Datasheet

Reference Voltage (REFIN)
The MAX15038 uses an internal 0.6V reference or an
external reference input. To use the internal 0.6V refer-
ence, install a shunt on jumper JU2 shorting U1’s REFIN
and SS pins.
When using an external reference, perform the follow-
ing steps:
1) Remove the shunt from jumper JU2.
2) Install a surface-mount 0603 capacitor at C7 for
soft-starting, if needed.
3) Connect a 0V to (VDD - 2V) reference across the
REF_IN and GND PCB pads.
The IC regulates FB to the voltage at U1’s REFIN pin.
The internal soft-start is not available when using an
external reference. Refer to the Soft-Start and REFIN
section in the MAX15038 IC data sheet for more infor-
mation on using the REFIN features. See Table 2 to
configure jumper JU2.
Evaluating Other Output Voltages
The EV kit comes preset to a 1.8V output voltage. The
output voltage is selectable using jumpers JU3 (CTL1)
and JU4 (CTL2) to provide three different logic level
inputs: VDD, unconnected, and GND. The logic states
of CTL1 and CTL2 should be selected only before
power-up. CTL1 and CTL2 should not be changed
once soft-start is complete. If the output voltage needs to
be reselected, perform the following steps:
1) Disable the regulator using jumper JU1, or remove
power.
2) Set the CTL1 and CTL2 logic states using jumpers
JU3 and JU4.
3) Enable the regulator, or apply power.
See Table 3 to configure jumpers JU3 and JU4.
When externally programming the MAX15038, install a
8.06kΩ surface-mount 0603 resistor at R8 and then
select a value for a surface-mount 0603 resistor at R9
using the following equation:
where V
OUT
is the desired output voltage and V
REFIN
is
the voltage applied at the REF_IN and GND PCB pads.
Refer to the MAX15038 IC data sheet for information on
selecting output inductor, capacitor, and compensation
components to optimize the circuit for different output
voltages.
Mode Selection
The MAX15038 IC’s three functional modes (forced
PWM, monotonic startup, and skip) are programmable
using jumper JU5. Refer to the MODE Selection section
in the MAX15038 IC data sheet for more information on
the IC’s three functional modes. See Table 4 to config-
ure jumper JU5.
R9
806
k
Vk
VV
if u
REFIN
OUT REFIN
Ω
Ω
[]
=
×
()
−
()
.
, siing external V
REFIN
R
0.6V
or9
806
06
k
k
VV
OUT
Ω
Ω
[]
=
×
()
−
()
.
.
Evaluates: MAX15038/MAX15039
MAX15038 Evaluation Kit
_______________________________________________________________________________________ 3
Table 1. Regulator Enable (JU1)
SHUNT
POSITION
EN PIN
CONNECTION
MAX15038
FUNCTION
Not installed
Pulled up to IN through
resistor R2
Enabled
Installed GND Disabled
Table 2. Reference Voltage (JU2)
SHUNT
POSITION
REFIN PIN
CONNECTION
REFERENCE
VOLTAGE
Installed U1 SS pin Internal 0.6V reference
Not installed
REF_IN PCB pad
through resistor R3
User-supplied reference
voltage
Range: 0V to (VDD - 2V)