DEMO MANUAL DC1921A LTC3375EUK 8-Channel Programmable, Parallelable, 1A Buck DC/DCs Description Demonstration circuit 1921A is a digitally programmable The LTC3375 has a default operating frequency of 2MHz, 8-output power supply with a pushbutton controller and or can be set between 1MHz to 3MHz using an external watchdog timer, featuring the LTC 3375. The LTC3375 has resistor. The LTC3375 also has a SYNC pin which allows eight synchronous buck regulators, each with an indepen- the internal oscillator to synchronize to an external clock dent V supply. The buck regulators may be paralleled from 1MHz to 3MHz. IN together to create a higher power buck regulator with a Refer to the LTC3375 data sheet for more details on the single inductor. The input range of the LTC3375 is ideal electrical and timing specifications. for single cell Li-Ion/Polymer battery applications. Design files for this circuit board are available at The switching regulator settings, such as enables, feedback DEMO MANUAL DC1921A Quick s Dp 2 Demo Circuit 1921A utilizes the DC590B USB to I C inter- 10. Turn on and set the VIN1 input power supply to 5V. face board to control the switching regulators functions, The DC590B board gets its power from the USB cable. to program the PGOOD and UVLO warnings, and to read NOTE: Make sure that the input voltage does not ex- the contents of the command and status registers. ceed 6V. The DC1921A is easy to set up to evaluate the performance 11. Start the Linear Technology QuikEval program. This of the LTC3375. Refer to Figure 1 and Figure 2 for proper program should automatically detect the presence of measurement equipment setup, and follow the evaluation the LTC3375 demo board (DC1921A) and activate the procedure below using the DC590B board. appropriate GUI, as seen in Figure 3. NOTE: When measuring the input or output voltage ripple, 12. On the LTC3375 control window, select the Buck1 care must be taken to avoid a long ground lead on the Enabled/Disabled button. Enabled is displayed, and oscilloscope probe. Measure the input or output voltage the button background color changes to yellow, but the ripple by touching the probe tip directly across the V IN Buck1 regulator is not yet enabled. The Buck1 Write or V and GND terminals. See Figure 2 for the proper OUT text box indicates the new value to be written to the scope probe technique. register, and the background color of the Write and 1. Refer to the DC590B Quick Start Guide for QuikEval Read text boxes turn yellow indicating that the controls setup and software installation details. have changed, but the part has not been written to or read from. 2. Set the VCCIO jumper, JP6, on the DC590B board to the 3.3V position. 13. On the LTC3375 control window, select the Write with- out Stop button on the LTC3375 control window. The 3. Make sure the USB cable is connected between the 2 Buck1 register is updated via the I C, but the Buck1 computer and the DC590B controller board. regulator has not yet been enabled. The Write text box 4. Set the JP1-JP8 jumpers on the DC1921A board to the background color changes to orange, indicating that OFF position. the Buck1 holding register has been updated, but a stop bit was not received. The data in the command 5. Set JP9 to the SCL position to observe how the watchdog registers will not be latched or acted upon until a stop timer operates using SCL when the program is running. bit is received. 6. Set JP10 to the +12V position to power HV from the IN 14. On the LTC3375 control window, select the Read DC590B board. Selected button. The Buck1 Read text box is updated 7. Set JP12 to the DC590 position to operate KILL from with the data in the Buck1 command register. software or to EXT to operate KILL from hardware. 15. On the LTC3375 control window, select the Write with NOTE: If JP12 is in the DC590 position and the LTC3375 Stop button. A stop bit is sent latching the Buck1 data GUI is not running, or the DC590 is not plugged in, then and enabling the regulator. If the status registers Auto the KILL pin will be low, preventing the regulators from Read Enabled button is selected, then PG1 HI is dis- enabling. played in the PG1 bit in the status register indicators. 8. Connect the DC1921A to the DC590B USB serial con- NOTE: If an IRQ fault was latched in the PGOOD or troller using the supplied 14-conductor ribbon cable, UVLO status registers, then the Clear Interrupt button as shown in Figure 1. on the LTC3375 control window needs to be selected 9. With the power off, connect a 0V to 6V, 3A power sup- in order to update the status registers. ply to each V and GND with a series ammeter and IN 16. With the power off, connect a 0V to 3A load to each a voltmeter, as shown in Figure 1. A single 0V to 6V, VOUT and GND with a series ammeter and a voltmeter, 10A supply can be used instead to supply all V inputs IN as shown in Figure 1. simultaneously. dc1921afa 2 ure roce tart