EL7512 ® Data Sheet May 23, 2005 High Frequency PWM Step-Up Regulator Features The EL7512 is a high frequency, high efficiency step-up DC:DC regulator operated at fixed frequency PWM mode. With an integrated 1A MOSFET, it can deliver up to 600mA output current at up to 90% efficiency. The adjustable switching frequency is up to 1.2MHz, making it ideal for DSL applications. • 90% efficiency FN7290.1 • Up to 600mA IOUT • 5V < VOUT < 18V • VIN > 2V • Up to 1.2MHz adjustable frequency When shut down, it draws <3µA of current. This feature, along with the minimum starting voltage of 2V, makes it suitable for portable equipment powered by one lithium ion or 3 to 4 NiMH cells. The EL7512 is available in a 10-pin MSOP package, with maximum height of 1.1mm. With proper external components, the whole converter takes less than 0.25in2 PCB space. This device is specified for operation over the full -40°C to +85°C temperature range. • < 3µA shutdown current • Adjustable soft-start • Low battery detection • Internal thermal protection • 1.1mm max height 10-pin MSOP package • Pb-Free available (RoHS compliant) Applications • 3V to 5V, 12V, and 18V converters Pinout • 5V to 12V and 16V converters EL7512 (10-PIN MSOP) TOP VIEW • TFT-LCD • DSL • Portable equipment L1 VIN (2V9V) D1 10µF R3 VOUT (12V up to 47µF 400mA) R4 1kΩ 10µH C1 1 PGND LX 10 2 SGND VDD 9 3 RT FB 8 4 EN SS 7 5 LBI LBO 6 100k • Desktop equipment C5 Ordering Information C4 PACKAGE TAPE & REEL PKG. DWG. # EL7512CY 10-Pin MSOP - MDP0043 EL7512CY-T7 10-Pin MSOP 7” MDP0043 EL7512CY-T13 10-Pin MSOP 13” MDP0043 EL7512CYZ (See Note) 10-Pin MSOP (Pb-free) - MDP0043 EL7512CYZ-T7 (See Note) 10-Pin MSOP (Pb-free) 7” MDP0043 EL7512CYZ-T13 (See Note) 10-Pin MSOP (Pb-free) 13” MDP0043 0.1µF C3 20nF R2 80.6k R1 10kΩ PART NUMBER C10 4.7nF NOTE: Intersil Pb-free products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate termination finish, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020. 1 CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 1-888-352-6832 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2002, 2003, 2005. All Rights Reserved All other trademarks mentioned are the property of their respective owners. EL7512 Absolute Maximum Ratings (TA = 25°C) EN, LBI, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .+18V LX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20V VDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12V Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C Operating Temperature . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C Operating Junction Temperature:. . . . . . . . . . . . . . . . . . . . . . . 135°C CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless otherwise noted, all tests are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA Electrical Specifications PARAMETER VIN = 5V, VOUT = 12V, IOUT = 0mA, RT = 100kΩ, TA = 25°C unless otherwise specified. DESCRIPTION CONDITION MIN TYP MAX UNIT 3 µA 2.5 4 mA 1.35 1.39 V 0.10 µA IQ1 Quiescent Current - Shut-down VEN = 0 IQ2 Quiensent Current VEN = 2V VFB Feedback Voltage IB Feedback Input Bias Current VIN Input Voltage Range 2 DMAX Maximum Duty Cycle 84 90 ILIM Current Limit - Max Average Input Current 1000 1250 ISHDN Shut-down Input Bias Current VLBI LBI Threshold Voltage VOL-LBO LBO Output Low ILEAK-LBO 1.31 V % 1500 mA 1 µA 220 250 mV ILBO = 1mA 0.1 0.2 V LBO Output Leakage Current VLBI = 250mV, VLBO = 5V 0.02 1 µA RDS-ON Switch On Resistance at 12V output 300 ILEAK-SWITCH Switch Leakage Current ∆VOUT/∆VIN Line Regulation 3V < VIN < 6V, VOUT = 12V, no load ∆VOUT/∆IOUT Load Regulation IOUT < 250mA FOSC-MAX Maximum Switching Frequency RT = 49.9kΩ FOSC1 Switching Frequency 530 VHI_EN EN Input High Threshold 1.6 VLO_EN EN Input Low Threshold 180 mΩ 1 µA 0.15 %/V 0.5 % 1200 kHz 670 800 kHz V 0.5 V Pin Descriptions PIN NUMBER PIN NAME PIN FUNCTION 1 PGND Power ground; connected to the source of internal N-channel power MOSFET 2 SGND Signal ground; ground reference for all the control circuitry; needs to have only a single connection to PGND 3 RT Timing resistor to adjust the oscillation frequency of the converter 4 EN Chip enable; connects to logic HI (>1.6V) for chip to function 5 LBI Low battery input; connects to a sensing voltage, or left open if