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SP6655EB Evaluation Board Manual
High Efficiency Synchronous Step-Down Converter with up to 98% efficiency 400mA Output Current, only 20uA Quiescent Current 2.7V-6.5V Input Voltage range, Output Adjustable down to 0.8V DFN Package & Ceramic Capacitors for small, low profile Power Supply Ideal for PDAs, Digital Cameras, Wireless Modems, Cellular Telephones DESCRIPTION The SP6655 Evaluation Board is designed to help the user evaluate the performance of the SP6655 for use as a single Li-Ion battery Step-Down DC-DC Converter. The SP6655 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 SP6655EB evaluation board is a complete power supply circuit to provide ease of evaluation for the DC/DC Converter performance. FIGURE 1. SP6655 1.8V OUTPUT EVALUATION BOARD SCHEMATIC
Vin = 2.7V to 5.0V
CIN
RVIN 10.0 1 2 1 3 4 5
10uF
BLON
U1 SP6655
PVin Vin BLON D1 D0 LX PGND GND Vout FB 10 9 8 7 6
L1
10uH
Vout = 1.8V
CF 22pF
RF 249K
D1
2 3 1
RI 200K CVIN 1.0uF
COUT 10uF
D0
2 3
USING THE EVALUATION BOARD 1) Powering up the SP6655 Circuit & Programming the UVLO threshold The SP6655 Evaluation Board can be powered from a single Li-Ion battery or a +2.7 to +5.0V power supply. Connect with short leads directly to the "Vin" and "Gnd" posts. Note the SP6655 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 SP6655 requires 2 feedback resistors to control the output voltage. Connect the appropriate resistors RF and RI (Table 2) from pin 6 SP6655 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. SP6655UEB BILL OF MATERIALS
Component L1 CIN COUT RVIN CVIN RI RF CF U1 Vo = 1.8V 10uH, Murata LQH32CN100K11, 0.3ohm, 0.45A, 1210 22uF, TDK C2012X5R0J106M, 0.005ohm, 6.3V, X5R, 0805 22uF, TDK C2012X5R0J106M, 0.005ohm, 6.3V, X5R, 0805 10 Ohm 5%, 0603 1uF, TDK C1608X5R0J105M, 0.03ohm, .3V, X5R, 0603 200k 1%, 0603 249k 1%, 0603 22pF ceramic, 0603 SP6655ER, 10 pin DFN
Table 3. SP6655 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: SP6655ER COMPONENT PLACEMENT
FIGURE 4: SP6655ER PC LAYOUT TOP SIDE
FIGURE 5: SP6655ER PC LAYOUT BOTTOM SIDE

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