AS1321

Da t as heet AS1321 1 3 0 m A St e p - U p D C - D C C o n v e r t e r 1 General Description The AS1321 is a high-efficiency step-up DC-DC converter designed to generate a fixed output voltage of +5.0V. The AS1321 achieves an efficiency of up to 96%. The minimum input voltage is +1.5V, the output voltage is fixed at +5.0V, and output current is up to 130mA (@ 2V VBATT). In order to save power the AS1321 features a shutdown mode, where it draws less than 1µA. In shutdown mode the battery is connected directly to the output enabling the supply of real-time-clocks. The AS1321 provides a power-on reset output that goes high-impedance when the output reaches 90% of its regulation point. The SHDNN trip threshold of the AS1321 can be used as an input voltage detector that disables the device when the battery voltage falls to a predetermined level. An internal synchronous rectifier is included, which is parallel with the external Schottky diode. The AS1321 is available in a 6-pin SOT23 package. 2 Key Features ! ! ! ! ! ! ! ! Fixed Output Voltage: +5.0V Output Current: Up to 130mA (@ 2V VBATT) Internal Synchronous Rectifier Shutdown Mode Supply Current: Less Than 1µA Efficiency: Up to 96% Minimum Input Voltage: +1.5V Accurate Shutdown Low-Battery Cutoff Threshold Battery Input Connected to Pin OUT in Shutdown Mode for Backup Power 6-pin SOT23 Package ! 3 Applications The AS1321 is ideal for low-power applications where ultra-small size is critical as in medical diagnostic equipment, hand-held instruments, pagers, digital cameras, remote wireless transmitters, cordless phones, and PC cards. The device is also perfect as a local +5.0V supply or as a battery backup. Figure 1. AS1321 - Typical Application Diagram 2 BATT 5 OUT COUT 22µF +5.0V Output R1 100kΩ RESETN Output +1.5V to +5.0V Battery CIN 22µF 4 L1 10µH LX AS1321 6 RESETN On Off 1 SHDNN 3 GND www.austriamicrosystems.com Revision 1.02 1 - 13 AS1321 Datasheet - P i n o u t 4 Pinout Pin Assignments Figure 2. Pin Assignments (Top View) SHDNN 1 6 RESETN BATT 2 AS1321 5 OUT GND 3 4 LX Pin Descriptions Table 1. Pin Descriptions Name SHDNN BATT GND LX OUT RESETN Pin Number 1 2 3 4 5 6 Description Active-Low Logic Shutdown Input 0 = The AS1321 is off and the current into BATT is ≤ 1µA (typ). 1 = The AS1321 is on. Battery Voltage Input Ground External Inductor Connection Output Voltage Active-Low reset output www.austriamicrosystems.com Revision 1.02 2 - 13 AS1321 Datasheet - A b s o l u t e M a x i m u m R a t i n g s 5 Absolute Maximum Ratings Stresses beyond those listed in Table 2 may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in Section 6 Electrical Characteristics on page 4 is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Table 2. Absolute Maximum Ratings Parameter All Pins to GND LX Current Latch-Up Package Power Dissipation (TAMB = +70ºC) Operating Temperature Range Electrostatic Discharge Humidity (Non-Condensing) Storage Temperature Range Junction Temperature -40 -500 5 -55 -100 Min -0.3 Max 7 1 100 500 +85 +500 85 125 150 Units V A mA mW ºC V % ºC ºC The reflow peak soldering temperature (body temperature) specified is in compliance with IPC/JEDEC J-STD-020D “Moisture/ Reflow Sensitivity Classification for Non-Hermetic Solid State Surface Mount Devices”. HBM MIL-Std. 883E 3015.7 methods JEDEC 78 (ΘJA = 9.1mW/ºC above +70ºC) Comments Package Body Temperature 260 ºC www.austriamicrosystems.com Revision 1.02 3 - 13 AS1321 Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s 6 Electrical Characteristics TAMB = -40 to +85ºC, VBATT = +2V, VOUT = +5.0, VSHDNN = +1.5V (unless otherwise specified). Typ values @ TAMB = +25ºC. Table 