Maxim MAX16825, MAX16824 Datasheet

General Description

The MAX16824/MAX16825 three-channel LED drivers
operate over a 6.5V to 28V input voltage range. These
devices provide three open-drain constant-current-sink­ing outputs that are rated to 36V and deliver up to
150mA of current to each string of high-brightness LEDs
(HB LEDs). The current at each output is programmable
by means of an external current-sense resistor. The
MAX16824 features three PWM inputs that control the
duty cycle of the output current, allowing a wide LED
dimming range to be implemented. The PWM inputs
also function as on/off control for each corresponding
output. The MAX16825 offers a 2Mbps, 4-wire serial
interface, a 3-bit shift register, and a 3-bit transparent
latch. The serial interface allows a microcontroller to
configure the output channels using four inputs (DIN,
CLK, LE, OE) and a data output (DOUT). DOUT allows
multiple drivers to be cascaded and operated together.

The MAX16824/MAX16825’s on-board pass elements
minimize the need for external components, while at the
same time, providing ±5% LED current accuracy.
Additional features include a +5V (±5%) regulated output
with 4mA output current capability and thermal protection.

The MAX16824/MAX16825 are available in a thermally
enhanced 16-pin TSSOP-EP package and specified over
the -40°C to +85°C temperature range.

Applications

Industrial Lighting

Architectural and Decorative Lighting

Mood Lighting

Indoor and Outdoor LED Video Displays

Automotive Lighting

LCD Display Backlighting

Features

♦ 6.5V to 28V Operating Range

♦ Outputs Connected to 36V Supply for Long LED

Strings

♦ Three 36V-Rated Output Channels with

Independently Adjustable LED Current

♦ 150mA Output Current Per Channel

♦ ±5% LED Current Accuracy

♦ PWM Dimming

Three Independent Dimming Control Inputs
(MAX16824)
4-Wire Serial Interface LED Current Chopping
(MAX16825)

♦ +5V (±5%) Regulated Output with 4mA Source

Capability

♦ Fast Transient Dimming Response

♦ 200mV Current-Sense Reference Reduces Power

Loss

♦ Thermal Shutdown

♦ -40°C to +85°C Operating Temperature Range

♦ Thermally Enhanced, 16-Pin TSSOP Exposed

Paddle Package

MAX16824/MAX16825

High-Voltage, Three-Channel Linear

High-Brightness LED Drivers

________________________________________________________________

Maxim Integrated Products

1

19-1107; Rev 0; 11/07

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

OUT1

OUT3

OUT2

CS1

CS2

CS3

IN

1

16

3

7

8

9

4

11

12

2

15

13

PWM1

PWM2

PWM3

REG

GND

C

REG

C

IN

V

IN

UP TO 36V

R

CS2

R

CS1

R

CS3

MAX16824

Typical Operating Circuits

Ordering Information

+

Denotes a lead-free package.

*

EP = Exposed paddle.

Pin Configurations appear at end of data sheet.

PART TEMP RANGE

PIN
PACKAGE

MAX16824EUE+ -40°C to +85°C 16 TSSOP-EP* U16E-3

MAX16825EUE+ -40°C to +85°C 16 TSSOP-EP* U16E-3

PKG

CODE

V

IN

C

IN

3

IN

MAX16825

6

CLK

7

DIN

MICROCONTROLLER

8

LE

9

OE

4

C

REG

REG

11

GND

1

OUT1

16

OUT2

12

OUT3

2

CS1

15

CS2

13

CS3

UP TO 36V

R

CS1

R

CS2

R

CS3

MAX16824/MAX16825

High-Voltage, Three-Channel Linear
High-Brightness LED Drivers

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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 to GND ...............................................................-0.3V to +30V

OUT1, OUT2, OUT3 to GND ..................................-0.3V to +40V

CS1, CS2, CS3, REG to GND...................................-0.3V to +6V

PWM1, PWM2, PWM3 to GND .................................-0.3V to +6V

DIN, CLK, LE, OE, DOUT to GND ............................-0.3V to +6V

Maximum Current into Any Pin

(except OUT1, OUT2, OUT3) ........................................±20mA

Maximum Current into OUT1, OUT2, OUT3......................160mA

Continuous Power Dissipation (T

A

= +70°C)

