19-0772; Rev 0; 3/07
MAX16823 Evaluation Kit
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).
o
6.5V to 16V Supply Voltage Range
o
Open LED Detection Output
o
On-Board or External LED Connections
o
50mA Load Current
o
Configurable 550mA Output Current at OUT_3
o
Separate PWM Dimming Control for Each Channel
o
Fully Assembled and Tested
Features
Evaluates: MAX16823
Ordering Information
PART
MAX16823EVKIT+
TEMP RANGE
0°C to +70°C*
IC PACKAGE
16 TQFN-EP
†
+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.
Component List
DESIGNATION
C1
C2, C3
QTY
0
2
DESCRIPTION
Not installed, ceramic capacitor (1206)
0.1µF ±10%, 50V X7R ceramic
capacitors (0603)
Murata GRM188R71H104K
0.015µF ±10%, 50V X7R ceramic
capacitor (0603)
Murata GRM188R71H153K
Red LEDs (4-PLCC)
OSRAM LR E6SF-AABB-1-1
3-pin headers
2-pin headers
80V, 3A npn transistor (D-PAK)
Fairchild Semiconductor MJD31CTF
Not installed, resistor (0805)
4.02Ω ±1% resistors (0805)
0.4Ω ±1%, 500mW sense resistor (1206)
IRC/TT Electronics LRC-LRF-
1206LF-01-R400-F
10kΩ ±5% resistor (0603)
0Ω ±5% resistor (1206)
PC mini red test point
MAX16823ATE+ (16-pin TQFN,
5mm x 5mm x 0.8mm)
Shunts (JU1–JU7)
PCB: MAX16823 Evaluation Kit+
Component Suppliers
SUPPLIER
Fairchild
Semiconductor
IRC/TT Electronics
Murata Mfg. Co., Ltd.
OSRAM Opto
Semiconductors
PHONE
888-522-5372
361-992-7900
770-436-1300
888-446-7726
WEBSITE
www.fairchildsemi.com
www.irctt.com
www.murata.com
www.osram-os.com
C4
1
D1–D9
JU1–JU4
JU5, JU6, JU7
Q1
R1
R2, R3, R4
R5
R6
R7
TP1
U1
—
—
9
4
3
1
0
3
1
1
1
1
1
7
1
Note:
Indicate that you are using the MAX16823 when contact-
ing these component suppliers.
Quick Start
•
16V adjustable, 1A power supply
•
Two digital voltmeters
Recommended Equipment
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.
________________________________________________________________
Maxim Integrated Products
1
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.
MAX16823 Evaluation Kit
Evaluates: MAX16823
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.
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:
R
_
=
203mV(typ)
I
LED
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.
where R_ is the external current-sense resistor at CS1,
CS2, CS3, or CS_3, and I
LED
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.
Table 1. PWM Configuration (JU1, JU2,
and JU3)
SHUNT
POSITION
1-2
2-3
Not installed
DIM1, DIM2, DIM3
PINS
REG
GND
Driven by external
source
EV KIT
FUNCTION
LEDs on
LEDs off
PWM operation
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 V
IN
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.
2
_______________________________________________________________________________________
MAX16823 Evaluation Kit
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:
C4
=
t
DELAY
257,900(
Ω
)
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.
Evaluates: MAX16823
where C4 is in farads and t
delay
is in seconds.
When shunts are not installed at jumpers JU4, JU6, or
JU7, LEDGOOD is low.
Table 3. OUT_3 LED Operation (JU4)
SHUNT
POSITION
1-2
2-3*
Uninstalled*
OUT3 PIN
Connects to Q1
Connects to D1
Open
EV KIT FUNCTION
External LED operation at
OUT_3
On-board LED operation
LEDGOOD = 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.
*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
Not installed
CURRENT
SETTING
50mA through
resistor R2
550mA through
resistors R2, R5
EV KIT FUNCTION
On-board LED operation
External LED operation
Table 2. OUT1 and OUT2 LED Operation
(JU6 and JU7)
SHUNT POSITION
Installed
Uninstalled*
EV KIT FUNCTION
On-board LED operation
External LED operation
Installed
*LEDGOOD
is low when the shunts are removed and external
LEDs are not connected at OUT1 and OUT2.
For proper operation when using higher current external
LEDs at OUT_3, the minimum input voltage must be:
V
IN(MIN)
= 1.2V + V
FT(MAX)
+
ΔV
DO
where 1.2V is the maximum collector-emitter saturation
voltage for the npn transistor Q1, V
FT(MAX)
is the total
forward voltage of all series-connected LEDs at OUT_3,
and
ΔV
DO
is the MAX16823 dropout voltage from IN to
OUT_.
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.
_______________________________________________________________________________________
3
MAX16823 Evaluation Kit
Evaluates: MAX16823
Input-Voltage Consideration
For proper operation, the EV kit’s minimum input volt-
age must always be:
V
IN(MIN)
≥
V
FT(MAX)
+
ΔV
DO
+ V
CS(MAX)
where V
FT(MAX)
is the total forward voltage of all series-
connected LEDs,
ΔV
DO
is the MAX16823 dropout volt-
age from IN to OUT_, and V
CS(MAX)
is the regulated
current-sense voltage.
The EV kit can operate below the minimum V
IN(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.
2
1
JU4
1
2
3
D1
IN
C1
OPEN
GND
LEDGOOD
R6
10kΩ
R7
0Ω
C2
0.1μF
50V
10
TP1
4
LEDGOOD
U1
9
MAX16823
REG
JU6
DIM1
1
2
3
DIM2
1
2
3
DIM3
GND
1
2
3
JU3
3 DIM3
8
LGC
JU2
JU1
D7
2 DIM2
D8
D9
CS1
13
R4
4.02Ω
1%
JU7
OUT1
CS1
1
12
CS2
16
OUT1
OUT2
CS2
R3
4.02Ω
1%
D5
D6
5
6
7
14
D3
JU5
R2
4.02Ω
1%
R5
0.4Ω
1%
CS_3
11
CS3
15
OUT2
D4
D2
IN IN IN OUT3
GND
R1
OPEN
OUT_3
Q1
3
DIM1
Figure 1. MAX16823 EV Kit Schematic
4
_______________________________________________________________________________________
MAX16823 Evaluation Kit
Evaluates: MAX16823
Figure 2. MAX16823 EV Kit Component Placement Guide—
Components Side
Figure 3. MAX16823 EV Kit PCB Layout—Component Side
_______________________________________________________________________________________
5
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