ALLEGRO A4490 User Manual

A4490

T riple Output Step-Down Switching Regulator

Features and Benefits

▪ Three buck converters
▪ 4.5 to 34 V input voltage range
▪ 550 kHz fixed frequency
▪ Multiphase switching
▪ Independent control of each converter
▪ Power-on-reset flag
▪ Internal compensation
▪ 4 × 4 mm QFN Package, small PCB footprint

Package: 20-contact QFN (suffix ES)

Description

Designed to provide the power supply requirements of printers,
office automation, industrial, and portable equipment, the
A4490 provides three high current, high performance, switching
regulator outputs with independent soft start.

High frequency switching allows selection of inexpensive
inductors and small ceramic output capacitors. The turn-on
cycles of the regulators are interleaved to minimize stresses on
the input capacitors and to reduce EMI. A charge pump is used
to provide the supply for driving the power switches, ensuring
operation at very wide operating duty cycles and avoiding the
need for power-draining clamp circuits.

A power-on-reset circuit with user configurable delay indicates
when enabled regulators are in specification. The power-on­reset flag also indicates when the input voltage drops below
specification, giving the system controller advance warning
while the switchers continue to operate down to the shutdown
level.

Internal diagnostics provide comprehensive protection against
overloads, input undervoltages, and overtemperatures.

Continued on the next page…

Approximate size

Microcontroller or
Controller Logic

Typical Application

V

BB

VDD

CP1 CP2 VCP

PORZ

CPOR

A4490

ENB1

ENB2

ENB3

PGND

GND

VBB1

LX1

FB1

VBB2

LX2

FB2

VBB3

LX3

FB3

V

V

V

REG1

REG2

REG3

4490-DS, Rev. 6

A4490

T riple Output Step-Down Switching Regulator

Description (continued)

The A4490 is provided in a 20-contact, 4 mm × 4 mm, 0.75 mm
nominal overall height QFN, with exposed pad for enhanced thermal
dissipation. It is lead (Pb) free, with 100% matte tin leadframe
plating.

Applications include the following:

▪ Photo, inkjet, and portable printers
▪ Industrial
▪ Hand-held devices
▪ Portable applications

Selection Guide

Part Number Packing

A4490EES-T 92 pieces per tube
A4490EESTR-T 1500 pieces per 7-in. reel

Operating Temperature Range

(°C)

–40 to 85

Absolute Maximum Ratings (reference to GND)

Characteristic Symbol Notes Rating Units

Load Supply Voltage V

LX1, LX2, and LX3 Pins V

PORZ and VDD Pins V

ENBx Pin Input Current I

Operating Ambient Temperature T

Maximum Junction Temperature TJ(max) 150 ºC

Storage Temperature T

BB

LXn

IN

ENBx

A

stg

Driven by a current-limited voltage source 1 mA

Range E –40 to 85 ºC

36 V

–1 to 36 V

–0.3 to 7 V

–55 to 150 ºC

Recommended Operating Conditions

Characteristic Symbol Conditions Min. Typ. Max. Units

Load Supply Voltage V

LX1, LX2, and LX3 Pins V

Operating Ambient Temperature T

Junction Temperature T

BB

LXn

A

J

To operate at VBB < 6 V, connect VDD
supply to the VBB supply. See Powering
Configurations section.

4.5 – 34 V

–0.7 – 34 V

–40 – 85 ºC

–40 – 125 ºC

Thermal Characteristics may require derating at maximum conditions, see application information

Characteristic Symbol Test Conditions* Value Units

Package Thermal Resistance

*Additional thermal information available on the Allegro website.

R

θJA

On 4-layer PCB based on JEDEC standard 37 ºC/W

Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

2

A4490

T riple Output Step-Down Switching Regulator

Functional Block Diagram

C2

47 nF

CP1

V

BB

CP2

V

BB

100 nF

100 kΩ

470 nF

V

C14

C1

DD

VDD

ENB1

ENB2

PORZ

CPOR

ENB3

PGND

Regulator

Switch

Bias Supply

SS

SS

POR Block

SS

Switcher #1

PWM Control

Switcher #2

PWM Control

Switcher #3

PWM Control

Charge Pump

VCP

VCP

VCP

VCP

VBB1

LX1

FB1

VBB2

LX2

FB2

VBB3

LX3

FB3

GND

C3

47 nF

C4

L1

D1

15 μH

L2

D2

D3

10 μH

L3

4.7 μH

10 μF

C5

10 μF

R1

R2

C6

10 μF

C7

10 μF

R3

R4

C9

10 μF

C10

10 μF

R5

R6

V

3.3 V / 1.5 A

C8

10 μF

C11

10 μF

V

REG1

5 V / 1.5 A

REG2

C12

10 μF

V

REG3

1.0 V / 1.5 A

C13

10 μF

V

BB

Note: All capacitors ceramic X5R.

Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

3

A4490

T riple Output Step-Down Switching Regulator

Pin-out Diagram

ENB1

LX1

VBB1

VBB3

LX3

2019181716

10

VCP

ENB3

15

FB3

14

PGND

13

CP1

12

CP2

11

FB1

1

VDD

2

GND

FB2

ENB2

3

4

5

PAD

678

LX2

VBB2

CPOR

9

PORZ

Terminal List

Number Name Function

1 FB1 Feedback REG1

2 VDD Bias supply

3 GND

4 FB2 Feedback REG2

5 ENB2 Enable REG2, logic input, active high

6 LX2 Switch node REG2

7 VBB2

8 CPOR POR delay adjustment

9 PORZ Power on reset output, active low

10 VCP Charge pump reservoir

11 CP2 Charge pump capacitor terminal

12 CP1 Charge pump capacitor terminal

13 PGND

14 FB3 Feedback REG3

15 ENB3 Enable REG3, logic input, active high

16 LX3 Switch node REG3

17 VBB3

18 VBB12 Input supply for REG1

19 LX1 Switch node REG1

20 ENB1 Enable REG1, logic input, active high

–PAD

1

GND and PGND should be connected externally.

2

The three VBBx pins should be connected together externally.

3

Thermal pad should be connected to the ground (0 V) plane using thermal vias.

1

Ground

2

Input supply for REG2

1

Ground for charge pump circuitry

2

Input supply for REG3

3

Exposed pad for enhanced thermal dissipation

Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

4

A4490

T riple Output Step-Down Switching Regulator

ELECTRICAL CHARACTERISTICS

1,2

at TA = 25°C, VBB = 6.0 to 34 V, VDD supplied externally, unless noted otherwise

Characteristics Symbol Test Conditions Min. Typ. Max. Units

General

VBB Quiescent Current

I

I

BBOFF

VDD Supply Range V

VDD Quiescent Current I

BBON

current drawn by feedback resistors ignored

ENBx = high, I

ENBx = 0 V – 1 – μA

3.3 – 5.5 V

DD

ENBx = high – – 5 mA

DD

ENBx = 0 V – 1 – μA

= 0 mA, VBB = 12 V,

LOAD

– 1 2 mA

REG1, REG2, and REG3

Feedback Input Bias Current I

Feedback Voltage V

Output Voltage Regulation

3

–400 –100 100 nA

BIAS

FB

V

OUT

With respect to 0.8 V target voltage – ±1.5 – %

V

= 5 V, I

REGx

V

= 5 V, I

REGx

= 0 to 1.5 A, TA = –20°C to 85°C –2.5 – 2.5 %

OUT

= 0 to 1.5 A, TA = –40°C to 85°C –3.5 – 3.5 %

OUT

PWM Frequency fSW 470 550 630 kHz

Maximum Duty Cycle DC

Minimum Duty Cycle DC

Buck Switch On-Resistance R

Current Limit Threshold I

90 – – %

max

– 5 – %

min

TJ = 25°C, I

TJ = 125°C, I

DS(on)

TJ = 25°C, I

TJ = 125°C, I

Peak current through switch with D = 0.9 2.0 A

LIM

= 1.5 A, VBB = 6.0 V – 450 – mΩ

LOAD

= 1.5 A, VBB = 6.0 V – 700 – mΩ

LOAD

= 1.5 A, VBB = 4.5 V – 560 – mΩ

LOAD

= 1.5 A, VBB = 4.5 V – 870 – mΩ

LOAD

Soft Start Duration tss 0.625 1.25 1.875 ms

Logic Inputs and Outputs

ENBx Input Voltage

ENBx Input Hysteresis V

VIL – – 0.8 V

VIH 2.0 – – V

I(hys)

300 500 – mV

ENBx Input Current IIL VIH ≤ 5 V –1 – 1 μA

PORZ Output (Open Drain) V

PORZ Output Leakage Current I

PORZL

PORZH

I

PORZL

V

PORZ

= 1 mA, fault asserted – – 0.4 V

= 5 V, fault not asserted –1 – 1 μA

Continued on the next page…

Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

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