AS1320_1 AMSCO
Document overview
- Manufacturer or author: Provided By digicamel.com
- PDF pages: 12
Technical content
1 General Description
verter designed to generate a fixed voltage of +3.3V. fixed at 3.3V, and output current is up to 200mA (@ 2V). the supply of real-time-clocks. when the battery voltage falls to a predetermined level. external transistor or Schottky diode is not required. The AS1320 is available in a 6-pin SOT23 package. Figure 1. Application Diagram
2 Key Features
3 Applications
4 Pinout
Figure 2. Pin Assignments (Top View) Table 1. Pin Descriptions 0 = The AS1320 is off and the current into BATT is ≤ 1µA (typ).
5 Absolute Maximum Ratings
Table 2. Absolute Maximum Ratings Solid State Surface Mount Devices”.
6 Electrical Characteristics
TAMB = -40 to +85ºC, VBATT = +2V, VOUT = +3.3, VSHDNN = +1.5V (unless otherwise specified). Typ values @ TAMB = +25ºC. Table 3. Electrical Characteristics
- Voltage which triggers next loading cycle. Ripple and rms value depend on external components.
1 IMAX
7 Typical Operating Characteristics
Figure 3. VOUT vs. VBATT; On, 16Ω Figure 4. VOUT vs. VBATT; On, 330Ω Figure 5. VOUT vs. VBATT; Shutdown, 200mA Load Figure 6. V OUT vs. VBATT; Shutdown, No Load Figure 7. Maximum Output Current vs. VBATT Figure 8. Startup Voltage vs. Load Resistance
8 Detailed Description
tions with one- or two-cells, such as lithium ion (Li+), nickel-metal-hydride (NiMH), or alkaline. Figure 15. Block Diagram tery can be used as a battery-backup or real-time-clock supply. ing the need for an external Schottky diode. threshold, another cycle begins. resulting in a significant reduction of the rectifier voltage drop, improving efficiency without external components. VOUT to avoid intermittently switching the device on. Note: If pin SHDNN is not used, it should be connected directly to pin OUT. time-clock, without the usual diode forward drop. In this way a separate backup battery is not needed. CIN and COUT partly determine the size and duration of this spike, as does the current-sink ability of the input device.
detection voltage (see Figure 16). Figure 16. Low-Battery Cutoff Application Diagram VOFF is the battery voltage at which the AS1320 shuts down. The value of R2 should be between 100kΩ and 1MΩ to minimize battery drain. resistor between pin RESETN and pin OUT can provide a microprocessor logic control signal. Note: Connect pin RESETN to GND when the power-on reset feature is not used.
www.austriamicrosystems.com Revision 1.03 9 - 12 AS1320 Data Sheet - Application Information
9 Application Information
The control circuitry of the AS1320 permits a wide range of inductor values to be selected – from 4.7 to 47µH; 10µH is ideal for most applications. The intended application should dictate the value of L. The trade-off between required PCB surface area and desired output ripple are the determining factors: smaller values for L require less PCB space, larger values of L reduce output ripple. If the value of L is large enough to prevent IMAX from being reached before tON expires, the AS1320 output power will be reduced. For maximum output current calculate the value for L as: (VBATT(MAX) (1µs))/0.7A < L < (VBATT(MIN)(7µs))/0.7A (EQ 2) IOUT(MAX) = [(0.7A/2)(VBATT(MIN) - (0.7A/2)(RNCH + RIND))]/VOUT (EQ 3) Where: RIND is the inductor series resistance. RNCH is the RDS(ON) of the N-channel MOSFET (0.3Ω typ). Note: Coils should be able to handle 500mARMS and have a ISAT ≥ 1A and should have a RIND ≤ 100mΩ. Capacitor Selection COUT Selection Choose a COUT value to achieve the desired output ripple percentage. A 22µF ceramic capacitor is a good initial value. The value for COUT can be determined by: COUT > (L + 2.5µH) x VBATT(MAX) / r% (EQ 4) Where: r is the desired output ripple in %. CIN Selection CIN reduces the peak current drawn from the battery and can be the same value as COUT. A larger value for CIN can be used to further reduce ripple and improve AS1320 efficiency. PC Board Layout and Grounding Well-designed printed circuit-board layout is important for minimizing ground bounce and noise. ! Place pin GND lead and the ground leads of CIN and COUT as close to the device as possible. ! Keep the lead to pin LX as short as possible. ! To maximize output power and efficiency and minimize output ripple voltage, use a ground plane and solder the GND pin directly to the ground plane.
The AS1320 is available in a 6-pin SOT23 package. Figure 17. 6-pin SOT23 Package
- All dimensions are in millimeters.
- Foot length is measured at the intercept point between datum
- Package outline exclusive of mold flash and metal burr.
- Pin 1 is the lower left pin when reading the top mark from left
- Pin 1 identifier dot is 0.3mm.φ min and is located above pin 1.
The AS1320 is available as the standard products shown in Table 4. Table 4. Ordering Information
www.austriamicrosystems.com Revision 1.03 12 - 12 AS1320 Data Sheet Copyrights Copyright © 1997-2007, 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