MAX15037ATE+T Maxim Integrated Products, MAX15037ATE+T Datasheet - Page 14

• Manufacturer Part Number: MAX15037ATE+T
• Description: IC DC/DC CONV 3A 16-TQFN-EP
• Manufacturer: Maxim Integrated Products
• Type: Step-Down (Buck)r

Specifications of MAX15037ATE+T

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 23 V
• Current - Output: 3A
• Frequency - Switching: 200kHz ~ 2.2MHz
• Voltage - Input: 4.5 ~ 23 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 16-TQFN Exposed Pad
• Power - Output: 2.67W
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The MAX15036/MAX15037 can operate with input sup-
plies ranging from 4.5V to 5.5V or 5.5V to 23V. The
input voltage range (V+) can be constrained to a mini-
mum by the duty-cycle limitations and to a maximum by
the on-time limitation. The minimum input voltage is
determined by:
D
V
that includes the diode’s forward voltage drop (or the
drop across the synchronous rectifier MOSFET), and
the drops across the series resistance of the inductor
and PCB traces. V
tors charging path, which includes the drop across the
internal power MOSFET, and the drops across the
series resistance of the inductor and PCB traces.
The maximum input voltage can be determined by:
where t
For 0.6V or greater output voltages, connect a resistive
divider from V
SGND resistor (R2) from 1kΩ to 10kΩ and calculate the
resistor from OUT to FB (R1) by the following equation:
where V
For designs that use a Type III compensation scheme,
first calculate R1 for stability requirements (see the
Compensation section) then choose R2 so that:
See Figure 4.
Three key inductor parameters must be specified for
operation with the MAX15036/MAX15037: inductance
value (L), peak inductor current (I
saturation current (I
2.2MHz, 3A Buck or Boost Converters
with an Integrated High-Side Switch
14
DROP1
MAX
______________________________________________________________________________________
V
IN MIN
ON_MIN
is the maximum duty cycle of 87.5% (typ).
FB
is the total drop in the inductor discharge path
_
= 0.6V, see Figure 3.
=
= 100ns and f
OUT
V
V
IN MAX
OUT
R
_
DROP2
1
R
SAT
to FB to SGND. Select the FB to
=
D
2
+
R
MAX
=
). The minimum required induc-
2
Effective Input Voltage Range
V
=
V
DROP
×
R
OUT
is the total drop in the induc-
t
⎡
⎢
⎣
1
ON MIN
SW
Setting the Output Voltage
V
×
V
OUT
FB
1
_
−
is the switching frequency.
V
V
+
OUT
V
FB
FB
V
−
DROP
PEAK
1
×
Inductor Selection
⎤
⎥
⎦
f
SW
), and inductor
2
−
V
DROP
1
tance is a function of operating frequency, input-to-out-
put voltage differential, and the peak-to-peak inductor
current (ΔI
value, while a lower ΔI
value. A lower inductor value minimizes size and cost,
improves large-signal and transient response, but
reduces efficiency due to higher peak currents and
higher peak-to-peak output voltage ripple for the same
output capacitor. On the other hand, higher inductance
increases efficiency by reducing the ripple current.
Resistive losses due to extra wire turns can exceed the
benefit gained from lower ripple current levels especial-
ly when the inductance is increased without also allow-
ing for larger inductor dimensions. A good compromise
is to choose ΔI
Use the following equation to calculate the inductance:
V
optimum for typical conditions. The switching frequency
is set by R
section). The peak-to-peak inductor current, which
reflects the peak-to-peak output ripple, is worse at the
maximum input voltage. See the Output Capacitor
Selection section to verify that the worst-case output rip-
ple is acceptable. The inductor saturation current is also
important to avoid runaway current during continuous
output short-circuit. At high input-to-output differential,
and high switching frequency, the on-time drops to the
order of 100ns. Though the MAX15036/MAX15037 can
control the on-time as low as 100ns, the internal current-
limit circuit may not detect the overcurrent within this
time. In that case, the output current during the fault
may exceed the current limit specified in the Electrical
Characteristics table. The overtemperature shutdown
protects the MAX15036/MAX15037 against the output
short-circuit fault. However, the output current may
reach 5.6A. Choose an inductor with a saturation current
of greater than 5.6A when the minimum on-time for a
given frequency and duty cycle is less than 200ns.
The discontinuous input current of the buck converter
causes large input ripple current. The switching frequen-
cy, peak inductor current, and the allowable peak-to-
peak input voltage ripple dictate the input capacitance
requirement. Increasing the switching frequency or the
inductor value lowers the peak-to-average current ratio
yielding a lower input capacitance requirement.
IN
and V
OSC
P-P
OUT
). Higher ΔI
P-P
(see the Setting the Switching Frequency
are typical values so that efficiency is
L
equal to 30% of the full load current.
=
V
V
OUT IN
I
N
P-P
×
P-P
(V
f
SW
requires a higher inductor
allows for a lower inductor
−
×
V
Δ
OUT
I
P P
−
)
Input Capacitors