DEMO CIRCUIT 1467A LTC3616 QUICK START GUIDE LTC3614 4A, 4MHz, MONOLITHIC SYNCHRONOUS DC/DC STEP-DOWN CONVERTER DESCRIPTION Demo Circuit 1467 is a high efficiency, high fre- DC1467A is a very efficient circuit - over 90%. The quency step-down converter, incorporating the DC1467A consumes less than 300 uA of quiescent LTC3614 monolithic synchronous regulator. The current during sleep operation, and during shut- DC1467A has an input voltage range of 2.25V to down, it consumes less than 1 uA. The DC1467A 5.5V, and is capable of delivering up to 4A of output can track another voltage, due to the LTC3614 current. The output voltage of the DC1467A can be track function, for easy power supply sequencing. set as low as 0.6V, the reference voltage of the Extra features include frequency and current fold- LTC3614. The operating frequency range of the back, and an adjustable 0.3V-to-0.6V external ref- DC1467A is either set to a fixed 2.25 MHz by con- erence. Because of the high switching frequency necting the frequency pin to SVin, set by an exter- of the LTC3614, which is programmable up to 4 nal resistor, or synchronized to an external clock, MHz, the DC1467A uses low profile surface mount with a range up to 4 MHz. At low load currents, the components. All these features make the DC1467A can operate in either noise sensitive ap- DC1467A perfectly suited for portable computer plications, due to the capability of the LTC3614 to and distributed power applications. operate in pulse-skipping mode, or in high effi- ciency applications, because the LTC3614 also has Design files for this circuit board are available. Call the Burst-Mode capability. The Burst Mode clamp can LTC factory. be set externally. Of course, in (forced) continuous mode, or large load current applications, the As Shipped Performance Summary PARAMETER CONDITIONS VALUE Minimum Input Voltage 2.25V Maximum Input Voltage 5.5V GND = Shutdown Run/Shutdown V = Run IN V = 2.25V to 5.5V, I = 0A to 4A 1.2V 4% (1.152V 1.248V) IN OUT V = 2.5V to 5.5V, I = 0A to 4A 1.8V 4% (1.728V 1.872V) IN OUT Output Voltage Regulation V = 3.3V to 5.5V, I = 0A to 4A 2.5V 4% (2.4V 2.6V) IN OUT V = 4.2V to 5.5V, I = 0A to 4A 3.3V 4% (3.168V 3.432V) IN OUT Typical Output V = 5V, V = 1.8V, I = 4A (20 MHz BW) <20mV IN OUT OUT PP Ripple Voltage Burst Mode V = 5V, V = 1.8V <1.6A IN OUT Pulse-Skip Mode V = 5V, V = 1.8V <1.5A IN OUT Nominal Switching R = 165k 2 MHz 20% T Frequency 1 L TC3616 Table 1. Jumper Description JUMPER FUNCTION RANGE/SETTING (DEFAULT) JP1 Output Voltage Setting. 1.2V J1 Mode: Forced Continuous Mode (FC), Burst Mode (BM or BMEC), or Pulse-Skip Mode(SYNC) (FC) BMEC BM - PSM J2 Run (ON) - OFF J3 Tracking (TRACK), Internal Soft-Start (INT SS), or External Soft-Start (EXT SS) (EXT SS) INT SS - TRACK J4 DDR Memory Termination (OFF) - ON J5 External or Internal ITH Compensation (EXT) INT J6 Frequency Setting: Timing Resistor (RT), Internally Synchronized (2.25 MHz), or Externally (Rt) INT SYNC EXT SYNC Synchronized J7 External Burst Mode Clamp Voltage (SET) EXT QUICK START PROCEDURE Demonstration Circuit 1467 is easy to set up to evalu- Vary the input voltage from 2.25V to 5.5V and adjust ate the performance of the LTC3614. For proper the load current from 0 to 4A. Vout should regulate measurement equipment configuration, set up the cir- around 1.2V. Measure the output ripple voltage it cuit according to the diagram in Figure 1. Before pro- should measure less than 40 mVAC. ceeding to test, insert shunts into the 1.2V position of the output voltage header JP1, into the FCM (Forced Con- Observe the voltage waveform at the switch pins (the tinuous Mode) position of MODE header J1, into the OFF other side of the inductor from the output). Verify the position of RUN header J2, into the EXT SS (external soft- switching frequency is between 1.6 MHz and 2.4 MHz start) position of Track/SS header J3, into the OFF posi- (T = 625 ns and 416 ns), and that the switch node tion of DDR header J4, into the EXT (external) position of waveform is rectangular in shape. COMP header J5, into the Rt position of Rt/SYNC header J6, and into the SET position of VBMCV header J7. Change the J1 shunt from forced continuous mode to Burst Mode or pulse-skip mode. Set the input voltage When measuring the input or output voltage ripple, to 5V and the output current to any current less than care must be taken to avoid a long ground lead on the 1A. Observe the discontinuous mode of operation at oscilloscope probe. Measure the input or output volt- the switch node, and measure the output ripple volt- age ripple by touching the probe tip directly across the age. It should measure less than 100 mV. Vin or Vout and GND terminals. See Figure 2 for proper scope probe measurement technique. Insert the J2 shunt into the OFF position and move the shunt in the 1.2V output JP1 header into any of the With the DC1467 set up according to the proper two remaining output voltage option headers: 1.8V measurement configuration and equipment in Figure (JP2), 2.5V (JP3), or 3.3V (JP4). Just as in the 1.2V 1, apply 6.3V at Vin (Do not hot-plug Vin or increase Vout test, the output voltage should read Vout +/- 2% Vin over the rated maximum supply voltage of 5.5V, or tolerance under static line and load conditions and +/- the part may be damaged.). Measure Vout it should 1% tolerance under dynamic line and load conditions read 0V. Turn on the circuit by inserting the shunt in (+/- 2% total). Also, the circuit operation in discon- header J2 into the ON position. The output voltage tinuous mode will be the same. When finished, turn should be regulating. Measure Vout - it should meas- off the circuit by inserting the shunt in header J2 into ure 1.2V +/- 2% (1.176V to 1.224V). the OFF position. 2