16-Pin TSSOP-EP (derate 18.9mW/°C above +70°C)....1500mW

Operating Temperature Range ...........................-40°C to +85°C

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

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

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

ELECTRICAL CHARACTERISTICS

(VIN= 12V, C

REG

= 1µF to GND, I

REG

= 0, R

CS_

= 2Ω from CS_ to GND, TJ= TA= -40°C to +85°C, unless otherwise noted. Typical

values are at T

J

= TA= +25°C.) (Note 1)

Supply Voltage Range V

GND Current I

LED Current-Sense Accuracy
(Note 2)

Dropout Voltage (Note 3) ΔV

Output Current Slew Rate Current rising, V

Output Current Leakage I

CURRENT SENSE

Regulated CS_ Voltage V

OVERTEMPERATURE PROTECTION

Thermal Shutdown Temperature 165 °C

Thermal Shutdown Hysteresis 23 °C

+5V REGULATOR (REG)

Output Voltage V

REG Output Current I

REG Short-Circuit Current I

LOGIC INPUT (PWM1, PWM2, PWM3)

PWM_ Input Bias Current I

PWM_ Input-Voltage High V

PWM_ Input-Voltage Low V

PWM_ Turn-On Delay 50% of V

PWM_ Turn-Off Delay 50% of V

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

IN

I

GND

OUT1

10mA < I
0°C ≤ T

10mA < I

-40°C ≤ T

I

DO

LEAK

CS_

REGIREG

REG

REGSCVREG

PWM

IH

IL

OUT_

I

OUT_

PWM1 = PWM2 = PWM3 = 0V 1 µA

V

CS1

V

CS1

4.75V < V

V

PWM1

= I

= 100mA (current pulsed) 0.75 1.5

= 150mA (current pulsed) 1.2 2.25

= V

= V

= 0mA (Note 4) 4.75 5 5.25 V

= 0V (Note 5) 15 40 90 mA

OUT2

OUT_

≤ 85°C

J

OUT_

≤ 85°C

J

CS2

CS2

REG

= V

PWM_

PWM_

= I

OUT3

< 100mA,

< 100mA,

OUT

= V

CS3

= V

CS3

= V

PWM2

to 50% of ΔV

to 50% of ΔV

=100mA 5 10 mA

= 4V 100 mA/µs

, 0°C ≤ TJ ≤ +85°C 190 200 210

, -40°C ≤ TJ ≤ +85°C 186 200 214

= 5V 1 µA

PWM3

OUT_

OUT_

6.5 28.0 V

5

7

4mA

4V

0.6 V

475 ns

150 ns

%

V

mV

MAX16824/MAX16825

High-Voltage, Three-Channel Linear

High-Brightness LED Drivers

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VIN= 12V, C

REG

= 1µF to GND, I

REG

= 0, R

CS_

= 2Ω from CS_ to GND, TJ= TA= -40°C to +85°C, unless otherwise noted. Typical

values are at T

J

= TA= +25°C.) (Note 1)

OUTPUTS (OUT1, OUT2, OUT3)

Turn-On Time t

Turn-Off Time t

SPI INTERFACE (CLK, LE, OE, DIN, DOUT) (Figures 3 and 4)

DIN, CLK, LE, OE Input Bias
Current

DIN, CLK, LE, OE Input-Voltage
High

DIN, CLK, LE, OE Input-Voltage
Low

CLK Clock Period t

CLK Pulse-Width High t

CLK Pulse-Width Low t

DIN Setup Time t

DIN Hold Time t

DOUT Propagation Delay t

DOUT Rise/Fall Time tDR/t

DOUT Voltage High V

DOUT Voltage Low V

LE Pulse-Width High t

LE Setup Time t

LE Rising to OUT_ Rising Delay t

LE Rising to OUT_ Falling Delay t

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

R

F

V

IH

V

IL

CP

CH

CL

DS

DH

DO

DOH

DOL

LW

LS

LRR

LRF

PWM_ rising time, tR, is measured from 20%
to 80% of I

PWM_ falling time, tF, is measured from
80% to 20% of I

DIN = CLK = LE = OE = 0 or 5V 1 µA

50% of CLK rising to 50% of next CLK
rising, Figure 3

50% of CLK rising to 50% of CLK falling,
Figure 3

50% of CLK falling to 50% of CLK rising,
Figure 3

50% of DIN rising to 50% of CLK rising,
Figure 3

50% of CLK rising to 50% of DIN falling,
Figure 3

50% of CLK rising to 50% of DOUT rising/
falling, Figure 3

C

DOUT

DF

rising/falling edge (Note 6)

