EL7640A, EL7641A, EL7642A ® Data Sheet PRELIMINARY May 15, 2006 TFT-LCD DC/DC with Integrated Amplifiers Features The EL7640A, EL7641A, and EL7642A integrate a high performance boost regulator with 2 LDO controllers for VON and VOFF, a VON-slice circuit with adjustable delay and either one (EL7640A), three (EL7641A), or five amplifiers (EL7642A) for VCOM and VGAMMA applications. The boost converter in the EL7640A, EL7641A, and EL7642A is a current mode PWM type integrating an 18V NHchannel MOSFET. Operating at 1.2MHz, this boost can operate in either P-mode for superior transient response, or in PI-mode for tighter output regulation. Using external low-cost transistors, the LDO controllers provide tight regulation for VON, VOFF, as well as providing start-up sequence control and fault protection. The amplifiers are ideal for VCOM and VGAMMA applications, with 150mA peak output current drive, 12MHz bandwidth, and 12V/µs slew rate. All inputs and outputs are rail-to-rail. Available in the 32 Ld thin QFN (5mm x 5mm) Pb-free packages, the EL7640A, EL7641A, and EL7642A are specified for operation over the -40°C to +85°C temperature range. Ordering Information PART NUMBER (Note) FN6270.0 • Current mode boost regulator - Fast transient response - 1% accurate output voltage - 18V/3A integrated FET - >90% efficiency • 2.6V to 5.5V VIN supply • 2 LDO controllers for VON and VOFF - 2% output regulation - VON-slice circuit • High speed amplifiers - 150mA short-circuit output current - 12V/µs slew rate - 12MHz -3dB bandwidth - Rail-to-rail inputs and outputs • Built-in power sequencing • Internal soft-start • Multiple overload protection • Thermal shutdown • 32 Ld 5x5 thin QFN package • Pb-free plus anneal available (RoHS compliant) PART TAPE & PACKAGE MARKING REEL (Pb-Free) PKG. DWG. # Applications • TFT-LCD panels EL7640AILTZ 7640AILTZ - 32 Ld 5x5 Thin QFN MDP0051 EL7640AILTZ-T7 7640AILTZ 7” 32 Ld 5x5 Thin QFN MDP0051 EL7640AILTZ-T13 7640AILTZ 13” 32 Ld 5x5 Thin QFN MDP0051 • LCD monitors EL7641AILTZ 7641AILTZ - 32 Ld 5x5 Thin QFN MDP0051 EL7641AILTZ-T7 7641AILTZ 7” 32 Ld 5x5 Thin QFN MDP0051 EL7641AILTZ-T13 7641AILTZ 13” 32 Ld 5x5 Thin QFN MDP0051 EL7642AILTZ 7642AILTZ - 32 Ld 5x5 Thin QFN MDP0051 EL7642AILTZ-T7 7642AILTZ 7” 32 Ld 5x5 Thin QFN MDP0051 EL7642AILTZ-T13 7642AILTZ 13” 32 Ld 5x5 Thin QFN MDP0051 • Notebooks • LCD-TVs NOTE: Intersil Pb-free plus anneal 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 1-888-468-3774 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright Intersil Americas Inc. 2006. All Rights Reserved All other trademarks mentioned are the property of their respective owners. EL7640A, EL7641A, EL7642A Pinouts 25 FBP 26 DRVP 27 FBN 28 DRVN 30 CTL 31 DRN 32 COM 25 FBP 26 DRVP 27 FBN 28 DRVN 29 DEL 30 CTL 31 DRN 32 COM 29 DEL EL7641A (32 LD QFN) TOP VIEW EL7640A (32 LD QFN) TOP VIEW SRC 1 24 COMP SRC 1 24 COMP REF 2 23 FB REF 2 23 FB 22 IN AGND 3 21 LX PGND 4 20 NC OUT1 5 NEG1 6 19 NC NEG1 6 19 NC POS1 7 18 IC POS1 7 18 IC 17 NC OUT2 8 17 OUT3 NC = NOT INTERNALLY CONNECTED IC = INTERNALLY CONNECTED NEG3 16 POS3 15 20 NC SUP 14 NC 13 NC 16 NC 15 SUP 14 NC 13 NC 12 BGND 11 IC 10 NC 9 NC 8 NC 12 OUT1 5 21 LX THERMAL PAD BGND 11 THERMAL PAD NEG2 9 PGND 4 22 IN POS2 10 AGND 3 NC = NOT INTERNALLY CONNECTED IC = INTERNALLY CONNECTED 25 FBP 26 DRVP 27 FBN 28 DRVN 29 DEL 30 CTL 31 DRN 32 COM EL7642A (32 LD QFN) TOP VIEW SRC 1 24 COMP REF 2 23 FB AGND 3 22 IN PGND 4 21 LX THERMAL PAD OUT1 5 20 OUT5 2 NEG4 16 POS4 15 SUP 14 17 OUT4 OUT3 13 OUT2 8 POS3 12 18 POS5 BGND 11 POS1 7 POS2 10 19 NEG5 NEG2 9 NEG1 6 FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A Absolute Maximum Ratings (TA = 25°C) COM, DRN to AGND . . . . . . . . . . . . . . . . . . . . -0.3V to VSRC +0.3V LX Maximum Continuous RMS Output Current. . . . . . . . . . . . . 1.6A OUT1, OUT2, OUT3, OUT4, OUT5 Maximum Continuous Output Current . . . . . . . . . . . . . . . . . . ±75mA Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C Maximum Continuous Junction Temperature . . . . . . . . . . . . +125°C Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Curves Operating Ambient Temperature . . . . . . . . . . . . . . . .-40°C to +85°C IN, CTL to AGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +6.5V COMP, FB, FBP, FBN, DEL, REF to AGND. . . . . -0.3V to VIN+0.3V PGND, BGND to AGND. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±0.3V LX to PGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +24V SUP to AGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +18V DRVP, SRC to AGND . