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.
Features
♦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
Evaluates: MAX16818
MAX16818 Evaluation Kit
________________________________________________________________
Maxim Integrated Products
1
19-0842; Rev 0; 6/07
Component List
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.
Ordering Information
PART TEMP RANGE IC PACKAGE
MAX16818EVKIT+ 0°C to +70°C* 28 TQFN-EP**
DESIGNATION QTY DESCRIPTION
C1 1
2.2µF ±10%, 50V X7R ceramic
capacitor (1206)
Murata GRM31CR71H225K
C2 1
1µF ±20%, 50V X7R ceramic
capacitor (0805)
Murata GRM21BR71H105M
C3 1
4.7µF ±10%, 6.3V X7R ceramic
capacitor (0603)
Murata GRM188R70J475K
C4 1
0.47µF ±10%, 6.3V X7R ceramic
capacitor (0603)
Murata GRM188R70J474K
C5 1
1000pF ±10%, 50V X7R ceramic
capacitor (0603)
Murata GRM188R71H102K
C6, C7 2
10µF ±10%, 50V X7R ceramic
capacitors (2220)
Murata GRM55DR71H106K
C8, C10 0 Not installed, capacitors (0603)
C9 1
0.22µF ±10%, 16V X7R ceramic
capacitor (0603)
Murata GRM188R71C224K
C11 1
2200pF ±10%, 50V X7R ceramic
capacitor (0603)
Murata GRM188R71H222K
DESIGNATION QTY DESCRIPTION
C12 1
0.1µF ±10%, 16V X7R ceramic
capacitor (0603)
Murata GRM188R71C104K
C13 1
100pF ±5%, 50V C0G ceramic
capacitor (0603)
Murata GRM1885C1H101J
C14 1
100µF, 50V electrolytic capacitor
(8mm x 10.2mm)
Panasonic EEEFK1H101P
D1 1 60V, 2A Schottky diode (SMB)
Diodes Inc. B260-13-F
JU1 1 3-pin header
JU2 1 2-pin header
L1 1 8.8µH, 4ADC inductor
Sumida CDEP105-8R8
N1 1 40V , 4.9A n- channel M OS FE T ( S O8)
V i shay S i 4446D Y
N2–N5 4
60V, 115mA n-channel MOSFETs
(SOT23)
Central Semiconductor 2N7002
LEAD-FREE
P1 1
-20V, -3.8A p-channel MOSFET
(TSOP-6)
Vishay Si3467DV-T1-E3
+
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.
Evaluates: MAX16818
MAX16818 Evaluation Kit
2 _______________________________________________________________________________________
Component List (continued)
DESIGNATION QTY DESCRIPTION
Q1 1 NPN bipolar transistor (SOT223)
Fairchild Semiconductor PZT3904
Q2 1
PNP bipolar transistor (SOT23)
Fairchild Semiconductor
MMBT3906
R1 1 1kΩ ±1% resistor (1206)
R2 1 12.1kΩ ±1% resistor (0603)
R3, R7, R15,
R16 4 10kΩ ±1% resistors (0603)
R4, R5 2 1Ω ±1% resistors (0603)
R6 1 4.99kΩ ±1% resistor (0402)
R8 1 221kΩ ±1% resistor (0402)
R9 1 100kΩ ±1% resistor (0402)
R10 1 12.4kΩ ±1% resistor (0402)
R11 1 105kΩ ±1% resistor (0603)
R12, R13 2 1kΩ ±5% resistors (0805)
R14 1
0.007Ω ±2%, 0.5W sense resistor
(2010)
IRC LRC-LRF2010LF-01-R007-G
R17 1 1kΩ ±1% resistor (0603)
DESIGNATION QTY DESCRIPTION
R18 1 2kΩ ±1% resistor (0603)
R19 1 499Ω ±1% resistor (0603)
R20 1
0.11Ω ±1%, 0.5W sense resistor
(1206)
IRC LRC-LRC1206LF-01-R11-F
R21 1 30.1kΩ ±1% resistor (0603)
R22 1 40.2kΩ ±1% resistor (0603)
R23 1 100kΩ SMT cermet trimmer, 11
turns
U1 1 MAX16818ATI+ (28-pin TQFN-EP,
5mm x 5mm)
U2 1
Voltage-output, high-side current-
sense amplifier
MAX4073TAXK+ (5-pin SC70-5)
U3, U4 2
Low-voltage, adjustable precision
shunt regulators (SOT23)
Texas Instruments
TL431AQDBZRQ1
— 2 Shunts
— 1 PCB: MAX16818 Evaluation Kit+
Component Suppliers
SUPPLIER PHONE WEBSITE
Central Semiconductor 631-435-1110 www.centralsemi.com
Diodes Inc. 805-446-4800 www.diodes.com
Fairchild Semiconductor 888-522-5372 www.fairchildsemi.com
IRC, Inc. 361-992-7900 www.irctt.com
Murata Mfg. Co., Ltd. 770-436-1300 www.murata.com
Panasonic Corp. 800-344-2112 www.panasonic.com
Sumida Corp. 847-545-6700 www.sumida.com
Vishay/Vitramon 203-268-6261 www.vishay.com
Note: Indicate that you are using the MAX16818 when contacting these component suppliers.
