ISL78234EVAL2Z

User Guide UG062 ISL7823xEVAL2Z Evaluation Board User Guide Description Key Features The ISL78233EVAL2Z, ISL78234EVAL2Z and ISL78235EVAL2Z evaluation boards are used to demonstrate the performance of the ISL78233, ISL78234 and ISL78235 low quiescent current, high efficiency synchronous buck regulators. 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 a 5A output current. • 2.7V to 5.5V input voltage range • 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 • 100ns maximum phase minimum on time allows wide output regulation operating at 2MHz The ISL78233, ISL78234 and ISL78235 are offered in a 5x5mm 16 Ld Wettable Flank QFN (WFQFN) package with 0.9mm maximum height. • Internal soft-start set to 1ms; adjustable with external soft-start capacitor Specifications PART NUMBER IOUT (MAX) (A) ISL78235 5 ISL78234 3 ISL78233 4 fSW RANGE (MHz) • Over-temperature, overcurrent, overvoltage and negative overcurrent protection VIN VOUT RANGE RANGE (V) (V) References PART SIZE (mm) • ISL78235 Datasheet Programmable 1MHz to 4MHz 2.7 to 5.5 0.8 to 5.5 • ISL78233, ISL78234 Datasheet 5x5 Ordering Information PCB SPECIFICATION Board Dimension: 2.025inx2.725in # of Layers: 4 FR-4 Thickness: 1.57mm Copper Weight: 2oz. PART NUMBER NOTES: 1. The evaluation board default VOUT = 1.8V. 2. The evaluation board default fSW = 2MHz. ISL78235EVAL2Z Evaluation Board for 5A Synchronous Buck ISL78235 ISL78234EVAL2Z Evaluation Board for 4A Synchronous Buck ISL78234 ISL78233EVAL2Z Evaluation Board for 3A Synchronous Buck ISL78233 16 VIN 15 PHASE 14 11 *ISL78235 3 10 SYNC 4 9 8 COMP 7 SS FS EN 6 5A LOAD DSP, FPGA 13 12 5 VOUT COUT 1 VDD 2 PG PHASE VIN CIN PHASE L 2.7V TO 5.5V DESCRIPTION PGND PGND SGND FB *Pin Compatible ISL78233 - 3A BUCK ISL78234 - 4A BUCK FIGURE 1. ISL7823xEVAL2Z BLOCK DIAGRAM December 9, 2015 UG06.0 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. User Guide UG062 Recommended Equipment Frequency Control The following equipment is recommended to perform testing: • 0V to 5V power supply with 10A source current capability • Electronic load capable of sinking current up to 10A • Digital Multimeters (DMMs) • 500MHz quad-trace oscilloscope The ISL78233, ISL78234 and ISL78235 have 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 (R6 = 0). By removing R6 and changing the value of R4, the switching frequency can be changed from 500kHz to 4MHz according to Equation 2: 220  10 3 R 4  k  = ------------------------------ – 14 f OSC  kHz  • Signal generator for EN and/or SYNC pins 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). 3. Connect the output load to VOUT, the plus terminal to VOUT (P3) and the negative return to PGND (P7). 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. (EQ. 2) Please refer to the ISL78235, ISL78233, ISL78234 datasheets for more details. Soft-Start Control The ISL78233, ISL78234 and ISL78235 have an SS pin that controls the soft start-up time. Short the SS pin to SGND for internal soft-start (approximately 1ms). Populate a capacitor at C6 to adjust the soft-start time. This capacitor, along with an internal 2.1µA current source sets the soft-start interval of the converter, tSS. C6  F  = 3.5  t SS  s  7. Verify the output voltage is 1.8V for VOUT. Functional Description The ISL78233EVAL2Z, ISL78234EVAL2Z and ISL78235EVAL2Z evaluation boards are used to demonstrate the performance of the ISL78233, ISL78234 and ISL78235 low quiescent current, high efficiency synchronous buck regulators. 