Datasheet

MaximIntegrated │ 3
Evaluates: MAX17503 in
5V Output-Voltage Application
MAX17503 5V Output Evaluation Kit
www.maximintegrated.com
Regulator Enable/Undervoltage-Lockout
Level (EN/UVLO)
The device offers an adjustable input undervoltage-
lockout level. For normal operation, a shunt should be
installedacrosspins1-2onjumperJU1.Todisablethe
output,installashuntacrosspins2-3onJU1andtheEN/
UVLOpinispulledtoGND.SeeTable1forJU1settings.
Setthevoltageatwhichthedeviceturnsonwiththeresis-
tivevoltage-dividerR1/R2connectedfromVIN_toSGND.
ConnectthecenternodeofthedividertoEN/UVLO.
ChooseR1tobe3.32MΩandthencalculateR2asfollows:
INU
R1 1.215
R2
(V 1.215)
×
=
−
where V
INU
is the voltage at which the device is required
to turn on.
MODE Selection (MODE)
The device’s MODE pin can be used to select among
PWM,PFM,orDCMmodesofoperation.Thelogicstate
oftheMODEpinislatchedwhenVCCandEN/UVLOvolt-
agesexceedtherespectiveUVLOrisingthresholdsand
allinternalvoltagesarereadytoallowLXswitching.State
changes on the MODE pin are ignored during normal
operation.RefertotheMAX17503ICdatasheetformore
informationonPWM,PFM,andDCMmodesofoperation.
Table 2 shows EV kit jumper settings that can be used to
configure the desired mode of operation.
External Clock Synchronization (SYNC)
The internal oscillator of the device can be synchronized
toanexternalclocksignalontheSYNCpin.Theexternal
synchronization clock frequency must be between 1.1f
SW
and 1.4f
SW
, where f
SW
is the frequency of operation
setbyR5.Theminimumexternalclockhighpulsewidth
should be greater than 50ns and the minimum external
clocklowpulsewidthshouldbegreaterthan160ns.
*Default position.
*Default position.
*Default position.
SHUNT
POSITION
EN/UVLO PIN MAX17503_ OUTPUT
1-2*
ConnectedtoVIN Enabled
Not
installed
Connected to the
center node of
resistor-dividerR1
andR2
Enabled,UVLOlevel
setthroughtheR1and
R2resistors
2-3 ConnectedtoSGND Disabled
SHUNT
POSITION
MODE PIN MAX17503_ MODE
Not installed* Unconnected
PFMmodeof
operation
1-2
Connected to
SGND
PWMmodeof
operation
2-3
Connected to
VCC
DCM mode of
operation
SHUNT
POSITION
SYNC PIN MAX17503_ SYNC
1-2
Connected to
testlooponPCB
Frequencycanbe
synchronized with an
external clock
2-3*
Connected to
SGND
SYNCfeatureunused
Table 1. Regulator Enable (EN/UVLO)
Description (JU1)
Table 2. MODE Description (JU2)
Table 3. SYNC Description (JU3)