MAX16823EVKIT+ - Maxim Integrated Products, Inc.

General Description

The MAX16823 evaluation kit (EV kit) circuit demon-

strates a current-controlled LED driver that uses the

MAX16823 current regulator. The EV kit is configured to

supply 50mA to each of the three output channels and

the circuit features 3 series LEDs per channel. Output

pads are provided at two channels to evaluate external

LEDs rated up to 70mA. Additional output pads are

available to evaluate LEDs rated up to 550mA (typ) on

one of the channels. The MAX16823 EV kit requires a

6.5V to 16V, 1A power supply for proper operation.

However, the MAX16823 IC can accept input voltages

from 5.5V to 40V.

The MAX16823 EV kit features pulse-width modulation

(PWM) dimming-control inputs and an open LED detec-

tion output. The MAX16823 EV kit is a fully assembled

and tested printed circuit board (PCB).

Features

o6.5V to 16V Supply Voltage Range

oOpen LED Detection Output

oOn-Board or External LED Connections

o50mA Load Current

oConfigurable 550mA Output Current at OUT_3

oSeparate PWM Dimming Control for Each Channel

oFully Assembled and Tested

Evaluates: MAX16823

MAX16823 Evaluation Kit

________________________________________________________________

Maxim Integrated Products

19-0772; Rev 0; 3/07

Component List

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.

Ordering Information

Component Suppliers

Denotes a lead-free and RoHS-compliant EV kit.

This limited temperature range applies to the EV kit PCB only.

The MAX16823 IC temperature range is -40°C to +125°C.

†

EP = Exposed paddle.

PART TEMP RANGE IC PACKAGE

MAX16823EVKIT+ 0°C to +70°C* 16 TQFN-EP†

SUPPLIER PHONE WEBSITE

Fairchild

Semiconductor 888-522-5372 www.fairchildsemi.com

IRC/TT Electronics 361-992-7900 www.irctt.com

M ur ata M fg . C o., Ltd . 770-436-1300 www.murata.com

OSRAM Opto

Semiconductors 888-446-7726 www.osram-os.com

Note: Indicate that you are using the MAX16823 when contact-

ing these component suppliers.

Quick Start

Recommended Equipment

•16V adjustable, 1A power supply

•Two digital voltmeters

Procedure

The MAX16823 EV kit is fully assembled and tested.

Follow the steps below to verify operation. Caution: Do

not turn on the power supply until all connections

are completed.

1) Connect the power supply’s positive terminal to the

IN PCB pad on the EV kit. Connect the power sup-

ply’s ground terminal to the GND PC pad located

directly above the IN pad.

DESIGNATION QTY DESCRIPTION

C1 0 N ot i nstal l ed , cer am i c cap aci tor ( 1206)

C2, C3 2

0.1µF ±10%, 50V X7R ceramic

capacitors (0603)

Murata GRM188R71H104K

C4 1

0.015µF ±10%, 50V X7R ceramic

capacitor (0603)

Murata GRM188R71H153K

D1–D9 9 Red LEDs (4-PLCC)

OSRAM LR E6SF-AABB-1-1

JU1–JU4 4 3-pin headers

JU5, JU6, JU7 3 2-pin headers

Q1 1 80V, 3A npn transistor (D-PAK)

Fairchild Semiconductor MJD31CTF

R1 0 Not installed, resistor (0805)

R2, R3, R4 3 4.02Ω ±1% resistors (0805)

R5 1

0.4Ω ± 1%, 500m W sense resi stor ( 1206)

IRC/TT Electronics LRC-LRF-

1206LF-01-R400-F

R6 1 10kΩ ±5% resistor (0603)

R7 1 0Ω ±5% resistor (1206)

TP1 1 PC mini red test point

U1 1 MAX16823ATE+ (16-pin TQFN,

5mm x 5mm x 0.8mm)

— 7 Shunts (JU1–JU7)

— 1 PCB: MAX16823 Evaluation Kit+

2) Connect a digital voltmeter across the IN and GND

pads and the other voltmeter across the LEDGOOD

and GND pads.

3) Verify that shunts are installed across pins 1-2 of

jumpers JU1, JU2, and JU3 (LEDs at full intensity).

4) Verify that a shunt is installed across pins 2-3 of

jumper JU4 (on-board LEDs selected at OUT3),

and that a shunt is not installed on jumper JU5

(LEDs current set to 50mA).

5) Verify that the shunts are installed on jumpers JU6

and JU7 (on-board LEDs selected at OUT1 and

OUT2).

6) Turn on the power supply and increase the input

voltage to 12V. The LEDs should illuminate with full

brightness.

7) Verify that the voltmeter at LEDGOOD measures

approximately 3.4V.

Detailed Description

The MAX16823 EV kit demonstrates the MAX16823 IC

LED driver. The MAX16823 outputs (OUT1, OUT2, and

OUT3) are configured to supply 50mA to the on-board

LEDs. The MAX16823 EV kit operates over the input-

voltage range of 6.5V to 16V and requires a 1A power

supply. The MAX16823 IC can operate from 5.5V to

40V. Refer to the MAX16823 data sheet for proper con-

figuration.