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 a 5A output current. The ISL78233, ISL78234 and ISL78235 are offered in a 5x5mm 16 Ld Wettable Flank QFN (WFQFN) package with 0.9mm maximum height. The schematics for the evaluation boards are shown in Figure 4 on page 5. The evaluation boards include all components to easily evaluate the performance of the buck regulator. Hardware included on the evaluation boards allows the user to operate the following functions: Toggle switch for Enable/Disable, Toggle switch for PFM/forced PWM operation and test points for monitoring the switching node and output voltage. Operating Voltage Range The ISL78233EVAL2Z, ISL78234EVAL2Z and ISL78235EVAL2Z evaluation boards are designed to operate with 2.7V to 5.5V VIN and the 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, R2, depends on the desired output voltage of the regulator. It is recommended to have R3 set to 100kΩ. The value for R2 is typically between 66kΩ and 450kΩ and is determined in Equation 1. (EQ. 3) C6 should be less than 33nF to insure proper soft-start reset after a fault condition. The ISL78233EVAL2Z, ISL78234EVAL2Z and ISL78235EVAL2Z have a default 33nF on the board for a ~10ms soft-start time. Control Switches for EN and SYNC The evaluation boards contain switches SW1 and SW2 for control of the EN and SYNC pin. Table 1 details this function. 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 FUNCTION Power Inductor The evaluation boards contain 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. (EQ. 1) R 2 = R 3  VO  VFB – 1  For faster transient response performance, add 10pF to 22pF in parallel to R2. Check loop compensation analysis to insure optimum performance before use of capacitance. Submit Document Feedback 2 UG06.0 December 9, 2015 User Guide UG062 FIGURE 2. ISL78235EVAL2Z TOP SIDE FIGURE 3. ISL78235EVAL2Z BOTTOM SIDE Submit Document Feedback 3 UG06.0 December 9, 2015 User Guide UG062 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 an 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 the COMP pin to GND is used to provide the external compensation. PCB Layout Recommendation The PCB layout is a very important converter design step to make sure the designed converter works well. For ISL78233, ISL78234 and 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. Refer to TB389 for via placement on the copper area of the PCB underneath the thermal pad for optimal thermal performance. For more information on the specification of the internal compensation network and designing for stability, refer to the ISL78235, ISL78233, ISL78234 datasheets for more details. Submit Document Feedback 4 UG06.0 December 9, 2015 User Guide UG062 ISL7823xEVAL2Z Schematics NOTES: 3. ISL78235EVAL2Z schematics are shown. 4. ISL78233EVAL2Z and ISL78234EVAL2Z schematics are equivalent. FIGURE 4. ISL7823xEVAL2Z SCHEMATICS Submit Document Feedback 5 UG06.0 December 9, 2015 Submit Document Feedback Bill Of Materials MANUFACTURER PART 6 REFERENCE DESIGNATOR ISL78233AARZ or ISL78234AARZ or ISL78235AARZ 1 U1 0603ZC104K4T2A 1 C5 131-4353-00 2 J1, J2 2N7002 1 Q1 AUTO-CAP-SM0603-OPEN 1 C9 DNP AUTO-RES-SM0603-DNP 3 R10, R12, R14 DNP C0603C332K4RACAUTO 1 C6 3300pF 10% CGA3E2COG1H221J080AA 1 C7 220pF 5% CRCW06030000Z0EA 1 R6 0 1% CRCW0603100KFKEA 1 R3 100k CRCW0603200KFKEA 