USERS MANUAL ISL80103EVAL2Z, ISL80102EVAL2Z AN1661 Rev 0.00 ISL80102, ISL80103 High Performance 2A and 3A LDOs Evaluation Board Sep 2, 2011 User Guide Description Required Equipment The ISL80102 and ISL80103 are high performance, low The following equipment is recommended to perform the voltage, high current low dropout linear regulator specified at tests: 2A and 3A, respectively. Rated for an input voltage from 2.2V 0V to 6V power supply capable of sourcing at least 5A to 6V, these LDOs can provide outputs from 0.8V to 5V on the Electronic load capable of sinking up to 5A adjustable version. The ISL80103EVAL2Z provides a simple platform to evaluate performance of the ISL80102, ISL80103. Digital multimeters The ISL80103EVAL2Z evaluation board comes with the 200MHz oscilloscope adjustable output version of the IC. Jumpers are provided to set the desired output voltage. Fixed output versions are Test Procedure sampled in the accompanying kit. 1) Select the desired output voltage by shorting one of the The figures with operating conditions at 3A in this Application jumpers from J1 through J6. Note are applicable only to the ISL80103. All other information 2) Ensure that output capacitor and Cpb are set according to is applicable to both the ISL80102 and ISL80103. recommended values shown in Table 1. 3) Place jumper JP1 in the enable position. It is Whats Inside recommended to not leave the ENABLE pin floating. The evaluation kit contains the following: 4) Set the power supply for the desired input voltage and the The ISL80103EVAL2Z load as desired and connect them to the input and output of the board, respectively. Fixed output versions of either the ISL80102 or the ISL80103 5) Turn the power supply on and observe the output. The ISL80102, ISL80103 data sheet (FN6660) This evaluation kit document FIGURE 1. ISL80103EVAL2Z AN1661 Rev 0.00 Page 1 of 8 Sep 2, 2011ISL80103EVAL2Z, ISL80102EVAL2Z TABLE 1. Optimizing LDO Performance V R R C C Performance of the ISL80102, ISL80103 can be optimized by OUT TOP BOTTOM PB OUT following these simple guidelines. 5.0V 2.61k 287 47pF 10F 3.3V 2.61k 464 47pF 10F Phase Boost Capacitor (CPB) 2.5V 2.61k 649 47pF 10F On the adjustable version of the ISL80102, ISL80103, phase margin and crossover frequency can be increased by placing a * 1.8V 2.61k 1.0k 47pF 10F small capacitor across the top resistor in the feedback resistor * 1.8V 2.61k 1.0k 82pF 22F divider. Cpb and Rtop as shown in Figure 2 place a zero at = 1/(2 R C ) F z TOP PB 1.5V 2.61k 1.3k 82pF 22F The zero increases the crossover frequency of the LDO and 1.2V 2.61k 1.87k 150pF 47F provides additional phase resulting in faster load transient 1.0V 2.61k 2.61k 150pF 47F response. 0.8V 2.61k 4.32k 150pF 47F VV OUT IN NOTE: *Either option could be used depending on cost/performance requirements ENABLE PG R C PB TOP Layout Guidelines ISL80102, ISL80103 ADJ A good PCB layout is important to achieve expected C OUT C IN performance. Consideration should be taken when placing the R components and routing the trace to minimize the ground BOTTOM SS impedance. Parasitic inductance should be kept to a minimum. The input and output capacitors should have a good ground connection and be placed as close to the IC as possible. The SENSE trace in fixed voltage parts and the ADJ trace in adjustable voltage parts must be away from noisy planes and traces. FIGURE 2. ISL80102, ISL80103 TYPICAL APPLICATION Output Capacitor (COUT) Output capacitor selection is important to achieve the desired load transient performance. The ISL80102, ISL80103 uses state- of-the-art internal compensation to be compatible with different types of output capacitors, including multi-layer ceramic, POSCAP and aluminum/tantalum electrolytic. There is a growing trend to use very-low ESR multi-layer ceramic capacitors (MLCC) for applications because they can support fast load transients and also bypass very high frequency noise from other sources. However, effective capacitance of MLCC s drops with applied voltage, age and temperature. X7R and X5R dielectric ceramic capacitors are strongly recommended as they typically maintain a capacitance range within 20% of nominal over full operating ratings of temperature and voltage. Table 1 gives the recommended values for output capacitor (MLCC X5R/X7R) and C for different voltage rails. PB The right selection of output capacitor and C also helps to PB provide better PSRR at high frequencies. AN1661 Rev 0.00 Page 2 of 8 Sep 2, 2011