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| SP6651AEU Evaluation Board Manual High Efficiency Synchronous Step-Down Converter with up to 98% efficiency 800mA Output Current, only 20uA Quiescent Current 2.7V-6.5V Input Voltage range, Output Adjustable down to 0.8V SOIC Package & Ceramic Capacitors for small, low profile Power Supply Ideal for PDAs, Digital Cameras, Wireless Modems, Cellular Telephones DESCRIPTION The SP6651A Evaluation Board is designed to help the user evaluate the performance of the SP6651A for use as a single Li-Ion battery Step-Down DC-DC Converter. The SP6651A operates from 2.7V to 6.5V input, with the highest efficiency in the range 3.0V to 4.2V where the Li-Ion battery has the most energy. The SP6651AEU evaluation board is a complete power supply circuit to provide ease of evaluation for the DC/DC Converter performance. FIGURE 1. SP6651A 3.3V OUTPUT EVALUATION BOARD SCHEMATIC Vin 2.7 - 6.5VDC CIN 22uF RVIN 10.0 BLON 1 2 1 3 4 5 U1 PVin Vin BLON D1 D0 LX PGND GND Vout FB 10 9 8 7 6 L1 10uH Vout 3.3V 800mA RF 825K CF 22pF D1 J1 2 3 COUT 22uF RI 261K 1 SP6651A CVIN 1.0uF D0 J2 2 3 FIGURE 2. SP6651A 1.5V OUTPUT EVALUATION BOARD SCHEMATIC Vin 2.7 - 6.5VDC CIN 22uF RVIN 10.0 BLON 1 2 1 3 4 5 U1 PVin Vin BLON D1 D0 LX PGND GND Vout FB 10 9 8 7 6 L1 10uH Vout 1.5V 800mA RF 226K CF 22pF D1 J1 2 3 COUT 22uF RI 261K 1 SP6651A CVIN 1.0uF D0 J2 2 3 USING THE EVALUATION BOARD 1) Powering up the SP6651A Circuit & Programming the UVLO threshold The SP6651A Evaluation Board can be powered from a single Li-Ion battery or a +2.7 to +6.5V power supply. Connect with short leads directly to the "Vin" and "Gnd" posts. Note the SP6651A will remain in "shutdown" until D0 or D1 of the Jumpers J1 or J2 are applied to the Vin or position 1 to 2. See Table 1 for UVLO threshold programming and D1 and D0 pin definition. Table 1. Operating Mode Definition D1 0 0 1 1 D0 0 1 0 1 Definition Shutdown. All internal circuitry is disabled and the power switches are opened. Device enabled, falling UVLO threshold = 2.70V Device enabled, falling UVLO threshold = 2.85V Device enabled, falling UVLO threshold = 3.00V 2) VOUT PROGRAMMING The SP6651A requires 2 feedback resistors to control the output voltage. Connect the appropriate resistors RF and RI (Table 2) from pin 6 SP6651A FB to Vout and to the GND. For Vout different from that shown in the Table 2, use equation: Vout RF = - 1 * RI 0.8 Table 2. SP6651AUEB BILL OF MATERIALS Component L1 CIN COUT RVIN CVIN RI RF CF U1 Vo = 3.3V Vo = 1.5V 10uH, CDRH5D28-100, Sumida 10uH, CDRH5D28-100, Sumida 22uF, TDK C3225X5R0J226M 22uF, TDK C3225X5R0J226M 10 Ohm 5% 1uF ceramic X7R SM 0805 261k 1% 825k 1% 22pF ceramic SP6651AEU 22uF, TDK C3225X5R0J226M 22uF, TDK C3225X5R0J226M 10 Ohm 5% 1uF ceramic X7R SM 0805 261k 1% 226k 1% 22pF ceramic SP6651AEU Table 3. SP6651A PIN ASSIGNMENT Pin Name PVin Vin BLON D1 D0 Pin Description Input voltage power pin. Inductor charging current passes through this pin. Internal supply voltage. Control circuitry powered from this pin. Open drain battery low output - need to pullup to supply externally. Vin - Vout below threshold pulls this node to ground. Vin - Vout above threshold, this node is open. Digital mode control input. See Table 1 for definition. Digital mode control input. See Table 1 for definition. External feedback network input connection. Connect a resistor from FB to ground and FB to Vout to control the output voltage. This pin regulates to the internal reference voltage of 0.8V. Output voltage sense pin. Used for internal timing and BLON circuitry. Internal ground pin. Control circuitry returns current to this pin. Power ground pin. Synchronous rectifier current returns through this pin. Inductor switching node. Inductor tied between this pin and the output capacitor to create Vout. Pin NO. 1 2 3 4 5 FB 6 Vout GND PGND LX 7 8 9 10 EVALUATION BOARD LAYOUT FIGURE 3: SP6651AEU COMPONENT PLACEMENT FIGURE 4: SP6651AEU PC LAYOUT TOP SIDE FIGURE 5: SP6651AEU PC LAYOUT BOTTOM SIDE |
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