Rainbow Electronics MAX16820 User Manual

General Description

The MAX16819/MAX16820, step-down constant-current
high-brightness LED (HB LED) drivers provide a cost­effective solution for automotive interior/exterior lighting,
architectural and ambient lighting, LED bulbs such as
MR16 and other LED illumination applications.

The MAX16819/MAX16820 operate from a 4.5V to 28V
input voltage range and feature a 5V/10mA on-board
regulator. A high-side current-sense resistor adjusts the
output current and a dedicated PWM input (DIM)
enables a wide range of pulsed dimming.

The MAX16819/MAX16820 are well suited for applica­tions requiring a wide input voltage range. The high-side
current-sensing and an integrated current-setting circuit­ry minimize the number of external components while
delivering an LED current with ±5% accuracy. A hys­teretic control algorithm ensures excellent input-supply
rejection and fast response during load transients and
PWM dimming. The MAX16819 features a 30% inductor
current ripple and the MAX16820 features a 10% current
ripple. These devices operate up to 2MHz switching fre­quency, thus allowing for small component size.

The MAX16819/MAX16820 operate over the -40°C to
+125°C automotive temperature range and are avail­able in 3mm x 3mm x 0.8mm, 6-pin TDFN packages.

Applications

Architectural, Industrial, and Ambient Lighting

Automotive RCL, DRL, and Fog Lights

MR16 and Other LED Bulbs

Indicators and Emergency Lighting

Features

o High-Side Current Sense
o Dedicated Dimming Control Input
o 20kHz Maximum Dimming Efficiency
o Hysteretic Control: No Compensation
o Up to 2MHz Switching Frequency
o ±5% LED Current Accuracy
o Adjustable Constant LED Current
o 4.5V to 28V Input Voltage Range
o Over 25W Output Power
o 5V, 10mA On-Board Regulator
o -40°C to +125°C Operating Temperature Range

Note: All devices are specified over the -40°C to +125°C oper­ating temperature range.

+

Denotes lead-free package.

*

EP = Exposed paddle.

MAX16819/MAX16820

2MHz High-Brightness LED Drivers with

High-Side Current Sense and 5000:1 Dimming

________________________________________________________________

Maxim Integrated Products

1

Pin Configuration

Ordering Information

MAX16819
MAX16820

IN

CSN

DIM

V

CC

C

IN

DRV

GND

C

VCC

V

IN

LR

SENSE

Typical Operating Circuit

19-0706; Rev 1; 3/07

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

PART PIN-PACKAGE PKG CODE

MAX16819ATT+T 6 TDFN–EP* T633-2 +ATB

MAX16820ATT+T 6 TDFN-EP* T633-2 +ATC

TOP

MARK

TOP VIEW

CC

DRV

V

654

MAX16819
MAX16820

+

1

23

IN

CSN

TDFN

GND

DIM

MAX16819/MAX16820

2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VIN= 12V, V

DIM

= VIN, C

VCC

= 1µF, R

SENSE

= 0.5Ω, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at

T

A

= +25°C.) (Note 1)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

IN, CSN, DIM to GND .............................................-0.3V to +30V

V

CC

, DRV to GND ....................................................-0.3V to +6V

CSN to IN...............................................................-0.3V to +0.3V

Maximum Current into Any Pin

(except IN, V

CC

, and DRV)............................................±20mA

Continuous Power Dissipation (T

A

= +70°C)

6-Pin TDFN (derate 18.17mW/

oC*

above +70°C).......1454mW

Operating Temperature Range .........................-40°C to +125°C

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

Pin-to-Pin ESD Ratings (HB Model).....................................2.5kV

*As per JEDEC51 Standard (Single-Layer Board).

