a8501klptr-b Allegro MicroSystems, Inc., a8501klptr-b Datasheet

a8501klptr-b

Manufacturer Part Number

a8501klptr-b

Description

2 Mhz, 4 Channel?100 Ma Wled/rgb Driver With Output Disconnect

Manufacturer

Allegro MicroSystems, Inc.

Datasheet

1.A8501KLPTR-B.pdf (24 pages)

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Price

Company:

H&T Electronics

Part Number:

A8501KLPTR-B

Quantity:

18 000

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Features and Benefits

▪ 600 kHz to 2.2 MHz switching frequency—ability to

▪ Internal bias supply for single-supply operation (V

▪ Boost converter with integrated 40 V DMOS switch and

▪ 3.5 μA shutdown current—limits battery drain

▪ Active current sharing between LED strings for

▪ Drive up to 9 series LEDs in 4 parallel strings, 36 LEDs

▪ LED sinks rated for 100 mA each (400 mA total)

▪ PWM dimming with LED PWM duty cycle control

▪ 4000:1 dimming range

▪ Extensive fault mode protection schemes:

Package:

8501-DS, Rev.1

operate above the AM band

OVP–load-dump protection

0.8% current matching and 0.7% accuracy

maximum (V

▫ Shorted LED protection against misconnected loads—

▫ Open LED disconnect protects against LED failures

▫ External thermistor sensing to limit LED temperature

▫ Output overvoltage protection (OVP): 19.5 V default can

▫ Open Schottky and open OVP resistor protection against

▫ Input under- and overvoltage protection (UVLO and

▫ Boost current limit, output short circuit limit,

with true output disconnect

be adjusted as high as 38 V

external component failure

OVLO) against V

overtemperature protection (OTP), and soft start

Figure 1. LCD monitor backlight driving

4 LED strings. On/off and dimming

control using ENABLE pin.

• Current = 50 mA per string

• OVP = 35 V nominal

• Switching frequency = 2 MHz

Not to scale

= 3.5 V, I

variation

= 100 mA)

Optional Configuration

for Thermal Derating

RVC

NTC

2 MHz, 4 Channel×100 mA WLED/RGB Driver

–t°

VTO

A8501

VTI

exposed thermal pad

8 to 21 V

28-pin TSSOP with

(package LP)

BAT

CBIAS

0.1 μF

10 V

CBAT

4.7 μF

35 V

CCOMP

1 μF

10 V

RISET

24.3 kΩ

Typical Application

= 8 to 21 V)

CIN

COMP

DIM

BIAS

SEL2

SEL1

VTO

VTI

ISET

AGND PGND

VIN

Description

The A8501 is a multioutput WLED/RGB driver for backlighting

medium-size displays. The A8501 integrates a boost converter

and four 100 mA current sinks. LED channels can be tied

together for up to 400 mA sink capability. It can work from

a single power supply of 8 to 21 V and withstand up to 40 V.

The boost converter is a constant frequency, current-mode

converter.

Operating frequency can be set to 2 MHz in order to avoid

interference with the AM radio band. The integrated boost

DMOS switch is rated for 40 V at 3.6 A. PWM dimming allows

LED currents to be controlled at up to a 1000:1 ratio. Additional

4:1 dimming can be achieved by using the DIM pin.

The A8501 provides protection against output connector shorts

through an integrated output disconnect switch. An optional

external thermistor can be used to limit LED current based on

panel temperature.

The device is supplied in a surface mount, 28-pin TSSOP

package (suffix LP), with exposed thermal pad for enhanced

thermal dissipation. It is lead (Pb) free, with a leadframe

plating choice of 100% matte-tin (suffix T) or tin-bismuth

(suffix B).

Applications include:

▪ GPS navigation systems

▪ Automotive infotainment

▪ Back-up camera displays

▪ Cluster backlighting

▪ Portable DVD players

▪ Industrial LCD displays

10 μH

PGND

A8501

PAD

PGND

ROVP

78.7 kΩ

with Output Disconnect

LGND

OVP CAP

DGND

FSET

LED1

LED2

LED3

LED4

OUT

RFSET

25.5 kΩ

COUT

4.7 μF

50 V

A8501

Related parts for a8501klptr-b

a8501klptr-b Summary of contents

Page 1

MHz, 4 Channel×100 mA WLED/RGB Driver Features and Benefits ▪ 600 kHz to 2.2 MHz switching frequency—ability to operate above the AM band ▪ Internal bias supply for single-supply operation (V ▪ Boost converter with integrated 40 V DMOS ...

Page 2

... Selection Guide Operating Part Number Temperature A8501ELPTR-T –40°C to 85°C A8501GLPTR-T –40°C to 105°C A8501KLPTR-B –40°C to 125°C A8501KLPTR-T –40°C to 125°C Absolute Maximum Ratings* Characteristic SW, OVP, CAP, OUT Pins LED1 through LED4 Pins VIN Pin ...

Page 3

... OVP Fault Reference References 1.23 V Minimum + Select – PGND PGND LGND DGND with Output Disconnect OVP CAP Charge Pump OUT Current Sinks LED1 LED2 LED3 LED4 ÷4 100 kΩ PAD DIM Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 3 ...

