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MAX887 Evaluation Kit
_______________General Description
The MAX887 evaluation kit (EV kit) provides a 3.3V output 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 (2.5A 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 surfacemount circuit board. It can be used to evaluate other output voltages by changing feedback resistors R1 and R2.
____________________________Features
o 3.3V Output Voltage o 600mA Output Current o Efficiency = 93%, VIN = 5V, VOUT = 3.3V @ IOUT = 0.2A o Low Dropout Voltage o 100% Max Duty Cycle o Internal MOSFET o Internal Synchronous Rectifier o 5A Max Shutdown Current o 300kHz Switching Frequency o 8-Pin SO, Surface-Mount Construction o Fully Assembled and Tested
Evaluates: MAX887
____________________Component List
DESIGNATION QTY C1, C2 C3 C4 C5 C6 C7 D1 JU1, JU2 L1 R1 R2 U1 None None None 2 1 1 1 1 0 1 2 1 1 1 1 2 1 1 DESCRIPTION 47F, 16V tantalum capacitors AVX TPSD47M016R0150 Sprague 593D476X0016D2W 0.33F ceramic capacitor 2.2F, 20V tantalum capacitor Sprague 595D225X0020A2T 0.047F ceramic capacitor 100pF ceramic capacitor Open Schottky diode Motorola MBRS130T3 Nihon EC10QS02 3-pin headers 33H inductor Sumida CD54-330 165k, 1% resistor 100k, 1% resistor MAX887HESA Shunts MAX887 PC board MAX887 data sheet
______________Ordering Information
PART MAX887EVKIT-SO TEMP. RANGE 0C to +70C BOARD TYPE Surface Mount
_________________________Quick Start
The 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. 1) Connect a +5V supply voltage to the VIN pad. The ground connects to the GND pad. 2) Connect a voltmeter and load, if any, to the VOUT pad. 3) For normal operation, place the shunt on JU1 across pins 2 and 3. 4) Turn on the power supply to the board, and verify that the output voltage is 3.3V. (To select other output voltages, refer to the Output Voltage Selection section in the MAX887 data sheet for instructions on selecting feedback resistors R1 and R2.)
______________Component Suppliers
SUPPLIER AVX Coilcraft Motorola Nihon Sprague Sumida Vishay/Vitramon PHONE (803) 946-0690 (800) 282-4975 (847) 639-6400 (602) 303-5454 (805) 867-2555 (603) 224-1961 (847) 956-0666 (203) 268-6261 FAX (803) 626-3123 (847) 639-1469 (602) 994-6430 (805) 867-2698 (603) 224-1430 (847) 956-0702 (203) 452-5670
________________________________________________________________ Maxim Integrated Products
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For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
MAX887 Evaluation Kit Evaluates: MAX887
VIN 3.5V TO 11V JU1 SHDN VL JU2 SYNC 3 6 2 1 SYNC 3 1 2 1 SHDN C1 47F 16V V+ LX C3 0.33F 8 7 L1 33H C2 47F 16V VOUT 3.3V C6 100pF R1 165k 1% 4 C4 2.2F 20V C5 0.047F VL REF 3 FB 2 C7 OPEN R2 100k 1% VOUT = (1 + R1/R2) x 1.25V
U1 MAX887
GND 5 D1 MBRS130
VL
Figure 1. MAX887 EV Kit Schematic
_______________Detailed Description
The MAX887 provides a 3.3V output from a +3.5V to +11V input voltage. It delivers up to 500mA, and operates with up to 100% duty cycle for low dropout voltage. Other output voltages can be programmed by changing feedback resistor R1. R1 is given by the following equation:
operation improves efficiency and reduces quiescent current typically to 200A. 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 Operation section in the MAX887 data sheet for more information.
Table 1. Jumper JU1 Functions
SHUNT LOCATION 1&2 2&3
SHDN PIN
V R1 = R2 OUT - 1 VFB
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 internal switching MOSFET and synchronous rectifier turn off and the output voltage falls to 0V. Connect the SHDN pin 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 dataacquisition circuits, a SYNC pad is provided on the board for synchronization to an external clock. When SYNC is connected to GND, Idle ModeTM operation is enabled and the MAX887 is placed in PFM mode at light loads. PFM
Idle Mode is a trademark of Maxim Integrated Products.
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MAX887 OUTPUT Shutdown mode, VOUT = 0V MAX887 enabled, VOUT = 3.3V
Connected to GND Connected to VIN
Table 2. Jumper JU2 Functions
SHUNT LOCATION 1&2 SYNC PIN Connected to GND OPERATING MODE Idle mode, PFM; IQUIESCENT = 200A Low-noise, fixed-frequency PWM operation; IQUIESCENT = 2.7mA
2&3
Connected to VL
Open
Connected to an Synchronization to an external SYNC pad external clock
_______________________________________________________________________________________
MAX887 Evaluation Kit Evaluates: MAX887
Figure 2. MAX887 EV Kit Component Placement Guide-- Component Side
Figure 3. MAX887 EV Kit PC Board Layout--Component Side
Figure 4. MAX887 PC Board Layout--Solder Side
_______________________________________________________________________________________
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MAX887 Evaluation Kit Evaluates: MAX887
NOTES
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.
4 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 (c) 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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