The MAX16823 EV kit outputs are current controlled by

monitoring the voltage across the respective output’s

external low-side sense resistors (R2, R3, and R4). The EV

kit features 3 series-connected LEDs at each channels’

output. All outputs provide pads to evaluate external

LEDs by bypassing the on-board LEDs after configur-

ing the appropriate jumpers. Two of the outputs can be

used to evaluate LEDs with current rated up to 70mA. A

third output (OUT_3) provides 550mA (typ) to the exter-

nal user-supplied LEDs using transistor Q1 and cur-

rent-sense resistor R5.

The MAX16823 EV kit features PC pads to control the

PWM dimming function of each output channel. The

MAX16823 EV kit also features a PCB pad to monitor

the status of the LEDGOOD output, which is pulled up

to REG by resistors R6 and R7.

Typically, capacitor C1 is not required if the power sup-

ply is relatively close to the EV kit. If long wires are

used to connect the power supply to the EV kit, sur-

face-mount 1206 PC pads are provided for adding

additional bulk capacitance at C1.

Output Current Setting

The output current for the on-board LEDs is set to

50mA (typ) with resistors R2, R3, or R4.

Use the following equation to adjust the respective

channel’s output current at OUT1, OUT2, OUT3, or

OUT_3:

where R_ is the external current-sense resistor at CS1,

CS2, CS3, or CS_3, and ILED is the desired output cur-

rent in milliamperes.

The output current for the LEDs, with the exception of

external LEDs at OUT_3, can be adjusted to a maxi-

mum 70mA by replacing the respective resistor.

When a shunt is installed across pins 1-2 of jumper

JU4, and a shunt is installed at jumper JU5, the output

current for the external LEDs at OUT_3 is set to 550mA

(typ) by the parallel resistors combination R2 and R5,

connected at CS_3.

PWM Dimming

The MAX16823 EV kit features PWM input PCB pads

(DIM1, DIM2, and DIM3) that can be used to control

LED brightness at each output using external logic sig-

nals. Jumpers JU1, JU2, and JU3 control the on and off

condition of the EV kit LEDs. Install shunts across pins

1-2 to turn on the LEDs current. Install shunts across

pins 2-3 to turn off the LEDs’ current. See Table 1 for

PWM configuration.

To operate the MAX16823 EV kit in PWM operation,

remove the shunts at jumpers JU1, JU2, or JU3 for indi-

vidual PWM control of the respective channels.

Connect digital PWM signals at the DIM1, DIM2, and

DIM3 pads with a 2.8V to VIN logic level and square-

wave frequencies from DC to 3kHz. Vary the duty cycle

to adjust the LED brightness. LED brightness increases

when the duty cycle increases and vice versa. When

the PWM signal duty cycle at DIM_ is 100%, the LEDs

are fully on.

R_=203mV typ

ILED

()

Table 1. PWM Configuration (JU1, JU2,

and JU3)

Evaluates: MAX16823

MAX16823 Evaluation Kit

2 _______________________________________________________________________________________

SHUNT

POSITION

DIM1, DIM2, DIM3

PINS

EV KIT

FUNCTION

1-2 REG LEDs on

2-3 GND LEDs off

Not installed Driven by external

source PWM operation

LEDGOOD Output

The MAX16823 EV kit features an output pad (LEDGOOD)

to monitor the LEDGOOD output logic signal. LEDGOOD

is low when one or more LEDs are open, or when a sig-

nal at any of the DIM inputs remains low for a period

greater than the programmed LEDGOOD delay time.

LEDGOOD output goes low after the programmed

delay period has elapsed. The EV kit delay time is pro-

grammed to 4ms (min) using C4. Refer to the

MAX16823 IC data sheet

LEDGOOD

section for setting

the LEDGOOD delay time. To adjust the minimum

LEDGOOD delay time, use the following equation:

where C4 is in farads and tdelay is in seconds.

When shunts are not installed at jumpers JU4, JU6, or

JU7, LEDGOOD is low.

Evaluating External LEDs

at OUT1 and OUT2

The MAX16823 EV kit can be used to evaluate external

LEDs rated up to 70mA at OUT1 and OUT2. Jumpers

JU6 and JU7 configure the EV kit for on-board or exter-

nal LED operation at outputs OUT1 and OUT2. Install

shunts at jumpers JU6 and JU7 to evaluate the EV kit’s

on-board LEDs. To evaluate external LEDs at OUT1,

remove the shunt at JU7. When connecting the external

LEDs at OUT1, connect the anode of the first LED at

OUT1 and the cathode of the last LED at CS1. To eval-

uate external LEDs at OUT2, remove the shunt at

jumper JU6. When connecting the external LEDs at

OUT2, connect the anode of the first LED at OUT2 and

the cathode of the last LED at CS2. See Table 2 for

jumpers JU6 and JU7 configurations.

