Datasheet

For the boost converter:
The power lost due to switching the internal power
MOSFET is:
t
R
and t
F
are the rise and fall times of the internal power
MOSFET measured at SOURCE.
The power lost due to the switching quiescent current
of the device is:
P
Q
= V
IN
x I
SW
(MAX15036)
The switching quiescent current (I
SW
) of the
MAX15036/MAX15037 is dependent on switching fre-
quency. See the Typical Operating Characteristics sec-
tion for the value of I
SW
at a given frequency.
In the case of the MAX15037, the switching current
includes the synchronous rectifier MOSFET gate-drive
current (I
SW-DL
). The I
SW-DL
depends on the total gate
charge (Q
g-DL
) of the synchronous rectifier MOSFET
and the switching frequency.
P
Q
= V
IN
x (I
SW
+ I
SW-DL
) (MAX15037)
I
SW-DL
= Q
g-DL
x f
SW
where the Q
g-DL
is the total gate charge of the synchro-
nous rectifier MOSFET at V
GS
= 5V.
The total power dissipated in the device is:
P
TOTAL
= P
MOSFET
+ P
SW
+ P
Q
Calculate the temperature rise of the die using the fol-
lowing equation:
T
J
= T
C
+ (P
TOTAL
x θ
JC
)
θ
JC
is the junction-to-case thermal resistance equal to
1.7°C/W. T
C
is the temperature of the case and T
J
is
the junction temperature, or die temperature. The case-
to-ambient thermal resistance is dependent on how
well heat can be transferred from the PCB to the air.
Solder the underside exposed pad to a large copper
GND plane. If the die temperature reaches +170°C the
MAX15036/MAX15037 shut down and do not restart
again until the die temperature cools by 25°C.
Compensation
The MAX15036/MAX15037 have an internal transcon-
ductance error amplifier with an inverting input (FB)
and output (COMP) available for external frequency
compensation. The flexibility of external compensation
and high switching frequencies for the MAX15036/
MAX15037 allow a wide selection of output filtering
components, especially the output capacitor. For cost-
sensitive applications, use high-ESR aluminum elec-
trolytic capacitors. For size-sensitive applications, use
low-ESR tantalum or ceramic capacitors at the output.
Before designing the compensation components, first
choose all the passive power components that meet
the output ripple, component size, and component cost
requirements. Secondly, choose the compensation
components to achieve the desired closed-loop band-
width and phase margin. Use a simple 1-zero, 2-pole
pair (Type II) compensation if the output capacitor ESR
zero frequency (f
ZESR
) is below the unity-gain
crossover frequency (f
C
). Use a 2-zero, 2-pole (Type
III) compensation when the f
ZESR
is higher than f
C
.
Buck Converter Compensation
Use procedure 1 to calculate the compensation net-
work components when f
ZESR
< f
C
.
Procedure 1 (see Figure 3)
Calculate the f
ZESR
and f
LC
double pole:
Calculate the unity-gain crossover frequency as:
f
f
C
SW
=
20
f
ESR C
f
LC
ZESR
OUT
LC
OUT
=
××
=
××
1
2
1
2
π
π
P
VI tt f
SW
IN OUT R F SW
=
××+
()
×
4
I
PK
=+
−
I
I
IN
PP
Δ
2
I
DC
=−
−
I
I
IN
PP
Δ
2
ΔI
VV D
Lf
PP
IN DROP
SW
−
=
−
()
×
×
I
VI
V
IN
OUT OUT
IN
=
×
×η
II+I+(II
D
3
RMS_MOSFET DC PK DC PK
MAX
22
=××())
MAX15036/MAX15037
2.2MHz, 3A Buck or Boost Converters
with an Integrated High-Side Switch
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