General Description AS1321 high-efficiency step-up DC-DC converte
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AS1321
General Description
AS1321 high-efficiency step-up DC-DC converter designed generate fixed output voltage +5.0V. AS1321 achieves efficiency 96%. minimum input voltage +1.5V, output voltage fixed +5.0V, output current 130mA VBATT). order save power AS1321 features shutdown mode, where draws less than 1µA. shutdown mode battery connected directly output enabling supply real-time-clocks. AS1321 provides power-on reset output that goes high-impedance when output reaches regulation point. SHDNN trip threshold AS1321 used input voltage detector that disables device when battery voltage falls predetermined level. internal synchronous rectifier included, which parallel with external Schottky diode. AS1321 available 6-pin SOT23 package.
Features
Fixed Output Voltage: +5.0V Output Current: 130mA VBATT) Internal Synchronous Rectifier Shutdown Mode Supply Current: Less Than Efficiency: Minimum Input Voltage: +1.5V Accurate Shutdown Low-Battery Cutoff Threshold Battery Input Connected Shutdown Mode Backup Power 6-pin SOT23 Package
Applications
AS1321 ideal low-power applications where ultra-small size critical medical diagnostic equipment, hand-held instruments, pagers, digital cameras, remote wireless transmitters, cordless phones, cards. device also perfect local +5.0V supply battery backup.
Figure Application Diagram
BATT
COUT 22µF
+5.0V Output 100k RESETN Output
+1.5 +5.0V Battery 22µF
10µH
AS1321
RESETN
SHDNN
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AS132 Data Sheet
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Absolute Maximum Ratings
Stresses beyond those listed Table cause permanent damage device. These stress ratings only, functional operation device these other conditions beyond those indicated Section Electrical Characteristics page implied. Exposure absolute maximum rating conditions extended periods affect device reliability. Table Absolute Maximum Ratings Parameter Pins Current Latch-Up Package Power Dissipation (TAMB Operating Temperature Range Electrostatic Discharge Humidity (Non-Condensing) Storage Temperature Range Junction Temperature -500 -100 -0.3 +500 Units reflow peak soldering temperature (body temperature) specified compliance with IPC/JEDEC J-STD-020C "Moisture/ Reflow Sensitivity Classification Non-Hermetic Solid State Surface Mount Devices". MIL-Std. 883E 3015.7 methods JEDEC above Comments
Package Body Temperature
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AS132 Data Sheet
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Electrical Characteristics
TAMB VBATT +2V, VOUT +5.0, VSHDNN +1.5V (unless otherwise specified). values TAMB Table Electrical Characteristics Parameter Battery Input Range Startup Battery Input Voltage Output Voltage
Symbol VBATT VOUT RNCH RPCH
Conditions RLOAD 100, TAMB RLOAD 100, TAMB TAMB TAMB 100mA, TAMB 100mA, TAMB 100mA, TAMB 100mA, TAMB TAMB TAMB TAMB TAMB TAMB TAMB VOUT +5.5V, TAMB VOUT +5.5V, TAMB VSHDNN TAMB VSHDNN TAMB VOUT +5.5V, TAMB VOUT +5.5V, TAMB VSHDNN TAMB VSHDNN TAMB VBATT +1.5 +5.0V Rising Edge, TAMB Rising Edge, TAMB Falling Edge, TAMB Falling Edge, TAMB IRESETN 1mA, VOUT +2.5V, TAMB IRESETN 1mA, VOUT +2.5V, TAMB VRESETN +5.5V, TAMB VRESETN +5.5V, TAMB TAMB TAMB
1.22 1.24
5.050 5.125
Unit
4.950 4.875
5.000
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 Shutdown Current into Quiescent Current into BATT Shutdown Current into BATT SHDNN Logic
IMAX
0.01 0.01 0.01
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
RESETN Voltage
1000
RESETN Leakage Current Leakage Current Maximum Load Current Efficiency ILOAD
VBATT VBATT +3V, ILOAD 100mA
Guaranteed design. Voltage which triggers next loading cycle. Ripple value depend external components.
