AS1322 AMSCO | Alldatasheet
Document overview
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Technical content
1 General Description
one NMOS switch and one PMOS synchronous rectifier. The AS1322 is available in a 6-pin TSOT-23 package.
2 Key Features
3 Applications
Table 1. Standard Products Figure 1. Typical Application Diagram – Single Cell to 3.3V Synchronous Boost Converter
4 Pin Assignments
Figure 2. Pin Assignments (Top View) Table 2. Pin Descriptions pin and the negative side of the output capacitor(s). Shutdown Pin. Logic controlled shutdown input. 1 = Normal operation, 1.2MHz typical operating frequency. Synchronous Rectifier. Bias is derived from VOUT when VOUT exceeds VIN.
6 VIN
5 VOUT
4 SHDNN
5 Absolute Maximum Ratings
Table 3. Absolute Maximum Ratings State Surface Mount Devices”. packages is matte tin (100% Sn).
6 Electrical Characteristics
Table 4. Electrical Characteristics
- Minimum VIN operation after start-up is only limited by the battery’s ability to provide the necessary power as it
enters a deeply discharged state.
- Specification is guaranteed by design and not 100% production tested.
- IQPWS is measured at VOUT. Multiply this value by VOUT/VIN to get the equivalent input (battery) current.
7 Typical Operating Characteristics
Figure 3. Powersave mode threshold vs. VIN, Figure 4. Efficiency vs. Output Current, Figure 5. Output Voltage vs. Temperature; Figu re 6. Output Voltage vs. Battery Voltage; Figure 7. Startup Voltage vs. Output Current; Fig ure 8. Output Current vs. Battery Voltage;
8 Detailed Description
internal NMOS and PMOS switches, the devices maintain high-efficiency from light to heavy loads. falls below a factory programmed threshold (see Figure 3 on page 5). low-frequency VOUT ripple at the expense of light load efficiency. Figure 15. Block Diagram allowing the devices to start up into an output load. supply sufficient energy to the output.
www.austriamicrosystems.com Revision 1.03 8 - 17 AS1322 austria micro systems Data Sheet Low-Noise Fixed-Frequency Operation Oscillator The AS1322 switching frequency is internally fixed at 1.2MHz allowing the use of very small external components. Error Amplifier The integrated error amplifier is an internally compensated trans-conductance (gm) type (current output). The internal 1.23V reference voltage is compared to the voltage at pin FB to generate an error signal at the output of the error amplifier. A voltage divider from VOUT to GND programs the output voltage from 2.5 to 5V via pin FB as: VOUT = 1.23V(1 + (R1/R2)) (EQ 1) Current Sensing A signal representing the internal NMOS-switch current is summed with the slope compensator. The summed signal is compared to the error amplifier output to provide a peak current control command for the PWM. Peak switch current is limited to approximately 850mA independent of VIN or VOUT. Zero Current Comparator The zero current comparator monitors the inductor current to the output and shuts off the PMOS synchronous rectifier once this current drops to 20mA (approx.). This prevents the inductor current from reversing polarity and results in improved converter efficiency at light loads. Anti-Ringing Control Anti-ringing control circuitry prevents high-frequency ringing on pin SW as the inductor current approaches zero. This is accomplished by damping the resonant circuit formed by the inductor and the capacitance on pin SW (CSW). Powersave Operation (AS1322A) In light load conditions, the integrated powersave feature removes power from all circuitry not required to monitor VOUT. When VOUT has dropped approximately 1% from nominal, the AS1322A powers up and begins normal PWM operation. COUT (see Figure 15 on page 7) recharges, causing the AS1322A to re-enter powersave mode as long as the output load remains below the powersave threshold. The frequency of this intermittent PWM is proportional to load current; i.e., as the load current drops further below the powersave threshold, the AS1322A turns on less frequently. When the load current increases above the powersave threshold, the AS1322A will resume continuous, seamless PWM opera- tion. Notes: 1. An optional capacitor (CFF) between pins VOUT and FB in some applications can reduce VOUTp-p ripple and input quiescent current during powersave mode. Typical values for CFF range from 15 to 220pF. 2. In powersave mode the AS1322A draws only 30µA from the output capacitor(s), greatly improving converter effi- ciency.
