MAX16809EVKIT+ Maxim Integrated Products, MAX16809EVKIT+ Datasheet - Page 3

• Manufacturer Part Number: MAX16809EVKIT+
• Description: Power Management Modules & Development Tools EVAL KIT FOR MAX16809
• Manufacturer: Maxim Integrated Products

Specifications of MAX16809EVKIT+

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

• One 16V, 5A adjustable power supply
• One 5V power supply
• 16 LED strings with a total forward voltage ≤ 32V
• One multimeter
• One PWM signal generator (optional)
The MAX16809 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 LED strings with operating voltage of
2) Connect the DC power supply (16V, 5A) to VIN and
3) Connect a DC power supply (0 to 5V) to VBIAS and
4) Turn on the power supplies and apply 10V to VIN
5) Increase the supply voltage to 16V and the LED
6) Apply a PWM signal with amplitude of 3V to 5V and
7) Connect SHDN to GND and all LEDs should turn off.
The MAX16809 EV kit is a 16-channel, constant-current
LED driver capable of driving 40mA each to 16 LED
strings, with a total forward voltage of up to 32V. The
MAX16809 EV kit can drive a total of 160 white LEDs in
16 strings, with operating current up to 40mA. The
MAX16809 EV kit can operate at input supply voltages
between 9V and 16V.
The MAX16809 EV kit evaluates the MAX16809 IC, which
has two major sections. The first section consists of 16
constant-current LED drivers capable of sinking up to
55mA when on and blocking up to 36V when off. The sec-
ond section is a high-performance current-mode PWM
approximately 32V between VLED (pins 1-4 of J1)
and OUT0–OUT15 (pins 5-20 of J1). All 16 channels
should have an LED string load connected of the
same type.
GND.
GND.
and 3V to 5V to VBIAS. Connect SHDN and PWM to
3V to 5V. All of the LEDs should turn on. Measure
the current through any LED string, which should be
40mA ±7%.
currents will be stable. Measure the current through
any LED string, which should be 40mA ±7%.
a frequency between 100Hz and 2kHz to the PWM
input. The LED brightness should increase as the
PWM duty cycle increases and viceversa.
_______________________________________________________________________________________
Recommended Equipment
Detailed Description
Quick Start
Procedure
MAX16809 Evaluation Kit
controller that can control a DC-DC converter to generate
the supply voltage for driving the LED strings. The
MAX16809 EV kit uses the PWM controller to drive a
boost converter, which takes a 9V to 16V input and gen-
erates a 33V LED supply voltage. To drive a constant cur-
rent into an LED string, connect the LED string between
the 33V output and any of the 16 constant-current-sink
outputs. The resistor (R1) from the SET pin to ground pro-
grams the sink current of each output. The sink current of
any output can be up to 55mA and the amplitude is the
same value for all the outputs. The difference between the
total forward voltage and the LED supply voltage drops
between the constant-current-sink output and ground,
and is dissipated as power in the device.
The LED supply voltage generated by the boost con-
verter in the MAX16809 EV kit is adaptive. The LED
string with the highest total forward voltage dominates
the control loop, and the boost-converter voltage is
adjusted so that the driver associated with that string
receives just enough voltage required for current drive.
All the other strings, with lower total forward voltages,
will have excess supply voltage, which is then dropped
in the associated driver. This feedback mechanism
ensures that the linear-current-control circuit dissipates
the minimum possible power. An on-board inverter
(U4A) is configured to generate the clock input for the
MAX16809. The constant-current output-driver circuits
and U4 need a 3.3V to 5V input, which should be sup-
plied externally. If 5V is not available, it can be generat-
ed using an emitter-follower buffer from the REF output
of MAX16809.
The boost converter that generates the 33V LED supply
voltage operates at a switching frequency of 350kHz in
continuous-conduction mode (CCM). The current-mode
PWM controller in the MAX16809 drives the external
MOSFET (Q2) to control the boost converter. The
MOSFET is turned on at the beginning of every switching
cycle and turned off when the current through the induc-
tor (L1) reaches the peak value set by the error-amplifier-
output voltage. Inductor current is sensed from the volt-
age across the ground-referenced current-sense resis-
tor (parallel combination of R12 and R13). This current-
sense information is passed on to the current-sense
comparators in the MAX16809 through the CS pin.
During the on period of the MOSFET, the inductor
stores energy from the input supply. When the switch is
turned off, the inductor generates sufficient voltage in
reverse direction to discharge the stored energy to
VLED. This generated voltage forms a source, in series
with the input supply voltage, and drives VLED through
the rectifier diode (D2).
Boost Converter
3