Allegro A8580 Guida rapida

Page 1 of 13 December 18th, 2012

Demo Note for the A8580

Evaluation Board

4.0VIN – 40VIN, 3.3VOUT, 2.5A, 425KHz

Asynchronous Buck Regulator with

Low IQ PFM Mode

Page 2 of 13 December 18th, 2012

GENERAL SPECIFICATIONS

Specification

Min

Nom

Max

Units

Absolute Maximum Input Voltage

–0.3

−

Volts

Operating Input Voltage Range

4.0

Volts

START Threshold, V

rising

3.6

3.8

4.0

Volts

STOP Threshold, V

falling

3.2

3.4

3.6

Volts

Output Voltage

(FB: 47K/147K, ±1%)

3.175

3.302

3.434

Volts

Steady-State Output Current (12V

)

−

2.5

−

Pulse-by-pulse Current Limit @ 30% duty

3.12

3.69

4.25

PWM/PFMn Input

–0.3

−

5.5

Volts

OPERATING INSTRUCTIONS

Input Power Connection:

Connect a 12V power supply from VIN to GND that is capable of at least 2.5A. Once

operational, VIN can fall as low as 3.4VTYP (3.6VMAX) before the A8580 is reset.

PWM/PFMn Input and DIP switch SW1 (SLEEPn):

Connect an external voltage to the PWM/PFMn input and set SW1 (SLEEPn) to control the

A8580’s operating mode.The following table summarizes the A8580’s operating modes based

on SW1 (SLEEPn) and the PWM/PFMn input. Also, PWM/PFMn may be used to synchronize

the A8580 PWM switching frequency by applying a square wave above 510KHz.

SW1

(SLEEPn)

PWM/PFMn Operating Mode

OFF

(SLEEPn<0.5V) N/A Low current SLEEP mode, no output voltage

(SLEEPn>2.1V)

< 0.8V Low IQ PFM mode, supports up to 500mATYP

> 2.6V Normal PWM mode at 425KHz, supports up to 2.5A

CLK signal Normal PWM mode, synchronized to external CLK

Note: Set SW1 to the “OFF” position before driving the SLEEPn test point by a pulse generator

or an external power supply.

Note: Continuously applying more than 5.5V to the PWM/PFMn pin may damage the A8580.

Output Load Connections:

Connect a load from VOUT to GND. The steady-state load current can be as high as 2.5A. Pulse-

by-pulse current limit and/or thermal shutdown will occur if the load is greater than 3.7A.

Page 3 of 13 December 18th, 2012

DEMO BOARD PICTURE

MODIFYING THE DEMO BOARD TO PRODUCE VOUT > 5.5V

If the demo board is modified to produce more than 5.5Vout two changes must be made:

1) Jumper J1 must be set to the “lower” position (shown below) so the on-board 3.3V LDO (U2)

will deliver the BIAS voltage to the A8580.

2) Diode D2 must be rotated 90°clockwise so it is “in circuit” and the 3.3V LDO (U2) will

operate. If U2 is operational, the Low IQ current of the EVB will increase.

SW1

(SLEEPn)

