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MAX887EVKIT
Evaluation Kit for the MAX887
_________________________Quick StartThe MAX887 EV kit is fully assembled and tested.
Follow these steps to verify board operation. Do not
turn on the power supply until all connections are
completed.Connect a +5V supply voltage to the VIN pad. The
ground connects to the GND pad.Connect a voltmeter and load, if any, to the VOUT
pad.For normal operation, place the shunt on JU1
across pins 2 and 3.Turn on the power supply to the board, and verify
that the output voltage is 3.3V. (To select other out-
put voltages, refer to the Output Voltage Selection
section in the MAX887 data sheet for instructions on
selecting feedback resistors R1 and R2.)
_______________General DescriptionThe MAX887 evaluation kit (EV kit) provides a 3.3V out-
put voltage from a +3.5V to +11V input. It delivers up to
600mA and operates with up to 100% duty cycle for low
dropout voltage. Typical efficiencies are 93%. The
MAX887 features a low-current (2.5µA typ) shutdown
mode, as well as current-mode operation for superior
load and line response. Cycle-by-cycle current limiting
protects the internal MOSFET and rectifier.
This EV kit is a fully assembled and tested surface-
mount circuit board. It can be used to evaluate other
output voltages by changing feedback resistors R1
and R2.
____________________________Features3.3V Output Voltage600mA Output CurrentEfficiency = 93%, VIN= 5V,
VOUT= 3.3V @ IOUT= 0.2ALow Dropout Voltage 100% Max Duty CycleInternal MOSFETInternal Synchronous Rectifier5µA Max Shutdown Current300kHz Switching Frequency8-Pin SO, Surface-Mount ConstructionFully Assembled and Tested
Evaluates: MAX887
MAX887 Evaluation Kit
____________________Component List
______________Ordering Information
Evaluates: MAX887
MAX887 Evaluation Kit
_______________Detailed DescriptionThe MAX887 provides a 3.3V output from a +3.5V to
+11V input voltage. It delivers up to 500mA, and oper-
ates with up to 100% duty cycle for low dropout voltage.
Other output voltages can be programmed by chang-
ing feedback resistor R1. R1 is given by the following
equation:
where R2 = 100k and VFB= 1.25V
The 3-pin header JU1 selects shutdown mode. Table 1
lists the selectable jumper options. In shutdown, the inter-
nal switching MOSFET and synchronous rectifier turn off
and the output voltage falls to 0V. Connect the SHDNpin
to VIN for normal operation.
The 3-pin header JU2 selects synchronization mode.
Table 2 lists the selectable jumper options.
To avoid RF interference with sensitive IF and data-
acquisition circuits, a SYNC pad is provided on the board
for synchronization to an external clock. When SYNC is
connected to GND, Idle Mode™ operation is enabled and
the MAX887 is placed in PFM mode at light loads. PFM
operation improves efficiency and reduces quiescent cur-
rent typically to 200µA. When SYNC is connected to VL,
forced PWM operation is enabled. PWM operation
reduces noise in sensitive communications applications.
Refer to the Forced PWM and Idle Mode Operationsec-
tion in the MAX887 data sheet for more information.
Figure 1. MAX887 EV Kit Schematic
Idle Mode is a trademark of Maxim Integrated Products.
Evaluates: MAX887
MAX887 Evaluation KitFigure 2. MAX887 EV Kit Component Placement Guide—
Component Side
Figure 3. MAX887 EV Kit PC Board Layout—Component SideFigure 4. MAX887 PC Board Layout—Solder Side
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Evaluates: MAX887
MAX887 Evaluation Kit
NOTES
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