9-2485; Rev 1; 10/02 Triple-Output TFT LCD Power Supply with Fault Protection The MAX1889 provides the three regulated output voltages required for active matrix, thin-film transistor liquid crystal displays (TFT LCDs). It combines a high-performance step-up regulator with two linear-regulator controllers and multiple levels of protection circuitry for a complete power-supply system.
MAX1889 Triple-Output TFT LCD Power Supply with Fault Protection ABSOLUTE MAXIMUM RATINGS IN, SHDN, OCN, OCP, FB, FBP, FBN, FREQ to GND ...............................-0.3V to +6V PGND to GND.....................................................................±0.3V LX to PGND ............................................................-0.3V to +14V DRVP to GND .........................................................-0.3V to +30V REF, GATE, TGND to GND ..........................-0.3V to (VIN + 0.
Triple-Output TFT LCD Power Supply with Fault Protection (VIN = 3V, SHDN = IN, CREF = 0.22µF, PGND = GND, TA = 0°C to +85°C. Typical values are at TA = +25°C, unless otherwise noted.) PARAMETER SYMBOL FBP Line Regulation CONDITIONS Bandwidth (Note 3) DRVP Sink Current MIN IDRVP = 0.2mA, VIN = 2.7V to 5.5V IDRVP DRVP Off-Leakage Current VFBP = 1.1V, VDRVP = 10V TYP MAX 1 mV 200 kHz 5 VFBP = 1.1V, VDRVP = 28V UNITS mA 0.
MAX1889 Triple-Output TFT LCD Power Supply with Fault Protection ELECTRICAL CHARACTERISTICS (VIN = 3V, SHDN = IN, CREF = 0.22µF, PGND = GND, TA = -40°C to +85°C.) (Note 4) PARAMETER IN Supply Range IN ULVO Threshold IN Quiescent Current SYMBOL VIN VUVLO IIN IN Shutdown Current REF Output Voltage CONDITIONS VREF MIN MAX UNITS V 2.7 5.5 VIN rising 2.55 2.85 VIN falling 2.2 2.5 V VFB = VFBP = 1.5V, VFBN = 0V (Note 1) 1.0 mA V SHDN = 0, VIN = 5V 1.0 µA 1.269 V -2µA < IREF < 50µA 1.
Triple-Output TFT LCD Power Supply with Fault Protection (VIN = 3V, SHDN = IN, CREF = 0.22µF, PGND = GND, TA = -40°C to +85°C.) (Note 4) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.3 x VIN V LOGIC SIGNAL (FREQ) Input Low Voltage 0.15 x VIN typical hysteresis Input High Voltage 0.7 x VIN Input Current V IFREQ 1 µA -5 +5 mV -50 +50 nA 0.
Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = +3.3V, VMAIN = +9V, VPL = +20V, VNL = -7V, SHDN = FREQ = IN, PGND = GND, TA = +25°C, unless otherwise noted.) STEP-UP REGULATOR OUTPUT VOLTAGE vs. LOAD CURRENT (VMAIN = 13V) MAX1889 toc06 1100 MAX1889 toc05 13.0 STEP-UP REGULATOR LOAD-TRANSIENT RESPONSE (0 TO 200mA) STEP-UP REGULATOR SWITCHING FREQUENCY vs. INPUT VOLTAGE MAX1889 toc04 13.
Triple-Output TFT LCD Power Supply with Fault Protection (Circuit of Figure 1, VIN = +3.3V, VMAIN = +9V, VPL = +20V, VNL = -7V, SHDN = FREQ = IN, PGND = GND, TA = +25°C, unless otherwise noted.
Typical Operating Characteristics (continued) (Circuit of Figure 1, VIN = +3.3V, VMAIN = +9V, VPL = +20V, VNL = -7V, SHDN = FREQ = IN, PGND = GND, TA = +25°C, unless otherwise noted.) 85 80 75 70 65 60 100 95 90 EFFICIENCY (%) -8.3 OUTPUT VOLTAGE (V) 90 NEGATIVE CHARGE-PUMP INCREMENTAL EFFICIENCY vs. LOAD CURRENT MAX1889 toc17 95 -8.4 -8.5 VIN = 3.3V IMAIN = 200mA 50 1 10 EFF = (VOUT ✕ IOUT) / (PIN(LOAD) - PIN(NOLOAD)) 55 -8.7 50 0.1 1 10 0.
Triple-Output TFT LCD Power Supply with Fault Protection (Circuit of Figure 1, VIN = +3.3V, VMAIN = +9V, VPL = +20V, VNL = -7V, SHDN = FREQ = IN, PGND = GND, TA = +25°C, unless otherwise noted.) OVERCURRENT PROTECTION RESPONSE TO OVERLOAD DURING STARTUP NEGATIVE LINEAR-REGULATOR LOAD-TRANSIENT RESPONSE MAX1889 toc23 MAX1889 toc22 A MAX1889 toc24 5V 0 5V -6.