Move J1 to the

“lower” position

Rotate D2 90°so it

connects to this pad

PWM/PFMn Input

> 2.6V for PWM

< 0.8V for PFM

Page 4 of 13 December 18th, 2012

DEMO BOARD SCHEMATIC

RFSET

60.4K

26.1K

0603

15pF

0603

470pF

1210

16V

CO2

22uF

7.6mmx 7.6mm

DR72-8R2-R

8.2uH

100V

0805

CIN2

0.47uF

VOUT

VIN SW

GND

VOUT

VIN

TP4 GND

TP3 GND

12.0Vin / 3.3Vout: RFB1 = 147K, RFB2 = 47K

A8580 Evaluation PCB

50V

8mm

47or33uF

CO MP

RFB1

147K

RFB2

47K

0603

CSS

22nF

16V

8mm

CO6

Empty

1210

16V

CO1

22uF

RPU

10K NPOR

SS FSET

TP1 GND

TP2 GND

50V

1210

CIN3

4.7uF

Rsnub

6.81

0603

Csnub

330pF

SS2P4

0603

CVREG

1uF

0603

CFB

10pF

0603

CBOOT

47nF

GND

SW1

10K

4.99M

VREG

BIAS

1210

16V

CO3

Empty 1210

16V

CO5

Empty

0805

100V

CO4

0.47uF 16V

8mm

CO7

Empty 16V

8mm

CO8

Empty

1206

16V

4.7uF 1206

16V

4.7uF 1206

16V

4.7uF

SOD123

D2 B140

10nF

In 1

En 3

LP2992IM5-3.3 xxV

16or18mm

Empty

BIAS

0603

16V

C52

Empty

0603

16V

C53

100nF

3.3V

Default jumper position

BIAS

PWM/PFM

SLEEP

50V

0603

CIN1

47nF

BODE

Empty

0603

50V

CO4 a

47nF50V

1210

CIN4

4.7uF

100V

0805

CIN5 a

0.47uF

50V

1210

CIN5

4.7uF 50V

0603

CIN5 b

47nF

BEAD1

0ohms

VIN_FILT

VIN

2SW 15

VIN

BOOT 16

GND

FB 10

SW 14

VREG

POR 7

SLEEP

FSET

BIAS

GND

COMP

PWM/PFM

A8580_LP

Note: CB is an optional, bulk, electrolytic capacitor for general supply filtering

DEMO BOARD BILL-OF-MATERIALS

REFERENCE DESIGNATORS DESCRIPTION FOOTPRINT QTY. MANUFACTURER MANUFACTURER P/N SOURCE PURCHASE P/N

PCB A8580 PCB for eTSSOP16, Rev 0.1 N/A 1

Allegro

MicroSystems

4pcb.com

U1 A8580, 2A Buck Regulator eTSSOP-16 1

Allegro

MicroSystems

A8580

U2 Regulator, LDO, 3.3V/250mA SOT23-5 1National Semi LP2992IM5-3.3 Digikey LP2992IM5-3.3CT-ND

R4 Resistor, 4.99MΩ, 1/10W, 1% 0603 1

R6, RPU Resistor, 10KΩ, 1/10W, 1% 0603 2

RFB1 Resistor, 147KΩ, 1/10W, 1% 0603 1

RFB2 Resistor, 47KΩ, 1/10W, 1% 0603 1

RFSET Resistor, 60.4KΩ, 1/10W, 1% 0603 1

Rsnub Resistor, 6.81Ω, 1/4W, 1% 1206 1

RZ Resistor, 26.1KΩ, 1/10W, 1% 0603 1

BEAD1 Resistor, 0Ω, 0805 0805 1

C1,C2,C3 Capacitor, Ceramic, 4.7µF, 16V, X7R 1206 3

C53 Capacitor, Ceramic, 100nF, 25V, X7R 0603 1

Capacitor, Electrolytic, 33µF or 47µF, 50V, <0.5Ω,

-40°C to 125°C

Thru Hole

8mm x11.5mm

Nichicon

UBW1H330MPD

UBT1H330MPD

UBT1H470MPD

DigiKey

Mouser

UBW1H330MPD-ND

647-UBT1H330MPD

647-UBT1H470MPD

CIN1, CIN5b, CO4a, CBOOT

Capacitor, Ceramic, 47nF, 50V, 10%, X7R, -55°C

to 125°C

0603 4Murata GRM188R71H473KA61D Digikey 490-3287-1-ND

CIN2, CIN5a, CO4

Capacitor, Ceramic, 0.47uF, 100V, 10%, X7R, -

55°C to 125°C

0805 3Murata GRM21BR72A474KA73L Digikey 490-3326-1-ND

CIN3, CIN4, CIN5 Capacitor, Ceramic, 4.7µF, 50V, X7R 1210 3TDK

C3225X7R1H475K

C3225X7R1H475M

Digikey 445-7726-1-ND

445-7727-1-ND

CFB Capacitor, Ceramic, 10pF, 50V, COG 0603 1

CO1, CO2 Capacitor, Ceramic, 22µF, 16V, X7R 1210 2TDK C3225X7R1C226K Digikey 445-3945-2-ND

