS-2

CS+3

CS3COMP

CS-3

CS+4

CS4COMP

CS-4

ELECTRICAL SPECIFICATIONS

Unless otherwise specified, these specifications apply over Vcc = 5V, EN=HIGH, and TA = 0 to 70oC. Typical values
refer to TA = 25oC. Low duty cycle pulse testing is used which keeps junction and case temperatures equal to the
ambient temperature.

VID Voltage(VID4, VID3,

VCC Voltage Range V
VCC Supply Current

Rev. 1.0
01/24/05

CC

I

CC

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4.5 5 5.5 V

- 5

mA

2

NEXSEM

PARAMETER

SYM

Test Condition

Min

TYP

MAX

Units

Enable(EN) & ENBUS

Oscillator (Rt)

Frequency

FS

Clock Freq.

600 KHz

Ramp Peak

2.5

V

Ramp Valley

1.5

V

Max Duty Cycle

F=600Khz

93%

Min duty Cycle

0

%

OVP latched Drive Current

2

mA

OVP delay

Freq per phase=200kHz

160

uSec

Amplifiers

Open Loop Gain

5065dB

Transconductance

1600

umoh

Input Offset Voltage

Vio 0 mV

Amplifier

Open Loop Gain

50

dB

Output LOW Voltage

0.5

V

Gain

0.995

1

1.005

V/V

Common Mode Range

-0.3

VccVCommon Mode Rejection

50

dB

Output LOW Voltage

0.5VSS (Internal )

Fclock=600Khz

200Khz/Phase

Delay before SS ramp up

320

uSec

Under Voltage, Vcc ,

NX2511

VCC-Threshold VCC_UVLO

VCC-Hysteresis VCC_Hyst

EN Threshold
EN Hysteresis

ENBUS Threshold ENBUS Rising 1.6 V

ENBUS Hysteresis

Ramp-Amplitude Voltage

Current Sense
Transconductance

RAMP

VCC Rising

EN Rising 0.6 V

4

0.2

0.1 V

0.16 V

1

V

V

V

V

Voltage Mode Error

Output Current Source or Sink 1 mA

Output HI Voltage Vcc-1.5 V

Remote Sense Differential
Amplifier (Vsen, Rgnd, Diff)

Output Current Source or Sink 5 mA
Output HI Voltage Vcc-1.5 V

Soft Start time

Rev. 1.0
01/24/05

Tss

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mS6.4

3

NEXSEM

PARAMETER

SYM

Test Condition

Min

TYP

MAX

Units

Power Good(Pgood)

Amplifier(CS+, CS-)

Input Offset Voltage

0 mVVoltage Gain

29.73030.3

V/V

(OFS)

Rofs connected to GND

1.25

OCP Adjust

OCP

per phase

Vref

Reference Voltage

1.6

V

to Vcc)

NX2511

Threshold V
Hysteresis 5 %V
PGood Voltage Low I

Current Sense

Pin Adjust Offset Voltage

Rofs connected to

Vcc(measured with respect

Blank time before activating

8 Clock cycles of 200 kHz

Falling 74 %V

SEN

=-5mA 0.5 V

PGood

1.25

40 uS

ID
ID

VVoltage at OFS Pin

Rev. 1.0
01/24/05

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NEXSEM

PIN DESCRIPTIONS

NX2511

Pin #

2,35

34

48

33, 32,

31, 30

38

40

6

Symbol

VCC

STRT

EN

PWM1,PWM2,
PWM3,PWM4

PHS_SEL

PGOOD

VP

Pin Description
IC’s supply voltage. This pin biases the internal logic circuits. An internal undervoltage

lockout keeps IC off till VCC reach 4V.
This pin is used to enable external drivers like NX3202. It goes high when all

Enable signal as well as internal UVLO is true.
This pin is used to enable the IC when is pulled high. The pin has a threshold

voltage of 0.6 volts.
These pins provide the PWM signal to the external drivers for phase 1, phase 2,

phase 3, and phase 4 respectively.
The pin selects the number of phases the converter will operatate. Connect to

GND for 4 phase, leave open for 3 phase or connect to 5V for 2 phase operation.
This pin is an open drain output. If used, it should be pulled to 5v with a resistor

greater than or equal to 10k, otherwise it my be left open. When soft start ends,
the PGOOD pin switches high. Any fault or under voltage on the enable pins will
cause the signal to be pulled low.

Input to the positive pin of the error amplifier. A resistor is connected from the
output of the DAC to this pin. Place a small capacitor from this pin to GND to filter
any noise as well as to provide a smooth transition during on the fly transistion.

7

4

37

14, 17
20, 23

15, 18
21, 24

16,
19,

22

8

5

FB

RT

OVP

CS+1,CS+2,

CS+3,CS+4

CS-1,CS-2,

CS-3,CS-4

CS2COMP,
CS3COMP,

CS4COMP

Vcomp

OFS

This pin is the error amplifier inverting input. It is connected via a resistor to the
output of the differential sense amplifier.

This pin programs the internal oscillator frequency using a resistor from this pin to
ground. The frequency of each phase is 1/N of this frequency. When N is selected
number of phases.

This pin indicates an over voltage fault has occurred. This pin switches high when
the Diff pin is greater than 200mV above the Vp pin. It can drive a SCR to turn off
the converter.

Positive input of the differential current sense amplifiers. It is connected directly to
the RC junction of the respective phase’s output inductor.

Negative input of the differential current sense amplifiers. It is connected directly to
the negative side of the respective phase’s output inductor.

The output of the transconductance op amp for current sharing circuit. An external
RC is connected from these pins to GND to stabilize the current loop.

This is the output pin of the error amplifier. The compensation network is attached
between this pin, the Fb pin and the Diff pins.

A resistor from this pin to ground or Vcc provides a positive or negative offset
respectively. This is accomplished using two different internal current sources.

Rev. 1.0
01/24/05

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NEXSEM

NX2511

Pin #

10,

11,9

13

3

47

39

46
45, 44,
43, 42,

41

Symbol

VSEN,

RGND,DIFF

OCP

VREF

ENBUS

ENDRV

VID12.5,
VID0, VID1,
VID2, VID3,

VID4

Pin Description
These pins are the input and output to a differential amplifier and are used to re-

motely sense the output voltage. Vsen is the positive input, Rgnd is the negative
input, and Diff is the output voltage to the differential amplifier.

A resistor divider connected from this pin to Vref programs the current limit thresh­old. The outputs of the internal current sense differential amplifiers are summed
together to represent the output current. This voltage is then compared to this
threshold and resets the soft start after 64 clock cycles.

A 1.6V buffered reference is brought out.
This pin is used to program the under voltage lockout of the bus supply. A resistor

divider from the bus voltage to this pin programs the under voltage lockout. When
the voltage of this pin is greater than 1.6V, the bus voltage is assumed operation.This
pin has a 10% hysterisis.

This pin is used to program the under voltage lockout of the gate driver supply. A
resistor divider from the gate driver voltage to this pin programs the under voltage
lockout. When the voltage of this pin is greater than 1.6V, the gate driver voltage
is assumed operation.This pin has a 10% hysterisis.

These are the inputs to the internal DAC that provides the reference voltage for the
regulated output. They can be connected directly to the open drain signal output or
pulled up externally up to Vcc. These pins have 40uA internal pull up current source
that goes to zero as the voltage rises above the logic threshold.

11

DROOP

A resistor from this pin to ground programs an internal current source that is fed
into the FB pin. This current source is proportional to the output current of the
regulator. The product of this current times the external resistor RFB provides a
droop voltage.

Rev. 1.0
01/24/05

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