DEMO C IR C U IT 1 4 6 0 A Q U IC K S TADC1223A-B R T G U IDE U L T R A L OW P OW ER 1 5 MA H IG H EF F IC IEN C Y S T EP -DOW N C ON V ER T ER L T C 3 6 2 0 EDC DESCRIPTION Demonstration circuit 1460A is a high efficiency stepdow n converter featuring the LTC3620EDC w ith internal high side and synchronous pow er sw itches that draw s only 18µA of quiescent current. It has an internal frequency clamp that forces a minimum sw itching frequency at light loads to minimize noise in the audio range. Its input volt-age ranges betw een 2.9V and 5.5V. If the input voltage falls below 2.8V, an undervoltage lockout circuit w illshut dow n the part. The demo circuit provides selectable jumper outputs for 1.1V, 1.2V and 1.8V. The output can supply up to 15mA of load current. G erber files for this circuit are available. Call the LTC Factory. L, LTC, LTM , LT, Burst M ode, O PTI-LO O P, O ver-The-Top and PolyPhase are registered trademarks of Linear Technology Corporation. Adaptive Pow er, C-Load, DirectSense, Easy Drive, FilterCAD, H ot Sw ap, LinearView , µM odule, M icropow er Sw itcherCAD, M ultimode Dimming, N o Latency , N o Latency Delta-Sigma, N o R SEN SE, O perationalFilter, PanelProtect, Pow erPath, Pow erSO T, SmartStart, SoftSpan, Stage Shedding, Sw itcherCAD, ThinSO T, U ltraFast and VLDO are trademarks of Linear Technology Corporation. O ther product names may be trademarks of the companies that manufacture the products. Table 1. Performance Summary (TA = 25ºC) PARAMETER CONDITION VALUE Input Voltage Range VIN Output Voltage VOUT 2.9V to 5.5V VIN=3.6V VOUT ± 1.4% (LTC3620EDC Output adj. version) VOUT ± 1% (LTC3620-1EDC Fixed 1.1V version) Maximum Output Current DC Quiescent Current 15mA No switching, VFB=0.65V, SW 18µA Pin Floating Minimum Switching Frequency (Internal) VFB=0.65V, fMIN/MODE=0 50kHz Q U ICK STA RT PROCEDU RE The DC1460A is easy to set up to evaluate the performance of the LTC3620EDC. For a proper measurement equipment configuration, set up the circuit according to the diagram in Figure 2. N O TE. W hen measuring the input or output voltage ripple, care must be taken to avoid a long ground lead on the oscilloscope probe. M easure the input or output voltage ripple by touching the probe tip di-rectly across the VIN or VO U T and G N D terminals. See the M easurement Equipment Set-up diagram in Figure 1 for proper scope probe technique. Please follow the procedure outlined below for proper operation. 1. Connect the input pow er supply to the VIN and G N D terminals. Connect the load betw een the VO U T and G N D terminals. R efer to Figure 2 for the proper measurement equipment setup. 2. Before proceeding to operation, insert jumper shunt XJP1 into the O FF position and insert a shunt jumper into JP2, JP3 or JP4 for voltages of 1.8V, 1.2V or 1.1V respectively. Set the load output current to 12ma. 3. Apply 3.6V at VIN . M easure VO U T; it should read 0V. If desired, one can measure the shutdow n supply current at this point. The supply current w ill be about <1 µA in shutdow n. Set the load output current back to 0mA. 4. Turn on VO U T by changing shunt XJP1 from the O FF position to the O N position. The output voltage should measure according to the voltage set by the shunt jumper in JP2. 