I

SOURCE

I

SINK

50% of LE rising to 50% of LE falling,
Figure 3

50% of CLK rising to 50% of LE rising,
Figure 3

50% of LE rising to 50% of OUT_ rising,
Figure 4

50% of LE rising to 50% of OUT_ falling,
Figure 4

OUT

OUT

= 10pF, 10% to 90% of DOUT

= 4mA 4.5 V

= 4mA 0.5 V

1µs

1µs

2.2 V

0.5 V

50 ns

24 ns

24 ns

5ns

10 ns

5ns

15 ns

20 ns

15 ns

150 ns

475 ns

MAX16824/MAX16825

High-Voltage, Three-Channel Linear
High-Brightness LED Drivers

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VIN= 12V, C

REG

= 1µF to GND, I

REG

= 0, R

CS_

= 2Ω from CS_ to GND, TJ= TA= -40°C to +85°C, unless otherwise noted. Typical

values are at T

J

= TA= +25°C.) (Note 1)

Note 1: All devices are 100% production tested at TJ= +25°C and TJ= +85°C. Limits to -40°C are guaranteed by design.
Note 2: This specification does not include sense resistor tolerance and ground error.
Note 3: Dropout is measured as follows: R

SC_

= 1.21Ω from CS_ to GND. Force 100mA into OUT_ and measure the dropout voltage

from OUT_ to CS_. DVDO = (ΔOUT_ - V

CS_

).

Note 4: OUT’s current regulation varies with load across REG (see the

Typical Operating Characteristics

).

Note 5: Overtemperature protection does not function if the output of the 5V reference (REG) is shorted to ground.
Note 6: Guaranteed by design, not production tested.

0

0.2

0.1

0.5

0.4

0.3

0.6

0.7

0.9

0.8

1.0

-40 -10 5-25 203550658095110125

DROPOUT VOLTAGE vs. TEMPERATURE

MAX16824toc01

TEMPERATURE (°C)

DROPOUT VOLTAGE (V)

I

LOAD

= 100mA

0.182

0.192

0.187

0.197

0.202

0.207

0604515 30 75 90 105 120 135 150

CS_ VOLTAGE vs. OUTPUT CURRENT

MAX16824 toc02

OUTPUT CURRENT (mA)

V

CS_

(V)

OUTPUT CURRENT vs. INPUT VOLTAGE

MAX16824 toc03

VIN (V)

OUTPUT CURRENT (mA)

262420 226 8 10 12 14 16 182 4

10

30

50

70

90

110

130

150

170

190

-10
028

I

LOAD

= 150mA

I

LOAD

= 100mA

Typical Operating Characteristics

(VIN= 12V, C

REG

= 1µF to GND, I

REG

= 0, R

CS_

= 2Ω from CS_ to GND, TA= +25°C, unless otherwise noted. Typical values are at

TA= +25°C.)

CLK Rising to OUT_ Rising Delay t

CLK Rising to OUT_ Falling Delay t

OE Rising to OUT_ Rising Delay t

OE Falling to OUT_ Falling Delay t

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

CRR

CRF

OEH

OEL

50% of CLK rising to 50% of OUT_ rising,
Figure 4

50% of CLK rising to 50% of OUT_ falling,
Figure 4

50% of OE rising to 50% of OUT_ rising,
Figure 3

50% of OE falling to 50% of OUT_ falling,
Figure 3

150 ns

475 ns

150 ns

475 ns

MAX16824/MAX16825

High-Voltage, Three-Channel Linear

High-Brightness LED Drivers

______________________________________________________________________________________________________________________________________________________________________________

5

Typical Operating Characteristics (continued)

(VIN= 12V, C

REG

= 1µF to GND, I

REG

= 0, R

CS_

= 2Ω from CS_ to GND, TA= +25°C, unless otherwise noted. Typical values are at

T

A

= +25°C.)