3. Electrical Characteristics Parameter Battery Input Range Startup Battery Input Voltage Output Voltage 2 1 Symbol VBATT VSU VOUT RNCH RPCH 1 Conditions RLOAD = 100Ω, TAMB = +25ºC RLOAD = 100Ω, TAMB = -40 to +85ºC TAMB = +25ºC TAMB = -40 to +85ºC ILX = 100mA, TAMB = +25ºC ILX = 100mA, TAMB = -40 to +85ºC ILX = 100mA, TAMB = +25ºC ILX = 100mA, TAMB = -40 to +85ºC TAMB = +25ºC TAMB = -40 to +85ºC TAMB = +25ºC TAMB = -40 to +85ºC TAMB = +25ºC TAMB = -40 to +85ºC VOUT = +5.5V, TAMB = +25ºC VOUT = +5.5V, TAMB = -40 to +85ºC VSHDNN = 0V, TAMB = +25ºC VSHDNN = 0V, TAMB = -40 to +85ºC VOUT = +5.5V, TAMB = +25ºC VOUT = +5.5V, TAMB = -40 to +85ºC VSHDNN = 0V, TAMB = +25ºC VSHDNN = 0V, TAMB = -40 to +85ºC VBATT = +1.5 to +5.0V Rising Edge, TAMB = +25ºC Rising Edge, TAMB = -40 to +85ºC Falling Edge, TAMB = +25ºC Falling Edge, TAMB = -40 to +85ºC IRESETN = 1mA, VOUT = +2.5V, TAMB = +25ºC IRESETN = 1mA, VOUT = +2.5V, TAMB = -40 to +85ºC VRESETN = +5.5V, TAMB = +25ºC VRESETN = +5.5V, TAMB = +85ºC TAMB = +25ºC TAMB = +85ºC Min 1.5 Typ 1.22 1.24 Max 5.0 1.5 5.050 5.125 1.2 1.5 1.3 1.6 850 950 9 10 60 65 55 60 1 2 1 2 1 2 0.3 Unit V V V Ω Ω mA µs mA µA µA µA µA V V V 4.950 4.875 5.000 0.3 0.4 N-Channel On-Resistance P-Channel On-Resistance N-Channel Switch Current Limit Switch Maximum On-Time Synchronous Rectifier Zero-Crossing Current Quiescent Current into OUT 3 IMAX tON 550 450 5 4 8 0 700 7 30 35 0.01 0.01 0.01 Shutdown Current into OUT Quiescent Current into BATT 3 Shutdown Current into BATT SHDNN Logic Low 1 SHDNN Threshold SHDNN Threshold Hysteresis RESETN Threshold 1.185 1.170 1.228 0.02 1.271 1.286 4.288 4.242 4.500 4.712 4.758 0.15 V RESETN Voltage Low V 0.2 0.1 1 0.1 10 130 91 1000 100 nA nA mA % RESETN Leakage Current LX Leakage Current Maximum Load Current Efficiency ILOAD η VBATT = +2V VBATT = +3V, ILOAD = 100mA 1. Guaranteed by design. 2. Voltage which triggers next loading cycle. Ripple and rms value depend on external components. 3. The Quiescent current is measured while the DC-DC Converter is not switching. www.austriamicrosystems.com Revision 1.02 4 - 13 AS1321 Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s 7 Typical Operating Characteristics VBATT = 2.0V, VOUT = 5.0V, TAMB = +25°C (unless otherwise specified). Figure 3. Efficiency vs. Load Current 100 Figure 4. Efficiency vs. Input Voltage 100 95 VBATT = 4.5V VBATT = 3V VBATT = 2.5V 90 Efficiency (%) 90 Efficiency (%) VBATT = 3.5V 80 85 VBATT = 2V VBATT = 1.5V 70 80 60 Iout = 1mA Iout = 10mA Iout = 100mA 75 1 10 100 1000 50 1 2 3 4 5 Load Current (mA) Figure 5. VOUT vs. VBATT; On, 39Ω 6 5 Battery Voltage (V) Figure 6. VOUT vs. VBATT; On, 470Ω 6 5 Output Voltage (V) 4 3 2 1 0 0 1 2 3 4 5 Output Voltage (V) 4 3 2 1 0 0 1 2 3 4 5 Battery Voltage (V) Figure 7. VOUT vs. VBATT; Shutdown, 130mA Load 6 5 Battery Voltage (V) Figure 8. VOUT vs. VBATT; Shutdown, no Load 6 5 Output Voltage (V) 4 3 2 1 0 1.5 2 2.5 3 3.5 4 4.5 5 Output Voltage (V) 4 3 2 1 0 0 1 2 3 4 5 Battery Voltage (V) www.austriamicrosystems.com Revision 1.02 Battery Voltage (V) 5 - 13 AS1321 Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s Figure 9. Maximum Output Current vs. VBATT 400 Figure 10. Startup Voltage vs. Load Resistance 5 Maximum Output Current (mA) 350 4 250 200 150 100 50 0 1.5 2 2.5 3 3.5 4 4.5 5 0 10 100 1000 10000 Supply Voltage (V) Battery Voltage (V) 300 3 2 1 Load Resistance (Ohm) Figure 11. Input Current vs. Input Voltage 400 Iout = 4µA Figure 12. Waveforms; RLOAD = 100Ω, VBATT = 3V Input Current (µA) 300 250 200 150 VOUT 350 Iout = 34µA 50 0 1 2 3 4 5 10µs/Div Battery Voltage (V) Figure 13. Line Transient Figure 14. Load Transient 