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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
available. See Ordering Information on page 18 for more information. internal operating blocks are turned off in order to save power. provided that the output is in regulation. is disconnected from the output. external resistors on pin LBI, the LBO output is pulled to logic low. The AS1310 is available in a TDFN (2x2) 8-pin package. Figure 1. AS1310 Typical Application Diagram
2 Key Features
3 Applications
wireless mouse or any light-load application.
4 Pin Assignments
Figure 2. Pin Assignments (T op View)
4.1 Pin Descriptions
Table 1. Pin Descriptions 3L X External Inductor Connector. 4V OUT Output V oltage. Decouple VOUT with a ceramic capacitor as close as possible to VOUT and GND. 5R EF Reference Pin. Connect a 100nF ceramic capacitor to this pin. 6L BO Low Battery Comparator Output. Open-drain output. Enable Pin. Logic controlled shutdown input. 0 = Shutdown; shutdown current <100nA. optimal thermal performance.
5 Absolute Maximum Ratings
maximum rating conditions for extended periods may affect device reliability. Table 2. Absolute Maximum Ratings
6 Electrical Characteristics
parameters with min and max values are guaranteed with production tests or SQC (Statistical Quality Control) methods. Table 3. Electrical Characteristics
2 ILBO = 1mA 20 100 mV
- The regulator is in startup mode until this voltage is reac hed. Caution: Do not apply full load current until the device output > 1.75V
- LBO goes low in startup mode as well as during normal operation if:
- The voltage at the LBI pin is below LBI threshold.
- The voltage at the LBI pin is below 0.1V and VOUT is below 92.5% of its nominal value.
7 Typical Operating Characteristics
TAMB = +25°C, unless otherwise specified.
8 Detailed Description
8.1 Hysteretic Boost Converter
determined by external component (inductor and capacitors) and also the loading on the output. value of VOUT (0.99 x VOUT). Inductor current is monitored by the control loop, ensuring that operation is always dis-continuous. offered as a guide to changing the passive components to more closely match the end requirement.
8.1.1 Input Loop Timing
independent of input voltage changes. As a result, no line regulation exists. Figure 12. Simplified Boost DCDC Architecture
Figure 13. Simplified Voltage and Current Waveforms threshold (0.99xVOUT), the output is assumed to be in regulation and no further switching occurs.
8.1.2 Inductor Choice Example
For the AS1310 VIN_MIN = 0.9V, VOUT_MAX = 3.3V, (EQ 5) gives Ton=2.66TOFF. Let the maximum operating on-time = 1µs. LMAX = 1.875µH. The nearest preferred value is 2.2µH. This value provides the maximum energy storage for the chosen fixed on-time limit at the minimum VIN.
www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 10 - 19 AS1310 Datasheet - Detailed Description Energy stored during the on time is given by: Joules (Region A in Figure 13)( EQ 6) If the overall time period (TON + TOFF) is T, the power taken from the input is: Watts (EQ 7) Assume output power is 0.8 PIN to establish an initial value of operating period T. TWAIT is determined by the time taken for the output voltage to fall to 0.99xVOUT. The longer the wait time, the lower will be the supply current of the converter. Longer wait times require increased output capacitance. Choose TWAIT = 10% T as a minimum starting point for maximum energy transfer. For very low power load applications, choose TWAIT ≥ 50% T.
8.1.3 Output Loop Timing
The output loop consists of the main inductor, P-channel synchronous switch (or diode if fitted), output capacitor and load. When the input loop is interrupted, the voltage on the LX pin rises (Lenz’s Law). At the same time a comparator enables the synchronous switch, and energy stored in the inductor is transferred to the output capacitor and load. Inductor peak current supports the load and replenishes the charge lost from the output capacitor. The magnitude of the current from the inductor is monitored, and as it approaches zero, the synchronous switch is turned off. No switching action continues until the output voltage falls below the output reference point (0.99 x VOUT). Output power is composed of the dc component (Region C in Figure 13): PREGION_C = (EQ 8) Output power is also composed of the inductor component (Region B in Figure 13), neglecting efficiency loss: PREGION_B = (EQ 9) Total power delivered to the load is the sum of (EQ 8) and (EQ 9): (EQ 10) From (EQ 3) (using nominal values) peak current is given by: (EQ 11) Substituting (EQ 11) into (EQ 10) and re-arranging: (EQ 12) 0.9T incorporates a wait time TWAIT = 10% T Output power in terms of regulated output voltage and load resistance is: (EQ 13) Combining (EQ 12) and (EQ 13): (EQ 14) Symbol η reflects total energy loss between input and output and is approximately 0.8 for these calculations. Use (EQ 14) to plot duty cycle (TON/T) changes for various output loadings and changes to VIN. E 0.5LI PK() 2= PIN 0.5LI PK() 2 VIN IPK 0.5LI PK() 2 PTOTAL VIN IPK IPK TON VIN PTOTAL INTON POUT OUT RLOAD OUT RLOAD INTON ams AG Technical content still valid
www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 11 - 19 AS1310 Datasheet - Detailed Description
8.1.4 Input Capacitor Selection
The input capacitor supports the triangular current during the on-time of the power switch, and maintains a broadly constant input voltage during this time. The capacitance value is obtained from choosing a ripple voltage during the on-time of the power switch. Additionally, ripple voltage is generated by the equivalent series resistance (ESR) of the capacitor. For worst case, use maximum peak current values from the datasheet. (EQ 15) Using TON = 1µs, and IPEAK = 480mA, and VRIPPLE = 50mV, EQ 15 yields: CIN = 9.6µF Nearest preferred would be 10µF. (EQ 16) Typically, the ripple due to ESR is not dominant. ESR for the recommended capacitors (Murata GMR), ESR = 5mΩ to 10mΩ. For the AS1310, ma ximum peak current is 480mA. Ripple due to ESR is 2.4mV to 4.8mV. Ripple at the input propagates through the common supply connections, and if too high in value can cause problems elsewhere in the s ystem. The input capacitance is an important component to get right.
