MAXIM MAX16819ATT+T

19-0706; Rev 0; 12/06
2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming
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
Features
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
♦
High-Side Current Sense
Dedicated Dimming Control Input
20kHz Maximum Dimming Efficiency
Hysteretic Control: No Compensation
Up to 2MHz Switching Frequency
±5% LED Current Accuracy
Adjustable Constant LED Current
4.5V to 28V Input Voltage Range
Over 25W Output Power
5V, 10mA On-Board Regulator
-40°C to +125°C Operating Temperature Range
Ordering Information
PART
PIN-PACKAGE
PKG CODE
TOP
MARK
MAX16819ATT+T
6 TDFN–EP*
T633-2
+ATB
MAX16820ATT+T
6 TDFN-EP*
T633-2
+ATC
Note: All devices are specified over the -40°C to +125°C operating temperature range.
+Denotes lead-free package.
*EP = Exposed paddle.
Automotive RCL, DRL, and Fog Lights
MR16 and Other LED Bulbs
Typical Operating Circuit
Indicators and Emergency Lighting
VIN
RSENSE
Pin Configuration
VCC
DRV
GND
TOP VIEW
6
5
4
L
CIN
CVCC
MAX16819
MAX16820
CSN
+
MAX16819
MAX16820
DRV
3
DIM
2
CSN
IN
1
VCC
IN
DIM
GND
TDFN
________________________________________________________________ Maxim Integrated Products
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.
1
MAX16819/MAX16820
General Description
MAX16819/MAX16820
2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming
ABSOLUTE MAXIMUM RATINGS
IN, CSN, DIM to GND .............................................-0.3V to +30V
VCC, DRV to GND ....................................................-0.3V to +6V
CSN to IN...............................................................-0.3V to +0.3V
Maximum Current into Any Pin
(except IN, VCC, and DRV)............................................±20mA
Continuous Power Dissipation (TA = +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).
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.
ELECTRICAL CHARACTERISTICS
(VIN = 12V, VDIM = VIN, CVCC = 1µF, RSENSE = 0.5Ω, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at
TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
Input Voltage Range
VIN
Maximum Current Regulator
Switching Frequency
fSW
Ground Current
IGND
Supply Current
IIN
Undervoltage Lockout
UVLO
CONDITIONS
MIN
TYP
MAX
UNITS
28.0
V
2
MHz
DRV open
1.5
mA
VDIM < 0.6V
425
µA
4.5
VIN = VCSN = VDIM, VIN rising from 4V until
VDRV > VCC - 0.5V
4.7
5.0
V
VIN = VCSN = VDIM, VIN falling from 6V,
VDRV < 0.5V
4.5
Undervoltage Lockout Hysteresis
0.5
V
SENSE COMPARATOR
Sense Voltage Threshold High
Sense Voltage Threshold Low
VSNSHI
VSNSLO
(VIN - VCSN) rising from 0V until VDRV <
0.5V (MAX16820)
195
210
225
(VIN - VCSN) rising from 0V until VDRV <
0.5V (MAX16819)
213
230
246
(VIN - VCSN) falling from 0.26V until VDRV >
(VCC - 0.5V) (MAX16820)
176
190
204
(VIN - VCSN) falling from 0.26V until VDRV >
(VCC - 0.5V) (MAX16819)
158
170
182
mV
mV
Propagation Delay to Output
High
tDPDH