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +36V POS1, NEG1, OUT1, POS2, NEG2, OUT2, POS3, OUT3, POS4, NEG4, OUT4, POS5, OUT5 to AGND . . -0.3V to VSUP+0.3V DRVN to AGND . . . . . . . . . . . . . . . . . . . . . . . VIN -20V to VIN +0.3V 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 VIN = 3V, VBOOST = VSUP = 12V, VSRC = 20V, Over temperature from -40°C to 85°C. Unless Otherwise Specified. PARAMETER DESCRIPTION CONDITIONS MIN TYP MAX UNIT 5.5 V SUPPLY VIN Input Supply Range VLOR Undervoltage Lockout Threshold VIN rising 2.4 2.5 2.6 V VLOF Undervoltage Lockout Threshold VIN falling 2.2 2.3 2.4 V IS Quiescent Current LX not switching 2.5 mA ISS Quiescent Current - Switching LX switching 5 10 mA TFD Fault Delay Time CDEL = 100nF 23 VREF Reference Voltage TA = 25°C SHUTDN 2.6 ms 1.19 1.215 1.235 V 1.187 1.215 1.238 V Thermal Shutdown Temperature 140 °C MAIN BOOST REGULATOR VBOOST Output Voltage Range FOSC Oscillator Frequency 1050 1200 DCM Maximum Duty Cycle 82 85 VFBB Boost Feedback Voltage 1.192 1.205 1.218 V 1.188 1.205 1.222 V 0.85 0.925 1.020 V (Note 1) TA = 25°C VIN+ 15% 18 V 1350 kHz % VFTB FB Fault Trip Level Falling edge ∆VBOOST/ ∆IBOOST Load Regulation 50mA < ILOAD < 250mA 0.1 % ∆VBOOST/ ∆VIN Line Regulation VIN = 2.6V to 5.5V 0.08 %/V IFB Input Bias Current VFB = 1.35V gmV FB Transconductance dI = ±2.5µA at COMP, FB = COMP RONLX LX On Resistance ILEAKLX LX Leakage Current VFB = 1.35V, VLX = 13V 0.02 ILIMLX LX Current Limit Duty cycle = 65% (Note 1) 3.0 A tSSB Soft-Start Period CDEL = 100nF 7 ms 3 500 nA 160 µA/V 160 mΩ 40 µA FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A Electrical Specifications VIN = 3V, VBOOST = VSUP = 12V, VSRC = 20V, Over temperature from -40°C to 85°C. Unless Otherwise Specified. (Continued) PARAMETER DESCRIPTION CONDITIONS MIN TYP MAX UNIT 18 V 600 800 µA 3 12 mV -50 +50 nA VSUP V OPERATIONAL AMPLIFIERS VSUP Supply Operating Range ISUP Supply Current per Amplifier VOS Offset Voltage IB Input Bias Current CMIR Common Mode Input Range 0 CMRR Common Mode Rejection Ratio 60 AOL Open Loop Gain VOH Output Voltage High VOL Output Voltage Low 4.5 90 dB 110 dB IOUT = 100µA VSUP -15 VSUP -2 mV IOUT = 5mA VSUP -250 VSUP -150 mV IOUT = -100µA IOUT = -5mA ISC Short-Circuit Current 100 ICONT Continuous Output Current ±50 PSRR Power Supply Rejection Ratio 60 BW-3dB 2 30 mV 100 150 mV 150 mA mA 100 dB -3dB Bandwidth 12 MHz GBWP Gain Bandwidth Product 8 MHz SR Slew Rate 12 V/µs POSITIVE LDO VFBP Positive Feedback Voltage IDRVP = 100µA, TA = 25°C 1.176 1.2 1.224 V IDRVP = 100µA 1.176 1.2 1.229 V 0.9 0.98 V 50 nA VFTP VFBP Fault Trip Level VFBP falling 0.82 IBP Positive LDO Input Bias Current VFBP = 1.4V -50 ∆VPOS/ ∆IPOS FBP Load Regulation VDRVP = 25V, IDRVP = 0 to 20µA IDRVP Sink Current VFBP = 1.1V, VDRVP = 10V ILEAKP DRVP Off Leakage Current VFBP = 1.4V, VDRVP = 30V tSSP Soft-Start Period CDEL = 100nF FBN Regulation Voltage IDRVN = 0.2mA, TA = 25°C 0.173 0.203 0.233 V IDRVN = 0.2mA 0.171 0.203 0.235 V 430 480 mV 50 nA 2 0.5 % 4 mA 0.1 10 7 µA ms NEGATIVE LDO VFBN VFTN VFBN Fault Trip Level VFBN rising 380 IBN Negative LDO Input Bias Current VFBN = 250mV -50 FBN Load Regulation VDRVN = -6V, IDRVN = 2µA to 20µA IDRVN Source Current VFBN = 500mV, VDRVN = -6V ILEAKN DRVN Off Leakage Current VFBP = 1.35V, VDRVP = 30V tSSN Soft-start Period CDEL = 100nF 4 2 0.5 % 4 mA 0.1 7 10 µA ms FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A Electrical Specifications VIN = 3V, VBOOST = VSUP = 12V, VSRC = 20V, Over temperature from -40°C to 85°C. Unless Otherwise Specified. (Continued) PARAMETER DESCRIPTION CONDITIONS MIN TYP MAX UNIT 0.4VIN V VON -SLICE CIRCUIT VLO CTL Input Low Voltage VIN = 2.6V to 5.5V VHI CTL Input High Voltage VIN = 2.6V to 5.5V 0.6VIN ILEAKCTL CTL Input Leakage Current CTL = AGND or IN -1 tDrise CTL to OUT Rising Prop Delay 1kΩ from DRN to 8V, VCTL = 0V to 3V step, no load on OUT, measured from VCTL = 1.5V to OUT = 20% 100 ns tDfall CTL to OUT Falling Prop Delay 1kΩ from DRN to 8V, VCTL = 3V to 0V step, no load on OUT, measured from VCTL = 1.5V to OUT = 80% 100 ns VSRC SRC Input Voltage Range ISRC SRC Input Current V 1 µA 30 V Start-up sequence not completed 150 250 µA Start-up sequence completed 150 250 µA RONSRC SRC On Resistance Start-up sequence completed 5 10 Ω RONDRN DRN On Resistance Start-up sequence completed 30 60 Ω RONCOM COM to GND On Resistance Start-up sequence not completed 1000 1800 Ω tON Turn On Delay CDEL = 100nF (See Figure 23) 10 ms tDEL1 Delay Between VBOOST and VOFF CDEL = 100nF (See Figure 23) 10 ms tDEL2 Delay Between VON and VOFF CDEL = 100nF (See Figure 23) 10 ms tDEL3 Delay From VON to VON-slice Enabled CDEL = 100nF (See Figure 23) 10 ms CDEL Delay Capacitor 100 nF 350 SEQUENCING 22 NOTE: 1. Guaranteed by design. 