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MAX770 Evaluation Kit
_______________General Description
The MAX770 evaluation kit (EV kit) provides a regulated 5V output voltage from a 3V input source. It drives loads up to 1A with greater than 80% conversion efficiency. This EV kit is a fully assembled and tested surfacemount circuit board. Additional pads on the bottom of the board accommodate the external feedback resistors for setting different output voltages. The MAX770 EV kit comes with a MAX770CSA IC, but it can also evaluate the 12V-output MAX771 or 15V-output MAX772--simply order a free sample of the MAX771CSA or MAX772CSA to substitute for the MAX770CSA.
____________________________Features
o 5V or Adjustable Output Voltage o 2.7V to 5.5V Input Range o Up to 1A Output Current o 5A Max Shutdown Current o 110A Max Supply Current o 300kHz Switching Frequency o 8-Pin SO, Surface-Mount Construction o Fully Assembled and Tested
Evaluates: MAX770
______________Ordering Information
PART MAX770EVKIT-SO TEMP. RANGE 0C to +70C PIN-PACKAGE Surface Mount
____________________Component List
DESIGNATION QTY DESCRIPTION 150F, 10V low-ESR tantalum capacitor Sprague 595D157X0010D7 AVX TPSE227M010R0100 330F, 10V low-ESR tantalum capacitor Sprague 595D337X001047 AVX TPSE337M006R0100 0.1F, 50V ceramic capacitors Schottky diode 1N5820 or Nihon NSQ03A02 (BV = 20V, IMAX = 3A) 3-pin header 22H power inductor Sumida CDR125-220 (ISAT = 2.3A, RSERIES = 50m) N-channel FET Motorola MTD20N03HDL (BV = 30V, RDS(ON) = 40m @ VGS = 5V) 0.075 resistor (low inductance) IRC LR2010-01-R075-F or Dale WSL-2512-01-R075-F Open MAX770CSA (8-pin SO) Shunt PC board MAX770 data sheet
______________Component Suppliers
SUPPLIER AVX PHONE (803) 946-0690 (800) 282-4975 (847) 639-6400 (561) 241-7876 (605) 668-4131 (512) 992-7900 (714) 969-2491 (602) 303-5454 (805) 867-2555 (408) 988-8000 (800) 554-5565 (603) 224-1961 (847) 956-0666 FAX (803) 626-3123 (847) 639-1469 (561) 241-9339 (605) 665-1627 (512) 992-3377 (714) 960-6492 (602) 994-6430 (805) 867-2698 (408) 970-3950 (603) 224-1430 (847) 956-0702
C1
1
C2
1
Coilcraft Coiltronics Dale IRC Matsuo Motorola Nihon Siliconix Sprague Sumida
C3, C4 D1 J1 L1
2 1 1 1
N1
1
R1 R2, R3 U1 None None None
1 0 1 1 1 1
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. For small orders, phone 408-737-7600 ext. 3468.
MAX770 Evaluation Kit Evaluates: MAX770
_________________________Quick Start
The MAX770 EV kit is a fully assembled and tested surface-mount printed circuit board. Follow these steps to verify board operation. Do not turn on the power supply until all connections are completed. 1) Connect a 2.7V to 5.5V supply to the pad marked V+ The ground connects to the GND pad. 2) Connect a voltmeter and load (if any) to the VOUT pad. 3) Place the shunt on J1 across pins 1 and 2, for normal operation. 4) Turn on the power and verify that the output voltage is 5.0V. 5) Refer to the sections Evaluating the MAX771/772 and Other Output Voltages to modify the board for different output voltages.
Inductor Selection
The 22H Sumida CDR125-220 inductor that comes mounted on the EV kit board is a low-resistance, shielded, medium-current inductor. It provides excellent performance over the line and load ranges of the MAX770/MAX771/MAX772. Refer to the section Choosing an Inductor in the MAX770/MAX771/MAX772 data sheet for instructions on selecting the inductor value.
Evaluating the MAX771/MAX772
The MAX770 can be replaced by a MAX771 to generate a 12V output voltage with up to 0.5A output current, or by a MAX772 to generate a 15V output voltage with up to 0.4A output current. Besides replacing the IC, the only other modification required is to use a low-ESR output capacitor with a voltage rating of 20V or greater.
_______________Detailed Description
Jumper Selection
The 3-pin header J1 selects shutdown mode. Table 1 lists the selectable jumper options.
Other Output Voltages
The MAX770, MAX771 and MAX772 are preset for 5V, 12V, and 15V output voltages, respectively. However, their outputs may also be adjusted via an external voltage divider formed by R2 and R3 (located on the bottom of the board). The only other modification required is to cut the trace across R3. The Output Voltage Selection section of the MAX770/MAX771/ MAX772 data sheet gives instructions for calculating R2 and R3 values. For input or output voltages greater than 10V, replace the 10V, C1 and C2 with higher voltage rating capacitors.
Table 1. Jumper J1 Functions
SHUNT LOCATION 2&3 1&2 SHDN PIN Connected to V+ Connected to GND MAX770 OUTPUT Shutdown mode, VOUT = V+ - 0.4V MAX770 enabled, VOUT = 5.0V
2.7V TO 5.5V V+ C1 150F 10V 3 2 1 J1 4 5 C3 0.1F 3 7 1 8 2 6 C4 0.1F R1 0.075 C2 330F 10V R2 OPEN L1 22H MTD20N03HDL SHDN REF FB GND EXT CS+ N1 D1 NSQ03A02 VOUT
SHDN
MAX770
V+ AGND
GND
R3 0 (SHORT)
Figure 1. MAX770 EV Kit Schematic Diagram
2 _______________________________________________________________________________________
MAX770 Evaluation Kit Evaluates: MAX770
Figure 3. MAX770 EV Kit Component Placement Guide-- Solder Side
Figure 2. MAX770 EV Kit Component Placement Guide-- Component Side
Figure 4. MAX770 EV Kit PC Board Layout--Component Side
Figure 5. MAX770 EV Kit PC Board Layout--Solder Side
_______________________________________________________________________________________
3
MAX770 Evaluation Kit Evaluates: MAX770
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) 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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