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
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.
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.
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.
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 (fSW) 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
For 40kΩ≤R11 ≤120kΩ
where fSW 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.
RfSW
11 640 1010
=
×
()
.
RfSW
11
625 10
10
=
×
()
.
Evaluates: MAX16818
MAX16818 Evaluation Kit
_______________________________________________________________________________________ 3
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.
Jumper Selection
Input-Voltage Range (VIN)
Jumper JU1 selects the input-voltage range for the
MAX16818 EV kit (see Table 1 for shunt positions).
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).
MAX16818 Evaluation Kit
4 _______________________________________________________________________________________
SHUNT
POSITION EN PIN CONNECTED TO EV KIT
FUNCTION
Installed GND Disabled
Not installed*
Overvoltage protection
circuitry
(R6–R10, Q2, U4)
Enabled
Table 2. JU2 Jumper Selection (EN)
*
Default position.
SHUNT
POSITION IN PIN CONNECTED TO VIN VOLTAGE
RANGE
1-2 VIN 8V to 28V*
2-3** VCC 6V to 28V
None
(Not allowed) No connect 0V
Table 1. JU1 Jumper Selection (IN)
*
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.
Evaluates: MAX16818
MAX16818 Evaluation Kit
_______________________________________________________________________________________ 5
R10
12.4kΩ
1%
5
2U4
1
R8
221kΩ
1%
R9
100kΩ
1%
1
2
Q2
3
R7
10kΩ
1%
R6
4.99kΩ
1%
VCC C4
0.47μF
R5
1Ω
1%
R4
1Ω
1%
C3
4.7μF
VCC
C2
1μF
JU1
1
2
3
4
Q1
3
2
R1
1kΩ
1%
R2
12.1kΩ
1%
C1
2.2μF
50V
C14
100μF
50V
VIN
VIN
PGND
R3
10kΩ
1%
1
2
U3
5
C5
1000pF
JU2
ENABLE
SGND
CLKOUT
R11
105kΩ
1% 14
12
9
1822 25 15
23
C13
100pF
R22
40.2kΩ
1%
R23
100kΩ
R21
30.1kΩ
1%
C12
0.1μF
VCC
2
3
GND
VCC
RS+
OUT
RS-
1
54
R20
0.11Ω
1%
VIN
2
N2
3
R13
1kΩ
6
5
2
1
P1
3
4
1
R12
1kΩ
LED-
LED+
PWMDIM
SGND
R15
10kΩ
1%
VCC
C7
10μF
50V
C6
10μF
50V
8
7
N1
3
2
1
4
56
D1
L1
8.8μH
13
10
3
72
26
27
28
4
11
PGND SGND SGND SGND OVI
24
1
2
3
R17
1kΩ
1%
19
18
R16
10kΩ
1%
17
3
1
2
N3
C9
0.22μF
C8
OPEN
1
3
2
N4
R19
499Ω
1%
VCC
1
3
2
N5
R18
2kΩ
1%
C11
2200pF
C10
OPEN
R14
0.007Ω
2%
16
20
21
5
6
DH
LX
CSP
CSN
CLP
EAOUT
EAN
DIFF
SENSE+
SENSE-
LIM
RT/SYNC
CLKOUT
EN
BST
VDD
VCC
IN
N.C. N.C. DL PGOOD V_IOUT
MAX16818
U1
MAX4073T
U2
1
Figure 1. MAX16818 EV Kit Schematic
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.
6
_____________________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.
Evaluates: MAX16818
MAX16818 Evaluation Kit
Boblet
Figure 2. MAX16818 EV Kit Component Placement Guide—
Component Side
Figure 3. MAX16818 EV Kit PCB Layout—Component Side
Figure 4. MAX16818 EV Kit PCB Layout—Solder Side
