Application Note 1759 3A/4A Low Quiescent Current High Efficiency Synchronous Buck Regulator Description Key Features The ISL8023EVAL3Z, ISL8024EVAL3Z boards are intended for use by individuals with requirements for point-of-load applications sourcing from 2.7V to 5.5V. The ISL8023EVAL3Z, ISL8024EVAL3Z simple smallest factor evaluation boards are used for a quick and easy demonstration of the performance of the ISL8023, ISL8024 low quiescent high efficiency synchronous buck regulator. • High efficiency synchronous buck regulator with up to 95% efficiency The ISL8023 and ISL8024 are offered in a 3mmx3mm 16 Ld TQFN package with 1mm maximum height. The complete area that the converter occupies can be as small as 0.22in2. • Soft-stop output discharge during disabled • 0.8% reference accuracy over temperature/load/line • Start-up with prebiased output • Internal soft-start - 1ms or adjustable • Adjustable frequency from 500kHz to 4MHz - default at 1MHz • External synchronization up to 4MHz • Negative OC protection Specifications PART NUMBER 8023 8024 VIN RANGE (V) VOUT RANGE (V) References IOUT (MAX) (A) 3 2.7V to 5.5V 4 fSW RANGE (MHz) PART SIZE (2mm) Programmable 0.5 to 4MHz 3x3 ISL8023, ISL8024 Datasheet Ordering Information PART NUMBER NOTES: 1. The evaluation boards default configuration is VOUT = 1.8V, fSW = 1MHz (FS tied to VIN) DESCRIPTION ISL8023EVAL3Z 3A low quiescent current high efficiency synchronous buck regulator ISL8024EVAL3Z 4A low quiescent current high efficiency synchronous buck regulator 2. VREF is 0.6V ISL8023, ISL8024 VIN PHASE PHASE PHASE VIN VOUT VIN GND VDD GND PGND PGND EPAD PG SGND COMP SS FS FB EN SYNC FIGURE 1. BLOCK DIAGRAM September 10, 2015 AN1759.1 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-468-3774 | Copyright Intersil Americas LLC. 2015. All Rights Reserved Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries. All other trademarks mentioned are the property of their respective owners. Application Note 1759 Recommended Equipment Frequency Control The following materials are recommended to perform testing: • 0V to 10V power supply with at least 10A source current capability or 5V battery • Electronic loads capable of sinking current up to 7A • Digital Multimeters (DMMs) • 100MHz quad-trace oscilloscope The ISL8023, ISL8024 has an FS pin that controls the frequency of operation. Programmable frequency allows for optimization between efficiency and external component size. Default switching frequency is 1MHz when FS is tied to VIN (R11 = 0 and R12 is open). By connecting R12 to GND, the switching frequency could be changed from 500kHz (R12 = 426k) to 4MHz (R12 = 40k) according to Equation 2: 220 10 3 R T k = ------------------------------ – 14 f OSC kHz • Signal generator Quick Setup Guide 1. Ensure that the circuit is correctly connected to the supply and loads prior to applying any power. 