9 Application Information
Figure 16. Single AA Cell to 3.3V Synchronous Boost Converter with Load Disconnect in Shutdown Figure 17. Single Lithium Cell to 5V, 250mA
external inductor (see Figure 15 on page 7). inductance above 10µH will increase size while providing negligible improvement in output current capability. which result in improved converter efficiency. Table 5. Recommended Inductors
Figure 20. Efficiency Comparison of Different Inductors, VIN = 1.5V, VOUT = 3.3V wide voltage and temperature ranges. input capacitor is sufficient for most applications. Larger values may be used without limitations. switch on. For VOUT < 4.5V a Schottky diode is optional, although using one will increase device efficiency by 2 to 3%. Note: Do not use ordinary rectifier diodes, since the slow recovery times will compromise efficiency. Table 6. Recommended Output Capacitor Table 7. Recommended Input Capacitor
! A large ground pin copper area will help to lower the device temperature. ! A multi-layer board with a separate ground plane is recommended. ! Traces carrying large currents should be direct. ! Trace area at pin FB should be as small as is practical. ! The lead-length to the battery should be as short as is practical. Figure 21. Recommended Single-Layer Component Placement
The device is available in a 6-pin TSOT-23 package. Figure 22. 6-pin TSOT-23 Package
- Dimensioning and tolerancing conform to ASME Y14.5M - 1994.
- Dimensions are in millimeters.
- Dimension D does not include mold flash, protrusions, or gate burrs. Mold flash, protrusions, and gate burrs shall
sion shall not exceed 0.15mm per side. Dimensions D and E1 are determined at datum H.
- The package top can be smaller than the package bottom. Dimensions D and E1 are determined at the outermost
mistmatches between the top of the package body and the bottom. D and E1 are determined at datum H.
- Datums A and B are to be determined at datum H.
www.austriamicrosystems.com Revision 1.03 15 - 17 AS1322 austria micro systems Data Sheet 6. These dimensions apply to the flat section of the lead between 0.08 and 0.15mm from the lead tip. 7. Dimension b does not include dambar protrusion. Allowable dambar protrusion shall be 0.08mm total in excess of the b dimension at the maximum material condition. The dambar cannot be located on the lower radius of the foot. Minimum space between the protrusion and an adjacent lead shall not be less than 0.77mm. Symbol Min Typ Max Notes A1 . 0 0 A1 0.01 0.05 0.10 A2 0.84 0.87 0.90 b 0.30 0.45 6,7 b1 0.31 0.35 0.39 6,7 c 0 . 1 20 . 1 50 . 2 0 6 c1 0.08 0.13 0.16 6 D 2.90BSC 3,4 E 2.80BSC 3,4 E1 1.60BSC 3,4 e 0.95BSC e1 1.90BSC L 0 . 3 00 . 4 00 . 5 0 L1 0.60REF L2 0.25BSC R0 . 1 0 R1 0.10 0.25 θ 0º 4º 8º θ1 4º 10º 12º Tolerances of Form and Position aaa 0.15 1,2 bbb 0.25 1,2 ccc 0.10 1,2 ddd 0.20 1,2
The device is available as the standard products listed in Table 8. Table 8. Ordering Information
www.austriamicrosystems.com Revision 1.03 17 - 17 AS1322 austria micro systems Data Sheet PCB Layout Guidelines Copyrights Copyright © 1997-2006, austriamicrosystems AG, Schloss Premstaetten, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered ®. All rights reserved. The material herein may not be reproduced, adapted, merged, trans- lated, stored, or used without the prior written consent of the copyright owner. All products and companies mentioned are trademarks or registered 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. austriami- crosystems 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 believed 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 personal 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 austriamicrosystems AG rendering of technical or other services. Contact Information Headquarters austriamicrosystems AG A-8141 Schloss Premstaetten, 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 austria micro systems – a leap ahead