OUTPUT CURRENT vs. TEMPERATURE

200

180

160

140

120

100

80

60

OUTPUT CURRENT (mA)

40

20

0

-40 -10 5-25 203550658095110125

CS_ VOLTAGE vs. REG OUTPUT CURRENT

0.200

0.199

0.198

0.197

0.196

0.195

0.194

0.193

0.192

(V)

0.191

CS_

V

0.190

0.189

0.188

0.187

0.186

0.185

0.184

0.183

0.182
010

I

= 150mA

OUT

I

= 95mA

OUT

I

= 10mA

OUT

TEMPERATURE (°C)

I

LOAD

I

LOAD

I

(mA)

REG

= 100mA

= 150mA

986 72 3 4 51

MAX16824toc04

MAX16824 toc07

(V)

V

3.45

3.25

3.05

2.85

2.65

SUPPLY CURRENT (mA)

2.45

2.25

-40 125

OUTPUT VOLTAGE vs. INPUT VOLTAGE

5.000

4.995

4.990

4.985

4.980

REG

4.975

4.970

4.965

4.960
028

SUPPLY CURRENT

vs. TEMPERATURE

VIN = 28V

VIN = 6.5V

V

= V

PWM

PWM

TEMPERATURE (°C)

I

= 0

REG

I

= 1mA

REG

I

= 4mA

REG

VIN (V)

OUTPUT VOLTAGE vs. TEMPERATURE

5.10

5.08

MAX16824 toc05

5.06

5.04

5.02

(V)

5.00

REG

V

4.98
I

= 4mA

LOAD

4.96

4.94

= V

= 0

PWM

1109580655035205-10-25

4.92

4.90

TEMPERATURE (°C)

LED CURRENT FALL TIME

MAX16824 toc08

24204 8 12 16

I

LOAD

I

= 1mA

LOAD

I

LED

V

IN

PULSED AT 200Hz
(50% DUTY CYCLE)

2μs/div

= 0

= 150mA

= 12V

MAX16824 toc09

1109580655035205-10-25-40 125

MAX16824 toc06

V

PWM_

2V/div

0V

I

OUT_

100mA/div

0A

LED CURRENT RISE TIME

I

= 150mA

LED

= 12V

V

IN

PULSED AT 200Hz
(50% DUTY CYCLE)

2μs/div

MAX16824 toc10

V

PWM_

2V/div

0V

I

OUT_

100mA/div

0A

330Hz DIMMED OPERATION

20μs/div

MAX16824 toc11

I

= 150mA

LOAD

= 12V

V

IN

PWM_ PULSED
AT 330Hz
(1% DUTY CYCLE)

V

PWM_

2V/div

0V

I

OUT_

100mA/div

0A

MAX16824/MAX16825

High-Voltage, Three-Channel Linear
High-Brightness LED Drivers

6 _______________________________________________________________________________________

Pin Description

PIN

MAX16824 MAX16825

1 1 OUT1

2 2 CS1

3 3 IN Positive Input Supply. Bypass with a 0.1µF (min) capacitor to GND.

4 4 REG +5V-Regulated Output. Connect a 1µF capacitor from REG to GND.

5, 6, 10, 14 5, 14 N.C. No Connection. Must be left unconnected.

7 — PWM1

8 — PWM2

9 — PWM3

11 11 GND Ground

12 12 OUT3

13 13 CS3

15 15 CS2

16 16 OUT2

—7DIN

NAME FUNCTION

Channel 1 LED Driver Output. OUT1 is an open-drain, constant-current-sinking output
rated to 36V.

Channel 1 Sense Amplifier Negative Input. Connect a current-sense resistor between
CS1 and GND to program the output current level for channel 1.

Dimming Input 1. PWM1 is a dimming input for channel 1. A logic-low turns off OUT1 and
a logic-high turns on OUT1.

