Datasheet

lower end of the AM band. The MAX5096 is suitable for
noise-sensitive applications like AM radio power supply.
For an application where size is more important, use the
MAX5097, which runs at 330kHz frequency. The high-
frequency operation reduces the size and cost of the
external inductor and capacitor. The MAX5096/MAX5097
can be synchronized using an external signal. The
MAX5096 can be synchronized from 120kHz to 500kHz,
while the MAX5097 is capable of synchronizing from
300kHz to 500kHz. The external synchronization feature
makes frequency hopping possible depending on the
selected AM channel. Connect SYNC to ground, if not
used.
Thermal Protection
When the junction temperature exceeds T
J
= +165°C,
an internal thermal sensor signals the shutdown logic,
which turns off the regulator (both in buck mode and LDO
mode), and discharges the soft-start capacitor allowing
the IC to cool. The thermal sensor turns the regulator
on again after the IC’s junction temperature cools by
20°C, resulting in a cycled output during continuous
thermal-overload conditions. The thermal hysteresis and
a soft-start period limit the average power dissipation
into the device during continuous fault condition. During
operation, do not exceed the absolute maximum junction
temperature rating of T
J
= +150°C.
Applications Information
Output Voltage Selection
The MAX5096/MAX5097 can be configured as either
a preset fixed-output voltage or an adjustable-output
voltage device. Connect ADJ to ground to select the
factory-preset output-voltage option (Figure 2). The
MAX5096A/MAX5097A and MAX5096B/MAX5097B
provide a fixed-output voltage equal to 3.3V and 5V,
respectively (see the Selector Guide). The MAX5096/
MAX5097 become an adjustable version as soon as the
devices detect about 125mV at the ADJ pin. The resistor-
divider at ADJ increases the ADJ voltage above 125mV
and also adjusts the output voltage depending upon the
resistor values. In adjustable mode, select an output
between +1.273V and +11V using two external resistors
connected as a voltage-divider to ADJ (Figure 4). Set the
output voltage using the following equation:
OUT ADJ
R1
VV1
R2

= ×+


where V
ADJ
= 1.273V and R2 is chosen to be approxi-
mately 100kΩ.
Connect ADJ to GND if adjustable mode is not used.
Inductor Selection
Three key inductor parameters must be specified for
proper operation with the MAX5096/MAX5097: induc-
tance value (L), peak inductor current (I
PEAK
), and
inductor saturation current (I
SAT
). The minimum required
inductance is a function of operating frequency, input-to-
output-voltage differential, and the peak-to-peak inductor
current (ΔI
P-P
). Higher ΔI
P-P
allows for a lower inductor
value, while a lower ΔI
P-P
requires a higher inductor
value. A lower inductor value minimizes size and cost
and 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, especially when the
inductance is increased while keeping the dimension of
the inductor constant. A good compromise is to choose
ΔI
P-P
equal to 40% of the full load current. Calculate the
inductor value using the following equation:
OUT IN OUT
IN SW P P
V (V V )
L
Vf I
−
−
=
× ×∆
Figure 3. Output Voltage Tracking/Sequencing
V
OUT3
V
OUT2
V
OUT1
SOFT-START
STOP
RATIOMETRIC TRACKING OUTPUTS
SEQUENCED OUTPUTS
STOP
SOFT-START
V
OUT3
V
OUT2
V
OUT1
MAX5096/MAX5097 40V, 600mA Buck Converters with Low-
Quiescent-Current Linear Regulator Mode
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