function is not used 6 LBO Low battery detection output; connected to the open drain of a MOSFET; able to sink 1mA current 7 SS Soft-start; connects to a capacitor to control the start-up of the converter 8 FB Voltage feedback input; needs to connect to resistor divider to decide VO 9 VDD 10 LX Control circuit positive supply Inductor drive pin; connected to the drain of internal N-channel power MOSFET 2 EL7512 Block Diagram VOUT 15µF 80.6k VIN 10kΩ 1kΩ 4.7nF 47µF 0.1µF FB VDD MAX_DUTY Thermal Shut-down 10µF LX RT Reference Generator 100kΩ VREF VRAMP PWM Logic PWM Comparator 0.3Ω EN LBO 12µA LBI - - Start-up Oscillator + + ILOUT 7.2k 80mΩ 210mV SGND SS 20nF 3 PGND EL7512 Typical Performance Curves 100 Efficiency VIN=3.3V, VO=12V 100 80 Efficiency (%) Efficiency (%) 80 Efficiency VIN=3.3V, VO=5V 60 40 20 60 40 20 0 10 FS=670kHz 60 110 0 10 210 160 FS=670kHz 110 210 IO (mA) 310 410 510 IO (mA) FS vs VDD 1400 100 Efficiency VIN=5V, VO=12V RT=51.1kΩ 1200 80 RT=71.5kΩ Efficiency (%) FS (kHz) 1000 800 RT=100kΩ 600 60 40 400 RT=200kΩ 20 200 0 5 6 7 8 9 10 11 0 10 12 FS=670kHz 60 110 160 210 Internal VREF vs TJ 1.4 360 760 740 VDD=5V 1.3 720 1.25 FS (kHz) VREF (V) 310 FS vs Temperature 1.35 1.2 1.15 700 VDD=10V 680 VDD=12V 1.1 660 1.05 1 -50 260 IO (mA) VDD (V) VDD=12V 0 50 TJ (°C) 4 100 150 640 -50 RT=100kΩ 0 50 TJ (°C) 100 150 EL7512 Typical Performance Curves (Continued) VFB vs VDD FS vs RT 1.355 1400 1.35 1200 1.345 1000 FS (kHz) VFB VDD=10V 1.34 1.335 800 600 1.33 400 1.325 200 1.32 5 6 7 8 9 10 11 0 50 12 VDD 100 150 RT (kΩ) Steady State Operation (inductor continuous conduction) VIN=5V, VO=12V, IO=300mA IDD vs FS 3.6 3.4 VDD=10V VO=12V-18V ∆VI IDD (mA) 3.2 3 2.8 VLX 2.6 ∆VO 2.4 iL 2.2 2 650 750 850 950 1050 1150 1250 FS (kHz) Steady State Operation (inductor discontinuous conduction) VIN=5V, VO=12V, IO=25mA Power-Up VIN=5V, VO=12V, IO=300mA ∆VI VLX VIN VO ∆VO iL iL Load Transient Response VIN=5V, VO=12V, IO=50mA-300mA iO ∆VO 5 200 EL7512 Applications Information where: The EL7512 is a step-up regulator, operated at fixed frequency pulse-width-modulation (PWM) control. The input voltage is 2V-12V and output voltage is 5V-18V. The switching frequency (up to 1.2MHz) is decided by the resistor connected to RT pin. ∆IL is the inductor peak-to-peak current ripple and is decided by: Start-Up D is the MOSFET turn-on ratio and is decided by: After VDD reaches a threshold of about 2V, the start-up oscillator generates fixed duty-ratio of 0.5-0.7 at a frequency of several hundred kilohertz. This will boost the output voltage. When VDD reaches about 3.7V, the PWM comparator takes over the control. The duty ratio will be decided by the multiple-input direct summing comparator, Max_Duty signal (about 90% duty-ratio), and the Current Limit Comparator, whichever is the smallest. V IN D ∆I L = --------- × ------L FS V O – V IN D = ----------------------VO FS is the switching frequency. The following table gives typical values: MAX CONTINUOUS OUTPUT CURRENTS VIN (V) VO (V) L (µH) FS (kHz) IOMAX (mA) 2 5 10 1000 360 2 9 10 1000 190 2 12 10 1000 140 3.3 5 10 1000 600 3.3 9 10 1000 310 3.3 12 10 1000 230 5 9 10 1000 470 Steady-State Operation 5 12 10 1000 340 When the output reaches the preset voltage, the regulator operates at steady state. Depending on the input/output conditions and component values, the inductor operates at either continuous-conduction mode or discontinuousconduction mode. 5 15 10 1000 260 9 12 10 1000 630 9 15 10 1000 470 12 15 10 1000 670 12 18 11 1000 510 The soft-start is provided by the current limit comparator. As the internal 12µA current source charges the external CSS, the peak MOSFET current is limited by the voltage on the capacitor. This in turn controls the rising rate of the output voltage. The regulator goes through the start-up sequence as well after the EN signal is pulled to HI. In the continuous-conduction mode, the inductor current is a triangular waveform and LX voltage a pulse waveform. In the discontinuous-conduction mode, the inductor current is completely dried out before the MOSFET is turned on again. The input voltage source, the inductor, and the MOSFET and output diode parasitic capacitors forms a resonant circuit. Oscillation will occur in this period. This oscillation is