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AS132 Data Sheet
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Typical Operating Characteristics
VOUT 5.0V, VBATT +2V, TAMB Figure VOUT VBATT;
Figure VOUT VBATT;
Output Voltage
Output Voltage
Battery Voltage
Battery Voltage
Figure VOUT VBATT; Shutdown, 130mA Load
Figure VOUT VBATT; Shutdown, Load
Output Voltage
Output Voltage
Battery Voltage
Battery Voltage
Figure Maximum Output Current VBATT
Figure Startup Voltage Load Resistance
Maximum Output Current (mA)
Supply Voltage
1000 10000
Battery Voltage
Load Resistance (Ohm)
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AS132 Data Sheet
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Figure Line Transient
Figure Load Transient
VOUT Coupled)
VOUT Coupled)
100mV/Div
1V/Div
130mA IOUT
100µs/Div
500µs/Div
Figure On/Off Response; RLOAD
Figure Shutdown Response; RLOAD
1V/Div
VOUT
VSDHNN
2ms/Div
1V/Div
500µs/Div
Figure Waveforms; RLOAD 100, VBATT
Figure Efficiency Load Current
VOUT Coupled)
50mV/Div
VBATT 4.5V VBATT 3.5V VBATT VBATT 2.5V
Efficiency
2V/Div
VBATT VBATT 1.5V
500mA
10µs/Div
Load Current
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2V/Div
1V/Div
VOUT
100mV/Div
1000
AS132 Data Sheet
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Control Circuitry
Detailed Description
AS1321 high-efficiency, compact step-up converter with 35µA quiescent supply current which ensures highest efficiency over wide load range. With minimum +1.5V input voltage, device well suited applications with one- two-cells, such lithium (Li+), nickel-metal-hydride (NiMH), alkaline. Figure Block Diagram
+1.5 +5.0V Battery 22µF
10µH
Zero Crossing Detector Startup Circuitry Driver Control Logic
COUT 22µF
+5.0V Output
+1.228V
BATT SHDNN
Current Limiter
VREF
RESETN
AS1321
+1.1V
input battery connected device through inductor internal P-FET when SHDNN low. this state, step-up converter voltage drop across P-FET body diode eliminated, input battery used battery-backup real-time-clock supply. built-in synchronous rectifier significantly improves efficiency.
Control Circuitry
AS1321 integrated current-limited circuitry provides quiescent current extremely-high efficiency over wide VOUT range without need oscillator. Inductor current limited switch maximum on-time 0.7A N-channel current limit. each cycle, inductor current must ramp down zero after on-time before next cycle start. When error comparator senses that output fallen below regulation threshold, another cycle begins.
Shutdown
When SHDNN AS1321 switched current drawn from battery; when SHDNN high device switched SHDNN driven from logic-level output, logic high-level (on) should referenced VOUT avoid intermittently switching device Note: SHDNN used, should connected directly OUT. shutdown battery input connected output through inductor internal synchronous rectifier PFET. This allows input battery provide backup power devices such idle microcontroller, memory, realtime-clock, without usual diode forward drop. this separate backup battery needed. cases where there residual voltage during shutdown, some small amount energy will transferred from BATT immediately after shutdown, resulting momentary spike voltage BATT. ratio COUT partly determine size duration this spike, does current-sink ability input device.
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AS132 Data Sheet
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Low-Battery Cutoff
Low-Battery Cutoff
AS1321 SHDNN trip threshold (1.228V) used input voltage detector that disables device when battery input voltage falls pre-set level. external resistor-divider network used batterydetection voltage (see Figure 15). Figure Low-Battery Cutoff Application Diagram
+1.5 +5.0V Battery 22µF
BATT
100k COUT 22µF
+5.0V Output
220k 10µH
AS1321
RESETN
Power-On Reset
10nF SHDNN
resistor-divider network shown Figure calculate value ((VOFF/VSHDNN) Where: VOFF battery voltage which AS1321 shuts down. VSHDNN 1.228V value should between 100k minimize battery drain. Note: Input ripple cause false shutdowns, therefore minimize effect ripple, low-value capacitor from SHDNN should used filter input noise. value capacitor should such that time constant 2ms.
Power-On Reset
AS1321 provides power-on reset output (RESETN) that goes high-impedance when output reaches regulation point. RESETN goes when output below regulation point. 100k pullup resistor between RESETN provide microprocessor logic control signal. Note: Connect RESETN when power-on reset feature used.
