19-0842; Rev 0; 6/07
MAX16818 Evaluation Kit
General Description
The MAX16818 evaluation kit (EV kit) is a fully assem-
bled and tested surface-mount printed-circuit board
(PCB) designed to evaluate the MAX16818 pulse-width
modulation (PWM) LED driver controller in a buck-boost
configuration.
The MAX16818 EV kit operates from a DC supply volt-
age of 6V to 28V. The EV kit’s output is configured to
deliver at least 1A of current into an 18V series LED
string. The LED brightness can be dimmed using a dig-
ital PWM signal.
The EV kit provides an option to configure the
MAX16818 IC’s overvoltage protection, switching fre-
quency, and frequency compensation. The MAX16818
EV kit also features a 180° out-of-phase clock output
PCB pad.
♦
6V to 28V Input-Voltage Range
♦
1A Output Current into an 18V LED String
♦
Pulse-Width Modulated LED Current Dimming
♦
Resistor-Adjustable Overvoltage Protection and
Switching Frequency
♦
180° Out-of-Phase Clock Output
♦
Fully Assembled and Tested
Features
Evaluates: MAX16818
Ordering Information
PART
MAX16818EVKIT+
TEMP RANGE
0°C to +70°C*
IC PACKAGE
28 TQFN-EP**
+Denotes
a lead-free and RoHS-compliant EV kit.
*This
limited temperature range applies to the EV kit PCB only.
The MAX16818 IC temperature range is -40°C to +125°C.
**EP
= Exposed paddle.
Component List
DESIGNATION
C1
QTY
1
DESCRIPTION
2.2µF ±10%, 50V X7R ceramic
capacitor (1206)
Murata GRM31CR71H225K
1µF ±20%, 50V X7R ceramic
capacitor (0805)
Murata GRM21BR71H105M
4.7µF ±10%, 6.3V X7R ceramic
capacitor (0603)
Murata GRM188R70J475K
0.47µF ±10%, 6.3V X7R ceramic
capacitor (0603)
Murata GRM188R70J474K
1000pF ±10%, 50V X7R ceramic
capacitor (0603)
Murata GRM188R71H102K
10µF ±10%, 50V X7R ceramic
capacitors (2220)
Murata GRM55DR71H106K
Not installed, capacitors (0603)
0.22µF ±10%, 16V X7R ceramic
capacitor (0603)
Murata GRM188R71C224K
2200pF ±10%, 50V X7R ceramic
capacitor (0603)
Murata GRM188R71H222K
DESIGNATION
C12
QTY
1
DESCRIPTION
0.1µF ±10%, 16V X7R ceramic
capacitor (0603)
Murata GRM188R71C104K
100pF ±5%, 50V C0G ceramic
capacitor (0603)
Murata GRM1885C1H101J
100µF, 50V electrolytic capacitor
(8mm x 10.2mm)
Panasonic EEEFK1H101P
60V, 2A Schottky diode (SMB)
Diodes Inc. B260-13-F
3-pin header
2-pin header
8.8µH, 4A
DC
inductor
Sumida CDEP105-8R8
40V, 4.9A n-channel MOSFET (SO8)
Vishay Si4446DY
60V, 115mA n-channel MOSFETs
(SOT23)
Central Semiconductor 2N7002
LEAD-FREE
-20V, -3.8A p-channel MOSFET
(TSOP-6)
Vishay Si3467DV-T1-E3
C2
1
C13
1
C3
1
C14
D1
JU1
JU2
L1
N1
1
1
1
1
1
1
C4
1
C5
1
C6, C7
C8, C10
C9
2
0
1
N2–N5
4
P1
1
C11
1
________________________________________________________________
Maxim Integrated Products
1
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.
