Single Output Mobile-Friendly PWM Controller ® Application Note The ISL6224 single PWM controller delivers high efficiency and tight regulation from a voltage regulating synchronous buck DC/DC converter. The ISL6224 PWM power supply controller was designed especially for chip set and memory bank applications in high performance notebook PCs, subnotebook PCs, and PDAs. The MOSFET drivers, output voltage monitoring, output current monitoring, and protection circuitry are included in a single 16 lead SSOP package. The ISL6224EVAL1 evaluation board reference design provides an efficient, cost effective and compact power solution. High efficiency is maintained over a wide load range through automatic selection of fixed frequency PWM synchronous rectification mode, also known as continuous conduction mode (CCM), or hysteretic diode emulation mode (HYS). The IC enters CCM in response to heavy loads and (HYS) mode in response to light loads, boosting efficiency. Forced CCM (FCCM) disables hysteretic mode. Efficiency is further enhanced by using the converters lower MOSFET RDS(ON) as a current sense element. Voltage feed-forward duty-cycle ramp modulation, average current mode control, and internal feedback compensation provide fast response to input voltage transients and output load transients. The ISL6224 features output voltage adjustable in the range from 0.9V to 5.5V and a selectable switching frequency of either 300kHz or 600kHz. When operated from battery voltages ranging from 4V to 24V, a switching frequency of 300kHz is recommended. When operating from 5V, a switching frequency of 300kHz may be used or, to reduce the size of the output filter, 600kHz may be used. Quick Start Evaluation Circuit Setup The ISL6224EVAL1 board is designed for easy evaluation using standard laboratory equipment. Refer to Table 2 for the range of input and output voltages and currents. Switch Settings The ISL6224EVAL1 board is shipped with the four position dip switch S1 set for 2.5V output. S1 controls the ENABLE function “EN” and selects the output voltage. Figure 1 illustrates S1 position names and Table 1 describes the function of each switch position. February 2003 AN9983.1 EN Vo #3 (1.25V) Vo #2 (2.5V) Vo #1 (3.3V) FIGURE 1. SWITCH S1 BIT POSITION NAMES TABLE 1. SWITCH S1 FUNCTIONAL DESCRIPTION POSITION STATE FUNCTION UP ENABLES CONVERTER DOWN DISABLES CONVERTER UP 3.3V OUTPUT SELECTED EN Vo #1 DOWN UP 3.3V OUTPUT DESELECTED 2.5V OUTPUT SELECTED Vo #2 DOWN UP 2.5V OUTPUT DESELECTED 1.25V OUTPUT SELECTED Vo #3 DOWN 1.25V OUTPUT DESELECTED NOTE: If Vo #1, Vo #2 and Vo #3 switches are all down, then the output voltage of the converter will be equal to Vref, which is 0.9 V. Only one voltage selection switch is UP at any time. Jumper Settings Jumper JP1 enables or inhibits hysteretic mode. If the shunt jumper is installed across the two pins located on the left, the IC will be allowed to operate in hysteretic mode, should the need arise. If the shunt jumper is installed across the two pins located on the right, the IC will be forced into continuous conduction mode. The evaluation board comes set for hysteretic mode. Jumper JP2 selects the optimum duty cycle ramp gain and switching frequency. Jumper JP2 has three different positions each of which will have one side of the shunt jumper connected to the pin labeled “U3p1”. Refer to Table 2 for the recommended jumper position. The ISL6224EVAL1 board is shipped with JP2 in the “5V 300kHz” position. JP3 is used to measure the current (ICC) drawn by the VCC pin from the 5V power supply. When making efficiency measurements that include VCC, be sure to measure ICC from JP3. A substantial current is drawn by the red and green LED and should not be included in determining the efficiency of the converter. 