5 FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A Pin Descriptions PIN NAME EL7642A EL7641A EL7640A SRC 1 1 1 Upper reference voltage for switch output REF 2 2 2 Internal reference bypass terminal AGND 3 3 3 Analog ground for boost converter and control circuitry PGND 4 4 4 Power ground for boost switch OUT1 5 5 5 Operational amplifier 1 output NEG1 6 6 6 Operational amplifier 1 inverting input POS1 7 7 7 Operational amplifier 1 non-inverting input OUT2 8 8 - Operational amplifier 2 output NEG2 9 9 - Operational amplifier 2 inverting input POS2 10 10 - Operational amplifier 2 non-inverting input BGND 11 11 11 POS3 12 15 - Operational amplifier 3 non-inverting input NEG3 - 16 - Operational amplifier 3 inverting input OUT3 13 17 - Operational amplifier 3 output SUP 14 14 14 POS4 15 - - Operational amplifier 4 non-inverting input NEG4 16 - - Operational amplifier 4 inverting input OUT4 17 - - Operational amplifier 4 output POS5 18 - - Operational amplifier 5 non-inverting input NEG5 19 - - Operational amplifier 5 inverting input OUT5 20 - - Operational amplifier 5 output LX 21 21 21 Main boost regulator switch connection IN 22 22 22 Main supply input; bypass to AGND with 1µF capacitor FB 23 23 23 Main boost feedback voltage connection COMP 24 24 24 Error amplifier compensation pin FBP 25 25 25 Positive LDO feedback connection DRVP 26 26 26 Positive LDO transistor drive FBN 27 27 27 Negative LDO feedback connection DRVN 28 28 28 Negative LDO transistor driver DEL 29 29 29 Connection for switch delay timing capacitor CTL 30 30 30 Input control for switch output DRN 31 31 31 Lower reference voltage for switch output COM 32 32 32 Switch output; when CTL = 1, COM is connected to SRC through a 15Ω resistor; when CTL = 0, COM is connected to DRN through a 30Ω resistor 6 PIN FUNCTION Operational amplifier ground Amplifier positive supply rail. Bypass to BGND with 0.1µF capacitor FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A Typical Performance Curves 100 94 90 92 70 VIN=5V VIN=3V 60 EFFICIENCY (%) EFFICIENCY (%) 80 50 40 30 20 88 86 0 82 200 400 600 800 1000 78 1200 0 200 FIGURE 1. BOOST EFFICIENCY AT VOUT = 12V (PI MODE) 800 1000 1200 0 -0.1 LOAD REGULATION (%) LOAD REGULATION (%) 600 FIGURE 2. BOOST EFFICIENCY AT VOUT = 12V (P MODE) 0 VIN=3V -0.2 -0.3 -0.4 VIN=5V -0.5 0 200 400 600 800 1000 -2 -6 -8 VIN=3.3V -10 -12 -14 1200 VIN=5.0V -4 0 200 LOAD CURRENT (mA) 0.1 3 LINE REGULATION (%) 3.5 0.08 0.06 0.04 0.02 3 3.5 4 4.5 5 5.5 6 INPUT VOLTAGE (V) FIGURE 5. BOOST LINE REGULATION vs INPUT VOLTAGE (PI MODE) 7 600 800 1000 1200 FIGURE 4. BOOST LOAD REGULATION vs LOAD CURRENT (P MODE) 0.12 0 400 LOAD CURRENT (mA) FIGURE 3. BOOST LOAD REGULATION vs LOAD CURRENT (PI MODE) LINE REGULATION (%) 400 LOAD CURRENT (mA) LOAD CURRENT (mA) -0.6 VIN=5V VIN=3V 84 80 10 0 90 2.5 2 1.5 1 0.5 0 3 3.5 4 4.5 5 5.5 6 INPUT VOLTAGE (V) FIGURE 6. BOOST LINE REGULATION vs INPUT VOLTAGE (P MODE) FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A Typical Performance Curves (Continued) BOOST OUTPUT VOLTAGE (AC COUPLING) BOOST OUTPUT CURRENT VBOOST=12V COUT=30µF LOAD REGULATION (%) 0 VON=20V -0.05 -0.1 -0.15 -0.2 -0.25 5 10 15 20 25 30 VON LOAD CURRENT (mA) FIGURE 7. BOOST PULSE LOAD TRANSIENT RESPONSE FIGURE 8. VON LOAD REGULATION 0 -0.02 LOAD REGULATION (%) LINE REGULATION (%) 0 -0.04 -0.06 -0.08 VON=20V ILOAD=20mA -0.1 -0.12 20 21 22 23 24 INPUT VOLTAGE (V) 25 26 VOFF=-8V -0.1 -0.2 -0.3 -0.4 -0.5 -0.6 -0.7 -0.8 -0.9 5 10 15 20 FIGURE 9. VON LINE REGULATION 30 FIGURE 10. VOFF LOAD REGULATION 0 LINE REGULATION (%) 25 LOAD CURRENT (mA) VCDEL -0.1 VBOOST -0.2 -0.3 VOFF -0.4 -0.5 -0.6 -15 VON VOFF=-8V ILOAD=50mA -14 -13 -12 -11 INPUT VOLTAGE (V) FIGURE 11. VOFF LINE REGULATION 8 -10 TIME (20ms/DIV) FIGURE 12. START-UP SEQUENCE FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A Typical Performance Curves (Continued) INPUT VOLTAGE INPUT VBOOST VOFF OUTPUT VON TIME (50µs/DIV) TIME (20ms/DIV) FIGURE 13. START-UP SEQUENCE JEDEC JESD51-3 AND SEMI G42-88 (SINGLE LAYER) TEST BOARD 0.7 758mW 3 POWER DISSIPATION (W) POWER DISSIPATION (W) 0.8 FIGURE 14. OP AMP RAIL-TO-RAIL INPUT/OUTPUT QFN32 0.6 θJA=125°C/W 0.5 0.4 0.3 0.2 0.1 JEDEC JESD51-7 HIGH EFFECTIVE THERMAL CONDUCTIVITY TEST BOARD QFN EXPOSED DIEPAD SOLDERED TO PCB PER JESD51-5 2.5 2.857W QFN32 2 θJA=35°C/W 1.5 1 0.5 0 0 0 25 75 85 100 50 125 0 150 FIGURE 15. PACKAGE POWER DISSIPATION vs AMBIENT TEMPERATURE The EL7640A, EL7641A, EL7642A integrate an N-channel MOSFET in boost converter to minimize the external component counts and cost. The VON, VOFF linearregulators are independently regulated by using external resistors. To achieve higher voltage than VBOOST, one or multiple stage charge pumps may be used. 9 50 75 85 100 125 150 FIGURE 16. PACKAGE POWER DISSIPATION vs AMBIENT TEMPERATURE Applications Information The EL7640A, EL7641A, EL7642A provide a highly integrated multiple output power solution for TFT-LCD applications. The system consists of one high efficiency boost converter and two low cost linear-regulator controllers (VON and VOFF) with multiple protection functions. The block diagram of the whole part is shown in Figure 17. Table 1 lists the recommended components. 