Page 4

... Function to I current gain When DIM = V SET LEDx ISET < 1.23 V. Tie directly to VTO pin to disable this feature. This pin can TI with Output Disconnect , A = 960 and when DIM 240. IL ISET IH , ISET Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 4 ...

Page 5

... Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com Max. Unit 21 V 6 μA 10 μ 0.4 V – μA 1 μ 217 μ ...

Page 6

... I . LED1 LED4 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com = 12.4 kΩ, ISET Max. Unit 12.8 μ Ω 1.33 V 2.4 MHz 1.285 MHz 0.8 MHz ...

Page 7

... AGND, LGND, PGND, and DGND xGND DGND ISET, VTO, and VTI VTI VTO 12 V ISET DGND SEL1, SEL2, and EN EN SEL2 SEL1 DGND Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 ...

Page 8

... PWM Duty Cycle (Startup) V PWM V OUT I OUT I BAT t Symbol Parameter Units/Division C1 V PWM C2 V OUT C3 I 500 mA OUT C4 I 500 mA BAT t time 100 ms with Output Disconnect = 200 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 8 ...

Page 9

... OUT . COMP pin is help low BIAS starts charging slowly (C COMP Symbol Parameter Units/Division time Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 10 V BAT I 500 mA BAT 20 V OUT 500 mA OUT BAT 20 V ...

Page 10

... PWM Duty Cycle (%) × 960 x PWM Duty cycle) . ISET Efficiency versus PWM Duty Cycle PWM Duty Cycle (%) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 80 90 100 PWM 100 Hz 200 100 10 ...

Page 11

... OUT LED1 C4 I 500 mA OUT t time 100 μs Symbol Parameter Units/Division BAT OUT LED1 C4 I 500 mA OUT t time 100 μs Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 11 ...

Page 12

... MHz, 4 Channel×100 mA WLED/RGB Driver Performance Characteristics ISET Characterization LED Current versus R ISET (kΩ) ISET LED Current versus 0.01 0.02 0.03 0.04 0.05 0.06 1 kΩ) ISET ISET with Output Disconnect ISET 0.07 0.08 0.09 0.10 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 12 ...

Page 13

... OVP, these are now cleared and the part is ready to be re-enabled. F. User re-enables operation. A8501 enters soft start mode. is still at ground G. Soft start mode finished. OUT with Output Disconnect Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 13 ...

Page 14

... OUT t time 1 μs Symbol Parameter Units/Division OUT CAP OUT t time 2 μs Symbol Parameter Units/Division C1 I 200 mA OUT OUT t time 20 μs Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 14 ...

Page 15

... PWM signals. Soft start behavior on evaluation All channels boards is shown in the Performance Characteristics section. with Output Disconnect . Refer to the LED LEDSC the set current until all the enabled 20 reaches OUT Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 15 ...

Page 16

... The A8501 has overvoltage pro- falls and current through the OUT D1 V BATT A8501 ROVP – Latch + 1.23 V OVP 18 V – + 1.23 V Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com V OUT COUT 16 ...

Page 17

... V, or falls below TI until the voltage reaches 1. shown by the red- VTO 1.23 V 2.46 V ÷2 VTI Minimum + Select –t° – ISET Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com for more than falls TI varying LEDX ( kΩ. ISET TI will ...

Page 18

... V ( versus V LED –40°C A 100 0.2 0.4 0.6 0 with Output Disconnect V Decreasing TI V Increasing TI 1 1.2 1.4 V Decreasing TI V Increasing TI 1 1.2 1.4 V Decreasing TI V Increasing TI 1 1.2 1.4 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 18 ...

Page 19

... MLCC. Increase the boost capacitor if noise exists at 0.25 V. with Output Disconnect (1 – FPWMmin 0.25 f PWM = 165 μ output and then select OUT 165 μA (1 – 0. μF 200 0.25 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com (5) 19 ...

Page 20

... D(max) = 1– (8 × 0.9) / 28.91 = 75% . (max) = D(max 0. × 375 ns . (min) × η (max) × OUT OUT BAT (max) = [28.91 × (0.080 × 3 × 0.9) = 963 mA. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com (7) ( OVPH . (9) (10) (max) (11) (12) ...

Page 21

... V LEDx + (I (av) +0.75 × V LEDx LEDx × quantity of remaining enabled LED strings), is the regulation voltage of the LEDx pins, 0.75 V LEDx (av) is 0.8 V. This assumes LEDx voltage: Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com (22) 1/2 ], (23) . OUT and OUT (max) BAT (24) ...

Page 22

... Schottky d (max) × (1–D) × BAT 2 × ( /12 × × I SWDISC(on) ODS(on) OUT = 2 × SWDISC(on) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com (29 (30) (31) (32 ODS(on) 22 ...

Page 23

... DIM FSET A8501 BIAS NC PAD SEL2 SEL1 VTO LED1 LED2 VTI LED3 LED4 ISET AGND PGND PGND PGND LGND DGND Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com COUT 4.7 μ RFSET 25.5 kΩ COUT 4.7 μ RFSET 25.5 kΩ 23 ...

Page 24

... The in for ma tion in clud ed herein is believed rate and reliable. How ev er, Allegro MicroSystems, Inc. assumes no re spon si bil i ty for its use; nor for any in fringe ment of patents or other rights of third parties which may result from its use. ...

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