2. Connect the bias supply to VIN, the plus terminal to VIN, P4 and the negative return to PGND, P5. (EQ. 2) When using R12 to adjust the operational frequency, this also sets external compensation mode. Please refer to the ISL8023, ISL8024 datasheet for more details. Soft-start Control 4. Verify that the position is PWM for SW2. Short CSS to SGND for internal soft-start (approximately 1ms). Populate CSS to adjust the soft-start time. This capacitor, along with an internal 1.6µA current source, sets the soft-start interval of the converter, tSS. 5. Verify that the position is ON for SW1. CSS F = 3.33 t SS s 3. Connect the output load to VOUT, the plus terminal to VOUT, P3 and the negative return to PGND, P7. (EQ. 3) 6. Turn on the power supply. CSS must be less than 33nF to insure proper soft-start reset after fault condition. 7. Verify the output voltage is 1.8V for VOUT. Evaluating the Other Output Voltage The ISL8023EVAL3Z, ISL8024EVAL3Z board output is preset to 1.8V for VOUT, however, output voltages can be adjusted from 0.6V to 5V. The output voltage programming resistor, R1, will depend on the desired output voltage of the regulator. The value for the feedback resistor is typically between 0Ω and 200kΩ as shown in Equation 1. VFB R 2 = R 1 ---------------------------------- V – VFB (EQ. 1) OUT If the output voltage desired is 0.6V, then R2 is left unpopulated and R1 is shorted. For faster response performance, add 10pF to 47pF in parallel to R1. Check bode plot to insure optimum performance. Submit Document Feedback 2 Switches Control The ISL8023, ISL8024 evaluation boards contain SW1 and SW2 for various controls of the ISL8023, ISL8024 circuitries. Table 1 details this function. TABLE 1. SWITCH SETTINGS SW1 ENABLE FUNCTION 1 OFF Disable VOUT 3 ON Enable VOUT SW2 MODE 1 PWM Fixed PWM frequency at light load 3 PFM Force continuous mode FUNCTION AN1759.1 September 10, 2015 Application Note 1759 ISL8023EVAL3Z and ISL8024EVAL3Z Evaluation Boards FIGURE 2. ISL8023EVAL3Z TOP FIGURE 3. ISL8023EVAL3Z BOTTOM FIGURE 4. ISL8024EVAL3Z TOP FIGURE 5. ISL8024EVAL3Z BOTTOM Submit Document Feedback 3 AN1759.1 September 10, 2015 Application Note 1759 ISL8023EVAL3Z, ISL8024EVAL3Z Schematic 1 2 16 15 14 13 VIN 0 C1 22UF PHASE 1 2 3 4 C2 22UF C3 OPEN VIN VDD PG SYNC 17 PG SYNC EP 3 22UF U1 ISL8023/24 C6 22UF R3 12 11 10 9 PGND PGND SGND FB P3 20 A C4 R2 100K 22PF 1 P7 2 A R1 2 200K CH8 1 A EN 5 6 7 8 P5 VO C5 VIN PHASE PHASE PHASE R10 L1 1.0UH A EN FS SS COMP P4 1 2 J2 4 3 J1 4 A R11 VIN DNP SS R12 191K C7 220PF CSS 0.033UF C8 OPEN R14 69.8K A A A VIN VIN R5 2K 32 P6 Q1 1 2 EN D1 2N7002 3 SW1 1 R6 200K ON OFF SYNC 2 3 SW2 P2 1 PWM PFM R9 OPEN R8 OPEN 2 P1 R7 200K 1 R4 200K PG VIN A A A FIGURE 6. SCHEMATIC Submit Document Feedback 4 AN1759.1 September 10, 2015 Application Note 1759 TABLE 2. BILL OF MATERIALS MANUFACTURER PART REFERENCE DESIGNATOR QTY UNITS ISL8023_24EVAL3ZREVAPCB 1 ea. C0603C0G500-220JNE 1 ea. C4 CAP, SMD, 0603, 22pF, 50V, 