Application Note 1636 Author: Paul Orfanu ISL85033-12VEVAL3Z Wide VIN Negative VOUT Buck-Boost Regulator With Up to 5A Output Current Hardware Description Evaluating the Other Output Voltages The ISL85033 is a wide input range, dual standard buck converter that can be configured to provide a negative output voltage. The ISL85033-12VEVAL3Z evaluation board is used in this application note to demonstrate the negative configuration. In this configuration, VIN can range from 4.5V to (28V - VOUT). The ISL85033-12VEVAL3Z kit output is preset to -12V; however, output voltages can be adjusted from -3.3V to -15V. The output voltage programming resistor, R3, depends on the desired output voltage of the regulator. The value for the feedback resistor is typically between 0Ω and 142kΩ as shown in Equation 1. The ISL85033 is offered in a 4mmx4mm 28 Ld TQFN package with 1mm maximum height. The complete converter occupies 6.25cm2 area. Key Features • Wide Input Voltage Range from 4.5V to (28V - VOUT) • Adjustable and Synchronizable Negative Output Voltage with Continuous Output Current up to 5A, depending on VOUT and VIN VOUT R3 = R2 ⎛ -------------- – 1⎞ ⎝ VFB ⎠ Table 1 summarizes the external component selection for VOUT = -5V, VOUT = -12V, and VOUT = -15V. TABLE 1. COMPONENT SELECTION FOR VOUT VOUT -5V • Current Mode Control • Adjustable Switching Frequency from 300kHz to 2MHz • Power-Good Detection (referenced to VOUT) • Boot Undervoltage Detection • Default Out-of-phase Channels Reduce Voltage Ripple and Component Size. User-selectable Phase Operation. Recommended Equipment The following materials are recommended to perform testing: • 0V to 30V power supply with at least 7A source current capability or a 5V battery EXTERNAL COMPONENTS R3 = 43.2k; R5 = 20k; C4 = 2.7nF C20 = 22µF (1210 ceramic) C17 = 22µF (1210 ceramic) C19 = 68µF (15mΩ polymer EEFUD0K680R) -12V R3 = 112k; R5 = 120k; C4 = 4.7nF C14, C17 = 22µF (2210 ceramic) C12, C19 = 68µF (70mΩ TaNbO2 TPSD686M020R0070) C20 = DNP -15V R3 = 142k; R5 = 120k; C4 = 4.7nF C14, C17 = 22µF (2210 ceramic) C12, C19 = 68µF (70mΩ TaNbO2 TPSD686M020R0070) C20 = DNP • Externally Adjustable Soft-start Time • Overcurrent and Hiccup Mode Short Circuit Protection, Thermal Overload Protection, UVLO (EQ. 1) The curves in Figure 1 indicate the maximum output current the converter can deliver as a function of the input voltage and the selected output voltage configuration. Figures 2, 3 and 4 show the efficiency for different VIN, VOUT and load combinations. • Electronic loads capable of sinking current up to 7A • Digital multimeters (DMMs) • 100MHz quad-trace oscilloscope • 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 VIN1, the plus terminal to VIN1, and the negative return to GND1. 3. Verify that the position is ON for S1. 4. Turn on the power supply. 5. Verify the output voltage is -12V for VOUT. July 27, 2011 AN1636.1 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. Copyright Intersil Americas Inc. 2011. All Rights Reserved. 