100mV/Div 1V/Div 130mA IOUT 2mA VIN 100µs/Div 500µs/Div www.austriamicrosystems.com Revision 1.02 100mV/Div VOUT VOUT 500mA/Div 100 IL 2V/Div VLX 50mV/Div 6 - 13 AS1321 Datasheet - Ty p i c a l O p e r a t i n g C h a r a c t e r i s t i c s Figure 15. On / Off Response; RLOAD = 100Ω Figure 16. Shutdown Response; RLOAD = 100Ω 1V/Div VOUT 1V/Div VSHDNN VOUT 2ms/Div 500µs/Div www.austriamicrosystems.com Revision 1.02 2V/Div VIN 1V/Div 7 - 13 AS1321 Datasheet - D e t a i l e d D e s c r i p t i o n 8 Detailed Description The AS1321 is a high-efficiency, compact step-up converter with 35µA quiescent supply current which ensures the highest efficiency over a wide load range. With a minimum of +1.5V input voltage, the device is well suited for applications with one- or two-cells, such as lithium ion (Li+), nickel-metal-hydride (NiMH), or alkaline. Figure 17. AS1321 - Block Diagram +1.5 to +5.0V Battery CIN 22µF 4 10µH LX Zero Crossing Detector Startup Circuitry Driver and Control Logic 5 OUT COUT 22µF +5.0V Output – + +1.228V 2 BATT 1 SHDNN Current Limiter VREF – 6 RESETN AS1321 GND 3 +1.1V + The input battery is connected to the device through an inductor and an internal P-FET when pin SHDNN is low. In this state, the step-up converter is off and the voltage drop across the P-FET body diode is eliminated, and the input battery can be used as a battery-backup or real-time-clock supply. The built-in synchronous rectifier significantly improves efficiency. Control Circuitry The AS1321 integrated current-limited key circuitry provides low quiescent current and extremely-high efficiency over a wide VOUT range without the need for an oscillator. Inductor current is limited by the 7µs switch maximum on-time or by the 0.7A N-channel current limit. At each cycle, the inductor current must ramp down to zero after the on-time before the next cycle may start. When the error comparator senses that the output has fallen below the regulation threshold, another cycle begins. Shutdown When pin SHDNN is low the AS1321 is switched off and no current is drawn from battery; when pin SHDNN is high the device is switched on. If SHDNN is driven from a logic-level output, the logic high-level (on) should be referenced to VOUT to avoid intermittently switching the device on. Note: If pin SHDNN is not used, it should be connected directly to pin OUT. In shutdown the battery input is connected to the output through the inductor and the internal synchronous rectifier PFET. This allows the input battery to provide backup power for devices such as an idle microcontroller, memory, or realtime-clock, without the usual diode forward drop. In this way a separate backup battery is not needed. In cases where there is residual voltage during shutdown, some small amount of energy will be transferred from pin OUT to pin BATT immediately after shutdown, resulting in a momentary spike of the voltage at pin BATT. The ratio of CIN and COUT partly determine the size and duration of this spike, as does the current-sink ability of the input device. www.austriamicrosystems.com Revision 1.02 8 - 13 AS1321 Datasheet - D e t a i l e d D e s c r i p t i o n Low-Battery Cutoff The AS1321 SHDNN trip threshold (1.228V) can be used as an input voltage detector that disables the device when the battery input voltage falls to a pre-set level. An external resistor-divider network can be used to set the batterydetection voltage (see Figure 18). Figure 18. Low-Battery Cutoff Application Diagram +1.5 to +5.0V Battery CIN 22µF 2 BATT 5 OUT R3 100kΩ COUT 22µF +5.0V Output 4 R1 220kΩ L1 10µH LX AS1321 6 RESETN Power-On Reset 1 R2 1MΩ 10nF SHDNN 3 GND For the