Triple-Output TFT LCD Power Supply with Fault Protection MAX1889 Pin Description PIN 10 NAME FUNCTION 1 SHDN Active-Low Shutdown Control Input. Pull SHDN below the 0.4V logic-low level to turn off all sections of the device and pull the GATE pin high. Pull SHDN above the 1.6V logic-high level to enable the device. Do not leave SHDN floating. 2 PGND Power Ground. PGND is the source of the N-channel power MOSFET. Connect PGND to the analog ground (GND) at the device’s pins. 3 GND Analog Ground.
Triple-Output TFT LCD Power Supply with Fault Protection P1 C2 3.3µF 6.3V R2 51.1kΩ 1% R1 10Ω C3 3.3µF 6.3V 13 14 C4 4.7µF 10V C5 4.7µF 10V C6 4.7µF 10V R17 1MΩ 11 OCN 15 D1 R15 43.2kΩ R16 150kΩ 1% 1% C22 C23 1000pF 100pF C1 0.47µF VMAIN 9V LX L1 4.7µH R6 75kΩ 1% LX GATE FB C16 0.01µF 5 R7 12.1kΩ 1% OCP R18 10kΩ C17 220pF R3 150kΩ 1% 16 IN TGND R5 1MΩ 12 R4 1MΩ 1 10 REF SHDN REF C7 0.22µF FREQ MAX1889 GND LX PGND C8 0.
MAX1889 Triple-Output TFT LCD Power Supply with Fault Protection VIN REF FREQ SHDN IN REFERENCE 1.25V REF EN EN GATE GATE DRIVER REFOK + + OCN - OCP 2.70V 2.35V + - OVERCURRENT COMPARATOR EN UVLO COMPARATOR OSCILLATOR OSC SLOPE_COMP VMAIN ONP ONMN SEQUENCE AND FAULT DETECTOR LX FAULTM FB MAIN STEP-UP WITH SOFT-START PGND EN THERMAL SHUTDOWN SSDONE DRVP + - VPL ANALOG GAIN BLOCK FBP + FAULT COMPARATOR + - + + - - 0.
Triple-Output TFT LCD Power Supply with Fault Protection DESIGNATION DESCRIPTION C2, C3 3.3µF, 6.3V X5R ceramic capacitors (0805) Taiyo Yuden JMK212BJ335MG C4, C5, C6 4.7µF, 10V X7R ceramic capacitors (1210) Taiyo Yuden LMK352BJ475MF 1.0A, 30V Schottky diode (S-flat) Toshiba CRS02 D1 D2, D3, D4 200mA, 25V dual-series Schottky diodes (SOT23) Fairchild BAT54S D5 250mA, 75V switching diode (SOT23) Central Semiconductor CMPD914 L1 6.8µH, 1.3A inductor Coilcraft LPO2506IB-682 P1 2.
MAX1889 Triple-Output TFT LCD Power Supply with Fault Protection Depending on the input-to-output voltage ratio, the regulator controls the output voltage and the power delivered to the output by modulating the duty cycle (D) of the power MOSFET in each switching cycle. The duty cycle of the MOSFET is approximated by: inductor. The inductor current ramps up linearly, storing energy in a magnetic field.
Triple-Output TFT LCD Power Supply with Fault Protection To enable the regulator using an external control signal, apply the logic-control input in series with a signal diode (Figure 1). Additional delay can be added with external circuitry. Note that the voltage rating of the DRVP output is 28V. If higher voltages are present, an external cascode NPN transistor should be used with the emitter connected to DRVP, the base to VMAIN, and the collector to the base of the PNP.
MAX1889 Triple-Output TFT LCD Power Supply with Fault Protection Power-Up Sequencing and Inrush Current Control Once SHDN is high, the MAX1889 enables the UVLO circuitry and compares the input voltage with the UVLO rising threshold (2.7V, typ). If the input voltage exceeds the UVLO rising threshold, the reference is enabled. When the reference voltage ramps up above 1.05V (typ), the MAX1889 enables the oscillator and turns on the external P-channel MOSFET P1 (Figure 1) by pulling GATE low.
Triple-Output TFT LCD Power Supply with Fault Protection V IN(TYP) L= V MAIN 2 V MAIN - VIN(TYP) 1 η IMAIN(MAX)fOSC LIR where η is the efficiency, fOSC is the oscillator frequency (see the Electrical Characteristics), and IMAIN includes the primary load current and the input supply currents for the charge pumps. Considering the typical application circuit, the maximum average DC load current (IMAIN(MAX)) is 200mA with a 9V output.
MAX1889 Triple-Output TFT LCD Power Supply with Fault Protection Therefore, the dominant pole and the RHP zero determine the loop response of the step-up regulator. The frequency of the dominant pole is: 1 fP _ DOMINANT = 2πRLC zero-pole pair to the loop by connecting an RC network from the FB pin to the main output (lead compensation). The frequencies of the pole and zero for the lag compensation are: fP _ FB = where RL is the load resistance and C is the output capacitor.
Triple-Output TFT LCD Power Supply with Fault Protection Rectifier Diode The MAX1889’s high switching frequency demands a high-speed rectifier. Schottky diodes are recommended for most applications because of their fast recovery time and low forward voltage. In general, a 1A Schottky diode complements the internal MOSFET well. Input P-Channel MOSFET Select the input P-channel MOSFET based on the current rating, voltage rating, gate threshold, and on-resistance.