25 AMBIENT TEMPERATURE (°C) AMBIENT TEMPERATURE (°C) TABLE 1. RECOMMENDED COMPONENTS DESIGNATION C1, C2, C3 D1 DESCRIPTION 10µF, 16V X5R ceramic capacitor (1210) TDK C3216X5R0J106K 1A 20V low leakage schottky rectifier (CASE 457-04) ON SEMI MBRM120ET3 D11, D12, D21 200mA 30V schottky barrier diode (SOT-23) Fairchild BAT54S L1 6.8µH 1.3A Inductor TDK SLF6025T-6R8M1R3-PF Q11 200mA 40V PNP amplifier (SOT-23) Fairchild MMBT3906 Q21 200mA 40V NPN amplifier (SOT-23) Fairchild MMBT3904 FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A VREF REFERENCE GENERATOR OSCILLATOR COMP SLOPE COMPENSATION Σ OSC LX PWM LOGIC CONTROLLER BUFFER VOLTAGE AMPLIFIER FBB GM AMPLIFIER CINT PGND CURRENT AMPLIFIER UVLO COMPARATOR CURRENT REF CURRENT LIMIT COMPARATOR SHUTDOWN & START-UP CONTROL VREF SS + DRVP BUFFER THERMAL SHUTDOWN FBP UVLO COMPARATOR SS + DRVN 0.2V BUFFER FBN 0.4V UVLO COMPARATOR FIGURE 17. BLOCK DIAGRAM Boost Converter The main boost converter is a current mode PWM converter operating at a fixed frequency. The 1.2MHz switching frequency enables the use of low profile inductor and multilayer ceramic capacitors, which results in a compact, low cost power system for LCD panel design. The boost converter can operate in continuous or discontinuous inductor current mode. The EL7640A, EL7641A, EL7642A are designed for continuous current mode, but they can also operate in discontinuous current mode at light load. In continuous current mode, current flows continuously in the inductor during the entire switching cycle in steady state operation. The voltage conversion ratio in continuous current mode is given by: V BOOST 1 ------------------------ = ------------V IN 1–D Figure 18 shows the block diagram of the boost controller. It uses a summing amplifier architecture consisting of GM stages for voltage feedback, current feedback and slope compensation. A comparator looks at the peak inductor current cycle by cycle and terminates the PWM cycle if the current limit is reached. An external resistor divider is required to divide the output voltage down to the nominal reference voltage. 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 in the order of 60kΩ is recommended. The boost converter output voltage is determined by the following equation: R1 + R2 V BOOST = --------------------- × V REF R1 Where D is the duty cycle of switching MOSFET. 10 FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A The current through MOSFET is limited to 3A peak. This restricts the maximum output current based on the following equation: V IN ∆I I OMAX = ⎛ I LMT – --------L⎞ × --------⎝ 2 ⎠ VO Where ∆IL is peak to peak inductor ripple current, and is set by: V IN D ∆I L = --------- × ----L fS where fS is the switching frequency. SHUTDOWN & START-UP CONTROL CLOCK SLOPE COMPENSATION IFB CURRENT AMPLIFIER PWM IREF LX LOGIC BUFFER IFB FBB GM AMPLIFIER IREF VOLTAGE AMPLIFIER REFERENCE GENERATOR COMP PGND FIGURE 18. THE BLOCK DIAGRAM OF THE BOOST CONTROLLER 11 FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A The following table gives typical values (margins are considered 10%, 3%, 20%, 10% and 15% on VIN, VO, L, fS and ILMT: TABLE 2. For low ESR ceramic capacitors, the output ripple is dominated by the charging and discharging of the output capacitor. The voltage rating of the output capacitor should be greater than the maximum output voltage. NOTE: Capacitors have a voltage coefficient that makes their effective capacitance drop as the voltage across them increases. COUT in the equation above assumes the effective value of the capacitor at a particular voltage and not the manufacturer’s stated value, measured at zero volts. VIN (V) VO (V) L (µH) fS (MHz) IOMAX (mA) 3.3 9 6.8 1.2 898 3.3 12 6.8 1.2 622 3.3 15 6.8 1.2 458 Compensation 5 9 6.8 1.2 1360 5 12 6.8 1.2 944 5 15 6.8 1.2 694 The EL7640A, EL7641A, EL7642A can operate in either P mode or PI mode. Connecting COMP pin directly to VIN will enable P mode; For better load regulation, use PI mode with a 2.2nF capacitor and a 180Ω