1 1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright © Intersil Americas Inc. 2003. All Rights Reserved All other trademarks mentioned are the property of their respective owners. Application Note 9983 TABLE 2. EVALUATION BOARD INPUT/OUTPUT REQUIREMENTS OPERATION MODE INPUT VOLTAGE (V) OUTPUT VOLTAGE (V) MIN OUTPUT CURRENT (A) TYPICAL OUTPUT CURRENT (A) MAX OUTPUT CURRENT (A) VIN 5-24V 300kHz 4 to 24 0.9 to 5.5 0 2 3 VIN 5V 300kHz 5 0.9 to 3.3 0 1 2 VIN 5V 600kHz 5 0.9 to 3.3 0 1 2 Connect the Input Power Supplies • Connect a 1AMP, 0 to +5VDC Power Supply as follows: - Before connecting to the evaluation board, turn on the power supply and adjust the output to +5V then turn off. - Power Supply positive terminal to the VCC post (J7). - Power Supply negative terminal to the GND post (J6). Vout (2V/div) SOFT Pin (1V/div) • Connect a 5AMP, 0 to +24VDC Power Supply as follows: - Before connecting to the evaluation board, turn on the power supply and adjust the output to +5V then turn off. - Power Supply positive terminal to the VIN post (J2). - Power Supply negative terminal to the GND post (J8). PGOOD Pin (5V/div) ENABLE Pin (5V/div) Connect the Output Load • Connect a 5AMP Electronic Load as follows: - Electronic Load positive terminal to the VOUT post (J4). - Electronic Load negative terminal to the GND post (J3). FIGURE 2. SOFT-START ON 3.3V OUTPUT (2ms/Div) Output Ripple Operation Examine Start-up Waveforms NOTE: VIN MUST BE TURNED ON BEFORE VCC IN ALL CASES Turn on the VIN power supply and the VCC power supply. Move the EN bit of S1 to the UP position. The start up sequence may be observed by using an oscilloscope. In Figure 2 the voltage on the SOFT pin of the IC, the output voltage at TP5, the power good signal at TP3, and the voltage of the enable signal at post J12 show typical waveforms. The voltage on the SOFT pin of the IC is produced by a 5µA current source charging a user supplied capacitor. The ramp time of the soft start voltage is controlled by the value of the charging capacitor. The output voltage follows the soft-start voltage. The green LED will illuminate when the output is within 10% of the nominal value. If the EN bit of switch S1 is moved to the DOWN position the LED will be red, indicating the converter is off. When a fault condition occurs the LED will be RED even though the EN bit of S1 is in the UP position. The fault latch may be cleared by turning the VCC power supply off, then on again. 2 The ISL6224EVAL1 evaluation board is populated with one 330µF/6.3V SANYO POSCAP output capacitor which has 40mΩ ESR at 100kHz. Figures 3 to 8 show the output voltage ripple and phase node voltage when the converter is operating in various modes and various combinations of VIN and Fs. Please see the ISL6224 data sheet for detailed instructions on how to select the output capacitor. Transient Response The transient response of the converter is the time interval ∆T required to slew the inductor current from an initial value to a final value such that the output voltage stays constrained within a specified range. The inductor ripple current affects the transient response