MAX16807EVKIT+ Maxim Integrated Products, MAX16807EVKIT+ Datasheet - Page 9

• Manufacturer Part Number: MAX16807EVKIT+
• Description: EVAL KIT FOR MAX16807
• Manufacturer: Maxim Integrated Products

Specifications of MAX16807EVKIT+

• Current - Output / Channel: 50mA
• Outputs And Type: 8, Non-Isolated
• Voltage - Output: 32V
• Features: Dimmable
• Voltage - Input: 9 ~ 16V
• Utilized Ic / Part: MAX16807
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The location of the zero (Z1), decided by R1 and C6, is
given by the following equation:
Place the high-frequency pole (P3), formed by C6, C7,
and R1, at half the switching frequency to provide further
attenuation to any high-frequency signal propagating
through the system. The location of the high-frequency
pole (F
be used to calculate the value of C7:
The MAX16807 EV kit uses electrolytic capacitors at the
output for filtering, so the zero produced by the ESR of
the capacitors can be low enough to be within or near
the crossover frequency. This zero should be compen-
sated using an additional pole (P4) placed at the ESR
zero location. The ESR zero frequency is calculated
using the following equation:
Use the following equation to calculate the value of
C25, to place the pole P4 at the ESR zero frequency:
If ceramic capacitors are used at the output for filtering,
the frequency of zero produced by the ESR and the
capacitance will be much above the crossover frequency
(0dB gain frequency) of the feedback loop, and hence,
need not be considered in the compensation design.
LED driver circuits based on the MAX16807 device use
a high-frequency switching converter to generate the
voltage for LED strings. Proper care must be taken while
laying out the circuit to ensure proper operation. The
switching-converter part of the circuit has nodes with
very fast voltage changes—producing high-frequency
electric fields and PCB traces with fast current
changes—resulting in high-frequency magnetic fields.
As the circuit converts power, the amplitude of these
P3
) is given by the following equation and should
F
P3
F
ZESR
C
=
25
_______________________________________________________________________________________
F
Z1
2π
=
=
=
2
×
2π
π
R
2π
×
1
Layout Considerations
×
×
F
×
ESR C
ZESR
⎛
⎜
⎝
R
C
1
1
1
1
1
1
6
×
×
C
+
×
R
6
C
OUT
12
1
7
⎞
⎟
⎠
−
1
MAX16807 Evaluation Kit
fields will be high and can easily couple to sensitive parts
of the circuit, creating undesirable effects. Follow the
guidelines below to reduce noise as much as possible:
1) Connect the bypass capacitors from REF and VCC
2) Keep the oscillator timing capacitor and resistor
3) Have a power ground plane for the switching-converter
4) There are two loops in the power circuit that carry
as close as possible to the device and connect the
capacitor grounds to the analog ground plane
using vias close to the capacitor terminals. Connect
the AGND pin of the device to the analog ground
plane using a via close to the pin. Lay the analog
ground plane on the inner layer, preferably next to
the top layer. Use the analog ground plane to cover
the entire area under critical signal components for
the power converter.
very close to the RTCT pin and make the connec-
tion as short as possible. Connect the ground of the
timing capacitor to the analog ground plane using a
via close to the capacitor terminal. Make sure that
no switching node is present near the RTCT node
and keep the area of the copper connected to the
pin small. Keep the REF connection to the timing
resistor short and away from any switching node.
power circuit under the power components (input filter
capacitor, output filter capacitor, inductor, MOSFET,
rectifier diode, and current-sense resistor). Connect
all the ground connections to the power ground
plane using vias close to the terminals.
high-frequency switching currents. One loop is
when the MOSFET is on—from the input filter
capacitor positive terminal, through the inductor,
the MOSFET, and the current-sense resistor, to the
input capacitor negative terminal. The other loop is
when the MOSFET is off—from the input capacitor
positive terminal, through the inductor, the rectifier
diode, output filter capacitor, to the input capacitor
negative terminal. Analyze these two loops and
make the loop areas as small as possible.
Wherever possible, have a return path on the power
ground plane for the switching currents on the top-
layer copper traces, or through power components.
This will reduce the loop area considerably and
provide a low-inductance path for the switching
currents. Reducing the loop area also reduces radi-
ation during switching.
9