Input Voltage Range V

Maximum Current Regulator
Switching Frequency

Ground Current I

Supply Current I

Undervoltage Lockout UVLO

Undervoltage Lockout Hysteresis 0.5 V

SENSE COMPARATOR

Sense Voltage Threshold High V

Sense Voltage Threshold Low V

Propagation Delay to Output
High

Propagation Delay to Output Low t

Current-Sense Input Current I

Current-Sense Threshold
Hysteresis

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

IN

f

SW

GND

IN

DRV open 1.5 mA

V

< 0.6V 425 µA

DIM

VIN = V
V

DRV

V

IN

V

DRV

(VIN - V

= V

CSN

> VCC - 0.5V

= V

= V

CSN

< 0.5V

) rising from 0V until V

CSN

0.5V (MAX16820)

SNSHI

(VIN - V

) rising from 0V until V

CSN

0.5V (MAX16819)

SNSLO

t

DPDH

DPDL

CSN

CS

HYS

(VIN - V
(V

CC

(VIN - V
(V

CC

Falling edge of (VIN - V
0V to DRV high, C

Rising edge of (VIN - V

0.26V to DRV low, C

(VIN - V

MAX16819 56 70 mV

MAX16820 17 35 mV

) falling from 0.26V until V

CSN

- 0.5V) (MAX16820)

) falling from 0.26V until V

CSN

- 0.5V) (MAX16819)

) = 200mV 1 µA

CSN

4.5 28.0 V

2 MHz

, VIN rising from 4V until

DIM

, VIN falling from 6V,

DIM

) from 0.26V to

CSN

= 1nF

DRV

) from 0V to

CSN

= 1nF

DRV

DRV

DRV

<

<

DRV

DRV

195 210 225

213 230 246

>

176 190 204

>

158 170 182

4.7 5.0

4.5

82 ns

82 ns

V

mV

mV

MAX16819/MAX16820

2MHz High-Brightness LED Drivers with

High-Side Current Sense and 5000:1 Dimming

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VIN= 12V, V

DIM

= VIN, C

VCC

= 1µF, R

SENSE

= 0.5Ω, TA= TJ= -40°C to +125°C, unless otherwise noted. Typical values are at

T

A

= +25°C.) (Note 1)

Note 1: All devices are 100% production tested at T

J

= +25°C and +125°C. Limits to -40°C are guaranteed by design.

GATE DRIVER

Gate Driver Source Current V

Gate Driver Sink Current V

Gate Driver Output-Voltage High V

Gate Driver Output-Voltage Low V

DIM INPUT

Maximum DIM Frequency f

DIM Input-Voltage High V

DIM Input-Voltage Low V

DIM Hysteresis DIM

DIM Turn-On Time t

DIM Turn-Off Time t

DIM Input Leakage High V

DIM Input Leakage Low V

VCC REGULATOR

Regulator Output Voltage V

Load Regulation I

Line Regulation VIN = 6V to 28V, I

Power-Supply Rejection Ratio PSRR VIN = 12V, I

Current Limit I

Regulator Startup Time t

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

= VIN, V

OH

OL

DIM

IH

IL

HYS

DIMON

DIMOFF

CC

LIM

STRAT

CSN

= VIN - 250mV, V

CSN

I

= 10mA VCC - 0.5 V

DRV

I

= -10mA 0.5 V

DRV

V

= VIN, increase DIM until V

CSN

- 0.5V)

(V

CC

V

= VIN, decrease DIM until

CSN

< 0.5V

V

DRV

DIM rising edge to V
C

DRV

DIM falling edge to V
C

DRV

= V

DIM

= 0V -1 +1 µA

DIM

I

= 0.1mA to 10mA, VIN = 5.5V to 28V 4.5 5.5 V

VCC

I

= 0.1mA to 10mA, VIN = 4.5V to 28V 4.0 5.5 V

VCC

= 0.1mA to 10mA, VIN = 12V 4 Ω

VCC

VIN = 4.5V, VCC = 0V 45 mA

VIN = 4.5V, VCC = 4V 18 mA

VCC = 0 to 4.5V 350 µs

= 1nF

= 1nF

IN

DRV

VCC

= 5mA, fIN = 10kHz -35 dB

VCC

= 0.5 x V

DRV

CC

= 0.5 x V

CC

0.5 A

1A

20 kHz

>

DRV

2.8 V

0.6 V

200 mV

= 0.5 x VCC,

DRV

= 0.5 x VCC,

DRV

100 ns

100 ns

10 µA

= 10mA 11 mV

MAX16819/MAX16820

2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming

4 _______________________________________________________________________________________

Typical Operating Characteristics

(VIN= V

DIM

= 12V, C

VCC

= 1µF, R

SENSE

= 0.5Ω connected between IN and CSN. Typical values at TA= +25°C, unless otherwise

noted.)