performance. Figures 9 to 14 show the transient performance of the evaluation board. NOTE: In following figures; CH1: Vout = 2.5 V, AC coupled. Application Note 9983 Evaluation Board Performance Graphs Vin=15 V, Fs=300kHZ Vin=15 V, Fs= 300kHz Vripple = 34mV Vripple = 50mV Phase Node Phase Node FIGURE 3. HYSTERETIC MODE AT ZERO LOAD CURRENT FIGURE 4. PWM MODE AT FULL LOAD CURRENT Vin=5 V, Fs=300kHz Vin=5 V, Fs=300kHz Vripple = 21mV Vripple = 28mV Phase Node FIGURE 5. HYSTERETIC MODE AT ZERO LOAD CURRENT 3 Phase Node FIGURE 6. PWM MODE AT FULL LOAD CURRENT Application Note 9983 Evaluation Board Performance Graphs (Continued) Vin=5 V, Fs=600kHz Vin=5 V, Fs=600kHz Vripple = 16mV Vripple = 19mV Phase Node Phase Node FIGURE 7. HYSTERETIC MODE AT ZERO LOAD CURRENT ∆V = 98mV Vin=15 V, Fs=300kHz FIGURE 8. PWM MODE AT FULL LOAD CURRENT Vin=15 V, Fs=300kHz ∆V = 104mV Vout=2.5V, AC Coupled, Load Current Load Current FIGURE 9. HYSTERETIC MODE TRANSIENT RESPONSE FIGURE 10. PWM MODE TRANSIENT RESPONSE 4 5 Application Note 9983 Evaluation Board Performance Graphs (Continued) ∆V = 84mV Vin=5 V, Fs=300kHz Vin=5 V, Fs=300kHz Load Current Load Current FIGURE 11. HYSTERETIC MODE TRANSIENT RESPONSE ∆V = 84mV Vin=5 V, Fs=600kHz Load Current FIGURE 13. HYSTERETIC MODE TRANSIENT RESPONSE 5 ∆V = 84mV FIGURE 12. PWM MODE TRANSIENT RESPONSE Vin=5 V, Fs=600kHz ∆V = 78mV Load Current FIGURE 14. PWM MODE TRANSIENT RESPONSE Application Note 9983 Over Current Protection Efficiency The ISL6224 monitors the converter output current by measuring the voltage developed across the RDS(ON) of the lower MOSFET and feeding it into the Isense pin through a scaling resistor. The current detection is used by the average current mode control loop and by the over current detection circuit. The scaling resistor is chosen such that it will flow 75µA of current when the converter is delivering full load current. It is important to understand that the current detected by the Isense pin is the sum of the DC AMPS at the output of the converter and the positive peak of the inductor ripple current. On page 9 of the ISL6224 data sheet is the formula to calculate the expected peak to peak inductor ripple current for a particular combination of VIN, VOUT, switching frequency, and output choke inductance. The value of “Iomax” is the sum of one half the calculated peak to peak inductor ripple current plus the value of the output full load current of the converter. The value of “Iomax” is now inserted into the Risen calculation on page 6 of the ISL6224 data sheet. The over current set point Ioc is typically set at 180% of “Iomax”. The value of Ioc and the value of Risen are inserted into the Rocset calculation on page 6 of the ISL6224 data sheet. The ISL6224EVAL1 evaluation board has been adjusted for 3.0 full load amps and approximately 6.3A peak inductor current for over current protection. Figure 15 shows a typical shutdown waveform when the load is over the limit. The ISL6224 evaluation was designed to use the lower MOSFETs RDS(ON) to increase efficiency. Figures 16 through 18 show the efficiency at various output currents and input voltages. 