DC2119A Analog Devices

DEMO MANUAL DC2119A LTC3115EDHD-2 40V, 2A Synchronous Buck-Boost DC/DC Converter Description Demonstration circuit 2119A features the LTC 3115-2, a The demo board also has optional provisions to back- high voltage monolithic synchronous buck-boost converter feed V in order to increase efficiency in some 5V output CC optimized for applications with fast input voltage transients. applications. There is also a provision for an optional Schottky diode from SW2 to V for applications where OUT The DC2119A demo board has two user selectable operat- V is greater than 20V and short-circuit protection is OUT ing modes: Burst Mode and Forced Continuous Operation desired. Consult the data sheet for more information on (Fixed Frequency PWM) (JP1). There is also an accurate these options. programmable RUN pin which is used to ENABLE the converter (JP2). Figures 1 and 2 show typical demo board efficiency. Figure 3 shows the response to an input voltage step. The DC2119A operates with a 2.7V to 40V input voltage range. The demo board has been designed with the output The LTC3115-2 data sheet has detailed information about voltage set to 5.0V. The LTC3115-2 incorporates a pro- the operation, specifications, and applications of the part. prietary low noise switching algorithm which optimizes The data sheet should be read in conjunction with this efficiency with input voltages above, below or equal to the Quick Start Guide. output voltage and ensures seamless transitions between Design files for this circuit board are available at operating modes. DEMO MANUAL DC2119A Quick s Dp Using short twisted pair leads for any power connections 3. Connect a 500mA load to V as shown in Figure 2 OUT and with all loads and power supplies off, refer to Figure 4 (10 for V = 5V). Connect an ammeter if accurate OUT for the proper measurement and equipment setup. The current measurement or monitoring is desired. Battery/Power Supply (PS1) should not be connected to 4. Turn on PS1 and slowly increase voltage until the volt- the circuit until told to do so in the procedure below. age at V is 4.0V. IN When measuring the input or output voltage ripple, care 5. Verify V is ~5.0V. OUT must be taken to avoid a long ground lead on the oscil- 6. V can now be varied between 2.7V and 40.0V. V loscope probe. Measure the input or output voltage ripple IN OUT should remain in regulation. by touching the probe tip directly across the V or V IN OUT and GND terminals (see Figure 5), or by using an oscil- 7. Load current (I ) can also be varied. The maximum OUT loscope probe tip jack. I is a function of V and the current limit. Consult OUT IN the datasheet for more information on I vs V . In 1. Jumper and PS1 settings to start: OUT IN general for V > 3.6V I can be increased to 0.8A. IN OUT PS1 = OFF For V > 6V I can be increased to 2A. IN OUT JP1 (PWM) = FIXED FREQUENCY 8. For operation in Burst Mode move Jumper JP1 to JP2 (RUN) = ON BURST. I is limited in Burst Mode. See the data OUT sheet for more information. 2. With power OFF connect the power supply (PS1) as shown in Figure 4. If accurate current measurements 9. NOTE: If V drops out of regulation, check to be sure OUT are desired (for efficiency calculation for example) then the maximum load has not been exceeded, or that V IN connect an ammeter in series with the supply as shown. is not below the minimum value for regulation (see data The ammeter is not required however. sheet) 100 100 90 90 80 80 70 70 LOAD = 50mA 60 60 LOAD = 500mA LOAD = 100mA LOAD = 200mA LOAD = 1A 50 50 0 5 10 15 20 25 30 35 40 0 5 10 15 20 25 30 35 40 V (V) V (V) IN IN Figure 1. DC2119A Efficiency in PWM Mode Figure 2. DC2119A Efficiency in Burst Mode dc2119af 2 Efciency (%) Efciency (%) ure roce tart