Dimming Input 2. PWM2 is a dimming input for channel 2. A logic-low turns off OUT2 and
a logic-high turns on OUT2.

Dimming Input 3. PWM3 is a dimming input for channel 3. A logic-low turns off OUT3 and
a logic-high turns on OUT3.

Channel 3 LED Driver Output. OUT3 is an open-drain, constant-current-sinking output
rated to 36V.

Channel 3 Sense Amplifier Negative Input. Connect a current-sense resistor between
CS3 and GND to program the output current level for channel 3.

Channel 2 Sense Amplifier Negative Input. Connect a current-sense resistor between
CS2 and GND to program the output current level for channel 2.

Channel 2 LED Driver Output. OUT2 is an open-drain, constant-current-sinking output
rated to 36V.

Serial-Data Input. Data is loaded into the internal 3-bit shift register on the rising edge of
CLK.

Latch-Enable Input. Data loaded transparently from the internal shift register to the

—8LE

—9OE

—10DOUT

— 6 CLK Clock Input

——EP

output latch while LE is high. Data is latched into the output latch on the LE’s falling edge
and retained while LE is low.

Output Enable Input. Drive OE high to place all outputs into a high-impedance mode
without altering the contents of the output latches. Drive OE low to force all outputs to
follow the state of the output latches.

Serial-Data Output. Data is clocked out of the internal 3-bit shift register to DOUT on the
rising edge of CLK. DOUT is a replica of the shift register’s last bit.

Exposed Paddle. Connect EP to a large-area ground plane for effective power
dissipation. Do not use as the IC ground connection.

Detailed Description

The MAX16824/MAX16825 are three-channel LED dri­vers that operate from a 6.5V to 28V input voltage
range. These devices provide three independent open­drain, constant-current-sinking outputs rated to 36V
and deliver up to 150mA of current to each HB LED
string. The current in each channel is programmable
using an external current-sense resistor in series with
each internal power MOSFET’s source. The MAX16824
features three separate PWM inputs that allow a wide
range of independent dimming level at each of the
three outputs. The PWM inputs also function as on/off
control inputs for each corresponding output (Figure 1).

The MAX16825 includes a 2Mbps, 4-wire serial inter­face to control the state of each output (Figure 2).

The 4-wire serial interface comprises a 3-bit shift regis­ter and a 3-bit transparent latch. The shift register is
updated using a clock input CLK and a data input DIN.
DOUT is the last bit of the shift register. This feature
allows multiple drivers to be cascaded and operated
together. The latch is transparent from the shift register
outputs to the LED output when LE is high while it latch­es the shift register state on the falling edge of LE. The
output-enable input OE allows simultaneous enabling
or disabling of all three outputs.

MAX16824/MAX16825

High-Voltage, Three-Channel Linear

High-Brightness LED Drivers

_______________________________________________________________________________________ 7

REG

Figure 1. Internal Block Diagram (MAX16824)

OUT1

THERMAL

SHUTDOWN

200mV

CS1

OUT2

CS2

OUT3

IN

BANDGAP AND
5V REGULATOR

PWM1

PWM

PWM2

PWM3

CONTROL AND

LOGIC

GND

CS3

MAX16824

MAX16824/MAX16825

High-Voltage, Three-Channel Linear
High-Brightness LED Drivers

8 _______________________________________________________________________________________

Figure 2. Internal Block Diagram (MAX16825)

IN

BANDGAP AND

5V REGULATOR

REG

THERMAL

SHUTDOWN

DIN

CLK

OUT1

200mV

CS1

OUT2

CS2

OUT3

CS3

DOUT

OE

SHIFT

REGISTER

LE

LATCH

SHIFT

REGISTER

LATCH

LOGIC

SHIFT

REGISTER

LATCH

MAX16825

GND

On-board pass elements minimize the need for external
components while providing ±5% LED current accura­cy. Additional features include a +5V (±5%) regulated
output with 4mA output current capability and thermal
protection.

The MAX16824/MAX16825 use a feedback loop to lin­early control the current at each output. The voltage
across each sense resistor is regulated to 200mV by
the internal feedback loop. The output current is set by
selecting the value of RCS.

