DC526A Analog Devices

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 526 MONOLITHIC BOOST CONVERTER WITH PHASE-LOCKED LOOP LT1310 DESCRIPTION Demonstration circuit 526 features the LT1310 1.5A an external clock selecting the Ext. Sync. option (jumper Monolithic Boost Regulator with PLL. DC526 converts a JP2) and by injecting the appropriate signal into the Ext. 5V input to a 12V output with an output load of up to Sync. pin. Additionally a work area is provided on the 400mA. The operating frequency of the LT1310 is easily backside of the board to simplify customization of the synchronizable over a wide frequency range. To demon- demo board. strate this, DC526 includes an on-board oscillator Design files for this circuit board are available. Call (based on the LT6900), which is tunable between the LTC factory. 1.2MHz and 2.4MHz. DC526 can also be synchronized to Table 1. Performance Summary PARAMETER CONDITION VALUE Minimum Input Voltage 3V Shutdown current Vin 5V 2A Maximum Input Voltage 12V V V = 3V to 7V, I = 0 to 250mA 12V 3% OUT IN OUT Switching Frequency Tunable 1.2Mhz to 2.4Mhz QUICK START PROCEDURE Demonstration circuit 526 is easy to set up to evaluate 3. With power off, connect the input power supply to Vin the performance of the LT1310. Refer to Figure 1 for and GND. proper measurement equipment setup and follow the 4. Turn on the power at the input. procedure below: NOTE: Make sure that the input voltage does not ex- NOTE: When measuring the input or output voltage rip- ceed 12V. ple, care must be taken to avoid a long ground lead on 5. Check for the proper output voltages. Vout = 12V the oscilloscope probe. Measure the input or output voltage ripple by touching the probe tip directly across If there is low output, temporarily disconnect the load the Vin or Vout and GND terminals. See Figure 2 for to make sure that the load is not set too high. proper scope probe technique. 6. Once the proper output voltage is established, adjust 1. Place SHDN jumper JP1 in the ON position. the load within the operating range and observe the output voltage regulation, ripple voltage, efficiency 2. Select either the internal or external sync source via and other parameters. the SYNC jumper, JP2 1 GND VIN QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 526 MONOLITHIC BOOST CONVERTER WITH PHASE-LOCKED LOOP + SCOPE OPTIONAL + FREQUENCY ADJUST LOAD Figure 2. Scope Probe Placement for Figure 1. Proper Measurement Equipment Setup Measuring Input or Output Ripple DC526 PINS SHDN PIN SYNC PIN The board can be placed in shutdown either by ground- The SYNC terminal is tied directly to the SYNC pin of the ing the shutdown pin or by placing the SHDN jumper LT1310. Phase locking of the LT1310 to the signal at the JP1 in the OFF position. The shutdown current is less SYNC pin can be observed by simultaneously observing than 2A if the jumper is used and is about 150uA if the the SYNC signal and the SW pin of the LT1310. Access pin is grounded due to the on-board pull-up resistor R8. to the SW pin is provided by the small turret labeled SW. When synchronization has occurred these two signals are in a fixed relationship to each other and an oscillo- EXTSYNC PIN scope should show both as stable waveforms. In the The EXTSYNC pin is the input for an external frequency event that the synchronization frequency is adjusted be- source to allow the board to be synchronized to a sys- yond the available tuning range then only the signal that tem clock. This clock signal must be between 1.2MHz is used for the trigger source of the scope will appear and 2.4MHz and meet the voltage and timing require- stable. ments outlined in the LT1310 data sheet. 2 + + + + +