7.2 V 10.8 V 14.4 V 24 V Efficiency 98.00% 93.00% 88.00% 83.00% 78.00% 0 0.5 1 1.5 2 2.5 3 3.5 Output Current FIGURE 16. EFFICIENCY WHEN VOUT = 5V 5V 7.2 V 10.8 V 14.4 V 24 V 98.00% 96.00% 94.00% Efficiency Vin=15 V, Fs=300kHz Vin=5.6 V 92.00% 90.00% 88.00% 86.00% 84.00% 82.00% 80.00% 0 1 1.5 2 2.5 FIGURE 17. EFFICIENCY WHEN VOUT = 3.3V Phase Node Efficiency T0 5.0 V 7.2 V 0.5 1 10.8 V 14.4 V 24 V 100% 98% 96% 94% 92% 90% 88% 86% 84% 82% 80% 78% 0 1.5 2 2.5 Output Current FIGURE 18. EFFICIENCY WHEN VOUT = 2.5V 6 3 Output Current Inductor Current FIGURE 15. OUTPUT OVERLOAD SHUT DOWN 0.5 3 Application Note 9983 Shutdown by Enable Output Voltage Setpoint Calculation When the EN bit of S1 is moved to the DOWN position the PWM stops and the inductor current decays to zero amps and the output capacitors discharge. A typical shutdown waveform is shown in Figure 19. The output voltage of the converter is set by connecting a two resistor voltage divider across the output. The feedback voltage divider output is connected to the VSEN pin of the IC. The voltage at the VSEN pin is 0.9V when the converter output is in regulation. The voltage at the VSEN pin is internally compared to a 0.9V reference voltage and passed on to the next stage of the PWM generation circuits. On the ISL6224EVAL1 evaluation board the two resistor voltage divider feedback network consists of R10 (top resistor) and (R15 or R16 or R17) bottom resistors. Each bottom resistor chooses a different output voltage. The resistors are selected by switch S1. The equation for the setpoint of the output voltage is shown below. Vin=15 V, Fs=300kHz , Vout R10 × Vref Ry = -----------------------------Vo – Vref Inductor Current Where Ry is bottom resistor, Vo is the required output voltage and Vref is the reference voltage. Enable Pin Some of the most popular output voltage setpoints are calculated in Table 3. TABLE 3. OUTPUT VOLTAGE SETPOINT FIGURE 19. SHUT DOWN BY ENABLE PIN 7 Vo 1.25V 1.5V 2.5V 3.3V 5.0V R10 11.8K 11.8K 11.8K 11.8K 11.8K Ry 30.1K 17.8K 6.65K 4.42K 2.59K 5 4 3 2 1 ICC MEASURE VCC J7 C4 R19 100K 1% 0805 2 1.0uF 1812 50V D3 4 1 R4 150K 1% 0805 BAT54WT1 SOT323 C10 C13 L1 D1 C2 C3 C6 C7 C8 C23 C24 L3 D4 1.0uF 1812 50V 10uF 1812 25V 0 OHM 2010 NI SMB NI 1812 NI 1812 NI 1812 NI 1812 NI 1812 NI 1812 NI 1812 NI 1812 NI SMB 8 TP2 ENABLE J12 GND J1 C25 R8 71.5K 1% 0805 1.0uF 10V 1206 C21 NI 0603 C12 16 Pgood Boot 15 3 EN Ugate 14 4 OCset Phase 13 Isense 12 5 Vout 6 Vsen Vcc 11 7 SOFT Lgate 10 8 GND Pgnd 9 ISL6224 15nF 10V 1206 GND PGND 0.0 0805 0.15uF 1206 16V L- U2 1 8 2 7 3 6 4 5 TP4 R9 5.1 5% 1206 C22 1.0uF 10V 1206 U1 4 R6 1.30K 1% 0805 J8 56u OSCON 25V 5 6 7 8 2 FCCM GND SO8 PHASE C C5 1800pF 50V 0805 FDS6912A PGND L2 6.2A 6.4uH U4 4 SO8 PGND VOUT J4 TP5 B B R10 11.8K 1% 0805 C18 1.0uF 10V 1206 + C16 + C17 NI NI D4 D4 GND C15 330u 6.3V D4 6TPB330M + J3 8 7 6 5 C19 0.1 uF 50V 0805 VOUT R12 680 5% 0805 1 2 CR1 RED A S1 KAL2104ER LXA3025IGC 3 4 3 PGOOD TP3 R13 680 5% 0805 1 2 3 4 R11 100K 1% 0805 GREEN Q1 BSS123LT1 1 2 ENABLE Vo#3 1.25V R14 100K 1% 0805 R16 30.1K 1% 0805 Vo#1 3.30V R17 4.42K 1% 0805 SOT23 A Building 2A,Suite 105 4020 Stirrup Creek Drive Durham, NC 27703 Phone: (919) 405 3650 Fax: (919) 405 3651 Title ISL6224 EVALUATION BOARD Size Date: 5 4 PGND GND Vo#2 2.50V R15 6.65K 1% 0805 3 FIGURE 20. ISL6224EVAL1 EVALUATION BOARD SCHEMATIC 2 Document Number Rev ISL6224EVAL1 B Sheet 1 1 of 1 Application Note 9983 C VIN C11 D C1 1 2 3 U3 1 R5 + 5 6 7 8 MODE SELECT J2 JP2 1 2 3 1 3 ETQP6F6R4HFA 68uF D Case 16V Tant VIN 300KHZ 4V-24V VIN 1 C20 FCCM L+ 3 + 2 300KHZ 5V VIN D CCM/HYS JP1 TP1 600KHZ 5V VIN GND J6 2 JP3 3 FCCM 1 Application Note 9983 TABLE 4. BILL OF MATERIALS REV B FOR ASSEMBLY ISL6224EVAL1 ITEM QTY UNITS REFERENCE DESIGNATOR 1 1 ea 2 1 3 DESCRIPTION