resistor-divider network shown in Figure 18, calculate the value for R1 by: R1 = R2 x ((VOFF/VSHDNN) - 1) Where: VOFF is the battery voltage at which the AS1321 shuts down. VSHDNN = 1.228V The value of R2 should be between 100kΩ and 1MΩ to minimize battery drain. Note: Input ripple can cause false shutdowns, therefore to minimize the effect of ripple, a low-value capacitor from SHDNN to GND should be used to filter out input noise. The value of the capacitor should be such that the R/C time constant is > 2ms. (EQ 1) Power-On Reset The AS1321 provides a power-on reset output (RESETN) that goes high-impedance when the output reaches 90% of its regulation point. RESETN goes low when the output is below 90% of the regulation point. A 100kΩ to 1MΩ pullup 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 1.02 9 - 13 AS1321 Datasheet - A p p l i c a t i o n I n f o r m a t i o n 9 Application Information Inductor Selection The control circuitry of the AS1321 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 AS1321 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 IOUT(MAX) = (0.7A/2)(VBATT(MIN) - (0.7A/2)(RNCH + RIND))/VOUT 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. (EQ 2) (EQ 3) 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% x 4) Where: r is the desired output ripple in %. 2 (EQ 4) 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 AS1321 efficiency. External Diode An external Schottky diode must be connected, in parallel with the on-chip synchronous rectifier, from LX to OUT. Use diodes such as MBR0520L, EP05Q03L, or the generic 1N5817. The diode should be rated for 500mA, since it carries current during startup and after the synchronous rectifier turns off. The Schottky diode must be connected as close to the IC as possible. Ordinary rectifier diodes must not be used, since the slow recovery rate will compromise 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. www.austriamicrosystems.com Revision 1.02 10 - 13 AS1321 Datasheet - P a c k a g e D r a w i n g s a n d M a r k i n g s 10 Package Drawings and Markings The AS1321 is available in a 6-pin SOT23 package. Figure 19. 6-pin SOT23 Package Notes: 1. All dimensions are in millimeters. 2. Foot length is measured at the intercept point between datum A and lead surface. 3. Package outline exclusive of mold flash and metal burr. 4. Pin 1 is the lower left pin when reading the top mark from left to right. 5. Pin 1 identifier dot is 0.3mm.φ min and is located above pin 1. 6. Meets JEDEC MO178. Symbol A A1 A2 b C D E E1 L e α Min Max 0.90 1.45 0.00 0.15 0.90 1.30 0.35 0.50 0.08 0.20 2.80 3.00 2.60 3.00 1.50 1.75 0.35 0.55 0.95 REF 0º 10º www.austriamicrosystems.com Revision 1.02 11 - 13 AS1321 Datasheet - O r d e r i n g I n f o r m a t i o n 11 Ordering Information The AS1321 is available as the standard products shown in Table 4. Table 4. Ordering Information Ordering Code AS1321-T Marking ASKX Description 130mA Step-Up DC-DC Converter Delivery Form Tape and Reel Package 6-pin SOT23 Note: All products are RoHS compliant and Pb-free. Buy our products or get free samples online at ICdirect: http://www.austriamicrosystems.com/ICdirect For further information and requests, please contact us mailto:sales@austriamicrosystems.com or find your local distributor at http://www.austriamicrosystems.com/distributor www.austriamicrosystems.com Revision 1.02 12 - 13 AS1321 Datasheet Copyrights Copyright © 1997-2009, 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. 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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 www.austriamicrosystems.com Revision 1.02 13 - 13