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| 19-0416; Rev 0; 7/95 MAX866 Evaluation Kit _______________General Description The MAX866 evaluation kit (EV kit) is a fully assembled and tested surface-mount printed circuit board. It can also evaluate the adjustable-output MAX867. The MAX866/MAX867 are CMOS, step-up, DC-DC switching regulators for small, low input voltage or battery-powered systems. The MAX866 accepts a positive input voltage between 0.8V and VOUT and converts it to a higher, pin-selectable output voltage of 3.3V or 5V. The MAX867 adjustable version accepts 0.8V to 6V input voltages and generates a higher, adjustable output voltage in the 2.7V to 6V range. Typical full-load efficiencies for the MAX866/MAX867 are greater than 80%. A movable jumper on the EV kit selects either a 3.3V or 5.0V output voltage. Additional pads on the board's solder side accommodate resistors for the LBI/LBO low battery detector or MAX867 output adjustment. ____________________________Features o Low 0.8V to 6V Input Supply Voltage o 0.9V Guaranteed Start-Up Supply Voltage o 27A Quiescent Current o 1A Shutdown Mode o Up to 250kHz Switching Frequency o 1.5% Reference Tolerance o Low-Battery Detector (LBI/LBO) o Ultra-Small 8-Pin MAX Package (1.11mm High) o Surface-Mount Construction o Fully Assembled and Tested Evaluates: MAX866/MAX867 ____________________Component List DESIGNATION C1 QTY 1 DESCRIPTION 0.1F ceramic capacitor 47F, 16V, low-ESR tantalum capacitors; Sprague 593D476X0016D2W or AVXTPSD476M016R0150 Open 330H inductor; CoilCraft D01608-334 20V, 500mA Schottky diode; Motorola MBR0520LTI MAX866CUA (8-pin MAX) 3-pin headers Shunts PC board MAX866 data sheet ______________Ordering Information PART MAX866EVKIT-MM TEMP. RANGE 0C to +70C BOARD TYPE Surface Mount C2, C3 2 _________________________Quick Start The MAX866 EV kit is a fully assembled and tested surface-mount board. Follow the steps below to verify board operation. Do not turn on the power supply until all connections are completed. 1) Connect a 1.5V supply to the pad marked VIN. 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. 4) Place the shunt on J2 across pins 1 and 2 for a 5V output voltage, or across pins 2 and 3 for a 3.3V output (input voltage less than 3.6V). 5) Turn on the power and verify that the output voltage is 5V. 6) Refer to the section Evaluating the MAX867 to modify the board for different output voltages. R1, R2, R3, R4, R5 L1 D1 U1 J1, J2 None None None 0 1 1 1 2 2 1 1 To contact Sprague, phone (603) 224-1961 or fax (603) 224-1430. To contact Murata Erie, phone (404) 436-1300. Refer to the MAX866/MAX867 data sheet for other component suppliers' phone numbers. ________________________________________________________________ Maxim Integrated Products 1 Call toll free 1-800-998-8800 for free samples or literature. MAX866 Evaluation Kit Evaluates: MAX866/MAX867 _______________Detailed Description Input Source In normal operation, the input source for the MAX866 evaluation board must be greater than 0.9V for start-up and less than the output voltage plus 0.3V. A typical input voltage range would be the 1.2V to 1.8V range of a 1-cell NiCd battery. An input voltage greater than the selected output voltage (but less than 7V) will not damage the circuit. However, the MAX866 output will equal the input voltage minus the 0.3V drop of the Schottky diode, D1. The input current depends on the power delivered to the load. The following equations show how to calculate the expected input current requirement. Input Power = Output Power / Efficiency and Input Current = Input Power / Input Voltage To calculate the input current for a typical operating circuit, assume a 2V input voltage, a 5V output voltage, and a 5mA load. The expected efficiency can be taken from the graphs on the MAX866/MAX867 data sheet. Under the above conditions, the MAX866 delivers 85% efficiency. Input Power = (5.0V x 5mA) / 85% Input Power = 29.41mW and Input Current = 29.41mW / 2.0V Input Current = 14.71mA Once started, the MAX866 actually operates from the regulated output voltage. This means that the input voltage can fall below the 0.9V minimum start-up voltage. Typically, the regulated output will be maintained even if the input voltage drops to 0.5V. See the Efficiency and Start-Up Voltage vs. Load Current graphs in the Typical Operating Characteristics section of the MAX866/MAX867 data sheet. Jumper Selection Two 3-pin headers select the shutdown mode and output voltage. Table 1 lists the selectable jumper options. Table 1. Jumper Selection J1 Shunt J2 Shunt SHDN Pin Location Location Connection 1&2 1&2 2&3 2&3 1&2 2&3 1&2 2&3 VOUT VOUT GND GND 3V/5V Pin Connection GND VOUT GND VOUT MAX866 Output 5.0V 3.3V VIN - 0.3V VIN - 0.3V Using the Low-Battery Indicator The MAX866 has an additional comparator useful for monitoring the input source's voltage level. Resistor locations R3 and R4 on the bottom of the printed circuit board are connected as a voltage divider between the LBI pad and the MAX866 LBI pin. Note that a printed circuit board trace across R4 shorts the LBI pin to ground when this function is not used. Cut the trace before installing R4. Refer to the Low-Battery Detection section of the MAX866/MAX867 data sheet for instructions on selecting values for resistors R3 and R4. Another location on the board facilitates the addition of a pull-up resistor on the LBO output. LBO is an opendrain output that can sink 2mA. Install resistor R5 if an external circuit is to be driven from LBO. 2 _______________________________________________________________________________________ MAX866 Evaluation Kit Evaluating the MAX867 The MAX866 EV kit can also evaluate the MAX867, which generates output voltages in the 2.7V to 6.0V range using external resistors. Besides replacing the IC, the only other modifications required are to remove the shunt on J2 and to add the output voltage-divider resistors R1 and R2 (located on the board's solder side). The Output Voltage Selection section of the MAX866/MAX867 data sheet gives instructions for calculating R1 and R2 values. Evaluates: MAX866/MAX867 VIN R5 OPEN 1 SHDN 3 R1 OPEN C2 47F 16V L1 330H LX 8 D1 MBRS0520 C3 47F 16V VOUT 2 J1 3 2 1 J2 R2 OPEN 1 SHDN U1 2 3/5 3 C1 0.1F 4 VREF LBO 7 MAX866 GND OUT LBI 6 5 R3 OPEN LBI R4 0 (SHORT) LBO Figure 1. MAX866 EV Kit Schematic _______________________________________________________________________________________ 3 MAX866 Evaluation Kit Evaluates: MAX866/MAX867 Figure 2. MAX866 EV Kit Component Placement Guide-- Component Side Figure 3. MAX866 EV Kit Component Placement Guide-- Solder Side Figure 4. MAX866 EV Kit PC Board Layout--Component Side Figure 5. MAX866 EV Kit 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. 4 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 (c) 1995 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. |
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