4 R2, R8, R11, R13 CRCW060320R0FKEA 1 CRCW06032K00FKEA VALUE TOL. VOLTAGE POWER PACKAGE TYPE WFQFN16 DESCRIPTION MANUFACTURER 3A, 4A, 5A Compact Synchronous Buck Regulator INTERSIL Ceramic Chip Cap (Automotive AEC-Q200) AVX CONN Scope Probe Test Point PCB Mount TEKTRONIX SOT23 N-Channel EMF Effect Transistor FAIRCHILD 603 Ceramic Chip Cap (Automotive AEC-Q200) Generic 603 Film Chip Resistor (Automotive AEC-Q200) Generic 16V 603 Ceramic Chip Cap (Automotive AEC-Q200) Kemet 50V 603 Ceramic Chip Cap (Automotive AEC-Q200) TDK 1/10W 603 Film Chip Resistor (Automotive AEC-Q200) VISHAY 1% 1/10W 603 Film Chip Resistor (Automotive AEC-Q200) VISHAY 200k 1% 1/10W 603 Film Chip Resistor (Automotive AEC-Q200) VISHAY R7 20 1% 1/10W 603 Film Chip Resistor (Automotive AEC-Q200) VISHAY 1 R9 2k 1% 1/10W 603 Film Chip Resistor (Automotive AEC-Q200) VISHAY CRCW060369K8FKEA 1 R5 69.8k 1% 1/10W 603 Film Chip Resistor (Automotive AEC-Q200) VISHAY CRCW060395K3FKEA 1 R4 95.3k 1% 1/10W 603 Film Chip Resistor (Automotive AEC-Q200) VISHAY GCM1885C1H220JA16D 1 C8 22pF 5% 50V 603 Ceramic Chip Cap (Automotive AEC-Q200) Murata GCM31CR71A226KE 2 C3, C4 22µF 10% 10V 1206 Ceramic Chip Cap (Automotive AEC-Q200) Murata GCM32ER71A226KE12L 2 C1, C2 22µF 10% 10V 1210 Ceramic Chip Cap (Automotive AEC-Q200) Murata GT11MSCKE 2 SW1, SW2 SMT SPDT On-None-On SMT Ultraminature Toggle Switch C&K H1082-OPEN 2 C14, C15 DNP 1210 Ceramic Chip Cap GENERIC H2511-00100-1/16W1 1 R1 10 1% 1/16W 603 Thick Film Chip Resistor GENERIC IHLP-2020CZ-ER-R68-M-01 1 L1 0.68µH 20% 10.2A SMD-S Low Profile High Current Inductor VISHAY JMK325B7476KMHTR 4 C10-C13 47µF 10% 1210 Ceramic Chip Cap (Automotive AEC-Q200) Taiyo Yuden LTST-C170CKT 1 D1 SMD AlGaAs on GaAs Red LED LITEON 0.10µF 10% 10V 6.3V 603 User Guide UG062 QTY UG06.0 December 9, 2015 User Guide UG062 ISL7823xEVAL2Z Board Layout FIGURE 5. TOP LAYER SILKSCREEN FIGURE 6. BOTTOM LAYER SILKSCREEN NOTES: 5. ISL78233 board silkscreen name is ISL78233EVAL2Z 6. ISL78234 board silkscreen name is ISL78234EVAL2Z Submit Document Feedback 7 UG06.0 December 9, 2015 User Guide UG062 ISL7823xEVAL2Z Board Layout (Continued) FIGURE 7. LAYER 1 PCB FIGURE 8. LAYER 2 PCB FIGURE 9. LAYER 3 PCB FIGURE 10. LAYER 4 PCB Submit Document Feedback 8 UG06.0 December 9, 2015 User Guide UG062 Typical Performance Curves 100 2.5 3.3VOUT 90 2.5VOUT POWER DISSIPATION (W) EFFICIENCY (%) 80 1.8VOUT 1.5VOUT 70 1.2VOUT 60 3.3VOUT 2.0 2.5VOUT 1.8VOUT 1.5 1.5VOUT 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 POWER DISSIPATION (W) 80 70 1.5VOUT 1.2VOUT 1.0VOUT 60 50 40 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 5.0 1.5 2.5VOUT 1.0 1.0VOUT 5.0 1.2VOUT 0.5 0 4.5 FIGURE 13. EFFICIENCY vs LOAD (3VIN; SYNC = VDD) COUT = 4x47µF RCOMP = 332kΩ CCOMP = 150pF ILOAD 2A/DIV 4.5 1.5VOUT 0 0.5 OUTPUT LOAD (A) VOUT 50mV/DIV AC COUPLED 4.0 1.8VOUT 2.0 1.8VOUT 3.5 2.5 2.5VOUT 90 EFFICIENCY (%) 2.0 FIGURE 12. POWER DISSIPATION vs LOAD (5VIN; SYNC = VDD) FIGURE 11. EFFICIENCY vs LOAD (5VIN; SYNC = VDD) 100 1.5 OUTPUT LOAD (A) OUTPUT LOAD (A) 400µs/DIV FIGURE 15. LOAD TRANSIENT 0A TO 5A; 0.5A/µs (SYNC = GND) 1.0 1.5 2.0 2.5 3.0 OUTPUT LOAD (A) 3.5 4.0 4.5 5.0 FIGURE 14. POWER DISSIPATION vs LOAD (3VIN; SYNC = VDD) VOUT 50mV/DIV AC COUPLED COUT = 4x47µF RCOMP = 332kΩ CCOMP = 150pF ILOAD 2A/DIV 400µs/DIV FIGURE 16. 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 9 UG06.0 December 9, 2015