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AS132 Data Sheet
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Inductor Selection
Application Information
Inductor Selection
control circuitry AS1321 permits wide range inductor values selected from 47µH; 10µH ideal most applications. intended application should dictate value trade-off between required surface area desired output ripple determining factors: smaller values require less space, larger values reduce output ripple. value large enough prevent IMAX from being reached before expires, AS1321 output power will reduced. maximum output current calculate value (VBATT(MAX) (1µs))/0.7A (VBATT(MIN)(7µs))/0.7A IOUT(MAX) (0.7A/2)(VBATT(MIN) (0.7A/2)(RNCH RIND))/VOUT Where: RIND inductor series resistance. RNCH RDS(ON) N-channel MOSFET (0.3 typ). Note: Coils should able handle 500mARMS have ISAT should have RIND 100m.
Capacitor Selection
COUT Selection
Choose COUT value achieve desired output ripple percentage. 22µF ceramic capacitor good initial value. value COUT determined COUT 2.5µH) VBATT(MAX) Where: desired output ripple
Selection
reduces peak current drawn from battery same value COUT. larger value used further reduce ripple improve AS1321 efficiency.
External Diode
external Schottky diode must connected, parallel with on-chip synchronous rectifier, from OUT. diodes such MBR0520L, EP05Q03L, generic 1N5817. diode should rated 500mA, since carries current during startup after synchronous rectifier turns off. Schottky diode must connected close possible. Ordinary rectifier diodes must used, since slow recovery rate will compromise efficiency.
Board Layout Grounding
Well-designed printed circuit-board layout important minimizing ground bounce noise.
Place lead ground leads COUT close device possible. Keep lead short possible. maximize output power efficiency minimize output ripple voltage, ground plane solder directly ground plane.
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AS132 Data Sheet
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Assignments
Pinout Packaging
Assignments
Figure Assignments (Top View)
SHDNN
RESETN
BATT
AS1321
Descriptions
Table Descriptions Name SHDNN BATT RESETN Number Description Active-Low Logic Shutdown Input AS1321 current into BATT (typ). AS1321 Battery Voltage Input Ground External Inductor Connection Output Voltage Active-Low reset output
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AS132 Data Sheet
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Package Drawings Markings
Package Drawings Markings
AS1321 available 6-pin SOT23 package. Figure 6-pin SOT23 Package
Notes: dimensions millimeters. Foot length measured intercept point between datum lead surface. Package outline exclusive mold flash metal burr. lower left when reading mark from left right. identifier 0.3mm. located above Meets JEDEC MO178.
Symbol
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
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AS132 Data Sheet
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Ordering Information
AS1321 available standard products shown Table Table Ordering Information Part AS1321-T Marking ASKX Description 130mA Step-Up DC-DC Converter Delivery Form Tape Reel Package 6-pin SOT23
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AS132 Data Sheet
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Copyrights
Copyright 1997-2006, austriamicrosystems Schloss Premstaetten, 8141 Unterpremstaetten, Austria-Europe. Trademarks Registered rights reserved. material herein reproduced, adapted, merged, translated, stored, used without prior written consent copyright owner. products companies mentioned trademarks registered trademarks their respective companies.
Disclaimer
Devices sold austriamicrosystems covered warranty patent indemnification provisions appearing Term Sale. austriamicrosystems makes warranty, express, statutory, implied, description regarding information forth herein regarding freedom described devices from patent infringement. austriamicrosystems reserves right change specifications prices time without notice. Therefore, prior designing this product into system, necessary check with austriamicrosystems current information. This product intended normal commercial applications. Applications requiring extended temperature range, unusual environmental requirements, high reliability applications, such military, medical life-support lifesustaining equipment specifically recommended without additional processing austriamicrosystems each application. shipments less than parts manufacturing flow might show deviations from standard production flow, such test flow test location. information furnished here austriamicrosystems believed correct accurate. However, austriamicrosystems shall liable recipient third party damages, including limited personal injury, property damage, loss profits, loss use, interruption business indirect, special, incidental consequential damages, kind, connection with arising furnishing, performance technical data herein. obligation liability recipient third party shall arise flow austriamicrosystems rendering technical other services.
Contact Information
Headquarters austriamicrosystems A-8141 Schloss Premstaetten, Austria Tel: 3136 Fax: 3136 Sales Offices, Distributors Representatives, please visit:
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