+5V Regulator (REG)

The MAX16824/MAX16825 include a fixed +5V output
regulator that delivers up to 4mA of load current for
auxiliary low power applications throughout the 6.5V to
28V input voltage range. Connect a 1µF compensation
capacitor from REG to ground.

Thermal Protection

The MAX16824/MAX16825 enter a thermal shutdown
mode in the event of overheating. When the junction
temperature exceeds T

J

= +165°C, the internal thermal
protection circuit turns off the series pass elements.
The MAX16824/MAX16825 recover from thermal shut­down mode when the junction temperature drops by
23°C. The thermal protection does not operate if the
regulator (REG) is in a short-circuit condition.

4-Wire Serial Interface (MAX16825)

The MAX16825 features a 4-wire serial interface (DIN,
CLK, LE, OE) and a data output (DOUT) that allows the
use of a microcontroller to write brightness data to the
MAX16825. The serial-interface data word length is 3
bits (D0, D1, D2). The functions of the interface inputs
are as follows: DIN is the serial-data input, which must
be stable when it is sampled by the MAX16825 on the
rising edge of CLK. Data shifts in with the MSB first.
This means that data bit D2 is clocked in first, followed
by 2 more data bits (D1 and finishing with the LSB D0).
CLK is the serial-clock input, which shifts data at DIN
into the MAX16825’s 3-bit shift register on the rising
edge. LE is the latch-enable input that allows the trans­fer of data from the MAX16825’s 3-bit shift register to its
3-bit latch when LE is high (transparent latch) and
latches the data on the falling edge of LE (Figure 4).

Output enable (OE) provides simultaneous control of
the output drivers. Driving OE high places outputs
OUT1, OUT2, and OUT3 into a high-impedance mode
without altering the contents of the output latches.
Driving OE low allows outputs OUT1, OUT2, and OUT3
to follow the state of the output latches.

OE is independent of the operation of the serial inter­face. Data can be shifted into the serial-interface shift
register and latched regardless of the state of OE.
DOUT is the serial-data output that shifts data out from
the MAX16825’s 3-bit shift register on the rising edge of
CLK. Data at DIN propagates through the shift register
and appears at DOUT three clock cycles later.

Applications Information

Programming the LED Current

The MAX16824/MAX16825 use sense resistors to set the
output current in each channel. To set the LED current
for a particular channel, connect a sense resistor across
the corresponding current-sense input (CS_) and GND.
For better performance, connect the low side of the cur­rent-sense resistors to the IC’s ground terminal and the
high side to the CS_ terminal with short traces. The value
of the sense resistor for a given desired current is calcu­lated with the following equation:

where V

CS_

is 200mV and I

OUT_

is I

LED

(see the

Electrical Characteristics

table).

Input Voltage Considerations

For proper operation, the minimum input voltage must
always be:

where V

CS_

is the voltage drop across the sense resis-

tor RCS_, V

FT(MAX)

is the total forward voltage of all
series connected LEDs and ΔVDOis the maximum
dropout voltage of the regulator. The minimum operat­ing voltage of the device is 6.5V. If the device is operat­ed below 6.5V, the output current may not meet the full
regulation specification (see the

Typical Operating

Characteristics

).

Pulse-Width Dimming (MAX16824)

The MAX16824 includes pulsed-width current dimming
inputs (PWM_) to control the LED brightness. An appli­cation of up to 5kHz signal or less is recommended at
PWM_ input for proper operation. PWM_ also functions
as an active-high enable input for each output channel.
A logic-low at PWM_ turns off OUT_ and a logic-high
turns on OUT_.

MAX16824/MAX16825

High-Voltage, Three-Channel Linear

High-Brightness LED Drivers

_______________________________________________________________________________________ 9

VV

()

CS

R

()

Ω=

CS

_

VVV V

IN MIN CS FT MAX DO() _ ( )

≥+ +Δ

_

IA

()

OUT

_

MAX16824/MAX16825

Pulse-Width Dimming (MAX16825)

The MAX16825 provides three methods of pulsed-width
current dimming.

