MAX5090EVKIT Maxim Integrated Products, MAX5090EVKIT Datasheet - Page 12

• Manufacturer Part Number: MAX5090EVKIT
• Description: EVAL KIT FOR MAX5090
• Manufacturer: Maxim Integrated Products

Specifications of MAX5090EVKIT

• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 5V
• Current - Output: 2A
• Voltage - Input: 7.5 ~ 76V
• Regulator Topology: Buck
• Frequency - Switching: 125kHz
• Board Type: Fully Populated
• Utilized Ic / Part: MAX5090
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

2A, 76V, High-Efficiency MAXPower Step-Down
DC-DC Converters
where:
I
and f
For example, at V
input capacitance are calculated for the input peak-to-
peak ripple of 100mV or less, yielding an ESR and
capacitance value of 40mΩ and 100µF, respectively.
Low-ESR ceramic multilayer chip capacitors are recom-
mended for size-optimized application. For ceramic
capacitors assume the contribution from ESR and capaci-
tor discharge is equal to 10% and 90%, respectively.
The input capacitor must handle the RMS ripple current
without significant rise in the temperature. The maxi-
mum capacitor RMS current occurs at approximately
50% duty cycle. Ensure that the ripple specification of
the input capacitor exceeds the worst-case capacitor
RMS ripple current. Use the following equations to cal-
culate the input capacitor RMS current:
where:
I
input average current, and η is the converter efficiency.
The ESR of the aluminum electrolytic capacitor increas-
es significantly at cold temperatures. Use a 1µF or
greater value ceramic capacitor in parallel with the alu-
minum electrolytic input capacitor, especially for input
voltages below 8V.
12
OUT
PRMS
______________________________________________________________________________________
SW
is the maximum output current of the converter
is the input switch RMS current, I
is the oscillator switching frequency (127kHz).
I
I
D
PRMS
I
PK
I
DC
AVGin
=
=
=
I
∆I
CRMS
I
V
=
OUT
I
OUT
V
=
L
OUT
ESR
C
IN
IN
V
IN
=
(
OUT x
I
+
PK
(
= 48V, V
V
IN
=
V
=
−
IN
IN
2
∆
I
=
OUT
2
∆
I
D
I
V
L
+
PRMS
−
2
x
∆
I
IN
L



=
V
I
V
I
I
OUT
DC
OUT
η
Q
OUT
×
×
V
∆
f
V
OUT
OUT
D
×
SW
2
2
V
IN
ESR
1 (
f
−
+
+
SW
)
I
×
−
AVGin
I PK xI DC
×
∆
= 3.3V, the ESR and
2
D
V
I
L
L
OUT
)



2
)
x
AVGin
D
3
is the
The output capacitor C
inductor and a zero with its ESR. The MAX5090’s inter-
nal fixed compensation is designed for a 100µF capaci-
tor, and the ESR must be from 20mΩ to 100mΩ. The
use of an aluminum or tantalum electrolytic capacitor is
recommended. See Table 2 to choose an output
capacitor for stable operation.
The output ripple is comprised of ∆V
capacitor discharge), and ∆V
of the capacitor). Use low-ESR tantalum or aluminum
electrolytic capacitors at the output. Use the following
equations to calculate the contribution of output capac-
itance and its ESR on the peak-to-peak output ripple
voltage:
The MAX5090 has a programmable soft-start time (t
The output rise time is directly proportional to the out-
put capacitor, output voltage, and the load. The output
rise time also depends on the inductor value and the
current-limit threshold. It is important to keep the output
rise time at startup the same as the soft-start time (t
to avoid output overshoot. Large output capacitors take
longer than the programmed soft-start time (t
cause error-amplifier saturation. This results in output
overshoot. Use greater than 2ms soft-start time for a
100µF output capacitor.
Figure 3. Forward-Voltage Drop vs. Temperature of the Internal
Body Diode of MAX5090
800
700
600
500
400
300
200
100
0
-40
∆
∆
V
V
OESR
OQ
25
≈
TEMPERATURE (°C)
=
8
OUT
xC
∆
Output Filter Capacitor
I x ESR
100
L
OUT
forms double pole with the
OESR
∆
I
L
x f
125
(caused by the ESR
SW
OQ
(caused by the
150
SS
) and
SS
SS
).
)