Demo Circuit1376A-A/-B LTC3555-1 AND LTC3555-3 QUICK START GUIDE LTC3555-1 and LTC3555-3 High Efficiency USB Power Manager + Triple Step Down DC/DC DESCRIPTION Demonstration circuits 1376A-A and 1376A-B are High nearly all of the 2.5W available from the USB port to the Efficiency USB Power Manager + Triple Step Down system load with minimal power wasted as heat. This DC/DC featuring the LTC3555-1 and LTC3555-3 respec- feature allows the LTC3555-1/LTC3555-3 to provide tively. The LTC3555-1/LTC3555-3 are highly integrated more power to the application and eases the constraint power management and battery charger ICs for Li- of thermal budgeting in small spaces. Two of the three Ion/polymer battery applications. It includes a high effi- general purpose switching regulators can provide up to ciency current limited switching PowerPath manager 400mA and the third can deliver 1A. The entire product with automatic charge current reduction, a battery can be started from an external push button and subse- 2 charger, an ideal diode and three general purpose syn- quently controlled via I C. The LTC3555-1/LTC3555-3 is chronous step-down switching regulators. Designed available in the 28-pin (4mm 5mm 0.75mm) QFN specifically for USB applications, the LTC3555- surface mount package. 1/LTC3555-3s switching power manager automatically Design files for this circuit board are available. Call limits input current to a maximum of either 100mA or the LTC factory. 500mA for USB applications or 1A for AC-powered appli- L, LTC, LTM, LT, Burst Mode, are registered trademarks of Linear Technology Corporation. cations. Unlike linear PowerPath controllers, the PowerPath are trademarks of Linear Technology Corporation. Other product names may be trademarks of the companies that manufacture the products. LTC3555-1/LTC3555-3s switching input stage transmits PERFORMANCE SUMMARY Specifications are at T = 25C A SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VBUS Input Supply Range 4.35 5.5 V VOUT VOUT Output Voltage Mode and load dependant 3.4 Bat + 0.3 4.7 V LDO3V3 LDO3V3 Output Voltage Load and VOUT dependant 3.3 V V BAT Regulated Output Voltage LTC3555-1 4.179 4.2 4.221 V FLOAT LTC3555-3 4.079 4.1 4.121 V I Constant Current Mode Charge Current R = 2K 460 511 532 mA BAT PROG VOUT1 VOUT1 Output Voltage 3.3 V VOUT2 VOUT2 Output Voltage Servo Voltage = 0.8 3.0 V VOUT3 VOUT3 Output Voltage Servo Voltage = 0.8 1.5 V QUICK START PROCEDURE Demonstration circuits 1376A-A and 1376A-B are easy difficult to match the impedance of a real battery. Ca- to set up to evaluate the performance of the LTC3555-1 pacitor C15 in combination with R9, R10, and R11 were and LTC3555-3. These circuits are best evaluated using added to simulate the low impedance of a real battery. a Li-Ion or Li-Polymer battery. When using a battery It will allow proper operation of the demo circuit with or simulator for evaluation, oscillations must be verified without a battery, or a battery simulator consisting of a with a real battery at the same conditions because it is power supply in parallel with a 3.6 Ohm resistor. 1 LTC3555-1 AND LTC3555-3 Complete the Quick Start Procedure outlined in the loads and jumpers are set. Connect the positive ter- Quick Start Guide for Demo Circuit 590 available from minal of a voltmeter to CLPROG and the negative the Linear Technology Web Site, prior to proceeding. terminal to GND to measure the average input cur- rent. The voltage on CLPROG will reach 1.188V when Refer to Figure 2 for proper measurement equipment the average input current limit is reached. Do not setup and follow the procedure below: use the USB input and an external supply at the 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 same time. input or output voltage ripple by touching the probe tip directly across the 4. Set JP1, (NTC) to INT to use the demo board re- VBUS or VOUT(x) and GND terminals. See Figure 3 for proper scope probe technique. sistor network. To use an external NTC resistor, con- nect the external NTC resistor between the J2-3 ter- 1. After following the software installation procedure minal and the GND terminal. Then set the NTC in the DC590 Quick Start Guide, connect the jumper to EXT. DC1376A, the DC590 and the Host PC as shown in Fi gure 2. 5. Set JP2 and JP3 (ILIM0 and ILIM1 respectively) to NOTE. If using the DC590B board, a specific DVCC voltage level may be LO. At Power-up, the average input current setting selected. This is done by setting the VCCIO jumper on the DC590 will be equal to the value set by the position of JP2 board to one of the following settings: 3.3V, 5V, removed for 2.7V or 2 set to external if an external supply is desired to be used. and JP3 until an I C command is received and over- writes that default value. 2. Run the QuikEval.exe software. The QuikEval soft- ware detects the DC1376A-A or the DC1376A-B TABLE 1. Input Current Limit Settings demo board and the LTC3555 Graphical User Inter- ILIM1 ILIM0 CURRENT LIMIT face (GUI), shown in Figure 1 , will pop-up. 0 0 100mA (1X) 0 1 1A (10X) 1 0 0.5mA (SUSP) 1 1 500mA (5X) 6. Connect a 0 to 25mA adjustable load in series with an ammeter between the LDO3V3 and GND termi- nals. Connect a voltmeter between the LDO3V3 and GND terminals. 7. Connect a 0 to 2A adjustable load in series with an ammeter between the VOUT terminal and the GND terminal. Connect a voltmeter between the VOUT and GND terminals. 8. Connect a 0 to 400mA adjustable load in series with an ammeter between the VOUT1 and GND terminals. Figure 1. Graphical User Interface Demonstration Software for Connect a voltmeter between the VOUT1 and GND DC1376A-A and DC1376A-B. terminals. 3. If using an external supply, connect a 0 to 6V, 1.5A 9. Connect a 0 to 400mA adjustable load in series with supply with voltage adjusted to 0V between the an ammeter between the VOUT2 and GND terminals. VBUS and GND terminals. Connect a voltmeter Connect a voltmeter between the VOUT2 and GND across the VBUS and GND terminals. If using the terminals. USB input option, plug in the USB cable after all 2