resistor in series between COMP pin and ground. To improve the transient response, either the resistor value can be increased or the capacitor value can be reduced, but too high resistor value or too low capacitor value will reduce loop stability. Input Capacitor The input capacitor is used to supply the current to the converter. It is recommended that CIN be larger than 10µF. The reflected ripple voltage will be smaller with larger CIN. The voltage rating of input capacitor should be larger than maximum input voltage. Boost Inductor The boost inductor is a critical part which influences the output voltage ripple, transient response, and efficiency. Value of 3.3µH to 10µH inductor is recommended in applications to fit the internal slope compensation. The inductor must be able to handle the following average and peak current: ∆I I LPK = I LAVG + --------L 2 Boost Feedback Resistors As the boost output voltage, VBOOST, is reduced below 12V the effective voltage feedback in the IC increases the ratio of voltage to current feedback at the summing comparator because R2 decreases relative to R1. To maintain stable operation over the complete current range of the IC, the voltage feedback to the FBB pin should be reduced proportionally, as VBOOST is reduced, by means of a series resistor-capacitor network (R7 and C7) in parallel with R1, with a pole frequency (fp) set to approximately 10kHz. for C2 effective = 10µF and 4kHz for C2 (effective) = 30µF. R7 = ((1/0.1 x R2) – 1/R1)^-1 IO I LAVG = -----------1–D C7 = 1/(2 x 3.142 x fp x R7) Linear-Regulator Controllers (VON and VOFF) Rectifier Diode A high-speed diode is desired due to the high switching frequency. Schottky diodes are recommended because of their fast recovery time and low forward voltage. The rectifier diode must meet the output current and peak inductor current requirements. The EL7640A, EL7641A, EL7642A include 2 independent linear-regulator controllers, in which there is one positive output voltage (VON), and one negative voltage (VOFF). The VON and VOFF linear-regulator controller function diagram, application circuit and waveforms are shown in Figure 19 and Figure 20 respectively. Output Capacitor The output capacitor supplies the load directly and reduces the ripple voltage at the output. Output ripple voltage consists of two components: the voltage drop due to the inductor ripple current flowing through the ESR of output capacitor, and the charging and discharging of the output capacitor. V O – V IN IO 1 V RIPPLE = I LPK × ESR + ------------------------ × ---------------- × ----VO C OUT f S 12 FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A VBOOST LX 0.1µF LDO_ON 0.9V PG_LDOP + - CP (TO 36V) 36V ESD CLAMP RBP 700Ω 0.1µF VON (TO 35V) DRVP FBP RP1 CON RP2 20kΩ + GMP The VOFF power supply is used to power the negative supply of the row driver in the LCD panel. The DC/DC consists of an external diode-capacitor charge pump powered from the inductor (LX) of the boost converter, followed by a low dropout linear regulator (LDO_OFF). The LDO_OFF regulator uses an external NPN transistor as the pass element. The onboard LDO controller is a wide band (>10MHz) transconductance amplifier capable of 5mA output current, which is sufficient for up to 50mA or more output current under the low dropout condition (forced beta of 10). Typical VOFF voltage supported by EL7640A, EL7641A and EL7642A ranges from -5V to -25V. A fault comparator is also included for monitoring the output voltage. The under-voltage threshold is set at 200mV above the 0.2V reference level. 1: Np Set-up Output Voltage FIGURE 19. VON FUNCTIONAL BLOCK DIAGRAM LX 0.1µF Refer to Typical Application Diagram, the output voltages of VON, VOFF and VLOGIC are determined by the following equations: R 12⎞ ⎛ V ON = V REF × ⎜ 1 + ---------⎟ R 11⎠ ⎝ R 22 V OFF = V REFN + ---------- × ( V REFN – V REF ) R 21 CP (TO -26V) LDO_OFF PG_LDON VREF + Where VREF = 1.2V, VREFN = 0.2V. 0.1µF High Charge Pump Output Voltage (>36V) Applications RN2 20kΩ 0.4V FBN 1: Nn RN1 VOFF (TO -20V) + GMN DRVN 36V ESD CLAMP RBN 700Ω COFF In the applications where the charge pump output voltage is over 36V, an external NPN transistor needs to be inserted in between the DRVP pin and the base of pass transistor Q3 as shown in Figure 21, or the linear regulator can control only one stage charge pump and regulate the final charge pump output as shown in Figure 22. VIN CHARGE PUMP OR VBOOST OUTPUT 700Ω FIGURE 20. VOFF FUNCTIONAL BLOCK DIAGRAM The VON power supply is used to power the positive supply of the row driver in the LCD panel. The DC/DC consists of an external diode-capacitor charge pump powered from the inductor (LX) of the boost converter, followed by a low dropout linear regulator (LDO_ON). The LDO_ON regulator uses an external PNP transistor as the pass element. The onboard LDO controller is a wide band (>10MHz) transconductance amplifier capable of 5mA output current, which is sufficient for up to 50mA or more output current under the low dropout condition (forced beta of 10). Typical VON voltage supported by EL7640A, EL7641A and EL7642A ranges from +15V to +36V. A fault comparator is also included for monitoring the output voltage. The undervoltage threshold is set at 25% below the 1.2V reference. 