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| AQ8211 Ultra-Low Dropout 500mA Voltage Regulator with Enable Product Specification Revision 2.1 January 22, 2007 General Description The AQ8211 is an ultra-low dropout voltage regulator capable of delivering 500 mA to the load. It is adjustable and can set a precise voltage from 1.22V to 12V with two external resistors. The AQ8211 meets all specifications down to 1.22V output, unlike CMOS LDO's which loose performance with outputs below 2.25V. The enable pin provides a remote turn-off for low power consumption. It draws virtually zero current in shutdown mode and implements Sequential, Ratiometric, or Simultaneous sequencing schemes. This also allows for a separate bias connection from the pass transistor in order to achieve ultra low dropout from VIN to VOUT. Reverse current protection blocks current flowing from VOUT to VIN when the AQ8211 is disabled. No current flows. To assure accuracy over temperature, the heart of the AQ8211 is a self-correcting AcuRefTM bandgap reference. On-chip current limit and thermal shutdown with hysteresis protects against any combination of overload and ambient temperature that might cause the junction temperature to exceed safe limits. Applications * Graphic cards and PC motherboards * Cell Phones * DVD video player Replacement for: * LX8211 Features * Extended Temp Range -40C 125C * Low dropout voltage (350mV at 500 mA) * Enable pin implements sequencing * Reverse current protection * Featured in the very small SOT-23 * * * * * package Stable with low cost 1F capacitor Low ground current <100 A Thermal protection with hysteresis Short circuit protection RoHS compliant Typical Application www.acutechnology.com AQ8211 Acutechnology Semiconductor Inc. AQ8211 Pin Configuration Pin Descriptions Pin Name VIN Ground ENABLE Adjust VOUT Function + Unregulated Input Voltage, Collector of Pass Transistor - Ground Active high, ENABLE > (0.95V + VOUT), Chip bias circuit supply OFF low, ENABLE < 0.25V Adjust input. Connect to resistive feed back divider. Regulated Output Functional Block Diagram www.acutechnology.com 2 Rev. 2.1 January 22, 2006 Acutechnology Semiconductor Inc. AQ8211 Ordering Information Device AQ8211 AQ8211 AQ8211 AQ8211 Note: The Operating Tj -40C 125C -40C 125C -40C 125C -40C 125C %Tol 1.0 1.0 1.0 1.0 PKG Type SOT-23-5 SOT-23-5 SOT-23-5 SOT-23-5 VOUT 1.8V 2.5V 3.3V ADJ Wrap T&R T&R T&R T&R Ordering Number AQ8211AY-M5-18-TRL AQ8211AY-M5-25-TRL AQ8211AY-M5-33-TRL AQ8211AY-M5-AJ-TRL TRL parts are Lead Free and RoHS compliant. Absolute Maximum Ratings Stress greater than those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These stress ratings only, and functional operation of the device at these or any conditions beyond those indicated under recommended Operating Conditions is not implied. Exposure to "Absolute Maximum Rating" for extended periods may affect device reliability. Use of standard ESD handling precautions is required. Parameter Maximum VIN Maximum VENABLE Power Dissipation (Internally limited) Maximum Junction Temperature Operating Junction Temperature Range Storage Temperature Range Lead Temperature (Soldering, 4 sec.) SOT- 23-5 package 150 -40C 125C -65 to 150 300 C C C C Value 18 18 Units Volts Volts Thermal Management Thermal Resistance (Junction to Ambient) SOT-23-5 (minimum foot print) Typical Value 220 Typical Value 170 Units C/W Units C/W Thermal Resistance (Junction to Ambient) SOT-23-5 (Soldered to 1 in2 1 oz. copper PCB) www.acutechnology.com 3 Rev. 2.1 January 22, 2006 Acutechnology Semiconductor Inc. AQ8211 Electrical Specifications Electrical characteristics are guaranteed over the full temperature range -40C www.acutechnology.com 4 Rev. 2.1 January 22, 2006 Acutechnology Semiconductor Inc. AQ8211 Application Notes www.acutechnology.com 5 Rev. 2.1 January 22, 2006 Acutechnology Semiconductor Inc. AQ8211 Application Notes 1. Typical Application Notes: 1. Output voltage is 1.22V * (R1 +R2)/R2 2. Input and output capacitors should be located close to the device. 3. The AQ8211 will remain stable with C1 and C3 as low as 0.1 F and 1.0 F respectively. Overall transient performance is improved with increased capacitance and the addition of C2. 4. The output is fully enabled when Enable is 950 mV above the expected VOUT. EN may be driven by either a digital or analog signal to control either turn-on time or to give full control of risetime. 5. Enable, tied to any separate source >0.95V + VOUT, will insure Ultra-low drop out voltage (350mV@ 500mA) from VIN to VOUT. Or, Enable, tied to Vin will support a low drop out voltage (0.95V). 2. Stability An Enable capacitor is recommended. A 100nF capacitor is a suitable input bypass for almost all applications. A larger capacitor is also suitable depending on the cleanliness of the Enable source. A Vin Capacitor is also recommended. A 1F capacitor is a bypassing for almost all applications. A larger capacitor is also suitable depending on the cleanliness of the VIN source. The Output capacitor is critical in maintaining regular stability. The AQ8211 is stable with an output capacitor greater than 1F. Any increase of the output capacitor will merely improve the loop stability and the load transient response. Tantalum Capacitors exhibit the best stability over a wide range of loads and are recommended. 