5%, C0G, ROHS VENKEL GRM188R71H221KA01D 1 ea. C7 CAP, SMD, 0603, 220pF, 50V, 10%, X7R, ROHS MURATA C0603X7R160-333KNE 1 ea. CSS CAP, SMD, 0603, 33000pF, 16V, 10%, X7R, ROHS VENKEL 0 ea. C3, C8 CAP, SMD, 0603, DNP-PLACE HOLDER, ROHS 2 ea. C2, C5 CAP, SMD, 1206, 22µF, 6.3V, 10%, X5R, ROHS 0 ea. C1, C6 CAP, SMD, 1206, DNP-PLACE HOLDER, ROHS DR73-1R0-R 1 ea. L1 131-4353-00 2 ea. J1, J2 1514-2 4 ea. 5002 3 LTST-C170CKT GRM31CR60J226KE19L DESCRIPTION MANUFACTURER PWB-PCB, ISL8023_24EVAL3Z, REVA, ROHS MURATA COIL-PWR INDUCTOR, SMD, 7.6mm, 1.0µH, 20%, 5.28A, ROHS, SHIELDED COOPER ELECTRONIC TECH. CONN-SCOPE PROBE TEST PT, COMPACT, PCB MNT, ROHS TEKTRONIX P4, P5, P7, P8 CONN-TURRET, TERMINAL POST, TH, ROHS KEYSTONE ea. P1, P2, P6 CONN-MINI TEST POINT, VERTICAL, WHITE, ROHS KEYSTONE 1 ea. D1 LED-GaAs RED, SMD, 2x1.25mm, 100mW, 40mA, 10mcd, ROHS LITEON/VISHAY ISL8023/24IRZ 1 ea. U1 IC-3A/4A BUCK REGULATOR, 16P, QFN, 3x3, ROHS INTERSIL 2N7002-7-F 1 ea. Q1 TRANSISTOR, N-CHANNEL, 3 LD, SOT-23, 60V, 115mA, ROHS DIODES, INC. 0 ea. R11 RESISTOR, SMD, 0603, 0.1%, MF, DNP-PLACE HOLDER ERJ-3EKF20R0V 1 ea. R3 RES, SMD, 0603, 20Ω, 1/10W, 1%, TF, ROHS PANASONIC CR0603-10W-000T 1 ea. R10 RES, SMD, 0603, 0Ω, 1/10W, TF, ROHS VENKEL CR0603-10W-1003FT 2 ea. R2, R14 RES, SMD, 0603, 100k, 1/10W, 1%, TF, ROHS VENKEL CR-0603-10W-1913FT 1 ea. R12 RES, SMD, 0603, 191k, 1/10W, 1%, TF, ROHS VENKEL CR0603-10W-2003FT 4 ea. R1, R4, R6, R7 RES, SMD, 0603, 200k, 1/10W, 1%, TF, ROHS VENKEL 0 ea. R5, R8, R9 RES, SMD, 0603, DNP-PLACE HOLDER, ROHS 2 ea. SW1, SW2 0 ea. P3 (3VH30/1JN5) GT11MSCBE Submit Document Feedback 5 SWITCH-TOGGLE, SMD, 6 PIN, SPDT, 2POS, ON-ON, ROHS ITT INDUSTRIES/C&K DIVISION DO NOT POPULATE OR PURCHASE AN1759.1 September 10, 2015 Application Note 1759 ISL8023EVAL3Z, ISL8024EVAL3Z Board Layout FIGURE 7. TOP LAYER COMPONENTS Submit Document Feedback 6 AN1759.1 September 10, 2015 Application Note 1759 ISL8023EVAL3Z, ISL8024EVAL3Z Board Layout (Continued) FIGURE 8. TOP LAYER ETCH Submit Document Feedback 7 AN1759.1 September 10, 2015 Application Note 1759 ISL8023EVAL3Z, ISL8024EVAL3Z Board Layout (Continued) FIGURE 9. SECOND LAYER ETCH Submit Document Feedback 8 AN1759.1 September 10, 2015 Application Note 1759 ISL8023EVAL3Z, ISL8024EVAL3Z Board Layout (Continued) FIGURE 10. THIRD LAYER ETCH Submit Document Feedback 9 AN1759.1 September 10, 2015 Application Note 1759 ISL8023EVAL3Z, ISL8024EVAL3Z Board Layout (Continued) FIGURE 11. BOTTOM LAYER ETCH Submit Document Feedback 10 AN1759.1 September 10, 2015 Application Note 1759 ISL8023EVAL3Z, ISL8024EVAL3Z Board Layout (Continued) FIGURE 12. BOTTOM LAYER COMPONENTS Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without notice. Accordingly, the reader is cautioned to verify that the document is current before proceeding. For information regarding Intersil Corporation and its products, see www.intersil.com Submit Document Feedback 11 AN1759.1 September 10, 2015