5. Set the load output current to 5mA. Vary the input voltage from 3.0V to 5.5V and VO U T should be w ithin a tolerance of ± 0.38% . 1 DC1460A 6. Set the input voltage to 3.6V. Vary the VO U T load current from 1mA to 12mA, and the output voltage should be w ithin a tolerance of ± 0.5% (typical). As the load is varied, there should not be any audible noise generated by the demo circuit. Warning. If the power for the demo board is carried in long leads, the input voltage at the part could “ring”, which could affect the operation of the circuit or even exceed the maximum voltage rating of the IC. To eliminate the ringing, insert an electrolytic capacitor (for instance, Panasonic part # EEAFC1A220 (22µF/10V) on the pads between the input power and return terminals on the bottom of the demo board. The (greater) ESR of the electrolytic will dampen the (possible) ringing voltage due to the use of long input leads. On a normal, typical PCB, with short traces, the capacitor is not needed. Figure 1. M easuring Input or O utput Voltage R ipple Figure 2. Equipm ent Setup to Test LTC3620ED C 2 DC1460A INDU CTOR COM PA RISON Demonstration circuit 1460A comes w ith a standard inductor (Coilcraft LPS3010-223M L) optimized for size and efficiency. For handheld applications requiring minimal board area, this inductor can be replaced w ith a small surface mount 0603 package inductor, for ex- ample, the Taiyo-Yuden CBM F1608T220K. Figure 3 show s the inductor size comparison on the demonstration board w hile Figure 4 show s the efficiency performance of these tw o inductors. Figure 3. LTC3620ED C O perating w ith D ifferent Size Inductors Efficiency vs Iout, L=22uH 100 (CBMF1608T220K - 1.52mmx0.76mm Taiyo Yuden) (LPS3010-223MLD - 2.95mmx 2.95mm Coil Craft) 1 95 2 Efficiency (%) 90 3 4 85 6 80 75 70 65 60 1.00 Notes: Vin = 3.6V FMIN/Mode=0V 5 1 – Vout=2.5V LPS3010 2 – Vout=1.8V LPS3010 3 – Vout=1.2V LPS3010 4 – Vout=2.5V CBMF1608T 5 – Vout=1.8V CBMF1608T 6 – Vout=1.2V CBMF1608T 10.00 100.00 Iout (mA) Figure 4. Typical Efficiency vs. Load Current for D ifferent Inductors 3 DC1460A 4 DC1460A Item Qty Reference Part Description REQUIRED CIRCUIT COMPONENTS 1 1 CFFW Cap., NPO 22pF 25V 10% 2 2 COUT,CIN Cap., X5R 1uF 6.3V 10% 3 1 CIN1 Cap., Tant. 10uF 16V 20% 4 1 L1 Inductor, 22uH 5 1 RFB1 Res., Chip 1.37M 0.06W 1% 6 1 RFB2 Res., Chip 681K 0.06W 1% 7 2 R1,R3 Res., Chip 1M 0.06W 5% 8 1 R2 Res., Chip 715K 0.06W 1% 9 1 U1 I.C., Volt. Reg. Manufacturer / Part # AVX 04023A220KAT2A Taiyo Yuden JMK107BJ105KA-T AVX TAJT106M016R Coilcraft LPS3010-223 Vishay CRCW04021M37FKED Vishay CRCW0402681KFKED Vishay CRCW04021M00JNED Vishay CRCW0402715KFKED Linear Tech. Corp. LTC3620EDC ADDITIONAL DEMO BOARD CIRCUIT COMPONENTS 1 1 COUT1 Cap., X5R 0.1uF 25V 10% AVX 06033D104KAT2A HARDWARE FOR DEMO BOARD ONLY 1 7 E1,E2,E3,E4,E5,E6,E7 Turret, Testpoint 2 1 JP1 Headers, 3 Pins 2mm Ctrs. 3 3 JP2,JP3,JP4 Jumper, 2 Pins 2mm Ctrs. 4 1 JP5 Headers, Dbl. Row 2 x 3 2mm Ctrs. 5 1 RFB3 Res., Chip 1.37M 0.06W 1% 6 1 RFB4 Res., Chip 1.65M 0.06W 1% 7 3 XJP1,XJP2,XJP5 Shunt, 2mm Ctrs. 8 1 FAB, PRINTED CIRCUIT BOARD 9 1 STENCIL Mill Max 2501-2-00-80-00-00-07-0 Samtec TMM-103-02-L-S Samtec TMM-102-02-L-S Samtec TMM-103-02-L-D Vishay CRCW04021M37FKED Vishay CRCW04021M65FKED Samtec 2SN-BK-G DEMO CIRCUIT #1460A STENCIL 1460A 5