8.1.5 Output Cap acitor Selection
The output capacitor supports the triangular current during the off-time of the power switch (inductor discharge period), and also the load current during the wait time (Region D in Figure 13) and on-time (Region A in Figure 13) of the power switch. (EQ 17) Note: There is also a ripple component due to the equivalent series resistance (ESR) of the capacitor.
8.2 Summary
User Application Defines: VINmin, VINmax, VOUTmin, VOUTmax, ILOADmin, ILOADmax Inductor Selection: Select Max on-time = 0.5µs to 3µs for AS1310. Use (EQ 3) to calculate inductor value. Use (EQ 5) to determine off-time. Use (EQ 6) to check that power delivery matches load requirements assume 70% conversion efficiency. Use (EQ 13) to find overall timing period value of T at min VIN and max VOUT for maximum load conditions. Input Capacitor Selection: Choose a ripple value and use (EQ 14) to find the value. Output Capacitor Selection: Determine TWAIT via (EQ 6) or (EQ 13), and use (EQ 16) to find the value. CIN IPEAK TON VRIPPLE ESR PKESRRIPPLEPK R IV =_ _ NOMOUT WAITONLOAD OUT V T T IC _) 99 . 0 1 ( ) ( ams AG Technical content still valid
9 Application Information
The AS1310 is available with fixed output voltages from 1.8V to 3.3V in 50mV steps. Figure 14. AS1310 Block Diagram
9.1 AS1310 Features
Shutdown. The part is in shutdown mode while the voltage at pin EN is below 0.1V and is active when the voltage is higher than 0.7V. Note: EN can be driven above VIN or VOUT, as long as it is limited to less than 3.6V. the device. This is true as long as the input voltage is higher than the output voltage. guarantee a proper function of the AS1310 it is not allowed that the supply exceeds the maximum allowed input voltage (3.6V).
9.1.1 Power-OK and Low-Battery-Detect Functionality
- The voltage at the LBI pin is below LBI threshold (0.6V). 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. with no additional external components. GND may be added to generate a power-on-reset delay. To obtain a logic-level output, connect a pull-up resistor R3 from pin LBO to pin VOUT. Figure 15. Typical Application with Adjustable Battery Monitoring
9.1.2 Thermal Shutdown
normal operation the temperature has to drop below 140°C. recommended to use multiple vias in the printed circuit board. It’s also recommended to solder the Exposed Pad (pin 9) to the GND plane. Note: Conti nuing operation in thermal overload conditions may damage the device and is considered bad practice.
9.2 Always On Operation
application. The efficiency at standby currents of e.g. 2µAs is around 45% (see Figure 17). Figure 17. Efficiency vs. Output Current for Always ON Operation
9.3 Component Selection
value, low profile inductors and tiny external ceramic capacitors.
9.4 Inductor Selection
500mA current rating and <500mΩ DCR is recommended.
9.5 Capacitor Selection
for a list of capacitors for input and output capacitor selection. On the pin REF a 10nF capacitor with an Insulation resistance >1GΩ is recommended.
9.6 Layout Considerations
loop formed by C1, VIN and GND pins should be minimized. Similarly, the output loop formed by C2, VOUT and GND should also be min imized. Ideally both loops should connect to GND in a “star” fashion. Finally, it is important to return CREF to the GND pin directly. Table 5. Recommended Input and Output Capacitors
The device is available in a TDFN (2x2) 8-pin package. Figure 18. Drawings and Dimensions
- Dimensioning & tolerancing conform to ASM E Y14.5M-1994.
- All dimensions are in millimeters. Angles are in degrees.
- Coplanarity applies to the exposed heat slug as well as the terminal.
- Radius on terminal is optional.
- N is the total number of terminals.
www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 17 - 19 AS1310 Datasheet - Package Drawings and Markings
Revision History
Note: Typos may not be explicitly mentioned under revision history. Revision Date Owner Description 1.0 afe Initial revision 1.6 06 Mar, 2012 Updated Detailed Description and Application Information sections 1.7 27 Apr, 2012 Detailed Description section updated 1.8 17 Aug, 2012 Updated thermal resistance value and (EQ 17) ams AG Technical content still valid
The device is available as the standard products shown in Table 7. Note: All products are RoHS compliant and austriamicrosystems green. Table 7. Ordering Information
- Non-standard devices are available between 1.8V and 3.3V in 50mV steps.
www.austriamicrosystems.com/DC-DC_Step-Up/AS1310 Revision 1.8 19 - 19 AS1310 Datasheet - Ordering Information Copyrights Copyright © 1997-2012, 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 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. 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 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 technical 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 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