EFFICIENCY vs. V

IN

MAX16819 toc01

VIN (V)

EFFICIENCY (%)

252010 15

65

70

75

80

90

85

95

100

60

530

LED 5

LED 4

L = 47µH

DRV SWITCHING FREQUENCY

vs. V

IN

MAX16819 toc02

VIN (V)

DRV SWITCHING FREQUENCY (kHz)

242016128

100

200

300

400

600
500

700

800

900

1000

1100

1200

1300

1400

1500

0

428

L = 47µH

LED 5

LED 4

LED 3

LED 1

LED 2

LED CURRENT VARIATION vs. V

IN

MAX16819 toc03

VIN (V)

LED CURRENT VARIATION FROM SET CURRENT (%)

252010 15

-1.5

-1.0

-0.5

0

1.0

0.5

1.5

2.0

-2.0
530

LED 5

LED 4

LED 3

LED 2

LED 1

I

LED(NOMINAL)

= 400mA

L = 47µH

VCC vs. V

IN

MAX16819 toc04

VIN (V)

V

CC

(V)

25.022.517.5 20.0

10.0

12.5 15.07.5

4.6

4.7

4.8

4.9

5.0

5.1

5.2

5.3

5.4

5.5

4.5

5.0 27.5

I

LED

= 0

VCC vs. TEMPERATURE

MAX16819 toc05

TEMPERATURE (°C)

V

CC

(V)

1109565 80-10 5 20 35 50-25

5.31

5.32

5.33

5.34

5.35

5.36

5.37

5.38

5.39

5.40

5.30

-40 125

VIN = 24V

VIN = 12V

V

DIM

= 0V

SUPPLY CURRENT vs. V

IN

MAX16819 toc06

VIN (V)

SUPPLY CURRENT (µA)

24.5

12.5

20.516.58.5

50

100

150

200

250

300

0

4.5 28.5

V

DIM

= 0V

PWM DIMMING AT 200Hz

(10% DUTY CYCLE)

MAX16819 toc07

1ms/div

V

DIM

2V/div

0V

0A

I

LED

200mA/div

V

IN

= 12V, L = 47µH,

1 LED MAX16819

PWM DIMMING AT 200Hz

(90% DUTY CYCLE)

MAX16819 toc08

1ms/div

V

DIM

2V/div

0V

0A

I

LED

200mA/div

V

IN

= 12V, L = 47µH,

1 LED MAX16819

MAX16819/MAX16820

PWM DIMMING AT 20kHz

(10% DUTY CYCLE)

MAX16819 toc12

10µs/div

V

DIM

2V/div

0V

0A

I

LED

200mA/div

V

IN

= 24V, L = 47µH,

4 LEDS MAX16820

PWM DIMMING AT 20kHz

(90% DUTY CYCLE)

MAX16819 toc13

10µs/div

V

DIM

2V/div

0V

0A

I

LED

200mA/div

V

IN

= 24V, L = 33µH,

4 LEDS MAX16820

2MHz High-Brightness LED Drivers with

High-Side Current Sense and 5000:1 Dimming

_______________________________________________________________________________________

5

Typical Operating Characteristics (continued)

(VIN= V

DIM

= 12V, C

VCC

= 1µF, R

SENSE

= 0.5Ω connected between IN and CSN. Typical values at TA= +25°C, unless otherwise

noted.)

PWM DIMMING AT 200Hz

(1% DUTY CYCLE)

V
1 LED MAX16819

10µs/div

MAX16819 toc09

= 12V, L = 47µH,

IN

V

DIM

2V/div

0V

I

LED

200mA/div

0A

PWM DIMMING EXPANDED

(50% DUTY CYCLE)

V

= 24V, L = 33µH,

IN

4 LEDS MAX16820

1µs/div

MAX16819 toc10

V

DIM

2V/div

0V

I

LED

200mA/div

0A

2.0

1.5

1.0

0.5

-0.5

-1.0

-1.5

LED CURRENT VARIATION FROM SET CURRENT (%)

-2.0

PWM DIMMING EXPANDED

(50% DUTY CYCLE)

V
1 LED MAX16819

4µs/div

I

VARIATION vs. TEMPERATURE

LED

I

LED(NOMINAL)