Evaluating Higher Current LEDs at OUT_3

The MAX16823 EV kit OUT_3 PCB pad can be used to

evaluate LEDs rated for 550mA (typ). A single BJT (Q1)

and resistor R5 provide increased output current capa-

bilities for external LEDs connected at OUT_3.

Jumpers JU4 and JU5 configure OUT_3 for external

LED operation. Jumper JU4 selects on-board or exter-

nal LED operation, while jumper JU5 selects the current

setting for the external LEDs.

To operate the MAX16823 EV kit with the on-board

LEDs, install a shunt across pins 2-3 of jumper JU4,

and remove the shunt from jumper JU5 to set the on-

board LEDs’ (D1, D2, and D3) current to 50mA by

resistor R2.

To operate the MAX16823 EV kit OUT_3 with external

LEDs, install a shunt across pins 1-2 of jumper JU4.

Install a shunt at jumper JU5 to set the external LEDs to

the 550mA (typ) current setting using the parallel resis-

tor combination of R2 and R5. When connecting the

external LEDs at OUT_3, connect the anode of the first

LED to the OUT_3 PCB pad, and the cathode of the last

LED at CS_3. See Tables 3 and 4 for on-board and

external LEDs and current-setting configurations.

For proper operation when using higher current external

LEDs at OUT_3, the minimum input voltage must be:

VIN(MIN) = 1.2V + VFT(MAX) + ΔVDO

where 1.2V is the maximum collector-emitter saturation

voltage for the npn transistor Q1, VFT(MAX) is the total

forward voltage of all series-connected LEDs at OUT_3,

and ΔVDO is the MAX16823 dropout voltage from IN to

OUT_.

CtDELAY

4257 900

=,()Ω

Evaluates: MAX16823

MAX16823 Evaluation Kit

_______________________________________________________________________________________ 3

Table 2. OUT1 and OUT2 LED Operation

(JU6 and JU7)

SHUNT POSITION EV KIT FUNCTION

Installed On-board LED operation

Uninstalled* External LED operation

LEDGOOD is low when the shunts are removed and external

LEDs are not connected at OUT1 and OUT2.

Table 3. OUT_3 LED Operation (JU4)

SHUNT

POSITION OUT3 PIN EV KIT FUNCTION

1-2 Connects to Q1 External LED operation at

OUT_3

2-3* Connects to D1 On-board LED operation

Uninstalled* Open LEDGOOD = low

LEDGOOD is low when a shunt is installed at pins 2-3 and

external LEDs are not connected at OUT_3.

Table 4. On-Board or External LED

Current Setting (JU5)

SHUNT

POSITION

CURRENT

SETTING EV KIT FUNCTION

Not installed 50mA through

resistor R2 On-board LED operation

Installed 550mA through

resistors R2, R5 External LED operation

Evaluates: MAX16823

Input-Voltage Consideration

For proper operation, the EV kit’s minimum input volt-

age must always be:

VIN(MIN) ≥VFT(MAX) + ΔVDO + VCS(MAX)

where VFT(MAX) is the total forward voltage of all series-

connected LEDs, ΔVDO is the MAX16823 dropout volt-

age from IN to OUT_, and VCS(MAX) is the regulated

current-sense voltage.

The EV kit can operate below the minimum VIN(MIN)

voltage; however, the output current may not meet the

full regulation specification.

Power Dissipation

Thermal shutdown turns the device off if power dissipa-

tion in the MAX16823 IC causes the junction tempera-

ture to reach +155°C (typ). The MAX16823 EV kit is

configured for operation between the 6.5V to 16V range

while powering the on-board LEDs. When configuring

the MAX16823 EV kit for other configurations, total

power dissipation on the PCB should be considered to

prevent thermal shutdown. Verify that components Q1

and R5 power-dissipation ratings are not exceeded

when operating external LEDs at OUT_3.

MAX16823 Evaluation Kit

4 _______________________________________________________________________________________

JU7

4.02Ω

OUT1

CS1

JU6

JU5

JU4

4.02Ω

OPEN

0.1μF

50V

10kΩ

OUT2

CS2

4.02Ω

CS_3

OUT_3

0.4Ω

OPEN

OUT3

GND

CS3

GND

LEDGOOD

OUT2

CS2

OUT1

LEDGOOD

REG

DIM1

DIM2

DIM3

LGC CS1

ININ

MAX16823

567 14

TP1

0Ω

JU1

DIM1 2

JU2

DIM2 2

JU3

DIM3

GND

Figure 1. MAX16823 EV Kit Schematic

Evaluates: MAX16823

MAX16823 Evaluation Kit

_______________________________________________________________________________________ 5

Figure 2. MAX16823 EV Kit Component Placement Guide—

Components Side

Figure 3. MAX16823 EV Kit PCB Layout—Component Side

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.

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

Evaluates: MAX16823

MAX16823 Evaluation Kit

Figure 4. MAX16823 EV Kit PCB Layout—Solder Side