1-888-INTERSIL or 1-888-468-3774 | 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 1636 6 95 EFFICIENCY (%) VOUT = -5V 4 IOUT (A) VIN = 12V 90 5 3 VOUT = -12V 2 VOUT = -15V 1 85 VIN = 5V 80 75 70 65 60 0 5 7 9 11 13 15 17 19 21 23 0 25 0.5 1.0 FIGURE 1. ISL85033-12VEVAL3Z BUCK BOOST: RECOMMENDED MAXIMUM IOUT (VIN) 95 VIN = 6V VIN = 15V VIN = 12V 2.5 VIN = 12V 90 90 85 EFFICIENCY (%) EFFICIENCY (%) 2.0 FIGURE 2. ISL85033-12VEVAL3Z EFFICIENCY: V OUT = -15V 95 VIN = 5V 80 75 70 85 VIN = 5V 80 VIN = 15V 75 70 65 65 60 0 1.5 IOUT (A) VIN (V) 60 0.5 1.0 1.5 2.0 0 2.5 0.5 IOUT (A) FIGURE 3. ISL85033-12VEVAL3Z EFFICIENCY: VOUT = -12V If the output voltage desired is -0.8V, then R3 is shorted. The value for R2 is typically between 1k and 10k. Note that if VOUT < |2.5V| (i.e., -0.8V), the switching frequency and compensation must be changed to accommodate the 300kHz operation, due to minimum on-time limitation. Please refer to the ISL85033 data sheet for further information. 1.5 2.0 2.5 IOUT (A) FIGURE 4. ISL85033-12VEVAL3Z EFFICIENCY: VOUT = -5V Disabling/Enabling Function The ISL85033-12VEVAL3Z evaluation board contains an S1 switch that enables or disables both channels, thus allowing a low quiescent current state. Table 2 details this function. TABLE 2. SWITCH SETTINGS Frequency Control S1 The ISL85033-12VEVAL3Z evaluation board 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 500kHz when FS is tied to VCC (R9 = 0). By removing R9 and connecting R10 to the most negative potential on the board (VOUT), the switching frequency could be changed from 300kHz (R10 = 383k) to 2MHz (R10 = 40.2k). See the ISL85033 data sheet for information about calculating the value of R10. Do not leave this pin floating. ON Enable VOUT OFF Disable VOUT 2 1.0 ON/OFF CONTROL NOTE: If driven externally, the EN signal (the same as all input logic signals) is referenced to VOUT (the most negative potential on the board) and not to GND. Therefore, the source cannot be GND referenced, and input level shifting is required. AN1636.1 July 27, 2011 ISL85033-12VEVAL3Z Schematic VCC PG1 FS VNEG SI SO PG2 DNP PGOOD2 SYNCIN VNEG PGOOD1 FS R12 NC1 R13 VIN 12 VNEG C6 10UF C7 10UF DNP A PGOOD1 R20 A AA DNP R7 R8 VNEG2 4 JLX2 GNDO2 3 VIN2 1 2 VNEG FB1 A C19 68UF C20 TBD R23 FB2 0 12 1 VNEG -12V (ADJUSTABLE) A COMP1 R24 COMP2 0 SS1 SS2 R17 DNP SYNCIN R10 R18 AN1636.1 July 27, 2011 DNP VNEG R25 DNP FS ON S1 1 OPEN OFF VNEG 3 COMP2 22 24 23 SYNCOUT PGOOD2 10UF 0 SS1 VNEG 0.01UF C8 R9 OPEN 3 EN2 OPEN VNEG C17 EN PGOOD2 OPEN 100K C9 22UF B340B VCC R4 5600PF BOOT2 10UH D2 VNEG GND1 R19 SS2 R16 VIN C18 VCC C11 2 VIN C2 A SYNCIN 25 26 NC SGND 27 FS B340B A FB2 C10 L2 21 22UF 21 68UF D1 4 R15 VNEG 10UH C14 SS2 15 VNEG A OPEN R11 16 OPEN OPEN 0 17 1 2 C16 VNEG OPEN OPEN 14 12 VIN2 EP 29 L1 C12 100UF PHASE2 4.7UF TBD A PHASE2 PHASE1 EN VCC EN C1 PHASE1 C15 R14 18 BOOT2 ISL85033IRTZ 13 12 A 7 VNEG GNDO1 BOOT1 6 VNEG 1 2 4 SS2 OPEN 19 FB2 PGND2 EN2 5 C5 21 COMP2 U1 PGND1 12 BOOT1 3 JLX1 SS1 4 0.01UF -12V FB1 VCC 3 EN1 VNEG 22 SS1 10 VNEG 5600PF C3 VNEG 120K COMP1 JVO2 0 VNEG SS2 Application Note 1636 VNEG1 8.06K 1 11 4700PF FB1 SS1 R2 R5 VIN1 C4 VIN1 C13 9 3 VNEG 113K COMP1 22PF 8 R3 PGOOD1 28 DNP A Application Note 1636 Bill of Materials PART NUMBER REFERENCE DESIGNATOR QUANTITY VALUE TOLERANCE