DEMO CIRCUIT 1610A LTC3604 QUICK START GUIDE LTC3604EUD 2.5A, 15V, MONOLITHIC SYNCHRONOUS STEP-DOWN REGULATOR DESCRIPTION Demonstration circuit 1610 is a step-down converter, DC1610A can track another voltage with the LTC3604 using the LTC3604 monolithic synchronous buck track function. Because of the high switching fre- regulator. The DC1610A has a maximum input voltage quency of the LTC3604, which is programmable up to 15V, and is capable of delivering up to 2.5A of output 4 MHz, the DC1610A uses low profile surface mount current at a minimum input voltage of 3.6V. The out- components. All these features make the DC1610A an put voltage of the DC1610A can be set as low as 0.6V, ideal circuit for use in Lithium-Ion Battery applications the reference voltage of the LTC3604. At low load cur- and distributed power systems. Gerber files for this rents, the DC1610A operates in discontinuous mode, circuit are available. Call the LTC Factory. and during shutdown, it consumes less than 40 uA of Design files for this circuit board are available. Call the quiescent current. In continuous mode operation, the LTC factory. DC1610A is a high efficiency circuit - over 80%. The As Shipped Performance Summary PARAMETER CONDITIONS VALUE Minimum Input Voltage 3.6V Maximum Input Voltage 15V GND = Shutdown Run/Shutdown V = Run IN V = 3.6V to 15V, I = 0A to 2.5A 1.2V 4% (1.152V 1.248V) IN OUT Output Voltage V = 3.6V to 15V, I = 0A to 2.5A 1.8V 4% (1.728V 1.872V) IN OUT Regulation V = 4.5V to 15V, I = 0A to 2.5A 3.3V 4% (3.168V 3.432V) IN OUT Typical Output Ripple Voltage V = 12V, V = 1.8V, I = 2.5A (20 MHz BW) < 20mV IN OUT OUT PP Burst Mode V = 12V, V = 1.8V < 700 mA IN OUT Nominal Switching Frequency R = 324k 1 MHz 20% T Table 1. Jumper Description JUMPER FUNCTION RANGE/SETTING (DEFAULT) JP1 Vout Setting. 1.2V JP5 Tracking or Soft-Start (SS) (SS) - TRACK JP6 Mode: Forced Continuous Mode (FCM), Burst Mode, or External Synchronization (SYNC) (FCM) SYNC Burst Mode JP7 Run (ON) - OFF JP8 Frequency (1 MHz) - 2 MHz JP9 ITH: Compensation INT (EXT) 1 LTC3604 QUICK START PROCEDURE Demonstration Circuit 1610 is easy to set up to evalu- output current to any current less than 400 mA. Ob- ate the performance of the LTC3604. For proper serve the discontinuous mode of operation at the measurement equipment configuration, set up the cir- switch node, and measure the output ripple voltage. It cuit according to the diagram in Figure 1. Before pro- should measure less than 150 mV. ceeding to test, insert shunts into the 1.2V position of the output voltage header JP1, into the SS (soft-start) posi- Insert the JP7 shunt into the OFF position and move tion of Track/SS header JP5, into the FCM (Forced Con- the shunt in the 1.2V output JP1 header into any of the tinuous Mode) position of MODE header JP6, into the OFF two remaining output voltage option headers: 1.8V position of RUN header JP7, into the 1 MHz position of (JP2) or 3.3V (JP3). Just as in the 1.2V Vout test, the FREQ header JP8, and into the EXT position of ITH header output voltage should read Vout +/- 2% tolerance un- JP9. der static line and load conditions and +/- 1% toler- ance under dynamic line and load conditions (+/- 2% When measuring the input or output voltage ripple, total). Also, the circuit operation in discontinuous care must be taken to avoid a long ground lead on the mode will be the same. oscilloscope probe. Measure the input or output volt- age ripple by touching the probe tip directly across the When finished, turn off the circuit by inserting the Vin or Vout and GND terminals. See Figure 2 for shunt in header JP7 into the OFF position. proper scope probe measurement technique. Low Output Voltage, 2MHz Operation With the DC1610 set up according to the proper In applications with low output voltages of less than measurement configuration and equipment in Figure 1.2V, and frequencies of 2 MHz or higher, the inductor 1, apply 6.3V at Vin (Do not hot-plug Vin or increase ripple current will be reduced significantly such that the Vin over the rated maximum supply voltage of 15V, or the part may be damaged.). Measure Vout it should internal current comparator will not be able to clearly read 0V. Turn on the circuit by inserting the shunt in differentiate it from surrounding noise. Sporadic ckt. header JP7 into the ON position. The output voltage operation will result. To avoid this effect, replace the should be regulating. Measure Vout - it should meas- standard 1 uH inductor with a 0.47 uH inductor. This ure 1.2V +/- 2% (1.176V to 1.224V). will make the inductor ripple current large enough so that the circuit operation will not be affected. Vary the input voltage from 3.6V to 15V and adjust the load current from 0 to 2.5A. Set the input voltage to Warning - If the power for the demo board is carried in 15V and the output current to 2.5A. Measure the out- long leads, the input voltage at the part could ring, put ripple voltage it should measure less than 20 which could affect the operation of the circuit or even mVAC. exceed the maximum voltage rating of the IC (which, of course, may damage the IC). To eliminate the ringing, a Observe the voltage waveform at the switch pins (the small tantalum capacitor has been inserted on the pads other side of the inductor from the output). Verify the between the input power and return terminals on the switching frequency is between 800 kHz and 1.2 MHz bottom of the demo board. The (greater) ESR of the (T = 1.25 us and 0.833 us), and that the switch node tantalum capacitor will dampen the (possible) ringing waveform is rectangular in shape. voltage due to the use of long input leads. On a normal, typical PCB, with short traces, the capacitor is not Change the JP6 shunt from forced continuous mode to needed. Burst Mode. Also set the input voltage to 12V and the 2