MAX16807EVKIT+ Maxim Integrated Products, MAX16807EVKIT+ Datasheet - Page 8

• 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

MAX16807 Evaluation Kit
the voltages at the eight constant-current sink outputs
and adjusts the feedback to control these voltages to a
minimum value. As the LEDs carry constant current, the
voltage across the LEDs does not change with varia-
tions in VLED. Any change in VLED directly reflects to
the constant-current sink outputs and to the error-
amplifier input, making G
The DC gain of the power circuit is expressed as the
change in the output voltage (ΔVLED), with respect to
the change in error-amplifier output voltage (ΔEA
As the boost converter in the MAX16807 EV kit drives a
constant-current load, the power circuit DC gain is cal-
culated by the following equation:
Calculate the power circuit DC gain using the following
equation:
where R
switching frequency, and the factor 3 is to account for
the attenuation of error-amp output before it is fed to
the current-sense comparator.
The power-circuit gain will be the lowest at the mini-
mum input supply voltage and highest at the maximum
input supply voltage. Any input supply voltage between
9V and 16V can be used for the power-circuit gain cal-
culation, since the final compensation values obtained
will be the same.
Calculate the frequency F
gain starts falling, at -20dB/decade using the following
equation:
where C
parallel combination of C1, C2, and C15. Adjust the
output capacitance such that the product of F
G
obtained this way will be much greater than the value
obtained using the maximum output voltage ripple
specification.
8
P
is below F
_______________________________________________________________________________________
G
P
OUT
CS
=
⎛
⎜
⎝
F
is the current-sense resistor, F
P
2
is the output filter capacitor, which is the
ZRHP
2
× ×
=
L F
2
/ 6. The value of output capacitance
π
G
SW
V
×
IN
P
C
2
=
×
FB
OUT
VLED
P2
Δ
(
1
Δ
EA
equal to unity.
−
VLED
, at which the power-circuit
D
× ×
1
OUT
MAX
3
2
+
R
V
)
I
CS
O
IN
⎞
⎟ ×
⎠
×
G
R
P
CS
SW
×
3
P2
is the
OUT
and
).
The compensation strategy is as follows. The gain-
frequency response of the feedback loop should cross
0dB at or below half of the RHP zero frequency, with a
slope of -20dB/decade for the feedback to be stable
and have sufficient phase margin. The compensation
network from the COMP pin to the FB pin of MAX16807
(formed by R1, C6, C7, and R11) offers one dominant
pole (P1), a zero (Z1), and a high-frequency pole (P3).
There are two very-low-frequency poles and a zero in
the loop before the crossover frequency. The function of
the zero (Z1) is to compensate for the output pole and
reduce the slope of the loop gain from -40dB/decade to
-20dB/decade, and also to reduce the phase lag by 90°.
Choose the crossover frequency to be half of the worst-
case RHP zero frequency:
Place the zero (Z1) at one-third of the crossover fre-
quency so that the phase margin starts improving from
a sufficiently lower frequency:
Use the following equation to calculate the dominant
pole location so that the loop gain crosses 0dB at F
As the open-loop gain of the error amplifier can have
variations, the dominant pole location can also vary
from device to device. In the MAX16807 EV kit, the
dominant pole location is decided by the error-amplifier
gain and so the combined effect is a constant gain-
bandwidth product.
Select the value of R11 such that the input bias current
of the error amplifier does not cause considerable drop
across it. The effective AC impedance seen from the
FB pin is the sum of R11 and R12. It is preferable to
keep R12 much less, compared to R11, to have better
control on the AC impedance. Find C6 using the follow-
ing equation:
C
6
=
F
P
2
1
π
=
×
F
G
C
2 G
F
Z
EA
F
=
×
1
ZRHP
=
×
F
TOT
ZRHP
(
R
F
2
3
1
C
11
×
×
F
+
F
Z
P2
R
1
12
)
×
F
P
1
C
: