AS1331_07 AMSCO
Document overview
- Manufacturer or author: Provided By digicamel.com
- PDF pages: 17
Technical content
The technical content of this austriamicrosystems datasheet is still valid. Contact information: Headquarters: ams AG Tobelbaderstrasse 30
8141 Unterpremstaetten, Austria
Tel: +43 (0) 3136 500 0 e-Mail: ams_sales@ams.com Please visit our website at www.ams.com
1 General Description
or equal to the output voltage. as well as single cell Li-Ion battery applications. conversion efficiency is provided. ackage with fixed and adjustable output voltage.
2 Key Features
3 Applications
NiMH or single cell Li battery powered products. Figure 1. AS1331 - Typical Application Diagram
4 Pin Assignments
Figure 2. Pin Assignments (Top View) Table 1. Pin Descriptions VOUT 1 Output of the Buck/Boost Converter. PGND 3 Power Ground. Both GND pins must be connected. Enable Pin. Logic controlled shutdown input. 0 = Shutdown; quiescent current <1µA. LBI 7 Low Battery Comperator Input. 1.25V Threshold. May not be left floating. If connected to GND LBO is working as Output Power okay. voltage on LBI is less than 1.25V. GND 9 Ground. Both GND pins must be connected. Note: F or the fixed Output Voltage Version contact this pin to V OUT. ground connection between GND and PGND.
5 Absolute Maximum Ratings
Table 2. Absolute Maximum Ratings State Surface Mount Devices”. packages is matte tin (100% Sn).
6 Electrical Characteristics
Table 3. Electrical Characteristics
SQC (Statistical Quality Control) methods.
- If the input voltage falls below this value during normal operation the device goes in startup mode.
- The regulator is in startup mode until this voltage is reached. Caution: Do not apply full load current until the
- LBO goes low in startup mode as well as during normal operation if:
1) The voltage at the LBI pin is below LBI threshold. 2) The voltage at the LBI pin is below 0.1V and VOUT is below 92.5% of its nominal value.
7 Typical Operating Characteristics
Circuit of Figure 24 on page 12, VIN = 2.4V, VOUT = 3.3V, TAMB = +25°C, unless otherwise specified. Figure 7. IOUT max vs. Input Voltage Figure 8. Sleep Currents vs. Input Voltage
8 Detailed Description
Power Save Mode puts the device into “sleep mode” when VOUT is above its programmed reference threshold. again when VOUT drops below the reference threshold and the output capacitor is charged again. capacitor, the load current, and the comparator hysteresis (~1%). Figure 23. AS1331 - Block Diagram - Fixed Output Voltage difference between VIN and VOUT the inductor current raises, falls or stays constant. VIN > VOUT: The inductor current is going up to 600mA. VIN ~ VOUT: The device stops after 2µs. VIN < VOUT: The inductor current falls down to 0mA. and SW D are closed until the inductor current is 600mA. => SW B+SW D => SW A+SW D...) are never used. reaches approximately 2.15V. The inductor current is controlled by an alternate algorithm during start-up. Note: Do not apply loads >1mA until VOUT = 2.3V is reached.
www.austriamicrosystems.com/DC-DC_Buck-Boost/AS1331 Revision 1.04 11 - 16 AS1331 Datasheet - Detailed Description Other AS1331 Features Shutdown The part is in shutdown mode while the voltage at pin EN is below 0.4V and is active when the voltage is higher than 1.4V. Note: EN can be driven above VIN or VOUT, as long as it is limited to less than 5.5V. Output Disconnect and Inrush Limiting During shutdown VOUT is going to 0V so that no current from the input source is running thru the device. The inrush current is also limited at turn-on mode to minimize the surge currents seen by the input supply. These features of the AS1331 are realized by opening both P-channel MOSFETs of the rectifiers, allowing a true output disconnect. Power-OK and Low-Battery-Detect Functionality LBO goes low in startup mode as well as during normal operation if: - The voltage at the LBI pin is below LBI threshold (1.25V). This can be used to monitor the battery voltage. - LBI pin is connected to GND and VOUT is below 92.5% of its nominal value. LBO works as a power-OK signal in this case. The LBI pin can be connected to a resistive-divider to monitor a particular definable voltage and compare it with a 25V internal reference. If LBI is connected to GND an inte rnal resistive-divider is activated and connected to the output. Therefore, the Power-OK functionality can be realised with no additional external components. The Power-OK feature is not active during shutdown and provides a power-on-reset function that can operate down to VIN = 1.8V. A capacitor to GND may be added to generate a power-on-reset delay. To obtain a logic-level output, connect a pull-up resistor from pin LBO to pin VOUT. Larger values for this resistor will help to minimize current consumption; a 100kΩ resistor is perfect for most applications (see Figure 25 on page 12). For the circuit shown in the left of Figure 24 on page 12, the input bias current into LBI is very low, permitting large- value resistor-divider networks while maintaining accuracy. Place the resistor-divider network as close to the device as po ssible. Use a defined resistor for R5 and then calculate R4 as: Where: VLBI (the internal sense reference voltage) is 1.25V. In case of the LBI pin is connected to GND, an internal re sist or-devider network is activated and compares the output voltage with a 92.5% voltage threshold. For this particular Power-OK application, no external resistive components are necessary. Thermal Shutdown To prevent the AS1331 from short-term misuse and overload conditions the chip includes a thermal overload protection. To block the normal operation mode all switches will be turned off. The device is in thermal shutdown when the junction temperature exceeds 145°C. To resume the normal operation the temperature has to drop below 135°C. A good thermal path has to be provided to dissipate the heat generated within the package. Otherwise it’s not possible t o operate the AS1331 at its useable maximal power. To dissipate as much heat as possible away from the package into a copper plane with as much area as possible, it’s recommended to use multiple vias in the printed circuit board. It’s also recommended to solder the Exposed Pad (pin 11) to the GND plane. Note: Continuing operation in thermal overload conditions may damage the device and is considered bad practice. (EQ 1)R4 R5 VIN VLBI ⎛⎞⋅= ams AG Technical content still valid
9 Application Information
allow the use of low value, low profile inductors and tiny external ceramic capacitors. current without saturating. A 6.8µH inductor with a >600mA current rating and <400mΩ DCR is recommended. capacitors for input and output capacitor selection. Table 4. Recommended Inductors Table 5. Recommended Input Capacitor Table 6. Recommended Output Capacitor
The device is available in a 10-pin 3x3mm TDFN package. Figure 26. 10-pin 3x3mm TDFN package Diagram
- Figure 26 is shown for illustration only.
- All dimensions are in millimeters, angle is in degrees.
- Dimensioning and tolerancing conform to ASME Y14.5M-1994.
- N is the total number of terminals.
- Terminal #1 identifier and terminal numbering convention shall conform to JESD 95-1 SPP-012. Details of ter-
her a mold, embedded metal or mark feature.
- Dimension b applies to metallized terminal and is me asured between 0.15 and 0.30mm from terminal tip.
- ND refers to the maximum number of terminals on D side.
- Unilateral coplanarity zone applies to the exposed heat sink slug as well as the terminals.
Table 7. 10-pin 3x3mm TDFN package Dimensions
The device is available as the standard products shown in Table 8. Note: All products are RoHS compliant and Pb-free. Table 8. Ordering Information
www.austriamicrosystems.com/DC-DC_Buck-Boost/AS1331 Revision 1.04 16 - 16 AS1331 Datasheet Copyrights Copyright © 1997-2010, austriamicrosystems AG, Tobelbaderstrasse 30, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered ®. All rights reserved. The material herein may not be reproduced, adapted, merged, translated, stored, or used without the prior written consent of the copyright owner. All products and companies mentioned are trademarks or reg istered trademarks of their respective companies. Disclaimer Devices sold by austriamicrosystems AG are covered by the warranty and patent indemnification provisions appearing in its Term of Sale. austriamicrosystems AG makes no warranty, express, statutory, implied, or by description regarding the information set forth herein or regarding the freedom of the described devices from patent infringement. austriamicrosystems AG reserves the right to change specifications and prices at any time and without notice. Therefore, prior to designing this product into a system, it is necessary to check with austriamicrosystems AG for current information. This product is intended for use in normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, or high reliability applications, such as military, medical life-support or life-sustaining equipment are specifically not recommended without additional processing by austriamicrosystems AG for each application. For shipments of less than 100 parts the manufacturing flow might show deviations from the standard production flow, such as test flow or test location. The information furnished here by austriamicrosystems AG is bel ieved to be correct and accurate. However, austriamicrosystems AG shall not be liable to recipient or any third party for any damages, including but not limited to pe rsonal injury, property damage, loss of profits, loss of use, interruption of business or indirect, special, incidental or consequential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the tech- nical data herein. No obligation or liability to recipient or any third party shall arise or flow out of austriam icrosystems AG rendering of technical or other services. Contact Information Headquarters austriamicrosystems AG Tobelbaderstrasse 30 A-8141 Unterpremstaetten, Austria Tel: +43 (0) 3136 500 0 Fax: +43 (0) 3136 525 01 For Sales Offices, Distributors and Representatives, please visit: http://www.austriamicrosystems.com/contact ams AG Technical content still valid