VOLTAGE POWER PACKAGE TYPE JEDEC TYPE MANUFACTURER DESCRIPTION CONN TEK1314353-00 TEKTRONIX Scope Probe Test Point PCB Mount SMD CAP_TANT AVX TQC Series Hi-Volt Low ESR Capacitor SMD2 DO_SMA DIODES 3A Low VF SCHOTTKY BARRIER RECTIFIER 131-4353-00 JLX1, JLX2, JVO2 3 TPSD686K020R00 070-T C12, C19 2 B340B D1, D2 2 C5750X7R1E226M C14, C17 2 22µF 20% 25V 2220 CAP_2220 TDK Ceramic Cap EEE-FK1V101P-T C2 1 100µF 20% 35V SMD CAPAE_315X 402 PANASONIC AL LYTIC FK SERIES CAP (RoHS COMP.) GMK325BJ106KN C6, C8 2 10µF 10% 35V 1210 CAP_1210 TAIYO YUDEN Ceramic Chip Cap GT13MCBE S1 1 SW SW_GT13MC BE C&K SPDT On-Off-On Ultraminiature Toggle Switch H1044-0022050V5 C13 1 22PF 5% 50V 402 CAP_0402 GENERIC Multilayer Cap H1044-0047250V10 C4 1 4700PF 10% 50V 402 CAP_0402 GENERIC Multilayer Cap 68µF 20% 20V H1044-OPEN C10, C15, C16 3 OPEN OPEN OPEN 402 CAP_0402 GENERIC Multilayer Cap H1045-0010350V10 C5, C9 2 0.01µF 10% 50V 603 CAP_0603 GENERIC Multilayer Cap H1045-0056250V10 C3, C11 2 5600PF 10% 50V 603 CAP_0603 GENERIC Multilayer Cap H1046-0047510V20 C7 1 4.7µF 20% 10V 805 CAP_0805 GENERIC Multilayer Cap H1065-0010625V10-T C18 1 10µF 10% 25V SMD CAP_1206 VENKEL Multilayer Cap H1082-TBD-TBD C1, C20 2 TBD TBD TBD 1210 CAP_1210 GENERIC Ceramic Chip Cap H2505-01003-1/ 16WR1 R4 1 100k 0.10% 1/16W 603 RES_0603 GENERIC Metal Film Chip Resistor H2505-DNP-DNP-1 R10, R17 2 DNP 1% DNP 603 RES_0603 GENERIC Metal Film Chip Resistor (Do Not Populate) H2505-DNP-DNPR1 R12, R13, R19, R20, R25 5 DNP 0.10% DNP 603 RES_0603 GENERIC Metal Film Chip Resistor (Do Not Populate) H2510-011331/16W1 R3 1 113k 1% 1/16W 402 RES_0402 GENERIC Thick Film Chip Resistor H2510-012031/16W1 R5 1 120k 1% 1/16W 402 RES_0402 GENERIC Thick Film Chip Resistor H2510-080611/16W1 R2 1 8.06k 1% 1/16W 402 RES_0402 GENERIC Thick Film Chip Resistor H2510-ROPENOPEN R7, R8, R11, R14-R16 6 OPEN 1% OPEN 402 RES_0402 GENERIC Thick Film Chip Resistor H2511-00R001/16W R23, R24 2 0 0% 1/16W 603 RES_0603 GENERIC Thick Film Chip Resistor H2511-00R001/16W1 R9, R18 2 0 1% 1/16W 603 RES_0603 GENERIC Thick Film Chip Resistor ISL85033IRTZ U1 1 QFN QFN28_157X 157_157_EP INTERSIL WIDE VIN DUAL STANDARD BUCK REGULATOR (Pb-FREE) PAD_100 EN, FS, SI, SO, PG1, PG2, SS1, SS2, VNEG 9 THOLE PAD-100 GENERIC 0.100 Pad with 0.037 Plated Thru Hole 4 AN1636.1 July 27, 2011 Application Note 1636 Bill of Materials (Continued) PART NUMBER REFERENCE DESIGNATOR QUANTITY PAD_150 VIN, GND1, GNDO1, GNDO2, VNEG1, VNEG2 6 SQ1004 L1, L2 2 VALUE TOLERANCE 10µH VOLTAGE POWER 25% 4.8A PACKAGE TYPE JEDEC TYPE MANUFACTURER DESCRIPTION THOLE PAD-150 GENERIC 0.150 Pad with 0.110 Plated Thru Hole SMD IND_SQ10XX FALCO SMT SHIELDED POWER INDUCTOR ISL85033-12VEVAL3Z Layout FIGURE 5. TOP LAYER COMPONENTS FIGURE 6. TOP LAYER ETCH FIGURE 7. SECOND LAYER ETCH FIGURE 8. THIRD LAYER ETCH 5 AN1636.1 July 27, 2011 Application Note 1636 ISL85033-12VEVAL3Z Layout (Continued) FIGURE 9. BOTTOM LAYER ETCH FIGURE 10. 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 Application Note or Technical Brief is current before proceeding. For information regarding Intersil Corporation and its products, see www.intersil.com 6 AN1636.1 July 27, 2011