MAX16818EVKIT+ Maxim Integrated Products, MAX16818EVKIT+ Datasheet - Page 3

• Manufacturer Part Number: MAX16818EVKIT+
• Description: KIT EVALUATION FOR MAX16818
• Manufacturer: Maxim Integrated Products

Specifications of MAX16818EVKIT+

• Current - Output / Channel: 1A
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 18V
• Features: Dimmable
• Voltage - Input: 6 ~ 28V
• Utilized Ic / Part: MAX16818
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Before beginning, the following equipment is needed:
• 6V to 28V, 5A DC power supply
• A series-connected LED string rated at 1A (maxi-
• A current probe to measure LED current
• One voltmeter
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
2) Verify that no shunt is installed across jumper JU2
3) Connect the anode end of the LED string to the
4) Connect the cathode end of the LED string to the
5) Clip on the current probe across the string wires to
6) Connect the positive terminal of the power supply to
7) Turn on the power supply and increase the voltage
8) Verify that the LED string current is approximately
9) Measure the voltage between the LED+ to LED-
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.
mum voltage on the string should not exceed 18V)
jumper JU1.
(EV kit on).
LED+ pad.
LED- pad.
measure the LED current.
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.
to 6V or above.
1A. Adjust potentiometer R23 to obtain 1A.
PCB pads.
_______________________________________________________________________________________
Recommended Equipment
Detailed Description
Quick Start
Procedure
MAX16818 Evaluation Kit
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.
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.
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.
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.
The MAX16818 EV kit switching frequency (f
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 f
Note: Other component values may need to be
changed for proper operation. Refer to the MAX16818
IC data sheet for additional information.
SW
is the desired switching frequency in Hz.
R
R
Output Overvoltage Protection
11
11
=
=
(
(
6 25 10
6 40
LED Brightness Dimming
.
.
f
f
SW
SW
Output Current Range
×
×
Switching Frequency
Input-Voltage Range
10
10
10
)
)
SW
) is con-
3