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1 19-295; Rev ; 8/1 High-Current VCOM Drive Buffer General Description The is a high-current operational transconductance amplifier. The is ideal for driving the backplane of an active matrix, dot inversion thin film transistor (TFT) liquid crystal display (LCD). The s high >5mA peak-current drive capability provides fast response to pulsed load conditions. The is stable from.47µf to an unlimited amount of output capacitance. The is available in the low-profile (1.1mm max) 5-pin Thin SOT23 package and fully specified over the -4 C to +85 C extended temperature range. Features Stable with.47µf to Unlimited Amount of Output Capacitance Over 5mA Peak Drive Current Excellent Settling Characteristics with Capacitive Load +4.5V to +13V Input Supply.45mA Quiescent Current Thermal Fault Protection Thin SOT23-5 Package (1.1mm max) Notebook LCD Panels Monitor LCD Panels Applications Ordering Information TOP PART TEMP. RANGE PIN- PACKAGE M ARK EZK -4 C to +85 C 5 Thin SOT23-5* ADQL *Requires a special solder temperature profile described in the Absolute Maximum Ratings section. Typical Operating Circuit Pin Configuration TOP VIEW V REF FB+ OUT V O OUT GND 1 5 FB- 2 FB- GND 3 4 FB+ THIN SOT23-5 Maxim Integrated Products 1 For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at , or visit Maxim s website at

2 ABSOLUTE MAXIMUM RATINGS to GND...-.3V to +14V FB-, FB+, OUT to GND...-.3V to ( +.3V) Continuous Power Dissipation (T A = +7 C) 5-Pin Thin SOT23 (derate 7.1mW C above +7 C)...727mW Operating Temperature Range...-4 C to +85 C Junction Temperature C Storage Temperature Range C to +15 C This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device can be exposed to during board level solder attach and rework. Maxim recommends the use of the solder profiles recommended in the industry-standard specification, JEDEC 2A, paragraph 7.6, Table 3 for IR/VPR and convection reflow processes. Preheating, per this standard, is required. Hand or wave soldering is not recommended. Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS ( = 1V, FB- = OUT, V FB+ = 5V, C OUT =.47µF, T A = -4 C to +85 C, unless otherwise noted. Typical values are at T A = +25 C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Input Supply Range V Supply Current I CC 45 9 µa Input Offset Voltage V OS V FB+ = +5V, no load -5 5 mv Input Bias Current I BIAS -1 1 na Input Offset Current I OS +1.2V < V CM < +8.8V -1 1 na Common-Mode Input Range V CM V OS < 1mV over CMR 1.2 Power-Supply Rejection Ratio PSRR +4.5V < < +13V, V FB+ = +2.25V 7 Common-Mode Rejection Ratio CMRR +1.2V < V CM < +8.8V 7 Gain-Bandwidth Product GBW Small signal 1/6πC L Hz Small signal (±1mV overdrive).3 Transconductance g m Large signal (±3mV overdrive) 1 ±1mV overdrive, T A = -4 C to +85 C ±175 ±55 Output Current Drive I OUT V OUT = 3V or 7V T A = C to +85 C ±25 Thermal Shutdown 17 C Thermal Shutdown Hysteresis 15 C Note 1: The is 1% production tested at T A = +25 C. Specifications over temperature are guaranteed by design V V db S ma SUPPLY VOLTAGE 3 REFERENCE 4 VOLTAGE V X R L CL Figure 1. Load Transient Test Circuit 2