Falling edge of (VIN - VCSN) from 0.26V to
0V to DRV high, CDRV = 1nF
82
ns
Propagation Delay to Output Low
tDPDL
Rising edge of (VIN - VCSN) from 0V to
0.26V to DRV low, CDRV = 1nF
82
ns
Current-Sense Input Current
ICSN
(VIN - VCSN) = 200mV
Current-Sense Threshold
Hysteresis
2
CSHYS
1
µA
MAX16819
56
70
mV
MAX16820
17
35
mV
_______________________________________________________________________________________
2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming
(VIN = 12V, VDIM = VIN, CVCC = 1µF, RSENSE = 0.5Ω, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at
TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
GATE DRIVER
Gate Driver Source Current
VCSN = VIN, VDRV = 0.5 x VCC
Gate Driver Sink Current
VCSN = VIN - 250mV, VDRV = 0.5 x VCC
Gate Driver Output-Voltage High
VOH
IDRV = 10mA
Gate Driver Output-Voltage Low
VOL
IDRV = -10mA
0.5
A
1
A
VCC - 0.5
V
0.5
V
20
kHz
DIM INPUT
Maximum DIM Frequency
fDIM
DIM Input-Voltage High
VIH
VCSN = VIN, increase DIM until VDRV >
(VCC - 0.5V)
DIM Input-Voltage Low
VIL
VCSN = VIN, decrease DIM until
VDRV < 0.5V
DIM Hysteresis
DIMHYS
DIM Turn-On Time
tDIMON
DIM Turn-Off Time
tDIMOFF
2.8
V
0.6
V
200
mV
DIM rising edge to VDRV = 0.5 x VCC,
CDRV = 1nF
100
ns
DIM falling edge to VDRV = 0.5 x VCC,
CDRV = 1nF
100
ns
DIM Input Leakage High
VDIM = VIN
10
µA
DIM Input Leakage Low
VDIM = 0V
-1
+1
µA
IVCC = 0.1mA to 10mA, VIN = 5.5V to 28V
4.5
5.5
V
IVCC = 0.1mA to 10mA, VIN = 4.5V to 28V
4.0
5.5
VCC REGULATOR
Regulator Output Voltage
VCC
Load Regulation
Line Regulation
Power-Supply Rejection Ratio
Current Limit
PSRR
ILIM
Regulator Startup Time
tSTRAT
V
4
Ω
VIN = 6V to 28V, IVCC = 10mA
11
mV
VIN = 12V, IVCC = 5mA, fIN = 10kHz
-35
dB
VIN = 4.5V, VCC = 0V
45
mA
VIN = 4.5V, VCC = 4V
18
mA
VCC = 0 to 4.5V
350
µs
IVCC = 0.1mA to 10mA, VIN = 12V
Note 1: All devices are 100% production tested at TJ = +25°C and +125°C. Limits to -40°C are guaranteed by design.
_______________________________________________________________________________________
3
MAX16819/MAX16820
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VIN = VDIM = 12V, CVCC = 1µF, RSENSE = 0.5Ω connected between IN and CSN. Typical values at TA = +25°C, unless otherwise
noted.)
DRV SWITCHING FREQUENCY
vs. VIN
LED 3
80
LED 2
70
65
LED 1
60
5
10
15
20
LED 1
L = 47µH
30
25
4
VIN (V)
8
12
16
20
24
ILED(NOMINAL) = 400mA
L = 47µH
1.5
1.0
LED 1
LED 2
0.5
0
-0.5
-1.0
-1.5
LED 4
LED 3
VCC vs. VIN
28
5
10
15
MAX16819 toc04
5.40
5.3
5.38
5.37
5.1
5.36
VCC (V)
5.2
5.0
5.34
4.8
5.33
4.7
5.32
VIN = 12V
4.5
300
250
200
150
100
50
5.31
ILED = 0
VDIM = 0V
5.30
5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5 25.0 27.5
-40 -25 -10 5 20 35 50 65 80 95 110 125
VIN (V)
TEMPERATURE (°C)
PWM DIMMING AT 200Hz
(10% DUTY CYCLE)
VDIM = 0V
0
4.5
8.5
12.5
16.5
MAX16819 toc07
24.5
MAX16819 toc08
VIN = 12V, L = 47µH,
1 LED MAX16819
VDIM
2V/div
VDIM
2V/div
0V
0V
ILED
200mA/div
ILED
200mA/div
0A
4
20.5