MAX1889 Triple-Output TFT LCD Power Supply with Fault Protection If the junction temperature is +100°C, the maximum onstate resistance overtemperature is: [ ] RDS(MAX) = 70mΩ × 1 + 0.005 × (100 - 25) = 100mΩ For given R1 and R2 values, the ideal ratio of R3/R4 can be determined: R3 R1+ R2 VIN - IPEAK(MAX) × RDS(MAX) = × -1 R4 R2 VIN ITH _ TYP = The following example shows how to apply the above equations in the design. If 1% resistors are used, then ε = 0.01.
Triple-Output TFT LCD Power Supply with Fault Protection NNEG = -VNL + VDOPOUT VMAIN - 2 × VD where NNEG is the number of negative charge-pump stages, V NL is the negative linear-regulator output, VMAIN is the main step-up regulator output, VD is the forward voltage drop of the charge-pump diode, and VDROPOUT is the dropout margin for the linear regulator. Use VDROPOUT = 2V.
MAX1889 Triple-Output TFT LCD Power Supply with Fault Protection The transistor’s current gain limits the guaranteed maximum output current to: V ILOAD(MAX) = IDRV - BE βMIN RBE where IDRV is the minimum base-drive current, and RBE is the pullup resistor connected between the transistor’s base and emitter. Furthermore, the transistor’s current gain increases the linear regulator’s DC loop gain (see the Stability Requirements section), so excessive gain destabilizes the output.
Triple-Output TFT LCD Power Supply with Fault Protection Stability Requirements The MAX1889 linear-regulator controllers use an internal transconductance amplifier to drive an external pass transistor. The transconductance amplifier, the pass transistor, the base-emitter resistor, and the output capacitor determine the loop stability. If the output capacitor and pass transistor are not properly selected, the linear regulator can be unstable.
MAX1889 Triple-Output TFT LCD Power Supply with Fault Protection Applications Information PC Board Layout Careful PC board layout is extremely important for proper operation. Use the following guidelines for good PC board layout: 1) Minimize the area of high-current loops by placing the input capacitors, inductor, output diode, and output capacitors less than 0.2in (5mm) from the LX and PGND pins. Connect these components with traces as wide as possible. Avoid using vias in the high-current paths.
Triple-Output TFT LCD Power Supply with Fault Protection Operation with Output Voltage >13V The maximum output voltage of the step-up regulator is 13V, which is limited by the absolute maximum rating of the internal power MOSFET. To achieve higher output voltage, an external N-channel MOSFET can be cascoded with the internal FET (Figure 9). Since the gate of the external FET is biased from the input supply, use a logic-level FET to ensure that the FET is fully enhanced at the minimum input voltage.
MAX1889 Triple-Output TFT LCD Power Supply with Fault Protection VP VN VIN VMAIN +9V LX FB STEP-UP REGULATOR VN PGND DRVN FBN VNL -7V NEGATIVE REGULATOR MAX1889 VP DRVP REF R1 REF VN R2 C POSITIVE REGULATOR FBP VPL +20V GND VPL Figure 10. Controlling Power-Up Sequence with External Delay If the voltage difference is less than 400mV, then the emitter of the PNP should be connected to a high supply voltage. The V P output has two charge-pump stages added to VMAIN.
Triple-Output TFT LCD Power Supply with Fault Protection MAX1889 VP VN VMAIN 9V VIN 3.3V OR 5V LX FB GATE IN OCP SWITCH CONTROL STEP-UP REGULATOR PGND OCN MAX1889 REF REF GND Figure 11.
MAX1889 Triple-Output TFT LCD Power Supply with Fault Protection VP VN VIN VMAIN +9V LX FB STEP-UP REGULATOR VN PGND DRVN VNL -7V FBN NEGATIVE REGULATOR MAX1889 DRVP REF REF POSITIVE REGULATOR FBP VGAMMA +8.9V GND Figure 12.
Triple-Output TFT LCD Power Supply with Fault Protection 32L QFN.EPS ______________________________________________________________________________________ 29 MAX1889 Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.
MAX1889 Triple-Output TFT LCD Power Supply with Fault Protection Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.
Triple-Output TFT LCD Power Supply with Fault Protection b CL 0.10 M C A B D2/2 D/2 PIN # 1 I.D. QFN THIN.EPS D2 0.15 C A D k 0.15 C B PIN # 1 I.D. 0.35x45 E/2 E2/2 CL (NE-1) X e E E2 k L DETAIL A e (ND-1) X e CL CL L L e e 0.10 C A C 0.08 C A1 A3 PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE 16, 20, 28, 32L, QFN THIN, 5x5x0.8 mm APPROVAL DOCUMENT CONTROL NO. REV.
MAX1889 Triple-Output TFT LCD Power Supply with Fault Protection Package Information (continued) (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) COMMON DIMENSIONS EXPOSED PAD VARIATIONS NOTES: 1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994. 2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES. 3. N IS THE TOTAL NUMBER OF TERMINALS. 4.