QUICK START GUIDE FOR DC1550A LTC3553EPD: Micropower USB Power Manager with Li-Ion Charger, Buck DC/DC, and LDO Regulator DESCRIPTION Demonstration Circuit DC1550A is a Micropower USB Power Manager with Li-Ion Charger, Buck DC/DC, and LDO Regulator featuring the LTC®3553. PERFORMANCE SUMMARY Specifications are at TA = 25°C SYMBOL VBUS V(BAT) I(BAT) VLDO VBUCK PARAMETER Bus Input Voltage Range Battery Float Voltage Battery Charge Current LDO Output Voltage Buck Regulator Output Voltage CONDITIONS Constant Voltage Mode Constant Current Mode, RPROG = 1.87k I(VLDO) ≤ 200mA I(VBUCK) ≤ 200mA MIN 4.35 4.15 420 3.25 1.15 TYP MAX 6 4.23 500 3.35 1.25 UNITS V V mA V V QUICK START PROCEDURE Refer to Figure 1 for the proper measurement equipment setup and jumper settings and follow the procedure below. NOTE. When measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across the VBUS or VOUT(x) and GND terminals. See Figure 2 for proper scope probe technique. 1. Set PS1 = 0V, PS2 = 3.6V. Press “ON” button for > 0.5s. Observe I(BAT) (AM2), VBUCK (VM5) and VLDO (VM6). The LTC3553 is in STBY which reduces the battery current to less than 15μA, even with both regulators running. In STBY the maximum current from regulators is reduced to as low as 10mA 2. Set STBY (JP6) to “OFF”, PS1 to 5V. Observe I(VBUS) (AM1), I(BAT) (AM2) and VPROG (VM2). The LTC3553 is now operating in normal mode drawing more current from the battery. However the regulators are now capable of delivering over 200mA each. Also, since VBUS is now available, the battery charger is operating, but charge current is limited by the input current limit to 100mA. 3. Set HPWR (JP2) to “500mA”. Observe I(VBUS) (AM1), I(BAT) (AM2) and VPROG (VM2). The input current limit is now 500mA, so the battery charger is delivering ~420mA to the battery. 4. Set LD2 to 200mA, LD3 to 200mA. Observe VBUCK (VM5), VLDO (VM6) and I(BAT) (AM2). Each regulator is supplying 200mA, and since the efficiency is ~90%, drawing ~225mA. So, the battery charger is only delivering approximately 50mA. This is because the input current limit is 500mA – 225mA – 225mA = 50mA. 1 LTC3553EPD 5. Set LD2 to 0A, LD3 to 0A. Press “OFF” button. Observe VBUCK (VM5) and VLDO (VM6). The regulators are now off and therefore supplying 0 current. The battery charger is once again supplying ~ 420mA to the battery. 6. Reset the Jumpers to their default position. 2 LTC3553EPD VM2 + - VM3 AM1 - + PS1 1A + + 4.35V - 5.5V supply - + - + VM1 - AM2 + 3.6Ω + VM4 - - + 1A - + + AM3 LD2 0V - 5V VM5 - + 2A AM4 + PS2 0V - 5V supply + - LD3 0V - 5V VM6 - 2A Note: All connections from equipment should be Kelvin connected directly to the board pins which they are connected on this diagram and any input or output leads should be twisted pair. Figure 1. Proper Measurement Equipment Setup for DC1550A GND VIN Figure 2. Measuring Input or Output Ripple 3 LTC3553EPD Figure 3. Circuit Schematic 4 LTC3553EPD Figure 4. Bill of Materials 5