13 DRVP Q11 NPN CASCODE TRANSISTOR VON EL764X FBP FIGURE 21. CASCODE NPN TRANSISTOR CONFIGURATION FOR HIGH CHARGE PUMP OUTPUT VOLTAGE (>36V) FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A LX 0.1µF VBOOST 0.1µF 700Ω DRVP Q11 0.47µF EL7642A 0.1µF 0.1µF 0.1µF VON (>36V) 0.22µF FBP FIGURE 22. THE LINEAR REGULATOR CONTROLS ONE STAGE OF CHARGE PUMP Calculation of the Linear Regulator Base-emitter Resistors (RBP and RBN) For the pass transistor of the linear regulator, low frequency gain (Hfe) and unity gain frequency (fT) are usually specified in the datasheet. The pass transistor adds a pole to the loop transfer function at fp = fT/Hfe. Therefore, in order to maintain phase margin at low frequency, the best choice for a pass device is often a high frequency low gain switching transistor. Further improvement can be obtained by adding a base-emitter resistor RBE (RBP, RBL, RBN in the Functional Block Diagram), which increases the pole frequency to: fp = fT*(1+ Hfe *re/RBE)/Hfe, where re = KT/qIc. So choose the lowest value RBE in the design as long as there is still enough base current (IB) to support the maximum output current (IC). We will take as an example the VON linear regulator. If a Fairchild MMBT3906 PNP transistor is used as the external pass transistor, Q11 in the application diagram, then for a maximum VON operating requirement of 50mA the data sheet indicates Hfe_min = 60. The base-emitter saturation voltage is: Vbe_max = 0.7V. For the EL7640A, EL7641A and EL7642A, the minimum drive current is: I_DRVP_min = 2mA The minimum base-emitter resistor, RBP, can now be calculated as: RBP_min = VBE_max/(I_DRVP_min - Ic/Hfe_min) = 0.7V/(2mA - 50mA/60) = 600Ω This is the minimum value that can be used – so, we now choose a convenient value greater than this minimum value; say 700Ω. Larger values may be used to reduce quiescent current, however, regulation may be adversely affected by supply noise if RBP is made too high in value. 14 Charge Pump To generate an output voltage higher than VBOOST, single or multiple stages of charge pumps are needed. The number of stage is determined by the input and output voltage. For positive charge pump stages: V OUT + V CE – V INPUT N POSITIVE ≥ -------------------------------------------------------------V INPUT – 2 × V F where VCE is the dropout voltage of the pass component of the linear regulator. It ranges from 0.3V to 1V depending on the transistor selected. VF is the forward-voltage of the charge-pump rectifier diode. The number of negative charge-pump stages is given by: V OUTPUT + V CE N NEGATIVE ≥ ------------------------------------------------V INPUT – 2 × V F To achieve high efficiency and low material cost, the lowest number of charge-pump stages, which can meet the above requirements, is always preferred. Charge Pump Output Capacitors Ceramic capacitor with low ESR is recommended. With ceramic capacitors, the output ripple voltage is dominated by the capacitance value. The capacitance value can be chosen by the following equation: I OUT C OUT ≥ -----------------------------------------------------2 × V RIPPLE × f OSC where fOSC is the switching frequency. Discontinuous/Continuous Boost Operation and its Effect on the Charge Pumps The EL7640A, EL7641A and EL7642A VON and VOFF architecture uses LX switching edges to drive diode charge pumps from which LDO regulators generate the VON and FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A VOFF supplies. It can be appreciated that should a regular supply of LX switching edges be interrupted, for example during discontinuous operation at light boost load currents, then this may affect the performance of VON and VOFF regulation – depending on their exact loading conditions at the time. Start-up Sequence Figure 23 shows a detailed start-up sequence waveform. For a successful power-up, there should be 6 peaks at VCDEL. When a fault is detected, the device will latch off until either EN is toggled or the input supply is recycled. To