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MAX887 Evaluation Kit
_______________General Description
The 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.
____________________________Features
o
3.3V Output Voltage
o
600mA Output Current
o
Efficiency = 93%, V
IN
= 5V,
V
OUT
= 3.3V @ I
OUT
= 0.2A
o
Low Dropout Voltage
o
100% Max Duty Cycle
o
Internal MOSFET
o
Internal Synchronous Rectifier
o
5µA 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
47µF, 16V tantalum capacitors
AVX TPSD47M016R0150
Sprague 593D476X0016D2W
0.33µF ceramic capacitor
2.2µF, 20V tantalum capacitor
Sprague 595D225X0020A2T
0.047µF ceramic capacitor
100pF ceramic capacitor
Open
Schottky diode
Motorola MBRS130T3
Nihon EC10QS02
3-pin headers
33µH inductor
Sumida CD54-330
165kΩ, 1% resistor
100kΩ, 1% resistor
MAX887HESA
Shunts
MAX887 PC board
MAX887 data sheet
______________Ordering Information
PART
MAX887EVKIT-SO
TEMP. RANGE
0°C to +70°C
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 out-
put 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
1
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
47µF
16V
V+
LX
C3
0.33µF
8
7
L1
33µH
C2
47µF
16V
VOUT
3.3V
C6
100pF
R1
165k
1%
4
C4
2.2µF
20V
C5
0.047µF
VL
REF
3
FB
2
C7
OPEN
R2
100k
1%
V
OUT
= (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 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:
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 Operation
sec-
tion 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
V
FB
where R2 = 100k and V
FB
= 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
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 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
Idle Mode is a trademark of Maxim Integrated Products.
2
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;
I
QUIESCENT
= 200µA
Low-noise, fixed-frequency
PWM operation;
I
QUIESCENT
= 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
_______________________________________________________________________________________
3
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
© 1996 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.

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