normal and will not affect the regulation. At very low load, the MOSFET will skip pulses sometimes. This is normal. Component Considerations It is recommended that CIN is larger than 10µF. Theoretically, the input capacitor has ripple current of ∆IL. Due to high-frequency noise in the circuit, the input current ripple may exceed the theoretical value. Larger capacitor will reduce the ripple further. The inductor has peak and average current decided by: Current Limit IO I LAVG = -----------1–D The MOSFET current limit is nominally 1.2A and guaranteed 1A. This restricts the maximum output current IOMAX based on the following formula: ∆I I LPK = I LAVG + --------L 2 V IN ∆I I OMAX = 1 – --------L × -------- 2 VO The inductor should be chosen to be able to handle this current. Furthermore, due to the fixed internal compensation, it is recommended that maximum inductance of 10µH and 15µH to be used in the 5V and 12V or higher output voltage, respectively. The output diode has average current of IO, and peak current the same as the inductor's peak current. Schottky 6 EL7512 diode is recommended and it should be able to handle those currents. Output voltage ripple is the product of peak inductor current times the ESR of output capacitor. Low ESR capacitor is to be used to reduce the output ripple. The minimum output capacitance of 330µF, 47µF, and 33µF is recommended for 5V, 12V, and 16V for 600kHz switching frequency, respectively. For 1MHz switching frequency, 220µF, 33µF, and 22µF capacitor can be used for the output voltages. In addition to the voltage rating, the output capacitor should also be able to handle the rms current is given by: I CORMS = 2 ∆I L 1 ( 1 – D ) × D + ------------------- × ------ × I LAVG 2 12 I LAVG Output Voltage An external resistor divider is required to divide the output voltage down to the nominal reference voltage. The current drawn by the resistor network should be limited to maintain the overall converter efficiency. The maximum value of the resistor network is limited by the feedback input bias current and the potential for noise being coupled into the feedback pin. A resistor network less than 300kΩ is recommended. The boost converter output voltage is determined by the relationship: R V OUT = V FB × 1 + ------2- R 1 where VFB slightly changes with VDD. The curve is shown in this data sheet. RC Filter The maximum voltage rating for the VDD pin is 12V and is recommended to be about 10V for maximum efficiency to drive the internal MOSFET. The series resistor R4 in the RC filter connected to VDD can be utilized to reduce the voltage. If VO is larger than 10V, then: V O – 10 R 4 = -------------------I DD where IDD is shown in IDD vs FS curve. Otherwise, R4 can be 10Ω to 51Ω with C4 = 0.1µF. Thermal Performance The EL7512 uses a fused-lead package, which has a reduced θJA of 100°C/W on a four-layer board and 115°C/W on a two-layer board. Maximizing copper around the ground pins will improve the thermal performance. This chip also has internal thermal shut-down set at around 135°C to protect the component. 7 Layout Considerations The layout is very important for the converter to function properly. Power Ground ( ) and Signal Ground (--) should be separated to ensure that the high pulse current in the Power Ground never interferes with the sensitive signals connected to Signal Ground. They should only be connected at one point. The trace connected to pin 8 (FB) is the most sensitive trace. It needs to be as short as possible and in a “quiet” place, preferably between PGND or SGND traces. In addition, the bypass capacitor connected to the VDD pin needs to be as close to the pin as possible. The heat of the chip is mainly dissipated through the SGND pin. Maximizing the copper area around it is preferable. In addition, a solid ground plane is always helpful for the EMI performance. The demo board is a good example of layout based on these principles. Please refer to the EL7512 Application Brief for the layout. EL7512 Package Outline Drawing NOTE: The package drawing shown here may not be the latest version. To check the latest revision, please refer to the Intersil website at <http://www.intersil.com/design/packages/index.asp> 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 8