optimize VON/VOFF regulation, the boundary of discontinuous/continuous operation of the boost converter can be adjusted, by suitable choice of inductor given VIN, VOUT, switching frequency and the VBOOST current loading, to be in continuous operation. When the input voltage is higher than 2.4V, an internal current source starts to charge CCDEL. During the initial slow ramp, the device checks whether there is a fault condition. If no fault is found during the initial ramp, CCDEL is discharged after the first peak. VREF turns on at the peak of the first ramp. The following equation gives the boundary between discontinuous and continuous boost operation. For continuous operation (LX switching every clock cycle) we require that: Initially the boost is not enabled so VBOOST rises to VINVDIODE through the output diode. Hence, there is a step at VBOOST during this part of the start-up sequence. I(VBOOST_load) > D*(1-D)*VIN/(2*L*FOSC) where the duty cycle, D = (VBOOST – VIN)/VBOOST For example, with VIN = 5V, FOSC = 1.2MHz and VBOOST = 12V we find continuous operation of the boost converter can be guaranteed for: L = 10µH and I(VBOOST) > 51mA L = 6.8µH and I(VBOOST) > 74mA L = 3.3µH and I(VBOOST) > 153mA 15 VBOOST soft-starts at the beginning of the third ramp, and is checked at the end of this ramp. The soft-start ramp depends on the value of the CDEL capacitor. For CDEL of 100nF, the soft-start time is ~7ms. VOFF turns on at the start of the fourth peak. VON is enabled at the beginning of the sixth ramp. VOFF and VON are checked at end of this ramp. FN6270.0 May 15, 2006 CHIP DISABLED FAULT DETECTED VON SOFT-START VOFF ON VBOOST SOFT-START VREF ON EL7640A, EL7641A, EL7642A VCDEL IN VREF VBOOST tON tDEL1 VOFF tDEL2 VON VON SLICE CIRCUIT tDEL3 START-UP SEQUENCE TIMED BY CDEL NOTE: Not to scale NORMAL OPERATION FAULT PRESENT FIGURE 23. START-UP SEQUENCE Component Selection for Start-up Sequencing and Fault Protection The CREF capacitor is typically set at 220nF and is required to stabilize the VREF output. The range of CREF is from 22nF to 1µF and should not be more than five times the capacitor on CDEL to ensure correct start-up operation. The CDEL capacitor is typically 100nF and has a usable range from 22nF minimum to several microfarads – only limited by the leakage in the capacitor reaching µA levels. 16 CDEL should be at least 1/5 of the value of CREF (see above). Note that with 100nF on CDEL the fault time-out will be typically 23ms and the use of a larger/smaller value will vary this time proportionally (e.g. 1µF will give a fault timeout period of typically 230ms). Fault Sequencing The EL7640A, EL7641A and EL7642A have an advanced fault detection system which protects the IC from both adjacent pin shorts during operation and shorts on the output FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A supplies. A high quality layout/design of the PCB, in respect of grounding quality and decoupling is necessary to avoid falsely triggering the fault detection scheme – especially during start-up. The user is directed to the layout guidelines and component selection sections to avoid problems during initial evaluation and prototype PCB generation. VON -Slice Circuit The VON-slice Circuit functions as a three way multiplexer, switching the voltage on COM between ground, DRN and SRC, under control of the start-up sequence and the CTL pin. During the start-up sequence, COM is held at ground via an NDMOS FET, with ~1k impedance. Once the start-up sequence has completed, CTL is enabled and acts as a multiplexer control such that if CTL is low, COM connects to DRN through a 5Ω internal MOSFET, and if CTL is high, COM connects to SRC via a 30Ω MOSFET. The slew rate of start-up of the switch control circuit is mainly restricted by the load capacitance at COM pin as in the following equation: Vg ∆V -------- = ----------------------------------( R i || R L ) • C L ∆t Driving Capacitive Loads EL7640A, EL7641A and EL7642A can drive a wide range of capacitive loads. As load capacitance increases, however, the –3dB bandwidth of the device will decrease and the peaking will increase. The amplifiers drive 10pF loads in parallel with 10kΩ with just 1.5dB of peaking, and 100pF with 6.4dB of peaking. If less peaking is desired in these applications, a small series resistor (usually between 5Ω and 50Ω) can be placed in series with the output. However, this will obviously reduce the gain. Another method of reducing peaking is to add a “snubber” circuit at the output. A snubber is a shunt load consisting of a resistor in series with a capacitor. Values of 150Ω and 10nF are typical. The