User Guide UG015 ISL7823xEVAL1Z Evaluation Board User Guide Description Key Features The ISL78233EVAL1Z, ISL78234EVAL1Z, ISL78235EVAL1Z evaluation boards are used to demonstrate the performance of the ISL78233, ISL78234, ISL78235 low quiescent current, high efficiency synchronous buck regulator. The evaluation boards are intended for use by customers with requirements for Point-of-load automotive applications with 2.7V to 5.5V input supply voltage, output voltages down to 0.8V and up to 5A output current. • 2.7V to 5.5V input voltage range The ISL78233, ISL78234, ISL78235 are offered in a 3x3mm 16 Ld TQFN package with 1mm maximum height. The complete area that the regulator occupies can be as small as 0.22in2. • 100ns maximum phase minimum on time allows wide output regulation operating at 2MHz Specifications PART NUMBER IOUT (MAX) (A) ISL78235 5 ISL78234 4 ISL78233 3 fSW RANGE (MHz) VIN VOUT RANGE RANGE (V) (V) • Synchronous buck regulator up to 95% efficiency • 1% reference accuracy over temperature • Resistor adjustable frequency from 500kHz to 4MHz; Default set to 2MHz • External synchronization from 1MHz to 4MHz • Internal soft-start set to 1ms; adjustable with external soft-start capacitor • Over-temperature, overcurrent, overvoltage and negative overcurrent protection PART SIZE (mm) References ISL78235 Datasheet Programmable 1 to 4MHz 2.7 to 5.5 0.8 to 5.5 3x3 ISL78233,ISL78234 Datasheet Ordering Information PART NUMBER PCB SPECIFICATION Board Dimension: 2.025 x 2.725 in # of Layers: 4 FR-4 Thickness: 1.57mm Copper Weight: 2oz. DESCRIPTION ISL78235EVAL1Z Evaluation Board for 5A Sync Buck ISL78235 ISL78234EVAL1Z Evaluation Board for 4A Sync Buck ISL78234 ISL78233EVAL1Z Evaluation Board for 3A Sync Buck ISL78233 NOTES: 1. The evaluation board default VOUT = 1.8V. 2. The evaluation board default fSW = 2MHz. FIGURE 1. ISL78235EVAL1Z EVALUATION BOARD PHOTO April 8, 2016 UG015.1 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, 2016. 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. User Guide UG015 Recommended Equipment The following equipment is recommended to perform testing: soft-start time. This capacitor, along with an internal 2.1µA current source sets the soft-start interval of the converter, tSS. CSS F = 3.5 t SS s (EQ. 3) • 0V to 5V power supply with 10A source current capability CSS should be more than 33nF to insure proper soft-start reset after fault condition. The ISL78233EVAL1Z, ISL78234EVAL1Z, ISL78235EVAL1Z has a default 33nF on the board for a ~10ms soft-start time. • Electronic load capable of sinking current up to 10A • Digital Multimeters (DMMs) • 500MHz quad-trace oscilloscope • Signal generator for EN and/or SYNC pins Control Switches for EN and SYNC Quick Setup Guide The evaluation board contain switches SW1 and SW2 for control of the EN and SYNC pin. Table 1 details this function. 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). 3. Connect the output load to VOUT, the plus terminal to VOUT (P3) and the negative return to PGND (P7). TABLE 1. SWITCH SETTINGS SW1 ENABLE FUNCTION 1 (LEFT) OFF DISABLE IC 3 (RIGHT) ON ENABLE IC SW2 SYNC 1 (LEFT) PFM Skip mode at light load 3 (RIGHT) PWM Fixed PWM frequency at light load 4. Verify that SW2 is in the proper position for PFM or PWM. 5. Verify that the position is ON for SW1. 6. Turn on the power supply and set for 2.7V to 5.0V. 7. Verify the output voltage is 1.8V for VOUT. Evaluating Other Output Voltages The ISL78233EVAL1Z, ISL78234EVAL1Z, ISL78235EVAL1Z evaluation boards outputs are preset to 1.8V for VOUT. The output voltage can be adjusted from 0.8V to 3.3V. The output voltage programming resistor, R1, depends on the desired output voltage of the regulator. It is recommended to have R2 set to 100kΩ. The value for R1 is typically between 66kΩ and 450kΩ, as shown in Equation 1. (EQ. 1) R 1 = R 2 VO VFB – 1 For faster transient response performance, add 10pF to 22pF in parallel to R1. Check loop compensation