QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1242A 600MA SYNCHRONOUS BOOST DC/DC CONVERTER AND 100MA LDO REGULATOR LTC3537 DESCRIPTION Demonstration circuit 1242A includes a high ef- operation. The 3X3 mm QFN thermally en- ficiency synchronous boost converter, a low hanced package with a 2.2MHz switching fre- dropout linear regulator and a low battery de- quency combined with the LDO regulator pro- tector. With a light load, the boost converter can vide a very tiny multi output solution. The LTC3537 boost converter also features output startup with an input voltage as low as 680mV and once started, the input can go as low as disconnect and the input voltage can be greater 500mV while maintaining a regulated output or less than the output voltage. voltage. With a 50mA load, the linear regulator This demonstration circuit allows the user to features a dropout voltage of less than 100mV. quickly evaluate the LTC3537 performance. Jumpers make selecting different output volt- Separate input terminals are provided for the boost and linear regulator, and a jumper that ages and low battery thresholds simple while allows the linear regulator to be powered from terminals on the board allow easy hookup to any one of three different sources. input supplies and output loads. Terminals and jumpers for shutting down or se- Design files for this circuit board are available. quencing each regulators output separately and Call the LTC factory. individual Power-Good outputs are included. LTC and Burst Mode are trademarks of Linear Technol- Jumpers are also provided for selecting a total ogy Corporation of six output voltages, three low battery volt- ages and a jumper to select BURST or PWM Table 1. Typical Specifications (25C) Conditions Limits Input Voltage Range V 0.68V to 5.5V IN Boost 1.8V V V = 1V, I = 100mA 1.8V 3.5% OUT IN OUT Boost 3.3V V V = 1.5V, I = 200mA 3.3V 3.5% OUT IN OUT Boost 5V V V = 1.5V, I = 200mA 5.0V 3.5% OUT IN OUT Output Ripple Voltage (burst mode) V = 1.5V, V = 3.3V I = 15mA 30mV p-p IN OUT OUT Output Ripple Voltage (fixed frequency) V = 1.5V, V = 3.3V I = 200mA 10mV p-p IN OUT OUT Boost Efficiency V = 1.8V, V = 3.3V I = 100mA 88% IN OUT OUT LDO Regulator 1.5V V V = 5V, I = 50mA 1.5V 2.5% OUT IN OUT LDO Regulator 3.0V V V = 5V, I = 50mA 3.0V 2.5% OUT IN OUT LDO Regulator 3.3V V V = 5V, I = 50mA 3.3V 2.5% OUT IN OUT LDO Regulator Drop Out Voltage V = 3.3V, I = 50mA, V drops 10% 100mV OUT OUT OUT Low Battery Threshold Voltage (dropping) 0.8V 800mV 5% Low Battery Threshold Voltage (dropping) 1.7V 1.7V 5% Low Battery Threshold Voltage (dropping) 3.0V 3V 5% 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1242A 600MA SYNCHRONOUS BOOST DC/DC CONVERTER AND 100MA LDO REGULATOR Figure 1. Demonstration Circuit Test Setup Select VOUT Select VOUT Low BAT BOOST Regulator LDO Regulator STATUS Outputs LDO Input Resistive V BOOST Converter Input Loads BOOST + A A Input V Power V Supply - V A or V PWRGOOD STATUS Outputs LDO & BOOST LDO ON/OFF Inputs EXT. STATUS power source input, Select BOOST select with JP4 ON/OFF/SEQ Note: Select resistors can PWM be replaced Select Select Select or BURST with LEDs LDO LOW STATUS Mode Select LDO ON/OFF BAT power input supply or SEQ threshold source QUICK START PROCEDURE The LTC3537 circuit can be evaluated using applied to the STATUS PWR IN terminal to be the setup shown in Figure 1. Most of the fea- used for the pull-up resistors. tures can be verified simply by placing jump- Connect voltmeters and ammeters as shown ers in various locations. It is recommended in the Figure 1 test setup. Connect a power that the LTC3537 data sheet be nearby for a supply to the VINBOOST and GND terminals more complete explanation of the various fea- and a suitable load resistor between VOUT tures and specifications. BOOST and GND. Avoid excessive wire Using jumpers JP5 and JP6, select the de- lengths between the input power supply and sired output voltages (with no jumpers in- the demonstration board. Wire lengths greater stalled, the output voltages are set for the than 18 inches may require additional capaci- highest voltage). Enable each regulator by tance near the input terminals. placing jumpers JP7 and JP8 in the ON posi- With a light load (1k resistor) at the output, tion and place the LDO IN jumper (JP3) to begin increasing the input power supply volt- the VINB (center) position which parallels age. At approximately 700mV, the output will the LDO and BOOST supply inputs. Set the rise to the selected regulated voltage. When STATUS PWR jumper (JP4) to the VOUTB the output voltage exceeds the input voltage position, which connects the open-drain by at least 240mV, the converter powers itself power good outputs and the low battery out- from the output instead of the input. This fea- put pull-up resistors to the output of the boost ture allows the input voltage to drop as low as regulator. JP4 also allows an external voltage 500mV (at light loads) and still maintain a 2