Csnub Capacitor, Ceramic, 330pF, 50V, X7R 0603 1

CSS Capacitor, Ceramic, 22nF, 50V, X7R 0603 1

CVREG Capacitor, Ceramic, 1µF, 50V, X7R 0603 1

CZ Capacitor, Ceramic, 560pF, 50V, X7R 0603 1

CP Capacitor, Ceramic, 15pF, 50V, C0G 0603 1

Cx Capacitor, Ceramic, 10nF, 50V, X7R 0603 1

BODE, C4, C52, CIN4, CO3, CO4,

CO5, CO6, CO7, CO8

Empty Various 0

D1 Schottky Diode, 40V, 2A SMP 1Vishay SS2P4-M3/84A

Digikey

Mouser

SS2P4-M3/84AGICT-ND

625-SS2P4-M3/84A

D2 Schottky Diode, 40V, 1A, SOD123 SOD123 1

Diodes, Inc

B140HW-7

Digikey

Mouser

B140HWDICT-ND

621-B140HW-7

LO Inductor, 8.2uH, 3.17A

SAT

@ 25C, 40mΩ

7.6mm x 7.6mm

4.35mm thick

1Cooper Bussmann DRA74-8R2-R

Digikey

Mouser

283-3644-1-ND

704-DRA74-8R2-R

3.3V, BIAS, COMP, FSET, NPOR,

PWM/PFM,SLEEP,SS, SW,VIN,

VOUT, VREG,

Test Points, Red, 0.063" diameter 0.063" 12 Keystone 5010 Digikey 5010K-ND

GND Test Points, Black, 0.063" diameter 0.063" 5Keystone 5011 Digikey 5011K-ND

Header, 3-pins, 0.1" spacing (Note: P/Nis for a 36-

pinstrip)

1Sullins PEC36SAAN Digikey S1012E-36-ND

SW1 DIP Switch, 1 position SMT 1C & K Components SDA01H0SBR Digikey CKN9490CT-ND

Rubber Feet Self stick rubber feet Clear 43M SJ-5303 (CLEAR) Digikey SJ5303-7-ND

Page 5 of 13 December 18th, 2012

DEMO BOARD PERFORMANCE

0500 1000 1500 2000 2500

Efficiency (%)

Iout (mA)

Efficiency vs IOUT (PWM Mode)

8Vin

12Vin

16Vin

10 100 1000 10000 100000

Efficiency (%)

Iout (µA)

Efficiency vs IOUT (PFM Mode)

Page 6 of 13 December 18th, 2012

DEMO BOARD PERFORMANCE

-0.40

-0.30

-0.20

-0.10

0.00

0500 1000 1500 2000 2500

Deviation from Vo at 100mA (%)

Iout (mA)

Load Regulation vs IOUT

8Vin

12Vin

16Vin

-0.50

-0.25

0.00

0.25

0.50

7 8 9 10 11 12 13 14 15 16 17 18

Line Regulation(%)

Vin(V)

Line Regulation vs VIN at 1.0A

Page 7 of 13 December 18th, 2012

DEMO BOARD PERFORMANCE

Bode Plot: 12VIN, 330mA Load: 0dB at 59.7KHz, PM=64.3deg, GM=11.3dB

Bode Plot: 12VIN, 2.5A Load: 0dB at 66.8KHz, PM=60deg, GM=8.6dB

Page 8 of 13 December 18th, 2012

DEMO BOARD PERFORMANCE

Component Temperatures: 12VIN, 3.3VOUT, 500mA Load, TAMB=25°C

No Airflow (still air)

Component Temperatures: 12VIN, 3.3VOUT, 2.5A Load, TAMB=25°C

No Airflow (still air)

Page 9 of 13 December 18th, 2012

DEMO BOARD PERFORMANCE

PWM Startup

12VIN, 2.5A (1.3Ω) load, PWM/PFMn=1

CH1=VOUT, CH2=COMP, CH3=SS, CH4=SLEEPn

PWM Shutdown

12VIN, 2.5A (1.3Ω) load, PWM/PFMn=1

CH1=VOUT, CH2=COMP, CH3=SS, CH4=SLEEPn

PWM Output Voltage Ripple

12VIN, 2.5A (1.3Ω) load, PWM/PFMn=1,

CH1=VOUT

PWM Transient Response

12VIN, 1A load step up/down,

PWM/PFMn=1

CH1=VOUT, CH2=COMP, CH4=IOUT

Page 10 of 13 December 18th, 2012

DEMO BOARD PERFORMANCE

PWM to PFM Transition

12VIN, 470mA (7Ω) load

CH1=VOUT, CH2=COMP, CH3=SW,

CH4=PWM/PFMn

PFM to PWM Transition

12VIN, 470mA (7Ω) load

CH1=VOUT, CH2=COMP, CH3=SW,

CH4=PWM/PFMn

PFM Output Voltage Ripple

12VIN, 1mA (3.3KΩ) load

CH1=VOUT

PFM Output Voltage Ripple

12VIN, 400mA (8Ω) load

CH1=VOUT

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