MAX16818 Evaluation Kit
Evaluates: MAX16818
Component List (continued)
DESIGNATION
Q1
Q2
R1
R2
R3, R7, R15,
R16
R4, R5
R6
R8
R9
R10
R11
R12, R13
R14
R17
QTY
1
1
1
1
4
2
1
1
1
1
1
2
1
1
DESCRIPTION
NPN bipolar transistor (SOT223)
Fairchild Semiconductor PZT3904
PNP bipolar transistor (SOT23)
Fairchild Semiconductor
MMBT3906
1kΩ ±1% resistor (1206)
12.1kΩ ±1% resistor (0603)
10kΩ ±1% resistors (0603)
1Ω ±1% resistors (0603)
4.99kΩ ±1% resistor (0402)
221kΩ ±1% resistor (0402)
100kΩ ±1% resistor (0402)
12.4kΩ ±1% resistor (0402)
105kΩ ±1% resistor (0603)
1kΩ ±5% resistors (0805)
0.007Ω ±2%, 0.5W sense resistor
(2010)
IRC LRC-LRF2010LF-01-R007-G
1kΩ ±1% resistor (0603)
DESIGNATION
R18
R19
R20
R21
R22
R23
U1
U2
QTY
1
1
1
1
1
1
1
1
DESCRIPTION
2kΩ ±1% resistor (0603)
499Ω ±1% resistor (0603)
0.11Ω ±1%, 0.5W sense resistor
(1206)
IRC LRC-LRC1206LF-01-R11-F
30.1kΩ ±1% resistor (0603)
40.2kΩ ±1% resistor (0603)
100kΩ SMT cermet trimmer, 11
turns
MAX16818ATI+ (28-pin TQFN-EP,
5mm x 5mm)
Voltage-output, high-side current-
sense amplifier
MAX4073TAXK+ (5-pin SC70-5)
Low-voltage, adjustable precision
shunt regulators (SOT23)
Texas Instruments
TL431AQDBZRQ1
Shunts
PCB: MAX16818 Evaluation Kit+
U3, U4
—
—
2
2
1
Component Suppliers
SUPPLIER
Central Semiconductor
Diodes Inc.
Fairchild Semiconductor
IRC, Inc.
Murata Mfg. Co., Ltd.
Panasonic Corp.
Sumida Corp.
Vishay/Vitramon
PHONE
631-435-1110
805-446-4800
888-522-5372
361-992-7900
770-436-1300
800-344-2112
847-545-6700
203-268-6261
www.centralsemi.com
www.diodes.com
www.fairchildsemi.com
www.irctt.com
www.murata.com
www.panasonic.com
www.sumida.com
www.vishay.com
WEBSITE
Note:
Indicate that you are using the MAX16818 when contacting these component suppliers.
2
_______________________________________________________________________________________
MAX16818 Evaluation Kit
Quick Start
Recommended Equipment
Before beginning, the following equipment is needed:
• 6V to 28V, 5A DC power supply
• A series-connected LED string rated at 1A (maxi-
mum voltage on the string should not exceed 18V)
• A current probe to measure LED current
• One voltmeter
Input-Voltage Range
The MAX16818 EV kit can operate from a DC supply
voltage of 6V to 28V and requires at least 5A. The input-
voltage range is jumper selectable (see the
Jumper
Selection
section). Transistor Q1, shunt regulator U3,
and resistors R1, R2, and R3 are used to regulate VCC
to 5V when the input voltage to the EV kit is between 6V
to 8V. If the minimum input voltage is 8V, jumper JU1
can be replaced by a shorting wire between pins 1-2.
Transistor Q1, shunt regulator U3, and resistors R1, R2,
and R3 can be omitted from the EV kit, saving compo-
nents and reducing the required PCB space.
Evaluates: MAX16818
Procedure
The MAX16818 EV kit is fully assembled and tested.
Follow the steps below to verify board operation.
Caution: Do not turn on the power supply until all
connections are completed.
1) Verify that a shunt is installed across pins 2-3 of
jumper JU1.
2) Verify that no shunt is installed across jumper JU2
(EV kit on).
3) Connect the anode end of the LED string to the
LED+ pad.
4) Connect the cathode end of the LED string to the
LED- pad.
5) Clip on the current probe across the string wires to
measure the LED current.
6) Connect the positive terminal of the power supply to
the VIN pad on the EV kit. Connect the negative ter-
minal of the power supply to the PGND pad next to
the VIN pad.
7) Turn on the power supply and increase the voltage
to 6V or above.
8) Verify that the LED string current is approximately
1A. Adjust potentiometer R23 to obtain 1A.
9) Measure the voltage between the LED+ to LED-
PCB pads.
Output Current Range
The MAX16818 EV kit can deliver up to 1A into an 18V
series LED string. The maximum output current is con-
figurable by sense resistor R14. The LED current can be
adjusted from 400mA to 1A using potentiometer R23.
LED Brightness Dimming
The LED brightness can be dimmed using a TTL PWM
signal with a frequency range of 80Hz to 5kHz.
Connect the TTL dimming signal to the PWMDIM and
GND pads to control the brightness of the LEDs.
Output Overvoltage Protection
The MAX16818 EV kit features overvoltage protection
circuitry to limit the voltage from LED+ to GND to 46V
when the LED string is opened. The overvoltage pro-
tection circuitry consists of resistors R6–R10, transistor
Q2, and shunt regulator U4. The overvoltage protection
circuitry is nonlatching.
