MAX16812EVKIT+ Maxim Integrated, MAX16812EVKIT+ Datasheet - Page 3

• Manufacturer Part Number: MAX16812EVKIT+
• Description: LED Lighting Development Tools Evaluation Kit for the MAX16812
• Manufacturer: Maxim Integrated
• Series: MAX16812r

Specifications of MAX16812EVKIT+

• Product: Evaluation Kits

Before beginning, the following equipment is needed:
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The MAX16812 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. Avoid powering up the EV kit with-
out connecting a load to the LED+ and LED- pads.
1) Connect the power supply’s positive terminal to the
2) Connect digital voltmeters across the IN and PGND
3) Install a shunt across jumper JU1 (MAX16812 EV kit
4) Install a shunt across jumper JU2 and verify that a
5) Connect the anode-end of the LED string to the
6) Connect the cathode-end of the LED string to the
7) Adjust potentiometer R9 clockwise.
8) Clip the current probe across the LED wire to mea-
9) Turn on the power supply and increase the input
10) Adjust potentiometer R2 counterclockwise until the
11) Measure the voltage between the LED+ to LED-
The MAX16812 evaluation kit (EV kit) demonstrates the
MAX16812 IC peak-current-mode PWM HBLED driver.
The MAX16812 EV kit is configured in a step-up/step-
down topology with peak-current-mode and average
LED current control for a string of user-supplied exter-
nal HBLEDs. The EV kit is capable of supplying stable
LED output currents up to 350mA and operates at sup-
ply voltages between 7V and 28V.
5V to 28V, 2A power supply
Two digital voltmeters
A series-connected LED string rated at 350mA
(15V, max)
One current probe to measure LED current
VIN PCB pad on the EV kit. Connect the power
supply’s ground terminal to PGND PCB pad.
PCB pads and the LED+ and LED- PCB pads.
enabled).
shunt is not installed across jumper JU3 (analog
dimming control).
LED+ pad.
LED- pad.
sure the LED current.
voltage to 7V.
LED current amplitude is 350mA.
PCB pads.
_______________________________________________________________________________________
Recommended Equipment
Detailed Description
Quick Start
Procedures
MAX16812 Evaluation Kit
The MAX16812 EV kit sets the inductor peak current to 2A
using parallel resistors R10 and R11. The average LED
current is set to a maximum of 360mA using parallel resis-
tors R13 and R14, and by adjusting potentiometer R2.
The MAX16812 EV kit is set to a 300kHz switching fre-
quency using resistor R8. Refer to the Internal Oscillator
Switching Frequency section in the MAX16812 IC data
sheet for information on setting other switching frequen-
cies. A PCB pad is available to monitor the MAX16812 ref-
erence voltage output (REF). A PCB pad is also provided
for the external LED intensity voltage-control input DIM.
Jumper JU1 controls the MAX16812 EV kit enable mode.
Place a shunt across pins 1-2 to enable the MAX16812
EV kit when VIN voltage rises above the IC’s 5V UVLO
default threshold. Place a shunt across pins 2-3 to dis-
able the EV kit. See Table 1 for JU1 jumper selection.
The parallel combination of current-sense resistors R10
and R11 sets the EV kit’s peak inductor current limit to
2A. Use the following equation to calculate the peak
current limit:
where I
the total parallel resistance placed at the R10 and R11
PCB pads.
Refer to the Internal Switching MOSFET Current Limit
section in MAX16812 IC data sheet for additional infor-
mation on setting the peak current-limit threshold.
Resistors R13 and R14 set the MAX16812 EV kit aver-
age LED current up to a maximum 360mA. The poten-
tiometer R2 allows the external LED current to be
adjusted from 175mA (min) to 360mA (max). The LED
string current can be programmed using the following
equation:
where I
TP1, and 0.82Ω is the parallel resistance of R13 and R14.
Table 1. JU1 Jumper Selection (EN)
SHUNT POSITION
ILIM
LED
1-2
2-3
Peak Inductor Current-Limit Setting
is the inductor peak current and R
is the LED current, V
Setting External LEDs Current
I
LED
Connected to GND
I
Connected to IN
ILIM
(A) =
EN PIN
=
4 x 0.82Ω
600mV
R
TOTAL
V
REFI
Input Supply UVLO
REFI
EV KIT FUNCTION
is the voltage at
Disabled
Enabled
TOTAL
is
3