L = 47µH

V

= 24V

IN

0

V

= 12V

IN

-40 125
TEMPERATURE (°C)

MAX16819 toc11

= 12V, L = 47µH,

IN

= 400mA

V

DIM

= 0V

11095-25 -10 5 35 50 6520 80

V

DIM

2V/div

0V

I

LED

200mA/div

0A

MAX16819 toc14

MAX16819/MAX16820

2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming

6 _______________________________________________________________________________________

Pin Description

Functional Diagram

Detailed Description

The MAX16819/MAX16820 are step-down, constant­current, high-brightness LED (HB LED) drivers. These
devices operate from a 4.5V to 28V input voltage range
and provide up to 0.5A of source and 1A of sink drive
capability to the gate of an external MOSFET. A high­side current-sense resistor sets the output current and

a dedicated PWM dimming input (DIM) allows for a
wide range of independent pulsed dimming.

The high-side current-sensing scheme and on-board
current-setting circuitry minimize the number of exter­nal components while delivering LED current with a
±5% accuracy, using a 1% sense resistor. See the

Functional Diagram

.

PIN NAME FUNCTION

1 IN Positive Supply Voltage Input. Bypass with a 1µF or higher value capacitor to GND.

2 CSN Current-Sense Input

3 DIM

4 GND Ground

5 DRV Gate Drive Output. Connect to the gate of an external n-channel MOSFET.

6VCCVoltage Regulator Output. Connect a 1µF capacitor from VCC to GND.

EP —

Logic-Level Dimming Input. Drive DIM low to turn off the current regulator. Drive DIM high to enable
the current regulator.

Exposed Paddle. Connect to a large-area ground plane for improved power dissipation. Do not use
as the only ground connection for the device.

CSN

DIM

IN

BANDGAP

REF

DIM

BUFFER

REGULATOR

COMPARATOR

1.23V

COMPARATOR

-

+

CS

GATE

DRIVER

+

-

UVLO

MAX16819
MAX16820

V

CC

DRV

GND

Undervoltage Lockout (UVLO)

The MAX16819/MAX16820 include a 4.5V undervoltage
lockout (UVLO) with 500mV hysteresis. When VINfalls
below 4.5V, DRV goes low, turning off the external n-chan­nel MOSFET. DRV goes high once V

IN

is 5V or higher.

5V Regulator

VCCis the output of a 5V regulator capable of sourcing
10mA. Bypass VCCto GND with a 1µF capacitor.

DIM Input

The MAX16819/MAX16820 allow dimming with a PWM
signal at the DIM input. A logic level below 0.6V at DIM
forces the MAX16819/MAX16820’s DRV output low,
turning off the LED current. To turn the LED current on,
the logic level at DIM must be at least 2.8V.

Applications Information

Selecting R

SENSE

to Set the LED Current

The MAX16819/MAX16820 feature a programmable LED
current using a resistor connected between IN and CSN.
Use the following equation to calculate the sense resistor:

For the values of V

SNSHI

and V

SNSLO,

see the

Electrical

Characteristics

.

Current Regulator Operation

The MAX16819/MAX16820 regulate the LED output
current using an input comparator with hysteresis
(Figure 1). As the current through the inductor ramps
up and the voltage across the sense resistor reaches
the upper threshold, the voltage at DRV goes low, turn­ing off the external MOSFET. The MOSFET turns on
again when the inductor current ramps down through
the freewheeling diode until the voltage across the
sense resistor equals the lower threshold. Use the fol­lowing equation to determine the operating frequency:

where n = number of LEDs, V

LED

= forward voltage

drop of one LED, and ∆V = (V

SNSHI

- V

SNSLO

).