VIN (V)
PWM DIMMING AT 200Hz
(90% DUTY CYCLE)
VIN = 12V, L = 47µH,
1 LED MAX16819
1ms/div
30
25
SUPPLY CURRENT vs. VIN
5.35
4.9
4.6
VIN = 24V
5.39
20
VIN (V)
VCC vs. TEMPERATURE
5.4
LED 5
-2.0
VIN (V)
5.5
MAX16819 toc03
2.0
MAX16819 toc06
75
LED 2
SUPPLY CURRENT (µA)
85
LED 3
MAX16819 toc05
EFFICIENCY (%)
90
LED 5
LED 4
LED CURRENT VARIATION vs. VIN
LED CURRENT VARIATION FROM SET CURRENT (%)
L = 47µH
LED 4
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
MAX16819 toc02
LED 5
95
DRV SWITCHING FREQUENCY (kHz)
100
MAX16819 toc01
EFFICIENCY vs. VIN
VCC (V)
MAX16819/MAX16820
2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming
0A
1ms/div
_______________________________________________________________________________________
28.5
2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming
PWM DIMMING AT 200Hz
(1% DUTY CYCLE)
PWM DIMMING EXPANDED
(50% DUTY CYCLE)
MAX16819 toc09
VIN = 12V, L = 47µH,
1 LED MAX16819
MAX16819 toc11
VIN = 24V, L = 33µH,
4 LEDS MAX16820
VIN = 12V, L = 47µH,
1 LED MAX16819
VDIM
2V/div
VDIM
2V/div
VDIM
2V/div
0V
0V
0V
ILED
200mA/div
ILED
200mA/div
ILED
200mA/div
0A
0A
0A
10µs/div
1µs/div
PWM DIMMING AT 20kHz
(10% DUTY CYCLE)
PWM DIMMING AT 20kHz
(90% DUTY CYCLE)
4µs/div
VDIM
2V/div
VDIM
2V/div
0V
0V
ILED
200mA/div
ILED
200mA/div
0A
0A
10µs/div
2.0
ILED(NOMINAL) = 400mA
L = 47µH
1.5
1.0
MAX16819 toc14
VIN = 24V, L = 33µH,
4 LEDS MAX16820
VIN = 24V, L = 47µH,
4 LEDS MAX16820
LED CURRENT VARIATION FROM SET CURRENT (%)
ILED VARIATION vs. TEMPERATURE
MAX16819 toc13
MAX16819 toc12
10µs/div
PWM DIMMING EXPANDED
(50% DUTY CYCLE)
MAX16819 toc10
VIN = 24V
0.5
0
-0.5
-1.0
VIN = 12V
-1.5
VDIM = 0V
-2.0
-40 -25 -10 5 20 35 50 65 80 95 110 125
TEMPERATURE (°C)
_______________________________________________________________________________________
5
MAX16819/MAX16820
Typical Operating Characteristics (continued)
(VIN = VDIM = 12V, CVCC = 1µF, RSENSE = 0.5Ω connected between IN and CSN. Typical values at TA = +25°C, unless otherwise
noted.)
2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming
MAX16819/MAX16820
Pin Description
PIN
NAME
1
IN
FUNCTION
2
CSN
Current-Sense Input
3
DIM
Logic-Level Dimming Input. Drive DIM low to turn off the current regulator. Drive DIM high to enable
the current regulator.
4
GND
Ground
5
DRV
Gate Drive Output. Connect to the gate of an external n-channel MOSFET.
6
VCC
Voltage Regulator Output. Connect a 1µF capacitor from VCC to GND.
EP
—
Positive Supply Voltage Input. Bypass with a 1µF or higher value capacitor to GND.
Exposed Paddle. Connect to a large-area ground plane for improved power dissipation. Do not use
as the only ground connection for the device.
Functional Diagram
REGULATOR
IN
VCC
+
CS
COMPARATOR
CSN
GATE
DRIVER
1.23V
BANDGAP
REF
DRV
+
-
UVLO
COMPARATOR
GND
DIM
DIM
BUFFER
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
6
MAX16819
MAX16820
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.
