AS1324 AMSCO
Document overview
- Manufacturer or author: Provided By digicamel.com
- PDF pages: 20
Technical content
1 General Description
perfect for any single Li-Ion battery-powered application. decreases to ≤1µA in shutdown mode. the use of small surface mount external components. nal 0.6V feedback reference voltage. The AS1324 is available in a 5-pin TSOT-23 package.
2 Key Features
3 Applications
tion with low power-consumption requirements. Table 1. Standard Versions Figure 1. Typical Application Diagram – High Efficiency Step Down Converter
5 VOUT
4 VIN
4 Pinout and Packaging
Figure 2. Pin Assignments (Top View) Table 2. Pin Descriptions goes high impedance, drawing <1µA supply current. Note: This pin should not be left floating. and synchronous power MOSFET switches. capacitor. Connect to any supply voltage between 2.7 to 5.5V.
5 VFB
5 Absolute Maximum Ratings
Table 3. Absolute Maximum Ratings Solid State Surface Mount Devices”.
6 Electrical Characteristics
VIN = EN = 3.6V, VOUT < VIN - 0.5V, TAMB = -40 to +85°C, typ. values @ TAMB = +25ºC (unless otherwise specified). Table 4. Electrical Characteristics
- The device is tested in a proprietary test mode where VFB is connected to the output of the error amplifier.
- Please see Feedback Resistor Selection on page 13 for resistor values.
7 Typical Operating Characteristics
Parts used for measurement: 4.7µH (MOS6020-472) Inductor, 10µF (GRM188R60J106ME47) CIN and COUT.
8 Detailed Description
contains two internal MOSFET switches and is available in adjustable- and fixed-output voltage versions. Figure 21. Block Diagram reversal comparator (IRCMP)), or the next clock cycle begins. The IRCMP detects the zero crossing. matches the new load current. and keeping it off until the transient is removed.
www.austriamicrosystems.com Revision 1.03 9 - 20 AS1324 Data Sheet - Detailed Description Powersave Operation The AS1324 uses an automatic powersave mode where the peak inductor current (IPK) is set to approximately 200mA while independent of the output load. In powersave mode, load current is supplied solely from the output capacitor. As the output voltage drops, the error amplifier output rises above the powersave threshold signaling to switch into PWM fixed frequency mode and turn the PMOS on. This process repeats at a rate determined by the load demand. Each burst event can last from a few cycles at light loads to almost continuous cycling (with short sleep intervals) at moderate loads. In between bursts, the power MOSFETs are turned off, as is any unneeded circuitry, reducing quies- cent current to 30µA. Short-Circuit Protection In cases where the AS1324 output is shorted to ground, the oscillator frequency (fOSC) is reduced to 1/13 the nominal frequency (≅ 115kHz). This frequency reduction ensures that the inductor current has more time to decay, thus pre- venting runaway conditions. fOSC will progressively increase to 1.5MHz when VFB/VOUT > 0V. Shutdown Connecting EN to GND or logic low places the AS1324 in shutdown mode and reduces the supply current to 0.1µA. In shutdown the control circuitry and the internal NMOS and PMOS turn off and SW becomes high impedance discon- necting the input from the output. The output capacitance and load current determine the voltage decay rate. For nor- mal operation connect EN to VIN or logic high. Note: Pin EN should not be left floating.
9 Application Information
camcorders, portabel MP3 and DVD players, PDA’s and palmtop computers and any other handheld instruments. Figure 22. Single Li-Ion 1.2V/600mA Regulator for High-Efficiency Figure 23. 5V Input to 3.3V/600mA Buck Regulator Figure 24. Single Li-Ion 1.5V/600mA Regulator for High-Efficiency
Figure 25. Single Li-Ion 1.8V/600mA Regulator for Low Output Ripple ΔIL) decreases with higher inductance and increases with higher VIN or VOUT. The recommended starting point for setting ripple current is ΔIL = 240mA (40% of 600mA). to prevent core saturation. Thus, a 720mA rated inductor should be sufficient for most applications (600mA + 120mA). Note: For highest efficiency, a low DC-resistance inductor is recommended. ripple, greater core losses, and lower output current capability.
- The losses in the core material (magnetic hysteresis loss, especially at high switching frequencies)
- Additional losses in the conductor from the skin effect (current displacement at high frequencies)
- Magnetic field losses of the neighboring windings (proximity effect)
Figure 26. Efficiency Comparison of Different Inductors, VIN = 2.7V, VOUT = 1.8V and 1.2V The advanced fast-response voltage mode control scheme of the AS1324 allows the use of tiny ceramic capacitors. output capacitor are recommended. Table 5. Recommended Inductors
put ripple and accommodate small circuit size. save mode and tighten DC output accuracy in powersave mode. for design because even significant deviations only provide negligible affects. exceeding the maximum ratings. When choosing ceramic capacitors for CIN and COUT, the X5R or X7R dielectric formulations are recommended. cies and therefore should not be used. that either a higher input capacity or a capacitance with a higher rated voltage is used. cuitry allows for remote voltage sensing and adjustment. Table 6. Recommended Input and Output Capacitor
Figure 27. Setting the AS1324 Output Voltage ommended to keep VIN 500mV higher than VOUT. L1, L2, L3, etc. are the individual losses as a percentage of input power. rent loss dominates the efficiency loss at very low load currents. Where: QPMOS and QNMOS are the gate charges of the internal MOSFET switches.
cycles (such as in dropout) the heat dissipated may exceed the maximum junction temperature of the device. ESR is the effective series resistance of COUT. would indicate a stability problem. load current requirement is 600mA (max) but most of the time the device will require only 2mA (standby mode current). Figure 28. Design Example Therefore, a standard 2.2µH inductor should be used for this design.
The device is available in an 5-pin TSOT-23 package. Figure 33. 5-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
trusion 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 outer-
The device is available as the following standard versions. All devices are RoHS compliant and free of halogene substances. Table 7. Ordering Information
www.austriamicrosystems.com Revision 1.03 20 - 20 AS1324 Data Sheet Copyrights Copyright © 1997-2009, 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. austria- microsystems 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 informa- tion. 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-us