advantage of a snubber is that it does not draw any DC load current and reduce the gain. Over-Temperature Protection An internal temperature sensor continuously monitors the die temperature. In the event that the die temperature exceeds the thermal trip point, the device will be latched off until either the input supply voltage or enable is cycled. Layout Recommendation Where Vg is the supply voltage applied to the switch control circuit, Ri is the resistance between COM and DRN or SRC including the internal MOSFET rDS(ON), the trace resistance and the resistor inserted, RL is the load resistance of the switch control circuit, and CL is the load capacitance of the switch control circuit. In the Typical Application Circuit, R8, R9 and C8 give the bias to DRN based on the following equation: V ON • R 9 + A VDD • R 8 V DRN = -----------------------------------------------------------R8 + R9 and R10 can be adjusted to adjust the slew rate. Op Amps The EL7640A, EL7641A and EL7642A have 1, 3 and 5 amplifiers respectively. The op amps are typically used to drive the TFT-LCD backplane (VCOM) or the gammacorrection divider string. They feature rail-to-rail input and output capability, they are unity gain stable, and have low power consumption (typical 600µA per amplifier). The EL7640A, EL7641A and EL7642A have a –3dB bandwidth of 12MHz while maintaining a 10V/µs slew rate. Short Circuit Current Limit The EL7640A, EL7641A and EL7642A will limit the short circuit current to ±180mA if the output is directly shorted to the positive or the negative supply. If an output is shorted for a long time, the junction temperature will trigger the Over Temperature Protection limit and hence the part will shut down. 17 The device’s performance including efficiency, output noise, transient response and control loop stability is dramatically affected by the PCB layout. PCB layout is critical, especially at high switching frequency. There are some general guidelines for layout: 1. Place the external power components (the input capacitors, output capacitors, boost inductor and output diodes, etc.) in close proximity to the device. Traces to these components should be kept as short and wide as possible to minimize parasitic inductance and resistance. 2. Place VREF and VDD bypass capacitors close to the pins. 3. Reduce the loop with large AC amplitudes and fast slew rate. 4. The feedback network should sense the output voltage directly from the point of load, and be as far away from LX node as possible. 5. The power ground (PGND) and signal ground (SGND) pins should be connected at only one point. 6. The exposed die plate, on the underneath of the package, should be soldered to an equivalent area of metal on the PCB. This contact area should have multiple via connections to the back of the PCB as well as connections to intermediate PCB layers, if available, to maximize thermal dissipation away from the IC. 7. To minimize the thermal resistance of the package when soldered to a multi-layer PCB, the amount of copper track and ground plane area connected to the exposed die plate should be maximized and spread out as far as possible from the IC. The bottom and top PCB areas especially should be maximized to allow thermal dissipation to the surrounding air. FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A 9. Minimize feedback input track lengths to avoid switching noise pick-up. 8. A signal ground plane, separate from the power ground plane and connected to the power ground pins only at the exposed die plate, should be used for ground return connections for feedback resistor networks (R1, R11, R41) and the VREF capacitor, C22, the CDELAY capacitor C7 and the integrator capacitor C23. A demo board is available to illustrate the proper layout implementation. Typical Application Circuit D11 0.1µF VCP D21 VCN D12 0.1µF 0.1µF 0.1µF VIN (2.6V-5.5V) AVDD (9V) D1 L1 6.8µH 10Ω 10µF C1 10µFx2 LX C2 IN FB 470nF R2 64.9kΩ R1 10.2kΩ PGND BOOST R7 OPEN C7 OPEN 180Ω COMP 2.2nF 700Ω GND VCN 0.1µF VNEG (-8V) DRVN Q21 R22 82kΩ NEG REG DRVP POS REG FBN FBP VCP 700Ω Q11 R12 182kΩ R11 9.76kΩ VON (24.5V) 470nF 10kΩ 470nF R21 0.1µF REF REF 0.1µF CONTROL INPUT SRC CTL COM SW CTL DEL 100nF DRN TO GATE DRIVER IC R10 1kΩ R8 68kΩ R9 1kΩ AVDD C8 0.1µF + OUT3 OP3 VGAMMA POS3 VGAMMA SET VMAIN AVDD NEG4 NEG5 VCOM FB3 VCOM FB4 OUT4 VCOM4 POS4 OP4 + + OUT5 OP5 VCOM3 POS5 VCOM SET3 VCOM SET4 NEG2 NEG1 VCOM FB1 VCOM FB2 OUT2 VCOM2 POS2 OP2 + + VCOM SET2 OUT1 OP1 VCOM1 POS1 VCOM SET1 AGND 18 FN6270.0 May 15, 2006 EL7640A, EL7641A, EL7642A QFN 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 19 FN6270.0 May 15, 2006