3 Typical Operating Characteristics ( = 1V, C OUT = 1µF, V CM = 5V, T A = +25 C, unless otherwise noted.) VOS (mv) INPUT OFFSET VOLTAGE DEVIATION vs. SUPPLY VOLTAGE V CM = / (V) toc1 VOS (mv) INPUT OFFSET VOLTAGE DEVIATION vs. TEMPERATURE = 1V V CM = / TEMPERATURE ( C) toc2 TRANSCONDUCTANCE (S) TRANSCONDUCTANCE vs. OUTPUT CURRENT T A = -4 C T A = +25 C T A = +85 C OUTPUT CURRENT (ma) toc C SUPPLY CURRENT vs. SUPPLY VOLTAGE +25 C toc NO-LOAD SUPPLY CURRENT vs. TEMPERATURE toc5 I OUT 5mA/div LOAD TRANSIENT ±1V toc6 SUPPLY CURRENT (ma) C SUPPLY CURRENT (ma) V OUT 2mV/div AC-COUPLED SUPPLY VOLTAGE (V) TEMPERATURE ( C) V X 1V/div R L = 2.5Ω, C L = 1nF, FIGURE 1 4µs/div SHORT-CIRCUIT WAVEFORMS I CC 5mA/div toc7 I OUT 5mA/div V OUT 2ms/div 3

4 Typical Operating Characteristics (continued) ( = 1V, C OUT = 1µF, V CM = 5V, T A = +25 C, unless otherwise noted.) I CC 5mA/div STARTUP WAVEFORM WITHOUT SOFT-START SUPPLY CAPACITOR CHARGING CURRENT toc8 I CC 5mA/div STARTUP WAVEFORMS WITH SOFT-START toc9 1V/div 1V/div V FB+ V FB+ V OUT C OUT =.47µF V OUT C OUT =.47µF 5µs/div 5µs/div Pin Description PIN NAME DESCRIPTION 1 OUT Output of Buffer Amplifier. Requires a minimum.47µf ceramic filter capacitor to GND. Place the capacitor close to OUT. 2 GND Ground Voltage-Supply Input. Bypass to GND with a.47µf capacitor close to the pin. Use the output 3 capacitor of the preceding voltage regulator as the additional filter capacitor. 4 FB+ Noninverting Input to Buffer Amplifier 5 FB- Inverting Input to Buffer Amplifier. Feedback must be taken from the output filter capacitor terminal. Detailed Description The operational transconductance amplifier (OTA) provides high-current output that is ideal for driving capacitive loads such as the backplane of a TFT LCD panel. The positive feedback input, FB+, allows common-mode biasing to mid-supply, or other VCOM voltage. The unity-gain bandwidth is GBW = g m /C OUT where g m is the amplifier s transconductance. Transconductance is the ratio of the output current to the input voltage. The gain of the amplifier is dependent upon the load. The requires only a small.47µf ceramic output capacitor for stability. The bandwidth is inversely proportional to the output capacitor, so large capacitive loads improve stability; however, lower bandwidth decreases the buffer s transient response time. To improve the transient response times, the s transconductance increases as the output current increases (see Typical Operating Characteristics). Applications Information Output Filter Capacitor The requires a minimum of.47µf output capacitance placed close to OUT. To ensure buffer stability, the output capacitor ESR must be 5mΩ or lower. Ceramic capacitors are an excellent choice. Input Bypass Capacitor The requires a.47µf input bypass capacitor (C2) close to the supply input (see Figure 2). Place the close to the preceding voltage regulator output capacitor so that the shares the same capacitor (C1). Minimize trace length and use wide 4

5 V IN SWITCHING REGULATOR C1 LINEAR REGULATOR SOURCE DRIVER VOLTAGE PC BOARD PARASITICS C2.47µF OPTIONAL REFERENCE VOLTAGE CIRCUIT µF TO LCD BACKPLANE GAMMA CORRECTION REFERENCE VOLTAGE Figure 2. Typical TFT LCD Backplane Drive Circuit traces between the voltage regulator output and the input to reduce PC board parasitics (inductance, resistance, and capacitance), which can cause undesired ringing. Voltage Reference The reference voltage for the input can be produced using the output of a linear regulator. The linear regulator will reject the ripple voltage produced by the source drivers (see Figure 2). The output of this linear regulator can also be used for the gamma correction reference voltage. TRANSISTOR COUNT: 121 PROCESS: BiCMOS Chip Information 5

6 Package Information 6

7 Package Information (continued) Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. Maxim Integrated Products, 12 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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