MFG PART NUMBER CR1 LED, SMD, 4P, POLARIZED, RED/GRN LUMEX SSL-LXA3025IGC-TR ea C1 CAP, OSCON, RADIAL, F-SIZE, 56µF, 25V, 20% SANYO 25SP56M 1 ea C13 CAP, X5R, 1812, 10µF, 25V, 20% TAIYO YUDEN CE-TMK432BJ106MM 4 2 ea C4, C10 CAP, X7R, 1812, 1.0µF, 50V, 10% KEMET C1812C105K5RAC 5 1 ea C5 CAP, X7R, 0805, 1800pF, 50V, 10% KEMET C0805C182K5RAC 6 1 ea C11 CAP, X7R, 1206, 0.15µF, 16V, 10% KEMET C1206C154K4RAC 7 1 ea C12 CAP, X7R, 1206, 0.015µF, 10V, 10% KEMET C1206C153K8RAC 8 3 ea C18, C22, C25 CAP, X7R, 1206, 1.0µF, 10V, 10% KEMET C1206C105K8RAC 9 1 ea C19 CAP, X7R, 0805, 0.1µF, 50V, 10% KEMET C0805C104K5RAC 10 1 ea C20 CAP, TANT, D-CASE, 68µF, 16V, 20% KEMET T494D686M016AS 11 1 ea C15 CAP, POSCAP, D4-CASE, 330µF, 6.3V, 20% SANYO 6TPB330M 12 1 ea D3 DIODE, SCHOTTKY BARRIER, SOT323, 30V, 200mA ON SEMICONDUCTOR BAT54WT1 13 1 ea Q1 TRANSISTOR, MOSFET, NCHANNEL, SOT23, 100V, 170mA ON SEMICONDUCTOR BSS123LT1 14 1 ea U3 IC, PWM CONTROLLER, 24V, 16PIN, SSOP INTERSIL ISL6224CA 15 1 ea U2 TRANSISTOR, MOSFET, NCHANNEL, DUAL, LOGIC LEVEL, 30V, 6.0A FAIRCHILD FDS6912A 16 1 ea L1 RESISTOR, Cu ALUMINA, 2010, 3.0 mΩ MAX, 30.0A IRC LRC-LRZ-2010-R000 17 1 ea L2 INDUCTOR, PWR, SMD, 5.7mm, 6.4uH, 6.2A, PANASONIC ETQP6F6R4H 18 1 ea R5 RESISTOR, TF, 0805, 0Ω, 125mW, 5% PANASONIC ERJ6GEY0R00V 19 1 ea R4 RESISTOR, TF, 0805, 150K, 1/10W, 1.0% PANASONIC ERJ6ENF1503V 20 1 ea R9 RESISTOR, TF, 1206, 5.1Ω, 250mW, 5% PANASONIC ERJ8GEYJ5R1V 21 1 ea R10 RESISTOR, TF, 0805, 11.8K, 100mW, 1.0% PANASONIC ERJ6ENF1182V 22 3 ea R11, R14, R19 RESISTOR, TF, 0805, 100K, 100mW, 1.0% PANASONIC ERJ6ENF1003V 23 2 ea R12, R13 RESISTOR, TF, 0805, 680Ω, 125mW, 5% PANASONIC ERJ6GEYJ681V 24 1 ea R15 RESISTOR, TF, 0805, 6.65K, 100mW, 1.0% PANASONIC ERJ6ENF6651V 25 1 ea R16 RESISTOR, TF, 0805, 30.1K, 100mW, 1.0% PANASONIC ERJ6ENF3012V 26 1 ea R17 RESISTOR, TF, 0805, 4.42K, 100mW, 1.0% PANASONIC ERJ6ENF4421V 9 Application Note 9983 TABLE 4. BILL OF MATERIALS REV B FOR ASSEMBLY ISL6224EVAL1 (Continued) ITEM QTY UNITS REFERENCE DESIGNATOR 27 1 ea 28 1 29 DESCRIPTION MFG PART NUMBER R6 RESISTOR, TF, 0805, 1.30K, 100mW, 1.0% PANASONIC ERJ6ENF1301V ea R8 RESISTOR, TF, 0805, 71.50K, 100mW, 1.0% PANASONIC ERJ6ENF7152V 3 ea TP1, TP2, TP3 TEST POINT, THRU HOLE, LOOP, WHITE KEYSTONE 5002 30 2 ea TP4, TP5 TEST POINT, THRU HOLE, SCOPE PROBE, COMPACT TEKTRONICS 131-5031-00 31 8 ea J1, J2, J3, J4, J6, J7, J8, J12 TERMINAL POST, THRU HOLE KEYSTONE 1502-2 32 2 ea JP1, JP2 HEADER, 1x3, THRU HOLE, 2.54mm PITCH BERG/FCI 68000-236-1X3 33 1 ea JP3 HEADER, 1x2, THRU HOLE, 2.54mm PITCH BERG/FCI 68000-236-1X2 34 3 ea JP1, JP2, JP3 SHUNT, TWO PIN, 2.54mm PITCH SULLINS SPC02SYAN 35 1 ea S1 SWITCH, FOUR POSITION, SM E-SWITCH KAL2104R C2, C3, C6, C7, C8, C16, C17, C21, C23, C24, D1, D4, L3, U1, U4 NO INSTALL 36 10 Application Note 9983 Silk Screens FIGURE 21. TOP LAYER FIGURE 22. SILK SCREEN TOP FIGURE 23. BOTTOM LAYER FIGURE 24. SILK SCREEN BOTTOM 11 Application Note 9983 Silk Screens (Continued) FIGURE 25. GROUND INTERNAL FIGURE 26. POWER INTERNAL All Intersil U.S. products are manufactured, assembled and tested utilizing ISO9000 quality systems. Intersil Corporation’s quality certifications can be viewed at www.intersil.com/design/quality Intersil products are sold by description only. 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 data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries. For information regarding Intersil Corporation and its products, see www.intersil.com 12