3. Output Voltage The AQ8211 meets all specifications down to 1.22V output. It does not suffer from performance degradation issues such as experienced with CMOS LDO's. Drop out voltage will be less than 350 mV at 500 mA load with the ENABLE pin held greater than 0.95V + Vout. www.acutechnology.com 6 Rev. 2.1 January 22, 2006 Acutechnology Semiconductor Inc. AQ8211 The AQ8211 develops a 1.22V reference voltage between the adjust pin terminal and ground. This voltage is applied across the resistor R2 to generate a constant current (I2). The current from the adjust terminal could introduce error to the output, but since it is very small (<0.5A) compared with the current I2 and very constant with line and load changes, the error can be ignored. The constant current I2 then flows through resistor R1 and sets the output voltage to the desired level. The AQ8211 regulates the voltage that appears between its output and ground pins or between its adjust and ground pins. In some cases, line resistances can introduce errors to the voltage across the load. To obtain the best load regulation a few precautions are needed. For example, it is important to minimize the line resistances to the load. So, the load itself should be tied directly to the output terminal on the positive side and directly to the ground terminal on the negative side. The best performance is obtained with the positive side of the resistor R1 tied near the load and with the ground side of the resistor R2 tied near the ground of the regulator. This will provide remote output sensing which will optimize regulation at the load. 4. Enable/Sequencing The AQ8211 provides an enable function. The EN pin has to be at least 950 mV higher than the output voltage for the device to be fully turned on. When the voltage of the EN pin is low the device is in shutdown mode and it will not draw any current from the VIN terminal. ENABLE OUT 0 FIG.2 ENABLE 0-5V, Output follows to 3.3V out (1V/div vertical, 200us/div horizontal) In addition the enable function includes a sequencing feature, because when the enable pin ramps in voltage the output voltage follows (it will be around 900 mV less than the enable voltage until it reaches the regulation voltage) as shown in Fig. 2 above. In applications where multiple regulated supply rails are required, it is often required that the relationship between the various supply voltages be controlled during start-up and shutdown. www.acutechnology.com 7 Rev. 2.1 January 22, 2006 Acutechnology Semiconductor Inc. AQ8211 To this end, the AQ8211 allows for an analog control of the output voltage via the ENABLE pin. This allows for sequential, ratio-metric and simultaneous sequencing schemes. 5. Protection Diodes Unlike older regulators, the AQ8211 requires no protection diodes between the ADJ pin and VOUT or from the VOUT to the VIN to prevent over-stressing the die. Internal resistors are limiting the internal current paths on the ADJ pin. Therefore, even with capacitors on the ADJ pin, no protection diode is needed to ensure device safety under short circuit conditions. External diodes between the VIN and VOUT are not usually needed. Only if high value output capacitors are used (> 1000uF) and the input is instantaneously shorted to ground, can damage occur. 6. Thermal Considerations When an integrated circuit operates with an appreciable current, its junction temperature is elevated. It is important to quantify its thermal limits in order to achieve acceptable performance and reliability. This limit is determined by summing the individual parts consisting of a series of temperature rises from the semiconductor junction to the operating environment. The heat generated at the device junction flows through the die to the die attach pad, through the lead frame to the surrounding case material, to the printed circuit board, and eventually to the ambient environment. The AQ8211 regulators have internal thermal shutdown to protect the device from overheating. Under all possible operating conditions, the junction temperature of the AQ8211 must be lower than 125C. A heatsink may be required depending on the maximum power dissipation and maximum ambient temperature of the application. To determine if a heatsink is needed, the power dissipated by the regulator, PD, must be calculated: PD= (Vc-VOUT) IL where the IL is the load current. The next parameter, which must be calculated, is the max. allowable temperature rise, T(max): T(max)=TJ(max)-TA(max) where TJ(max) is the maximum allowable junction temperature (125C), and TA(max) is the maximum ambient temperature, which will be encountered in the application. Using the calculated values for T(max) and PD, the maximum allowable value for the junction to ambient thermal resistance (JA) can be calculated: JA=T(max)/ PD If the maximum allowable value for JA is found to be greater than the junction to ambient thermal resistance for the package used, no heatsink is needed since the package alone will dissipate enough heat to satisfy these requirements. 7. Ultra low Dropout Operation The AQ8211 allows for ultra low dropout operation by connecting the pin ENABLE to >0.95V + Vout. This results in a dropout of 350 mV at 500 mA of load current, between Vin and VOUT. This feature is important when the supply voltage is dropping near the output regulated voltage. Furthermore if the voltage dropout is low, the internal power dissipation is also reduced and the thermal requirements of the device are less stringent. www.acutechnology.com 8 Rev. 2.1 January 22, 2006 Acutechnology Semiconductor Inc. AQ8211 Package Dimensions www.acutechnology.com 9 Rev. 2.1 January 22, 2006 Acutechnology Semiconductor Inc. AQ8211 Contact Information Acutechnology Semiconductor Inc. 3487 McKee Rd. Suite 52 San Jose CA , USA 95127 Disclaimer The information furnished by Acutechnology in this data sheet is believed to be accurate and reliable. However, Acutechnology assumes no responsibility for its use. Acutechnology reserves the right to change circuitry and specifications at any time without notification to the customer. TEL: FAX: website: (408) 259-2300 (408) 259-9160 www.acutechnology.com Life Support Policy Acutechnology Products are not designed or authorized for use as components in life support devices or systems where malfunction of a product can reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. AcuRef is a trademark of Acutechnology Semiconductor Inc www.acutechnology.com 10 Rev. 2.1 January 22, 2006 |
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