_______________________________________________________________________________________
2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming
5V Regulator
VCC is the output of a 5V regulator capable of sourcing
10mA. Bypass VCC to 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 RSENSE 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:
RSENSE (Ω) =
1 (VSNSHI + VSNSLO )(V )
2
ILED (A )
For the values of VSNSHI and VSNSLO, 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:
fSW =
(VIN − n × VLED ) × n × VLED × RSENSE
VIN × ∆V × L
where n = number of LEDs, VLED = forward voltage
drop of one LED, and ∆V = (VSNSHI - VSNSLO).
For proper component selection, please use the design
tool available at: http://www.maxim-ic.com/MAX1681920-Tool.
HYSTERETIC MODE
TSW = 1
fSW
ILED
∆I
AVG. LED
CURRENT
t
VDIM
t
Figure 1. Current Regulator Operation
_______________________________________________________________________________________
7
MAX16819/MAX16820
Undervoltage Lockout (UVLO)
The MAX16819/MAX16820 include a 4.5V undervoltage
lockout (UVLO) with 500mV hysteresis. When VIN falls
below 4.5V, DRV goes low, turning off the external n-channel MOSFET. DRV goes high once VIN is 5V or higher.
MAX16819/MAX16820
2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming
MOSFET Selection
PCB Layout Guidelines
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
VIN, output current ILED, 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.
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—RSENSE—
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 RSENSE as close as possible to the input filter
and IN. For better noise immunity, a Kelvin connection
is strongly recommended between CSN and RSENSE.
Connect the exposed paddle to a large-area ground
plane for improved power dissipation.
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.
8
Chip Information
PROCESS: BiCMOS
_______________________________________________________________________________________
2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming
6, 8, &10L, DFN THIN.EPS
PACKAGE OUTLINE, 6,8,10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm
21-0137
H
1
2
_______________________________________________________________________________________
9
MAX16819/MAX16820
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.)
MAX16819/MAX16820
2MHz High-Brightness LED Drivers with
High-Side Current Sense and 5000:1 Dimming
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.)
COMMON DIMENSIONS
PACKAGE VARIATIONS
SYMBOL
MIN.
MAX.
PKG. CODE
N
D2
E2
e
JEDEC SPEC
b
A
0.70
0.80
T633-1
6
1.50±0.10
2.30±0.10
0.95 BSC
MO229 / WEEA
0.40±0.05
1.90 REF
D
2.90
3.10
T633-2
6
1.50±0.10
2.30±0.10
0.95 BSC
MO229 / WEEA
0.40±0.05
1.90 REF
[(N/2)-1] x e
E
2.90
3.10
T833-1
8
1.50±0.10
2.30±0.10
0.65 BSC
MO229 / WEEC
0.30±0.05
1.95 REF
A1
0.00
0.05
T833-2
8
1.50±0.10
2.30±0.10
0.65 BSC
MO229 / WEEC
0.30±0.05
1.95 REF
L
0.20
0.40
T833-3
8
1.50±0.10
2.30±0.10
0.65 BSC
MO229 / WEEC
0.30±0.05
1.95 REF
2.30±0.10
0.50 BSC
MO229 / WEED-3
0.25±0.05
2.00 REF
2.00 REF
k
0.25 MIN.
T1033-1
10
1.50±0.10
A2
0.20 REF.
T1033-2
10
1.50±0.10
2.30±0.10
0.50 BSC
MO229 / WEED-3
0.25±0.05
T1433-1
14
1.70±0.10
2.30±0.10
0.40 BSC
----
0.20±0.05
2.40 REF
T1433-2
14
1.70±0.10
2.30±0.10
0.40 BSC
----
0.20±0.05
2.40 REF
PACKAGE OUTLINE, 6,8,10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm
-DRAWING NOT TO SCALE-
21-0137
H
2
2
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.
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© 2006 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.