Switching Frequency
The MAX16818 EV kit switching frequency (f
SW
) is con-
figured to 600kHz by resistor R11. To reconfigure the
MAX16818 switching frequency from 125kHz to
1.5MHz, replace resistor R11 using the equation below:
For 120kΩ
≤
R11
≤
500kΩ
Detailed Description
The MAX16818 EV kit is designed to evaluate the
MAX16818 PWM LED driver controller in a buck-boost
configuration. The EV kit PCB is designed with two
layers and has 1oz copper traces. All components on
the EV kit are installed on the top layer. The EV kit
includes an on-board VCC regulating circuit for opera-
tion with input voltage between 6V to 8V. The EV kit also
includes on-board output overvoltage protection circuitry
to limit the output voltage.
(
6.25
×
10
)
R11
=
10
f
SW
For 40kΩ
≤
R11
≤
120kΩ
(
6.40
×
10
)
R11
=
10
f
SW
where f
SW
is the desired switching frequency in Hz.
Note:
Other component values may need to be
changed for proper operation. Refer to the MAX16818
IC data sheet for additional information.
3
_______________________________________________________________________________________
MAX16818 Evaluation Kit
Evaluates: MAX16818
Clock Output
The MAX16818 EV kit also features a digital clock out-
put that is 180° out-of-phase with respect to the high-
side driver, N1. The clock output is available at the
CLKOUT PCB pad.
Output Enable (EN)
Jumper JU2 controls the output enable pin on the
MAX16818 IC. The MAX16818 output enable pin (EN)
is also connected to the overvoltage protection circuitry
on the EV kit (see Table 2 for shunt positions).
Jumper Selection
Input-Voltage Range (VIN)
Jumper JU1 selects the input-voltage range for the
MAX16818 EV kit (see Table 1 for shunt positions).
Table 2. JU2 Jumper Selection (EN)
SHUNT
POSITION
Installed
EN PIN CONNECTED TO
GND
Overvoltage protection
circuitry
(R6–R10, Q2, U4)
EV KIT
FUNCTION
Disabled
Enabled
Table 1. JU1 Jumper Selection (IN)
SHUNT
POSITION
1-2
2-3**
None
(Not allowed)
IN PIN CONNECTED TO
VIN
VCC
No connect
VIN VOLTAGE
RANGE
8V to 28V*
6V to 28V
0V
Not installed*
*Default
position.
*When
operating in the 8V to 28V input-voltage range, jumper
JU1 can be replaced by a shorting wire between pins 1-2.
**Default
position.
4
_______________________________________________________________________________________
VIN
L1
8.8μH
D1
VIN
PGND
2 4
1
Q1
2
7
10
5
6
C6
10μF
50V
VCC
6
1
LX
27
V
CC
CSN
VCC
28
V
DD
CLP
3
1
2
3
N4
2
R13
1kΩ
3
1
3
N3
C9
0.22μF
2
VIN
R17
1kΩ
1%
SENSE+
14
LIM
SENSE-
24
2
23
3
1
R20
0.11Ω
1%
N2
2
1
16
R19
499Ω
1%
R12
1kΩ
4
1
3
1
2
R5
1Ω
1%
U1
4
BST
C11
2200pF
C8
OPEN
ENABLE
11
EN
EAOUT
EAN
CLKOUT
9
CLKOUT
RT/SYNC
12
R11
105kΩ
1%
DIFF
19
18
17
JU2
C5
1000pF
R16
10kΩ
1%
C10
OPEN
R18
2kΩ N5
1%
R7
10kΩ
1%
C4
0.47μF
20
SGND
C3
4.7μF
R14
0.007Ω
2%
CSP
21
R15
10kΩ
1% PWMDIM
LED+
5
4
C7
10μF
50V
13
3
1
JU1
26
IN
DH
2
3
R3
10kΩ
1%
C2
1μF
VCC
N.C. N.C. DL PGOOD V_IOUT
3
C14
100μF
50V
R1
1kΩ
1%
C1
2.2μF
50V
1
R2
12.1kΩ
1%
8
7
N1
3
2
Figure 1. MAX16818 EV Kit Schematic
R4
1Ω
1%
LED-
U3
2
5
VCC
R6
4.99kΩ
1%
MAX16818
2
P1
6
5
Q2
1
3
R8
221kΩ
1%
SGND
1
U4
5
R9
100kΩ
1%
2
R10
12.4kΩ
1%
R23
100kΩ
R21
30.1kΩ
1%
1
C13
100pF
VCC
5
RS-
U2
OUT
4
RS+
3
VCC
PGND SGND SGND SGND OVI
1
8
22
25
15
R22
40.2kΩ
1%
MAX4073T
C12
0.1μF
GND
2
Evaluates: MAX16818
_______________________________________________________________________________________
MAX16818 Evaluation Kit
5
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