analysis to insure optimum performance before use of capacitance. Frequency Control The ISL78233, ISL78234, ISL78235 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 2MHz when FS is tied to VIN (R11 = 0 and R12 is open). By removing R11 and changing the value of R12, the switching frequency can be changed from 500kHz to 4MHz according to Equation 2: 220 10 3 R T k = ------------------------------ – 14 f OSC kHz (EQ. 2) Please refer to the ISL78235, ISL78233, ISL78234 datasheets for more details. Soft-Start Control The ISL78233, ISL78234, ISL78235 has an SS pin that controls the soft-start up time. Short SS pin to SGND for internal soft-start (approximately 1ms). Populate a capacitor CSS to adjust the Submit Document Feedback 2 FUNCTION Power Inductor The evaluation board contains a 0.68µH output power inductor. It has a 13.5A saturation current that is able to handle the peak current limit of the IC. The inductor is chosen to optimize performance for VIN = 5V, VOUT = 1.8V at 2MHz switching frequency for up to 5A output currents. Internal vs External Compensation The ISL78233, ISL78234 and ISL78235 feature an internal compensation network on the output of the error amplifier. The internal compensation simplifies design by reducing external components while stabilizing the regulator under transient load response. To use internal compensation network, tie the COMP pin to VDD. The restriction of an internal compensation network is that it does not provide flexibility to optimize the compensation network for conditions when additional output capacitance is needed to minimize output overshoot from fast transient loading. The added capacitance affects the stability and response of the feedback loop. The internal compensation network is well suited for a wide range of switching frequencies and load di/dt transients, however if the feedback network needs to be better optimized for the application, external compensation should be used. When the COMP pin is not connected to VDD, an RC network from COMP pin to GND is used to provide the external compensation. For more information on the specification of the internal compensation network and designing for stability, refer to ISL78235, ISL78233, ISL78234 datasheets for more details. UG015.1 April 8, 2016 User Guide UG015 PCB Layout Recommendation The PCB layout is a very important converter design step to make sure the designed converter works well. For ISL78233, ISL78234, ISL78235, the power loop is composed of the output inductor Lo, the output capacitor (COUT), the PHASE pins and the PGND pins. It is necessary to make the power loop as small as possible and the connecting traces among them should be direct, short and wide. The switching node of the converter (PHASE pins) and the traces connected to the node are noisy. Keep the voltage feedback trace away from these noisy traces. The input capacitor should be placed as close as possible to the VIN/VDD and GND pin. The ground of input and output capacitors should be connected as close as possible. The heat of the IC is mainly dissipated through the thermal pad. Maximizing the copper area connected to the thermal pad is preferable. In addition, a solid ground plane is helpful for better EMI performance. It is recommended to add at least 5 vias ground connection within the pad for the best thermal relief. Submit Document Feedback 3 UG015.1 April 8, 2016 User Guide UG015 ISL78233EVAL1Z, ISL78234EVAL1Z, ISL78235EVAL1Z Schematic NOTES: 3. ISL78235EVAL1Z schematics shown. 