One method of pulse dimming the output channels is to
drive OE low while latching a different set of three bits

data. Holding OE low allows the output channels to fol­low the state of the output latches. The duty cycle
depends on LE’s frequency. All output channels are
affected at the same time.

High-Voltage, Three-Channel Linear
High-Brightness LED Drivers

10 ______________________________________________________________________________________

Figure 3. 4-Wire Serial-Interface Timing Diagram

LE

t

CH

50%

CLK

DIN

50%

t

DH

t

DS

DO

DOUT

50%

50%

50%

t

t

CL

50%

D1

t

CP

t

DO

50%

LS

50%

D2

t

LW

DO

50%

t

OUT_

OE

50%

OEW

t

OEL

t

F

80%

20%

50%

t

OEH

t

R

MAX16824/MAX16825

High-Voltage, Three-Channel Linear

High-Brightness LED Drivers

______________________________________________________________________________________ 11

OUT_

Figure 4. LE and CLK to OUT_ Timing

50%

LE

t

LRF

50%

50%

LE

t

LRR

50%

OUT_

CLK

OUT_

CLK

OUT_

50%

50%

t

CRF

50%

t

CRR

50%

MAX16824/MAX16825

Another method of pulse dimming the outputs is to hold
LE high and drive OE with a PWM signal. Because the
input bits are always latched, the serial input constantly
refreshes the register. The control bits must be carefully
selected to dim the outputs properly.

A third method is to hold both LE and OE in the
enabled state. This allows the data bits to directly con­trol the output channels, and hence, pulse dim the out­put current. Make sure that the clock frequency does
not exceed the maximum rate at which the device can
change the state of the output channels.

Power Dissipation

The power dissipation (PD) of the MAX16824/
MAX16825 is determined from the following equation:

where:

V

IN

= supply voltage

V

INL

= supply Voltage to the LED strings

I

IN

= supply current

V

LED_

= total forward voltage for one LED string

I

LED_

= LED current

VCS= 200mV drop across R

CS_

DUTY = PWM_ duty cycle

The worst-case power dissipation occurs when the
drop across each internal MOSFET is at its maximum
with all three channels delivering the maximum allow­able output current. The maximum drop across the
internal MOSFETs is determined by:

V

INL

- V

LED_

- V

CS_

when V

LED_

is at its minimum.

Higher ambient temperature increases the thermal stress
even further due to the reduction in voltage drop across
the LEDs. The MAX16824/MAX16825 thermal specifica­tions are given according to the JEDEC-51 guidelines.
Good mechanical/thermal design practices must be
applied to help maintain the device junction temperature
below the absolute maximum ratings at all times.

Chip Information

PROCESS: BiCMOS-DMOS

High-Voltage, Three-Channel Linear
High-Brightness LED Drivers

12 ______________________________________________________________________________________

P V I V V V I DUTY

=×+ − − × ×

()( )( )

D IN IN INL LED CS LED

V V V I DUTY

+− − × ×

()()

INL LED CS LED

V V V I DUTY

+− − × ×

()()

INL LED CS LED

22 2

33 3

11 1

2

3

1

MAX16824/MAX16825

High-Voltage, Three-Channel Linear

High-Brightness LED Drivers

______________________________________________________________________________________ 13

Pin Configurations

TOP VIEW

OUT1

CS1

REG

N.C.

N.C.

PWM1

PWM2

IN

+

1

2

3

4

5

6

7

8

MAX16824

TSSOP-EP

TOP VIEW

CS1

REG

N.C.

CLK

DIN

+

1

2

IN

3

MAX16825

4

5

6

7

LE

8

16

OUT2

15

CS2

14

N.C.

13

CS3

12

OUT3

GND

11

10

DOUT

9

OE

16

OUT2

15

CS2

14

N.C.

13

CS3

12

OUT3

GND

11

10

N.C.

9

PWM3

OUT1

TSSOP-EP

MAX16824/MAX16825

High-Voltage, Three-Channel Linear
High-Brightness LED Drivers

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.

14

____________________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.

Boblet

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

.)

AA AA

TSSOP 4.4mm BODY.EPS