For proper component selection, please use the design
tool available at: http://www.maxim-ic.com/MAX16819­20-Tool.

f

VnV nV R

VVL

SW

IN LED LED SENSE

IN

=

−×

()

×× ×

××∆

R

VVV

IA

SENSE

SNSHI SNSLO

LED

Ω

()

=

+

()()

()

1
2

MAX16819/MAX16820

2MHz High-Brightness LED Drivers with

High-Side Current Sense and 5000:1 Dimming

_______________________________________________________________________________________ 7

Figure 1. Current Regulator Operation

HYSTERETIC MODE

I

LED

AVG. LED
CURRENT

V

DIM

1

T

=

SW

f

SW

∆I

t

t

MAX16819/MAX16820

MOSFET Selection

The MAX16819/MAX16820’s gate driver is capable of
sourcing 0.5A and sinking 1A of current. MOSFET selec­tion is based on the maximum input operating voltage
V

IN

, output current I

LED

, and operating switching fre­quency. Choose a MOSFET that has a higher break­down voltage than the maximum operation voltage, low
R

DS(ON)

, and low total charge for better efficiency.
MOSFET threshold voltage must be adequate if operat­ed at the low end of the input-voltage operating range.

Freewheeling Diode Selection

The forward voltage of the freewheeling diode should
be as low as possible for better efficiency. A Schottky
diode is a good choice as long as the breakdown volt­age is high enough to withstand the maximum operat­ing voltage.

The forward current rating of the diode must be at least
equal to the maximum LED current.

LED Current Ripple

The LED current ripple is equal to the inductor current
ripple. In cases when a lower LED current ripple is
needed, a capacitor can be placed across the LED ter­minals.

PCB Layout Guidelines

Careful PCB layout is critical to achieve low switching
losses and stable operation. Use a multilayer board
whenever possible for better noise immunity. Minimize
ground noise by connecting high-current ground
returns, the input bypass-capacitor ground lead, and
the output-filter ground lead to a single point (star
ground configuration). In normal operation, there are
two power loops. One is formed when the MOSFET is
on and the high current flows through IN—R

SENSE

—
LEDs—Inductor—MOSFET—GND. The other loop is
formed when the MOSFET is off when the high current
circulates through R

SENSE

—LEDs—Inductor—free­wheeling diode. To minimize noise interaction, each
loop area should be as small as possible.

Place R

SENSE

as close as possible to the input filter
and IN. For better noise immunity, a Kelvin connection
is strongly recommended between CSN and R

SENSE

.
Connect the exposed paddle to a large-area ground
plane for improved power dissipation.

2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming

8 _______________________________________________________________________________________

Chip Information

PROCESS: BiCMOS

MAX16819/MAX16820

2MHz High-Brightness LED Drivers with

High-Side Current Sense and 5000:1 Dimming

_______________________________________________________________________________________ 9

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages

.)

6, 8, &10L, DFN THIN.EPS

PACKAGE OUTLINE, 6,8,10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm

21-0137

1

H

2

MAX16819/MAX16820

2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

10

____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages

.)

Revision History

Pages changed at Rev 1: 1, 4, 10

COMMON DIMENSIONS

SYMBOL

MIN. MAX.
A 0.70 0.80
D 2.90 3.10
E 2.90 3.10

0.00 0.05

A1
L 0.20 0.40

0.25 MIN.k

A2 0.20 REF.

PACKAGE VARIATIONS
PKG. CODE N D2 E2 e JEDEC SPEC b [(N/2)-1] x e

T633-2 6 1.50±0.10 2.30±0.10

1.50±0.10
T833-2 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF
T833-3 8 1.50±0.10 2.30±0.10 0.65 BSC MO229 / WEEC 0.30±0.05 1.95 REF

1.50±0.10

1.50±0.1010T1033-2

2.30±0.101.50±0.106T633-1 0.95 BSC MO229 / WEEA 1.90 REF0.40±0.05

0.40±0.05 1.90 REF

2.30±0.10

0.95 BSC MO229 / WEEA
MO229 / WEEC

MO229 / WEED-3

0.50 BSC

0.40 BSC - - - - 0.20±0.05 2.40 REFT1433-2 14 2.30±0.101.70±0.10

MO229 / WEED-3

1.95 REF0.30±0.050.65 BSC2.30±0.108T833-1

2.00 REF0.25±0.050.50 BSC2.30±0.1010T1033-1

2.00 REF0.25±0.05

2.40 REF0.20±0.05- - - - 0.40 BSC1.70±0.10 2.30±0.1014T1433-1

PACKAGE OUTLINE, 6,8,10 & 14L,

-DRAWING NOT TO SCALE-

TDFN, EXPOSED PAD, 3x3x0.80 mm

21-0137

2

H

2