4. ISL78233EVAL1Z and ISL78234EVALZ schematics are equivalent. Submit Document Feedback 4 UG015.1 April 8, 2016 User Guide UG015 Bill Of Materials PART NUMBER QTY UNITS REFERENCE DESIGNATOR DESCRIPTION MANUFACTURER MANUFACTURER PART ISL78233EVAL1Z 1 ea. PWB-PCB, ISL78235, REVA, RoHS IMAGINEERING INC ISL78233EVAL1Z ISL78234EVAL1Z 1 ea. PWB-PCB, ISL78234, REVA, RoHS IMAGINEERING INC ISL78234EVAL1Z ISL78235EVAL1Z 1 ea. PWB-PCB, ISL78235, REVA, RoHS IMAGINEERING INC ISL78235EVAL1Z ISL78233ARZ or ISL78234ARZ or ISL78235ARZ 1 ea. U1 IC- 3A, 4A, or 5A BUCK REGULATOR, 16P, QFN, INTERSIL 3x3, RoHS ISL78233ARZ or ISL78234ARZ or ISL78235ARZ H1045-00220-50V5-T 1 ea. C4 CAP, SMD, 0603, 22pF, 50V, 5%, C0G, RoHS C0603C0G500-220JNE H1045-00221-50V10-T 1 ea. C7 CAP, SMD, 0603, 220pF, 50V, 10%, X7R, RoHS MURATA GRM188R71H221KA01D H1045-00333-16V10-T 1 ea. CSS CAP, SMD, 0603, 33000pF, 16V, 10%, X7R, RoHS VENKEL C0603X7R160-333KNE C0603X7R160-104KNE VENKEL H1045-00104-16V10-T 1 ea. C3 CAP, SMD, 0603, 0.1µF, 16V, 10%, X7R, RoHS VENKEL H1045-DNP 0 ea. C8 CAP, SMD, 0603, DNP-PLACE HOLDER, RoHS H1065-00226-10V10-T 4 ea. IHLP2020CZERR68M01-T 1 ea. L1 131-4353-00 2 ea. J1, J2 1514-2 4 ea. 5002 3 LTST-C170CKT C1, C2, C5, C6 CAP, SMD, 1206, 22µF, 10, 10%, X7R, RoHS COIL-PWR INDUCTOR, SMD, 5.49x5.18, 0.68µH, 20%, 10.2A, RoHS TAIYO YUDEN MURATA LMK316AB7226KL-TR GRM31CR71A226KE15L VISHAY IHLP2020CZERR68M01 CONN-SCOPE PROBE TEST PT, COMPACT, PCB TEKTRONIX MNT, RoHS 131-4353-00 P4, P5, P7, P8 CONN-TURRET, TERMINAL POST, TH, RoHS KEYSTONE 1514-2 ea. P1, P2, P6 CONN-MINI TEST POINT, VERTICAL, WHITE, RoHS KEYSTONE 5002 1 ea. D1 LED-GaAs RED, SMD, 2x1.25mm, 100mW, 40mA, 10mcd, RoHS LITEON/VISHAY LTST-C170CKT 2N7002-7-F-T 1 ea. Q1 TRANSISTOR, N-CHANNEL, 3 LD, SOT-23, 60V, DIODES, INC. 115mA, RoHS 2N7002-7-F H2511-00200-1/10W1-T 1 ea. R3 RES, SMD, 0603, 20Ω, 1/10W, 1%, TF, RoHS PANASONIC ERJ-3EKF20R0V RES, SM, 0603, 0Ω, 1/10W, 5%, TF, RoHS GENERIC H2511-00R00-1/10W-T 2 ea. R10, R11 H2511-01003-1/10W1-T 1 ea. R2 RES, SMD, 0603, 100k, 1/10W, 1%, TF, RoHS VENKEL CR0603-10W-1003FT H2511-02001-1/10W1-T 1 ea. R5 RES, SMD, 0603, 2k, 1/10W, 1%, TF, RoHS RK73H1JTTD2001F H2511-02003-1/10W1-T 4 ea. R1, R4, R6, R7 RES, SMD, 0603, 200k, 1/10W, 1%, TF, RoHS VENKEL CR0603-10W-2003FT H2511-06982-1/10W1-T 1 ea. R14 RES, SMD, 0603, 69.8k, 1/10W, 1%, TF, RoHS VENKEL CR0603-10W-6982FT H2511-09532-1/10W1-T 1 ea. R12 RES, SMD, 0603, 95.3k, 1/10W, 1%, TF, RoHS VENKEL CR0603-10W-9532FT H2511-DNP 0 ea. R8,R9 GT11MSCBE-T 2 ea. SW1, SW2 Submit Document Feedback 5 KOA RES, SMD, 0603, DNP-PLACE HOLDER, RoHS SWITCH-TOGGLE, SMD, 6 PIN, SPDT, 2POS, ON-ON, RoHS ITT INDUSTRIES/ C&K DIVISION GT11MSCBE UG015.1 April 8, 2016 User Guide UG015 ISL78233EVAL1Z, ISL78234EVAL1Z, ISL78235EVAL1Z Board Layout FIGURE 2. TOP LAYER SILKSCREEN FIGURE 3. BOTTOM LAYER SILKSCREEN NOTES: 5. ISL78233 board silkscreen name is ISL78233EVAL1Z 6. ISL78234 board silkscreen name is ISL78234EVAL1Z Submit Document Feedback 6 UG015.1 April 8, 2016 User Guide UG015 ISL78233EVAL1Z, ISL78234EVAL1Z, ISL78235EVAL1Z Board Layout FIGURE 4. LAYER 1 PCB FIGURE 5. LAYER 2 PCB FIGURE 6. LAYER 3 PCB FIGURE 7. LAYER 4 PCB Submit Document Feedback 7 UG015.1 April 8, 2016 User Guide UG015 Typical Performance Curves 100 2.5 3.3VOUT 3.3VOUT 80 2.5VOUT 1.8VOUT 1.5VOUT 2.0 POWER DISSIPATION (W) EFFICIENCY (%) 90 1.2VOUT 70 60 2.5VOUT 1.5 1.8VOUT 1.0 0.5 50 1.2VOUT 0 40 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 0 5.0 0.5 1.0 2.5 3.0 3.5 4.0 4.5 5.0 2.5 2.5VOUT 1.8VOUT 90 2.0 POWER DISSIPATION (W) EFFICIENCY (%) 2.0 FIGURE 9. POWER DISSIPATION vs LOAD (5VIN; SYNC = VDD) FIGURE 8. EFFICIENCY vs LOAD (5VIN; SYNC = VDD) 100 1.5 OUTPUT LOAD (A) OUTPUT LOAD (A) 80 1.8VOUT 1.5VOUT 1.2VOUT 70 1.0VOUT 60 50 2.5VOUT 1.5 1.5VOUT 1.0 1.0VOUT 0.5 1.2VOUT 40 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 4.5 5.0 0 0.5 1.0 OUTPUT LOAD (A) FIGURE 10. EFFICIENCY vs LOAD (3VIN; SYNC = VDD) COUT = 4x22µF VOUT 100mV/DIV AC Rcomp = 154kΩ Ccomp = 220pF I_LOAD 2A/DIV 500µs/DIV FIGURE 12. LOAD TRANSIENT 0A TO 5A; 0.5A/µs (SYNC = GND) 1.5 2.0 2.5 3.0 OUTPUT LOAD (A) 3.5 4.0 4.5 5.0 FIGURE 11. POWER DISSIPATION vs LOAD (3VIN; SYNC = VDD) COUT = 4x22µF VOUT 100mV/DIV AC Rcomp = 154kΩ Ccomp = 220pF I_LOAD 2A/DIV 500µs/DIV FIGURE 13. LOAD TRANSIENT 0A TO 5A; 0.5A/µs (SYNC = VDD) 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 8 UG015.1 April 8, 2016