QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 761 LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN LTC3204-5 and LTC3204-3.3 DESCRIPTION Demonstration circuit 761 is a low noise regulated charge pump in 2X2 DFN. There are two assembly versions, DC761A-A and DC761A-B for featuring the LTC3204-5 and LTC3204-3.3 respectively. The DC761A-A produces a regulated 5V output from a 2.7V to 5.5V input. The guaranteed output load current is 150mA for VIN between 3.1V and 5.5V, and 65mA for VIN less than 3.1V. The DC761A-B produces a regulated 3.3V output from a 1.8V to 4.5V input. The guaranteed output current is 50mA from VIN between 1.9V and 4.5V, and 40mA for VIN less than 1.9V. The circuit requires only three tiny 0603 surface mount capacitors and consumes minimal board space. No inductor and diode are needed. The circuit features automatic Burst Mode® operation at light loads to maintain low supply current. Built-in softstart circuitry prevents excessive inrush current during start-up. Thermal shutdown and current-limit circuitry allow the parts to survive a continuous output short circuit. These circuits are particularly useful in systems that require extremely low quiescent current, such as battery-powered systems. Design files for this circuit board are available. Call the LTC factory. , LTC and LT are registered trademarks of Linear Technology Corporation. PERFORMANCE SUMMARY PARAMETER CONDITION MIN TYP MAX DC761A-A (for LTC3204-5) 2.7V 5.5V DC761A-A (for LTC3204-3.3) 1.8V 4.5V Input Voltage Range DC761A-A (for LTC3204-5) Output Voltage VOUT 3.1V< VIN <5.5V, IOUT<150mA 4.8V 5V 5.2V 3.168V 3.3V 3.432V VIN = 3.6V, IOUT = 150mA (DC761A-A) 20mVP–P 50mVP–P VIN = 2.4V, IOUT = 50mA (DC761A-B) 10mVP–P 20mVP–P 2.7V< VIN <5.5V, IOUT<65mA DC761A-B (for LTC3204-3.3) 1.9V< VIN <4.5V, IOUT<50mA 1.8V< VIN <4.5V, IOUT<40mA Output Ripple VOUT Nominal Switching Frequency Efficiency 1.2MHz VIN = 3.0V, IOUT = 150mA (DC761A-A) 81.3% VIN = 1.8V, IOUT = 25mA (DC761A-B) 88.7% 1 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 761 LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN 4. NOTE: Make sure that the input voltage does not exceed 5.5V for DC761A-A or 4.5V for DC761A-B. To prevent input voltage overshoot when the circuit is connected to a live supply, an aluminum electrolytic capacitor can be added to bypass the VIN at the input terminals. See Linear Technology Application Note 88 for a complete discussion. QUICK START PROCEDURE Demonstration circuit 761 is easy to set up to evaluate the performance of the LTC3204-5 and LTC32043.3. Refer to Figure 1 for proper measurement equipment setup 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 VIN or VOUT and GND terminals. See Figure 2 for proper scope probe technique. 1. 5. 6. ON 2. With power off, connect the input power supply to VIN and GND terminals. 3. Connect the load between VOUT and GND terminals. Check for the proper output voltages. VOUT = 4.8V to 5.2V for DC761A-A, VOUT = 3.168V to 3.432V for DC761A-B NOTE: If there is no output, temporarily disconnect the load to make sure that the load is not set too high. Place jumpers in the following positions: JP1 Turn on the power at the input. Once the proper output voltages are established, adjust the loads within the operating range and observe the output voltage regulation, ripple voltage, efficiency and other parameters. Figure 1. Proper Measurement Equipment Setup 2 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 761 LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN GND VIN Figure 2. Measuring Input or Output Ripple OPERATING PRINCIPLES The LTC3204-5/LTC3204-3.3 use a switched capacitor charge pump to boost VIN to a regulated voltage. Regulation is achieved by sensing the output voltage through an internal resistor divider and modulating the charge pump output current based on the error signal. A 2-phase non-overlapping clock activates the charge pump switches. The flying capacitor is charged from VIN on the first phase of the clock. On the second phase of the clock, it is stacked in series with VIN and connected to VOUT. This sequence of charging and discharging the flying capacitor continues at a free running frequency of 1.2MHz. Other operation principles, such as Burst Mode® and Soft-Start, can be found on the LTC3204-5/LTC32043.3 datasheet at www.linear.com. 3 QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 761 LOW NOISE REGULATED CHARGE PUMP IN 2X2 DFN 4