Datasheet

MAX15036/MAX15037
Inductor
Choose the minimum inductor value so the converter
remains in continuous mode operation at minimum out-
put current (I
OUTMIN
).
where
and I
OUTMIN
= 0.25 x I
OUT
.
The V
D
is the forward voltage drop of the external
Schottky diode, D is the duty cycle, and V
DS
is the volt-
age drop across the internal switch. Select the inductor
with low DC resistance and with a saturation current (I
SAT
)
rating higher than the peak switch current limit of 5.6A.
Input Capacitor
The input current for the boost converter is continuous
and the RMS ripple current at the input is low. Calculate
the capacitor value and ESR of the input capacitor
using the following equations.
where
where V
DROP
is the total voltage drop across the inter-
nal MOSFET plus the voltage drop across the inductor
ESR. ΔI
P-P
is the peak-to-peak inductor ripple current
as calculated above. ΔV
Q
is the portion of input ripple
due to the capacitor discharge and ΔV
ESR
is the contri-
bution due to ESR of the capacitor.
Output Capacitor
For the boost converter, the output capacitor supplies
the load current when the main switch is on. The
required output capacitance is high, especially at high-
er duty cycles. Also, the output capacitor ESR needs to
be low enough to minimize the voltage drop due to the
ESR while supporting the load current. Use the follow-
ing equation to calculate the output capacitor for a
specified output ripple tolerance.
I
OUT
is the load current, ΔV
Q
is the portion of the ripple
due to the capacitor discharge, and ΔV
ESR
is the con-
tribution due to the ESR of the capacitor. D
MAX
is the
maximum duty cycle at minimum input voltage.
Power Dissipation
The MAX15036/MAX15037 are available in thermally
enhanced 16-pin, 5mm x 5mm TQFN packages that
dissipate up to 2.7W at T
A
= +70°C. When the die tem-
perature reaches +170°C, the MAX15036/MAX15037
shut down (see the Thermal-Overload Protection sec-
tion). The power dissipated in the device is the sum of
the power dissipated from supply current (P
Q
), power
dissipated due to switching the internal power MOSFET
(P
SW
), and the power dissipated due to the RMS cur-
rent through the internal power MOSFET (P
MOSFET
).
The total power dissipated in the package must be lim-
ited so the junction temperature does not exceed its
absolute maximum rating of +150°C at maximum ambi-
ent temperature.
The power dissipated in the switch is:
P
MOSFET
= I
RMS_MOSFET
x R
ON
For the buck converter:
ΔI
P-P
is the peak-to-peak inductor current ripple.
IID
ID
RMS MOSFET OUT
PP
_
()=×+
×
⎛
⎝
⎜
⎜
⎞
⎠
⎟
⎟
−
2
2
12
Δ
C
ID
Vf
OUT
OUT MAX
QSW
=
×
×Δ
ESR
V
I
ESR
OUT
=
Δ
ΔI
VV D
Lf
PP
IN DROP
SW
−
=
−
()
×
×
ESR
V
I
ESR
PP
=
−
Δ
Δ
C
ID
fV
IN
PP
SW Q
=
×
××
−
Δ
Δ4
D
VVV
VVV
OUT D IN
OUT D DS
=
+−
+−
L
VD
fV I
MIN
IN
SW OUT OUTMIN
=
××
×× ×
2
2
η
2.2MHz, 3A Buck or Boost Converters
with an Integrated High-Side Switch
16 ______________________________________________________________________________________